The AIChE Ammonia Safety Symposium 50 Years of Shared Experiences

ABSTRACT

It has been 50 years since the first AIChE ammonia safety symposium was held and a comprehensive review was made of more than 1200 papers that were presented over the last 49 years. This review includes various topics such as accidents, fires, explosions, safety developments, benchmark studies, technological advances, and process and maintenance improvements. The paper also highlights the key lessons learned by the ammonia and syngas industries across the globe from past experiences.

Venkat Pattabathula, Incitec Pivot Ltd

Gibson Island Works, Brisbane, Australia

Bhaskar Rani, Terra Industries Courtright, Ontario, Canada

And

D.H. Timbres, Agrium, Inc.

Fort Saskatchewan, Alberta, Canada INTRODUCTION The AIChE organisation has played an important role in providing the platform, which has no doubt improved the safety of our plants, and saved lives and expense. The symposium also prevented many similar incidents from ever happening due to people being aware of what has happened elsewhere.

The first AIChE Safety in Ammonia Plants and Related Facilities Symposium was held in 1956. At that time, the symposium was called Safety in Air and Ammonia Plants. This year, we are celebrating the 50th anniversary of the Symposium, which has become the premier forum for sharing experiences in the nitrogen fertiliser and syngas chemicals industry.

Through the papers presented at these Symposiums we have been able to make our industry safer and more efficient. Knowledge of the bad experiences has helped others to avoid them. Knowledge of the positive experiences and design improvements has contributed to a more efficient industry.

In the 50 years of the Symposium there have been more than 1200 papers presented. The titles alone of many of the papers reflect the advances in the technology used in our industry. Others reflect lessons learned the hard way through accidents and near misses. In this paper, we will review what we consider to be some of the most important developments and lessons learned from the past.

Over the last 50 years, the global ammonia industry has grown ten folds from about 14 million tonnes per year to 140 million tonnes per year today. PLANT SAFETY PERFORMANCE

Fires, Lost Time Injuries, Explosions and Ruptures in Ammonia Plants

Plant Surveys International (PSI) and others have conducted ammonia plant benchmarking surveys for many years. The surveys demonstrate that fires or incidents in ammonia plants have been significantly reduced over the last 30 years.

Figure 1 shows that ammonia plants reporting no fires have increased from 7% to 42% over the last 30 years and it has been held at 42% since 1998.

No Fires

7%

23%

30%

41%

42%

42%

0% 10% 20% 30% 40% 50%

1973-76

1978-81

1982-85

1994-96

1997-98

2000-01

Figure 1. Ammonia Plants Reporting No Fires

Figures 2, 3, and 4 show the trend of Fatalities, Lost Time Injuries (LTI) and Explosions/Ruptures reported for benchmarking survey periods. This information is limited to the plants that participated in the surveys and it does not reflect the whole ammonia industry. However, the survey was wide ranging and plants represented were from all the regions of the world.

Fata lities

1%

1%

2%

0% 1% 2% 3% 4% 5%

1973-76

1978-81

1982-85

1994-96

1997-98

2000-01

Figure 2. Ammonia plants reporting Fatalities

One fatality was reported in each benchmarking survey period.

In 2000-01 survey, a contractor’s employee accidentally fell through a plastic sky light on the roof of the compressor house. He fell 15 meter and died from his injuries the following day. Work on the roof was authorised and the work area was defined by taping. The incident occurred outside of the authorised work area.

In 1997-98 survey, a contract employee died when he fell in to a high temperature shift reactor while loading catalyst in to the vessel.

In 1994-96 survey, a welder died from burns received while working inside a steam boiler.

L o st T im e

39%

32%

35%

0% 10% 20% 30% 40% 50%

1973-76

1978-81

1982-85

1994-96

1997-98

2000-01

Figure 3. Ammonia Plants reporting Lost Time

Ex plosion/Rupture s

14%

18%

7%

0% 5% 10% 15% 20%

1973-76

1978-81

1982-85

1994-96

1997-98

2000-01

Figure 4. Ammonia plants reporting Explosion/Ruptures Major Safety Incidents

All the safety incidents that include fires, explosions, and equipment failures reported at most of the AIChE symposiums since 1956 are listed in Table-1.

We consider the most significant incidents from 290 reported over the last 49 years are as follows:

1. Compressor explosion during a routine shop test killed 6 people.

A major disaster occurred during a routine shop test of a centrifugal compressor at the Ingersoll-Rand Phillipsburg, N.J. plant. The accident killed 6 people and hospitalised 6 more for varying periods of time.

The reference for this example provides an external view of the building and gives an idea of the damage done. The investigation team identified the probable cause was the ignition of an oil-air mixture that occurred in the compressor as air was used for testing the compressor.

To prevent a recurrence, it was recommended to use only inert gas in all future testing of compressors.

2. One person killed in an explosion while breaking in a compressor.

An explosion on the fourth stage synthesis gas compressor discharge killed one person.

The cause of the accident was the use of air to lubricate the compressor at higher pressures, which increased the air temperature.

It was suggested to use only nitrogen to lubricate compressors.

3. Suffocation of workers in CO shift converter killed 3 people.

The accident occurred on 17 December 1960 at Asahi Chemical Industry Co. Ltd, Japan. Three people died from suffocation due to lack of oxygen in the CO shift converter.

One person entered the shift converter without knowing that the vessel was being purged with nitrogen after a catalyst change out. Two other workers also died from suffocation as they tried rescuing the first worker.

New safety measures were implemented for confined space entry.

4. Many failures were reported on front-end waste heat boilers.

A) Cause of damage and repair of reformed gas fire tube boiler

The secondary reformer waste heat boiler was damaged due to the high pH level of boiler water at Jianfeng Chemicals, Fuling, Sichuan, Peoples Republic of China.

The boiler was repaired in-situ in 115 days and the repaired unit achieved the design heat transfer rate.

B) Experience with metal dusting in waste heat boilers

Metal dusting was reported to occur in ammonia plant 3 of DSM Fertilisers, The Netherlands. In ammonia plants metal dusting can occur in the process equipment between the secondary reformer outlet and the inlet of the high temperature shift converter.

Modern ammonia plants generally operate at low steam/carbon ratios and higher front end pressures. Both conditions will increase the CO-content in the process gas leaving the secondary reformer and will therefore increase the temperature range over which the formation of carbon can happen.

The metal dusting process can be slowed or even halted by:

- The prevention of carbon formation.

- the prevention of carbon adsorption, and

- The formation of a less stable intermediate carbide.

C) Failures in waste heat boilers

Thielsch Engineering presented a paper in 1994 with case histories of waste heat boiler failures and the remedial actions taken to restore those boilers for continued service.

The failures were caused by various factors including design deficiencies; defects introduced during manufacturing or fabrication, service-related deterioration and/or upset plant operating conditions.

D) Failure and repair of two primary make gas boilers

ICI Chemicals and Polymers Ltd, Billingham plant in England reported tube failure of primary waste heat boilers.

The principal damage had occurred as a consequence of ferrule failures and subsequent loss of refractory. The importance of ferrules and refractory cannot be over emphasised. The choice of material should be taken into consideration both from mechanical and corrosion resistance aspects.

The total duration of the inspection and repair including the replacement of ferrules was 35 days and involved approximately 4,000 man-hours.

Another lesson learned from this failure is that prolonged operation with serious tube leaks should be avoided, as it will almost inevitably lead to severe boiler damage.

E) Repair and retubing of reformed gas boiler

Tube leaks were detected on the reformed gas boiler after 600 days of plant operation at Rashtriya Chemicals & Fertilisers Ltd (RCF)) ammonia plant in India. The leaks were found from the cracks behind the tube-to-tubesheet weld joint on the hot compartment of the boiler.

On some occasions the water level in the boiler was very low while the plant was still in operation. About 33 tubes were leaking badly and half of the tubes collapsed within one-meter distance from the inlet. Some tubes had pits up to 2 mm diameter and 1-2 mm deep.

Also, a whitish layer of phosphate deposit was noticed on the tube surfaces with a possible accumulation of sludge and sediments inspite of continuous and intermittent boiler blow down.

In-situ retubing of the boiler was completed in about 34 days.

F) Failure of a waste heat boiler after debottlenecking process air compressor

In November 1991 BASF’s ammonia plant No.3 in Ludwigshafen, Germany had an emergency shutdown caused by an untypical failure of the waste heat boiler downstream from the secondary reformer. The high-pressure steam generating system had a sudden loss of water due to a ruptured tube in one of the boilers. Upon inspection, one hole, several small leaks, and erosion on the tubes were noticed.

The complete boiler was replaced by a new one in a 4-week shutdown period.

With the debottlenecking of the process air compressor, the ammonia plant capacity was increased and this contributed to a higher thermal load on waste heat boiler, which caused two-phase flow in the boiler tubes and hence eroded tubes.

G) Failure of a waste heat boiler downstream of secondary reformer

Waste heat boiler failures were experienced at Krishak Bharati Cooperative Ltd (KRIBHCO)’s ammonia plant in India.

The most likely cause was the sludge deposits that were left in during initial chemical cleaning, as there was no means of cleaning the shell side. No intermittent blow down was operated on the boiler side. The boiler was planned to be replaced with a new design and a new blow down installed on the existing boiler after its repairs.

H) Failure and repair of a primary waste heat boiler

A rupture occurred in the bottom-dished head of the primary waste heat boiler at P.T.Pupuk Kalimantan Timur, Kaltim ammonia plant in Indonesia.

Localised refractory failure and subsequent overheating resulted in a short-term high temperature stress rupture. There was no evidence of hydrogen damage.

The head was replaced with a new one and the skirt was cleared of all debris.

I) Failure and repair of the shell of a primary waste heat boiler

A primary waste heat boiler shell on an 1100-tpd-ammonia plant failed at Fertilisers of Trinidad & Tobago Limited.

Analysis of the failure revealed an extensive surface cracking pattern on the OD surface of the waste heat boiler shell, extending downward to the centre-line of the process gas outlet nozzle.

The failure mechanism clearly involved localised corrosion, aggravated by periodic mechanical stress. The cracking involved a slow step-like progression and was not restricted to the water jacket portion of the shell. Thermally induced surface stresses due to liquid level fluctuation, local boiling or splashing within the water jacket was also accepted as the failure mechanism.

To prevent a recurrence of similar failures, the level in the water jacket was increased by 51 mm, a coating to the exposed shell area and, use of an oxygen scavenger were also considered.

J) Failure, repair and replacement of a waste heat boiler

A double compartment designed waste heat boiler downstream from the secondary reformer failed at Fauji Fertiliser Co. Ltd in Pakistan.

The main cause of the failure was the loss of water level in the steam drum and subsequent steam heat up of the waste heat boiler from steam flow through the process air coil while the pressure control on the steam drum remained in the manual mode.

The observed defects were visible cracks in the tube-to-tubesheet ligaments; microcracks on the tube-to-tubesheet weld; tube holes; ligaments and welding lips.

A partial retubing was carried out on the WHB with the replacement of 101 tubes in the upper portion. This repair lasted for only nine months. Finally, the WHB was replaced with an improved design boiler.

K) Failure of a boiler pressure shell

The primary waste heat boiler shell failed at an ammonia plant of Commercial Solvents Corp.; Sterlington, LA.

The probable cause of the failure was deterioration of refractory, which allowed the wall temperatures to exceed the design limits. This deterioration was aided by having to hammer the shroud slip joints to facilitate installation of the tube bundle.

A section of shell was replaced and separate flow meters were installed to each of the three water jackets. The new refractory was superior to the original installation for this type of service.

L) Failure of a primary waste heat boiler

A pressure shell of primary waste heat boiler suddenly ruptured at Terra Chemicals ammonia plant in Sioux City, Iowa.

A metallurgical examination of the rupture area revealed that the failure was due to a short time high temperature stress rupture.

The vessel was repaired and a new low silica (less than 0.1%) bubbled alumina refractory was installed.

M) Waste heat boiler failure and modifications

Two horizontal fire tube waste boilers failed at an ammonia plant of Petrochemical Industries Co, Kuwait.

The boilers had long tubes with thick tube sheet design, which is very sensitive to thermal shocks.

Both waste boilers were replaced with a double compartment design after repairing and operating the old boilers for a few months until the new boilers arrived at the site.

N) Fire in secondary reformer outlet line to waste heat boiler

A fire occurred on the pressure shell-interconnecting pipe between the secondary reformer and primary waste heat boiler at KRIBHCO’s ammonia unit-2 in India.

The interconnecting pipe bulged and water jacket burst open. All electrical and instrument cables in that area were damaged.

The reasons for the failure of the pressure shell could have been hydrogen attack or creep of the pressure shell. The refractory failure may have been due to thermal cycling of the transfer line.

To avoid hydrogen embrittlement, the shroud material was changed to Inconel-601. Jacket water level indications were brought on to DCS and four thermocouples were provided on each jacket of the interconnecting pipe to the waste heat boiler.

O) Catastrophic failure of tubesheet in fire tube reformed gas waste heat boiler

The reformed gas waste heat boiler failed after nine years in service at Terra Nitrogen’s, Courtright plant in Canada.

A drop in gas temperature at the inlet to the boiler indicated evidence of a leak. Inspection of the boiler revealed two failures. One was a tube failure just behind the tubesheet to tube weld joint and the other was a failure at the tubesheet to shell forging weld joint.

The cause of the failure was attributed to departure from nucleate boiling, initiated by an increase in plant rates earlier in the year.

A new front section of boiler was designed for

higher plant rates and with more equitable distribution of the heat load between the two sections of the boiler. A new riser design was also required in view of the increased steam flow and also to mitigate the formation of regions of stable/semi stable pockets of steam.

The new boiler design included the installation of larger diameter tubes in the front section to keep the heat flux below the critical value. This increased the heat flux to the second section, but care was taken to have the heat flux within the critical values. The new design necessitated an increase in the diameter of the shell and the new section was installed in October 1996.

P) Ammonia process primary waste heat boiler shell failure experience

Canadian Fertilisers Ltd at Medicine Hat have experienced shell failures on ammonia plant primary waste heat boilers. The failure was two types at shell plate cracks and ruptures, and shell nozzle attachment weld cracks.

The pressure shell of the waste heat boiler failed due to thick-lip stress rupture (creep). The damage was due to prolonged exposure of the shell material, in the temperature range of 480-620oC. No evidence of hydrogen related damage or cracking was noted in the samples examined.

The stainless steel internal shrouds and refractory were removed from the vessel. The entire shell section was “baked out” to remove hydrogen prior to attempting any welding. The vessel was repaired and returned to operation after 15 days of production interruption.

CFL felt that the use of 1.25 Cr-0.5Mo or higher alloy shell material would offer the increased margin of protection that may avoid shell failures due to overheating. Both the resistances to hydrogen attack and creep resistance of 1.25 Cr-0.5Mo material in this temperature range is substantially better.

Q) Remedial actions to reformer waste heat boilers

Several repeated failures were experienced on reformer waste heat boilers in two Asmidal Ammonia Plants, at Arzew in Algeria.

Localised refractory failures and subsequent overheating resulting in short-term high temperature caused the failures.

Partial repairs were carried on one ammonia plant boiler whereas as the boiler was replaced on other ammonia plant.

R) Failure of a secondary waste heat boiler

A secondary waste heat boiler (102C) failed in one of the ammonia plants at KRIBHCO, India.

The main cause of the failure was sludge formation and accumulation due to lower circulation rate that resulted from reduced heat load than design. Also, there was no intermittent blowdown for the initial four years; conventional solid treatment till 1998 and improper tube expansion contributed to the failure.

Sleeves were inserted in the weakened tubes and this helped to prolong boiler life. Also, new coordinated phosphate treatment, and continuous blowdown of boiler were implemented. Finally, a new exchanger with modified design was procured and installed.

5. Ammonia storage bullet failure killed 18 people.

A pressure storage ammonia bullet failed on 13 July 1973 at AE&CI Ltd, Potchefstroom, South Africa. An estimated 30 tonnes of anhydrous ammonia was released which caused the deaths of 18 people.

The failure resulted from the brittle fracture of a dished end of the bullet. The vessel was not stress relieved after manufacture and strain aging had weakened the metal of the vessel.

6. Synthesis converter start up heater failures damaged plants.

A) During start up of the synthesis loop, a violent explosion occurred at about 8 P.M. on 9 December 1973 at Shellstar Ltd Ince, ammonia plant in England.

The temperature imbalance in 2-parallel coils and nitriding of coils caused the failure.

B) A fire occurred on 6 February 1979 at Monsanto, Luling, LA ammonia plant that resulted from a rupture in one of the two-synthesis start up heater coils. The rupture of the coil was primarily caused by an inadequate flow of process gas through the coil.

Following the accident, new interlocks were provided to trip fuel gas to heater on low synthesis gas flow. Also, the coil material was upgraded from 2.25 Cr-0.5Mo to TP304H.

C) A fire occurred on start up heater on 25 November 1983 at BASF Ludwigshafen plant in West Germany.

The damage of coil was caused by hydrogen induced cracks from too high hardness and condensing of moisture on the tube outer surface.

The coil was repaired and later on, its material was upgraded. New thermocouples were installed to measure coil wall temperatures during operation.

D) At Standard Oil Chemical Co. Lima, OH, a tube in converter start up heater ruptured on 9 July 1985 resulting in a fire and plant shutdown. The rupture occurred during the refractory dry out. One damaged coil was removed, and the converter was heated with three coils.

Stresses from thermal cycling and continued nitride formation during subsequent start-ups propagated the crack to a depth where circumferential stress from the tube internal pressure together with the stress intensification of the crack caused a ductile failure through the remaining wall.

The coil was replaced with a new material of 9% Cr-1% Mo to provide a somewhat greater resistance to diffusion of nitride layer.

7. Fatal accident in CO2 removal section killed 9 people.

On 22 June 1974, at Madras Fertilisers Ltd (MFL) in India, a fatal accident took place when a 400 mm (16-inch) elbow ruptured and sprayed hot potassium carbonate solution into the control room, killing nine operators and seriously injuring the tenth operator.

Of 10 persons in the control room at the time, 8 died almost instantaneously, one died after 5 hours in the hospital; and one recovered after long hospitalisation.

The root cause of the incident was the erosion by impingement of a high velocity stream of liquid from a faulty control valve upstream elbow. The hydrogen gas from the absorber that escaped through the ruptured elbow caught fire. MFL contacted other ammonia producers in Europe and the USA and received many suggestions on improved materials of construction.

MFL replaced the carbon steel elbow with an SS lined elbow as a quick fix and then changed to a complete SS material. Glass panels in the control room were reduced in size although retained to maintain some visibility. 8. Two people killed when NH3 loading line

ruptured.

A serious accidental rupture of a rubber hose unloading anhydrous ammonia from a tanker to a quayside storage sphere caused two deaths at Supra Aktiebolag facilities in Sweden.

Time elapsed between the rupture to closure of the valve on board was 50 minutes and about 180 tons of ammonia leaked out on to the quay. Two people were drenched in liquid ammonia, which resulted in edema of the lungs. They had been standing close to the rubber hose when it ruptured and had then run in to vapour cloud.

The cause of the hose rupture was wrongly specified polyester hose, which was destroyed by a form of hydrolysis resulting from the reaction of ammonia.

After the accident, the hose was replaced and new procedures were put in place to improve ammonia ship loading operations.

9. Accident in Lithuanian plant killed 7 people.

On 20 March 1989, an accident took place in a Lithuanian fertiliser plant, which destroyed a 10,000 tonne ammonia storage tank.

The whole ammonia tank was dislodged from its foundation, smashed with great force through the surrounding wall of reinforced concrete and finally landed about 40 meters from the foundation.

Devastation around the tank was enormous and liquid ammonia around the plant site was 70 cm deep. Large quantities of ammonia evaporated, the ammonia gas caught fire and the whole plant area was engulfed in flames.

About 32,000 people were evacuated from a nearby town, the rescue operation continued for three days and the total fatalities were 7 with 57 people injured.

It was reported that ammonia tank over pressured due to roll over of its contents resulting from the warm ammonia being supplied to the bottom of the tank while at the same time, tank refrigeration compressors were out of service.

10. Explosion of ammonia separator led to a major plant outage.

Hans-Dieter Marsch of Uhde GMBH presented a paper in 1990 symposium on explosion of a multishell ammonia separator that had been in operation for ten years. The vessel exploded into at least 80 fragments in a 1000-tpd ammonia plant.

The most likely cause was the presence of mercury, which affected steel properties and formed explosive compounds.

The average mercury (Hg) content of the feed gas was 150-180 microgram/cu.m and it was equivalent to 60-72 kg of mercury per year. Experts estimated that 1 kg of mercury is

equivalent to approximately 2 kg of TNT or 9.2 MJ. Assuming 10 kg of Hg was present at the time of rupture at the bottom of separator, it would have been a charge of 92 MJ in addition to the stored energy of 473 MJ in the gas.

The paper message was, if mercury is detected in the feed gas, it should be removed to the lowest possible level.

11. Failure of ammonia injector in urea plant killed 2 people.

In July 1989, the casing of a high-pressure ammonia injector in the urea plant operated by ICI Chemicals and Polymers at Billingham, U.K. failed catastrophically without any warning. The release of ammonia resulted in the deaths of two employees who were close to the injector.

The crankshaft had fractured allowing plungers to come out of the cylinders thus causing an uncontrolled release of ammonia.

The crankshaft fracture was due to a fatigue crack. Also, the initial design of the machine should have ensured that the plungers do not come out of the cylinders in the event of crankshaft failure and loss of containment could have been minimised by better process plant design.

ICI developed an extensive list of improvements to prevent a recurrence of this incident, which included design changes to the urea injector pumps and modified emergency and operating procedures.

12. Explosion and fire in synthesis section damaged plant.

A loud explosion followed by a large fire occurred on 26 September 1991 at 0117 hours, in Ammonia Unit 2 of Krishak Bharati Cooperative Limited (KRIBHCO), India.

Due to the intensity of the explosion, one of the relief valves was thrown off to the nearby pipe rack.

The synthesis loop exchangers were exposed to flames and shells of the exchangers were over-heated. Cold insulation on syngas chillers and ammonia separator burnt off. Motorised actuators burned off, many instruments and power cables were damaged. Control room window panels and frames shattered, a false ceiling gave way and instrument panels were dislodged. A relief valve on the suction of the syngas compressor and about 20 control valves were damaged.

The most probable cause of the incident was popping of one of the relief valves in the synthesis

loop causing an explosive mixture in the vent header with ingress of air from the drain line on the tail pipe due to a valve being left open after manual draining of condensate. The spark for ignition might have been provided by a friction in the pipeline at uneven welding penetration and a rise in temperature due to hydrogen gas expansion.

Many remedial actions were taken to prevent the recurrence of the incident: - new location of the relief valve with proper support of the tail pipe; new RV with K orifice; high pressure trip of syngas compressor; continuous purging of the cold vent with nitrogen; new water seals on vent header drain lines; and reduction of glass window panels on the control room.

13. Many failures reported on Synthesis loop heat exchangers.

A) Brittle fracture of an ammonia synthesis heat exchanger

On 19 March 1970, an explosion occurred at Typpi Oy ammonia plant in Finland due to the failure of the forged steel chamber in one of the effluent water coolers in the synthesis loop.

The syngas, at a pressure of 235 bar escaped and caught fire and the height of the flame was about 30 m. The force of the explosion threw the exchanger cover weighing 250 kg horizontally about 100 m and bounced another 100 m. In addition windows were broken within a radius of hundreds of meters around the centre of the explosion.

The explosion also damaged the multilayer ammonia reactor. The hydrogen flame partly loosened the outermost layer, which was repaired by the vessel manufacturer.

The basic reasons of the failure are the selection of material, too light forging and defective heat treatment. The method of heat treatment used resulted in a bainitic structure, which is brittle.

B) Failure of ammonia converter feed/effluent exchanger

About 15% of production loss was estimated from an internal leak of the converter feed/effluent exchanger (121C) at Sherritt Gordan Mines Limited, ammonia plant in Canada.

Both shell and tubes were designed for a pressure of 15,169 kPa and the tube sheets were designed for a maximum differential pressure of 2,069 kPa.

Finite element stress analysis was carried out after a third failure and it was decided to install a packed gland at the cold end.

The gland and gland follower were prefabricated and they were installed in a 15-day outage. The repaired heat exchanger was hydrotested at 16,680 kPa. The synthesis loop performed well after fixing the internal leak in 121C.

C) Further cracking in converter Effluent BFW exchanger

A 1993 inspection of the ammonia converter effluent boiler water exchanger revealed more cracks than those discovered previously at ICI Chemicals and Polymers Ltd, Billingham plant in England. The primary cause was identified as hydrogen embrittlement of a locally hardened region.

A Fitness For Purpose assessment was carried out and operating limitations and inspection requirements were defined until a replacement vessel could be installed.

The limitations included an external ultrasonic examination prior to any cold start up and also a maximum pressure of 100 bar was imposed until the converter outlet gas temperature reached 200C.

D) Stress corrosion cracking in syngas heat exchangers

In October 1982 severe damage was discovered in two synloop feed/effluent heat exchangers at a UKF ammonia plant in Geleen, The Netherlands.

When the problem of gas pocketing in leaking water coolers was solved by making a vent in the outlet cooling water nozzle, a fine mist of cooling water escaping from this vent wetted the insulation material of other equipment including the feed-effluent exchanger. The wall temperature of the steel pressure shell underneath the insulation of the exchanger was in the temperature range likely to cause stress corrosion.

Due to ammonia leakage into cooling water, more nitric acid had to be added to control the pH at the desired level, resulting in a higher nitrate content than is usual in the cooling water. Stress corrosion occurs even in stress relieved equipment such as this exchanger.

The counter measures were- protective painting underneath insulation material and avoiding unnecessary wetting by watertight insulation sheeting especially at nozzles

E) Repair of a waste heat boiler in synloop of ammonia plant

Damage to the synloop waste heat boiler was reported at the BASF AG, Ludwigshafen ammonia plant in Germany.

The leak occurred because of the failure of the heat protection shield. 71 boiler tubes were removed, repaired and re-installed. The design of the heat protection shield was changed to avoid this kind of damage in the future. F) Tube failure in a waste heat boiler in

ammonia synthesis section A tube failure occurred in an 1800 tpd ammonia plant at BASF Antwerp in Germany.

The damaged tubes were plugged. The pore in the leaking plug weld seam was ground away and rewelded. The reason for the damage was inadequate design of the product steam lines not considering the fluctuating pressure drops in the separate product steam lines upstream the common steam line due to load changes.

These fluctuating pressure drops resulted in large fluctuations in the steam drum level, which dropped below the local level glass gauge for some time. The drop of level below the lower level glass gauge led to a collapse of the water circulation in the vessel, which resulted in local superheating/cooling down, of the tube wall. This also led to a continued loss of protective magnetite layers and thinning of tube wall. Finally the remaining tube wall failed.

Counteractions were installation of orifice plate in the product steam line and installation of level indication with alarm.

14. Significant incidents reported on reformer tube dissimilar weld failures.

A) Abu Qir Fertilisers Co., Egypt reported dissimilar metal weld failures on the reformer tube to outlet manifold.

The mechanism of hydrogen induced crack formation was considered to be the most probable cause of the weld failures. The counter measure to this type of failure is to increase the temperature above dew point at the dissimilar weld. This was achieved by adding outside surface insulation and the installation of windshields on 3 sides of the furnace.

B) ICI Chemicals and Polymers Ltd, Billingham, England also reported dissimilar weld cracking on reformer tube outlet headers.

The reformer tubes were fitted with both inlet and outlet pigtails in Incoloy 800H sub-headers. In turn these sub-headers were connected to larger diameter carbon steel refractory lined headers via sixteen transition cones. Each of these transition cones incorporated a dissimilar weld at the change of material.

The explanation for the cause of cracking was that the wall temperature had dropped below the process dew point which resulted in the condensation and hence corrosion. This corrosion then lead to hydrogen liberation which diffused into the hard fusion zone of the weld causing hydrogen induced cracking on subsequent cooling down. The action taken was to fit a local windshield and local lagging.

C) Agrium Borger (TX) Nitrogen Operations also reported dissimilar metal weld failures, on reformer tube top transition pieces between cast tube and P11. This was identified from a new inspection technique using electromagnetic testing (EMT). A new tube design was developed with a transition piece of SS304H and all the tubes that had weld failures were replaced with the new design top transition pieces.

15. Explosion of Benfield and aMDEA storage tanks.

A) At 11.40 A.M. on 4 April 1984, a violent explosion occurred in the Benfield storage tank at Farmland Industries, Pollock, LA plant, completely destroying the tank and causing extensive damage to synthesis gas piping.

At the time of the explosion, Benfield solution was being transferred from the stripper to the tank. The explosion sent the tank roof and side walls some 37 meters in to the air expelling an estimated 114 cu.m of solution in to the process area.

Although standard operating procedures were followed, hydrogen accumulated inside the storage tank with sufficient oxygen, which, with a static charge or auto ignition, caused the explosion.

Damages to process piping caused by the explosion were repaired and a new tank was designed and built to prevent any ingress of hydrogen from the process system with an air induced purge system.

A new operating procedure for pumping out the Benfield system to the storage tank was prepared with emphasis on not allowing any gas to enter the storage tank or solution sump.

B) In August 1999, an explosion occurred in aMDEA storage tank at Alaska Nitrogen Products plant in Kenai, Alaska. The explosion propelled the MDEA storage tank off of its base and in to the air. The tank landed on an adjacent air-cooled heat exchanger, which was also filled with synthesis make up gas. The impact of the tank on the air-cooled heat exchangers initiated a second explosion and fire. Three operators were treated for minor injuries.

The reverse flow phenomena caused process gas ingress into the MDEA storage tank, which was ignited by some unknown source.

As a result of this incident, check valves were installed in the MDEA system and the storage tank was equipped with inert gas blanketing system. Process Hazard Analysis (PHA) was conducted on the aMDEA system and operating procedures were revised to improve the focus on reverse flow and other start up/shutdown conditions.

16. Explosion of H2 in CO2 line.

On 13 April 1997, the transfer pipe for carbon dioxide gas from the ammonia plant exploded at Hydro Agri, Prosgrunn facilities in Norway. There were no injuries, but 850 meters of the line was totally destroyed and a large number of glass windows on nearby buildings were broken.

The line was temporarily out of service and the investigation team concluded that the trip system had been disabled prior to the explosion, hydrogen rich gas had entered the pipeline, the nitrogen purge had not been effective, allowing air leakage into the line and forming an explosive mixture, which ignited.

The trip system was modified and separate sampling lines with block valves were installed for each analyser in order to eliminate a common mode failure caused by, for example, freezing in the wintertime. A new analyser was also installed for use in the reformer section for the start up.

17. Reformer tubes burn out, a big impact on business.

The Agrium Fort Saskatchewan Nitrogen Operations experienced a massive reformer failure on 16–17 November 1998 during start up after a short maintenance outage.

The incident happened during the reformer start up when the reformer furnace was fired harder while observing the process gas outlet temperature rather than flue gas temperature, when there was no steam flow through the radiant tubes.

It was noted that the flue gas temperature had reached a maximum value of 1071oC. The tube melting point is typically quoted at about 1343oC and complete melting will be finished at 1400oC. It’s probable that the localised flue gas temperatures were much higher than the temperatures reported by thermocouples at the outlet of the radiant box. Uneven firing or the relatively high air leakage rate at low firing rates could cause this.

Approximately 50% of the tubes had completely failed and the tube failures were observed mainly at welds. No risers failed, but overheating was evident.

All the reformer radiant tubes were replaced in just 39 days after the damage to the furnace occurred. Russian built cargo planes were used to transport radiant tubes from the U.K. to Canada.

An automatic shutdown system was installed to protect against overheating during start up. Operating procedures were modified to reflect changes in communication between the shifts.

18. Failure of a molecular sieve dryer.

At 11.30 P.M on 24 May 2000, a molecular sieve vessel failed catastrophically at CF Industries Donaldsonville, Louisiana, Ammonia plant 3. Vessel fragments were projected throughout Ammonia plant 3, Urea plant 2 and the adjacent offsite operating areas causing extensive damage to equipment in the fragments’ path. The resulting fire from escaping process gas caused burn injuries to several personnel working in the local area.

The failure resulted from a delayed hydrogen crack that originated at the toe of a repaired fillet weld. The crack propagated into the vessel head to a critical flaw and then fast-fractured through the shell thickness. The vessel shell continued to fast-fracture from the origin into approximately forty fragments in less than one-tenth of a second.

Minimising the weldment hardness and residual welding stress would have increased the critical flaw size preventing this type of failure.

19. Failures on ammonia synthesis converters

A) Failure and repair of ammonia converter basket

The Shahpur Chemical Co., ammonia plant in Iran experienced failure of ammonia converter basket, which led to plant shutdown.

Hot spots appeared on the converter pressure shell and upon inspection, vertical cracks were observed on the basket. The repair of the basket was accomplished by lining the inside with two layers of 6.5-mm (¼ in) thick plates. A liner was welded to the grid at the bottom of each bed.

The cause of the basket failure attributed to chloride stress corrosion cracking as the basket materials were made of 304SS. Records showed that water used for the final pressure test of the shell with the basket insulation in position contained 11 ppm of chlorides.

Lessons from this failure that hydrostatic testing should be carried out with water containing less than 1-ppm chlorides. The use of moisture retaining insulation for the basket to be avoided and the insulation should not contain chlorides.

B) Ammonia converter basket failure

Agrico Chemical Co., Donaldsonville, La also reported ammonia converter basket failures caused by stress corrosion. A series of hot spots were noticed even after repairs made to basket and the basket was finally replaced with a new one.

The main cause of the failure appears to be high chloride levels in the basket insulation material i.e-spun rock wool. The catalyst, insulation and hydrotest water also had chlorides in varied ranges.

Construction and shipping photographs indicated the side of the vessel was cracked during hydrotesting and shipping.

Good design with the right equipment materials of construction is not enough to prevent stress corrosion cracking. Particular attention must be given to water, which comes in contact with the materials of construction. Analysis of insulating materials, which do not include tests for particular contaminants such as chlorides in the 0 to 500-ppm range, should not be accepted.

C) Damage and repair of a 1000 tpd horizontal ammonia converter

In March 1984, the diaphragm and impeller of the high-pressure case of the synthesis gas compressor failed, resulting in a plant shutdown at the Sheritt Gordan Mines ammonia plant in Canada.

The basket internals suffered significant, but readily repairable damage. Catalyst plugging of the Bed2A distributor grids caused a high-pressure drop across the converter resulting in a reduction in plant capacity. Damage was also found in downstream exchangers 120C, 121C and 123C.

Repairs and modifications made to converter basket allowed the plant to operate the plant at full capacity.

D) Failure and novel repair of thick wall synthesis converter forgings

During a routine ultrasonic inspection, severe cracks were discovered in the 5-Cr converter bottom forgings at an ammonia plant of Arcadian Corporation, Augusta, GA.

The investigations concluded that low cycle thermal fatigue was a key element in initiation of

the cracking of the Inconel 182 overlay at the I.D. of the forgings. Once cracking had progressed through the In-182 there was considerable evidence to indicate that propagation within F-5 forging material was enhanced and possibly accelerated by the nitriding effect of the process.

Repairs were made by selecting an alternate design that improved vessel safety and integrity. The key lesson from this is that any users of vessels with thick wall components subject them to periodic examination.

E) Inner basket failure of ammonia booster reactor

A major failure involving the inner basket of the ammonia booster reactor after a scheduled turnaround caused an additional down time of 31 days at ABF Bintulu’s ammonia plant in Malaysia.

In August 1997, the inner basket of the booster reactor had partially failed and leaked catalyst, resulting in plugging of downstream synthesis loop high-pressure equipment and piping.

The possible cause of the failure was the missing bolts on catalyst basket and strips, which were replaced, reinforced after unloading the catalyst. The numerous trips coupled with the defective valves caused the failure of the bolts and thus the catalyst leak. The booster reactor internals can be improved to increase their robustness.

F) Ammonia converter leakage and repairs

The centre screen on 2nd bed failed in ammonia converter basket at Fauji Fertiliser Co. Ltd in Pakistan.

The main cause of the failure suspected to be the weaker design of the centre screen to bear the actual compression stresses caused by the combined action of thermal expansion of the screen and the opposite forces resulting from friction of catalyst and/or expansion bellows.

The entire catalyst was removed and a new modified design, centre screen was installed and new catalyst charge was loaded.

G) Ammonia converter weld joint failure

On 25 April 1995, at Tata Chemicals Ltd ammonia plant in India, a fire was noticed at the joints of the insulation cladding close to the location of the first circumferential site weld joint from the bottom of the second ammonia converter. Immediately after the incident the plant was shutdown, as they couldn’t extinguish the fire with dry chemical powder.

Various tests carried out have established the root cause of the failure as hydrogen induced cracking due to unsatisfactory PWHT on the original P22 converter shell.

The failed joint was repaired in-situ in the following steps:

- The entire defective portion was removed by gouging, drilling and grinding.

- The stresses developed were relieved by heating the entire seam to 700 oC with a soaking period of 1 hour and 45 minutes.

- Hardness was measured after stress relieving and was found within 185 Hv.

- Surface preparation followed by dye penetrate check was done.

H) Failure of internals of ammonia converter

In 1999, Ammonia converter internals failed at PTPK ammonia plant in Indonesia.

The sliding expansion joint of the gas return pipe in bed no.3 and 4 and the screen of the support thermowell on the inner collector of the fourth bed were found broken.

The sliding expansion joint was repaired and the support of the thermowell was relocated.

The possible causes of the internal damage to the ammonia converter include:

- The design of the expansion joint did not absorb the thermal expansion leading to the expansion joint collapse on the wire mesh and catalyst filling the gas return pipe.

- The internal damage occurred during the ammonia plant start-ups and shutdowns. When the temperature changes produced excessive differential growth and movements of the gas return pipe may have caused deformation of the centre pipe.

- The support of the thermowell pipe and wire screen of the inner collector was not strong enough to support this pipe, so the wire screen and catalyst spilled from the basket.

20. Failures on ammonia storage tanks

A) Overflow of an ammonia storage tank

On 16 November 1970, Gulf’s refrigerated ammonia storage tank at Blair, Nebraska overflowed, causing considerable concern to residents of the community but, fortunately, no serious injuries. About 150 tonnes of ammonia were lost to atmosphere and three city firemen were treated for fume inhalation.

The tank high level alarm and shutdown system did not work which resulted in to this incident.

Lessons from this incident that tanks equipped with overflow systems like this tank should have the relief valve and block valve separated by sufficient distance to allow closing the block valve when relief is open. At Blair, the block valve was directly below the relief and showered with liquid ammonia during an overflow. There should be back up level indications on the tank.

B) Partial collapse of an ammonia storage tank

On 13 November 1978, a 6,349 tonne atmospheric ammonia storage tank located at J.R. Simplot’s Pocatello plant, partially collapsed when a vacuum developed in the tank.

The tank, which was approximately one third full at the time partially collapsed on the one side and developed a small rupture near the top portion of the tank, well above the liquid level. The tank was subsequently drained, cleaned and repaired before decommissioning.

The cause of the tank collapse was the result of several conditions. The initial failure was precipitated by the failure of the pressure transmitter following the power outage. It was believed that moisture in the instrument air froze during the power outage and caused the failure. The only other pressure indicator in the tank was a gauge, which received a signal from the same transmitter, as did the controller. A manometer on top of the tank had been allowed to fall into disrepair and the regular operator checks on the manometer were not conducted.

The ultimate cause of the tank collapse was the failure of the vacuum relief valves.

The controller failure and lack of any warm ammonia from the plant following power failure coupled with the cold weather and atmospheric conditions were sufficient to create vacuum in the tank. With no vacuum relief on the tank, the tank collapsed when the structural design conditions were exceeded.

Several preventive measures were taken to exclude any recurrence of the tank collapse. An additional pressure indicator was installed on the tank, using an electronic transmitter and sensor. The pressure recorder-controller and auxiliary pressure indicator remain a pneumatic system.

The nitrogen blanketing of ammonia storage tank shall be avoided. Sub-cooling of the ammonia in the tank, which results in temperatures well below the design of the tank steel and foundations.

C) Damage to ammonia storage tank foundation

M.W.Kellogg reported a foundation damage on an ammonia storage tank at the Asmidal plant in Algeria. This was caused by freezing and heaving leading to movement, tilting, tearing, cracking, bending and fracture.

The integrity of the tank was not affected and the tank foundation was repaired to modern design.

It was concluded that the most probable scenario of events was damage due to ground movement of the 19 April 1981 earthquake to the foundation insulation system. This damage was spreading and slight tilting of the segments, failure of anchor bolts, breaking of the cork insulation, tearing of the water proofing and outer fabric and local punching failure of the vermiculite insulating concrete. Water then entered the foundation system both from above and laterally, increasing the conductivity of the thermal system, and froze. The soil below also froze. The expansion forces of frozen vermiculite concrete, soil and ice in the joints further acted to distort and fail other elements.

Much attention must be placed on details of design especially in the area of water proofing and peripheral drainage to the concentrated compression forces caused by the rocking action of tanks especially when they are in a near full condition subject to earthquake induced sloshing action.

D) Stress corrosion in an ammonia storage tank

BASF Chemicals Ltd, Middelesbrough in England reported stress corrosion cracking of 12,000 tonne ammonia storage tank during first inspection after nine years in operation.

The material used and the weld procedures adopted on site produced microstructures susceptible to both stress corrosion cracking and hydrogen cracking.

All the defects were repaired and tank was recommissioned.

It was recommended that wherever possible cleats be made on the outside of tanks and proper weld procedures employed for those inside the vessel. It was also recommended that where practicable consideration should be given to limiting the parent metal to lower yield strength steels when constructing new tanks.

E) Failure of inner shell on double integrity ammonia storage tank

A 5,000 tonne ammonia storage tank which was originally commissioned in 1998, needed to be decommissioned and repaired due to the failure of the inner shell of the double wall tank at Coromandel Fertilisers Ltd, India.

Ammonia liquid level was noticed in annulus area of the two tanks and hence, a decision was made to decommission the tank for inspection as they thought inner cup failed.

The liquid level in the annular space of the tank was measured by a level transmitter, which had high level alarm. But, level transmitter was reading zero since “as built” drawings were wrong to which the annulus level transmitter connected to.

No action was initiated to drain annulus area as they thought it did not have high level whereas it actually had 6.5 m of level. It appeared that some ammonia had started collecting in the annulus due to splashing from the inner cup during ship unloading at high levels.

The inner cup was drained to 0.813 mm for decommissioning and then failure occurred due to hydrostatic head of ammonia in annulus acting below the bottom plate, ultimately resulting in the fracture of the bottom side plates as well as the circumferential weld.

The tank was repaired and it involved the repair of the concrete kerb, removal and refilling of bottom sand layer, repair of and replacement of shell courses, bottom plate renewal, and other modifications.

Following actions were taken to prevent recurrence of the incident:

- The tank was derated to, 4,865 Te and setting of alarms and trips changed accordingly so as to provide a minium 500 mm of free board between maximum allowable liquid level and overflow level.

- A separate recording instrument to record tank inner cup and annulus levels. A parallel independent level indication was also provided for the annulus.

- All indicators were changed to fail-safe.

- A temperature indicator to monitor annulus temperature, with a low temperature alarm.

- Interlock to trip the ammonia pumps if annulus level reaches 400-mm level.

- The annulus drain line permanently connected to the drain pot and routine of draining the

annulus into the drain pot every weekend was initiated.

- The siphon breaking on the liquid inlet line into the tank was modified, so that the top most hole of the dip pipe is above the maximum liquid level in the tank.

- All documents have been updated to reflect “as built” conditions.

ENVIRONMENTAL ISSUES

Some plants have installed continuous emission monitoring system (CEMS) on the primary furnace stack. This system monitors O2, NOX and CO emissions. It has become a useful tool to indicate deviation from optimum combustion conditions within the furnace. CEMS eliminates the need to estimate or calculate the emissions of NOX and CO from the reformer furnace and it can easily determine the total quantity of each pollutant emitted during the calendar year for reporting purposes.

Process condensate from a few ammonia plants is reused by putting it back into the reforming system through natural gas saturators. In some plants, process condensate is purified by HP or LP stage stripping.

NOISE

Noise has been defined as unwanted sound. Its undesirable effects can be temporary or permanent hearing loss, inability of personnel to communicate effectively and reduction of efficiency.

The potential sources of noise are commissioning blow-offs, relief valve blow offs, suction silencers, fans, ducts, pressure reducing stations etc. It’s far more preferable to design noise control systems into the plant rather than wait until an aroused public compels remedial action.

Noise levels in ammonia plants have been reduced by improving the design of Greenfield sites (largely by World Bank legislation) and by installing acoustical insulation, barriers, energy absorption devices and implementation of ear protection in the operating plants.

PLANT OPERATION PERFORMANCE

Plant on stream performance is summarised for the benchmarking surveys conducted by Plant Surveys International, Inc. (PSI) in Table 2.

There have been a total of 8 benchmarking surveys, the first beginning in 1969. The first 3 surveys were limited to North America. Since then, all the surveys have been worldwide although plants in Russia and China have not participated.

The poor operating factor in Survey No. 5 was due to excessive inventory control downtime. The service factor is more representative of plant performance since service factor downtime excludes business-related downtime (inventory control, feedstock curtailment, loss of utilities, etc.).

There has been a steady increase in ammonia plant service factor over the years from 87% to 92%.

DESULFURIZATION

In the earlier days of desulphurisation, activated carbon drums were used to remove sulfur compounds. Later on, Sulfatreat (iron sponge) and molecular sieve dryers were also used to remove low-level sulfur compounds.

The hot desulphurisation process using Ni-Mo or CoMo with ZnO has now become the industry standard in removing sulfur compounds from feed gas. This has increased catalyst life of both the primary reformer and the LT shift converter.

CO2 REMOVAL SYSTEM

Different solvents were used over the years. These included:

• Physical solvents such as Selexol, Fluor 1 and Rectisol (methanol);

• Chemical solvents such as MEA, TEA, and Sulfinol;

• Alkaline salts like Benfield (vanadium as corrosion inhibitor), Catacarb (organic borate and vanadium as corrosion inhibitor); Vetrocoke (arsenic as corrosion inhibitor), and Giammarco Vetrocoke (glycine and vanadium pentoxide as corrosion inhibitor).

• Alkanolamines such as Dow GasSpec, UCARSOL and BASF aMDEA.

BASF aMDEA has become one of the most popular solvents in modern ammonia plants.

PROCESS TECHNOLOGY DEVELOPMENTS

Prereforming technology

Many plants have installed prereformers to increase production rates and also to meet fluctuations in feed gas compositions. Prereformers can easily be integrated into existing plants.

Pressure drop improvements on shift converters

Johnson Matthey developed a new catalyst support system for shift converters, which is known as StreamLine.

Haldor Topsoe has developed a new catalyst support grid, which was applied on the vessels that had elephant stools in original design.

Ammonia Casale have installed axial-radial flow baskets on shift converters.

All three systems have reduced the pressure drop across the shift converters by about 50%.

Catalyst loading technology

Norsk Hydro developed the Unidense loading system for primary reformers. The technique to load other reactors was known as Densicat.

Haldor Topsoe developed the SpiraLoad catalyst loading method, another dense loading technique that is used mainly for primary reformer tube catalyst loading.

It has become a standard practice to use these dense loading systems in place the old sock loading system. The advantage for primary reformer furnaces is the tubes can be loaded with a very uniform range differential pressure (dP) which reduces the likelihood of hot tubes during operation.

Low energy accelerated startups

Hays Mayo suggested this well-known accelerated ammonia plant start up technique in eighties that many North American plants have implemented. Typical start up times are about 12 hours and consume only 12 giga joules of energy.

Hydrogen recovery from purge gas

Three types of hydrogen recovery systems were installed in different plants. Those are: membrane separators, cryogenic separation using a cold box and pressure swing absorption systems.

Each has advantages and disadvantages and all these have improved ammonia plant efficiency and increased plant production rates by about 6%.

Selectoxo process

A new process was developed which selectively oxidises CO, and this has increased plant yield by 3-5% and extended LTS catalyst life. Some plants installed this system in the early years of the industry and those plants are still in operation.

KAAP, KRES, KBR Purifier process

M.W.Kellogg developed large-scale single train ammonia plants using centrifugal compressors in the 1960’s. Also, in the 1960’s C.F.Braun developed the Purifier process. M.W.Kellogg along with BP developed the Kellogg Advanced Ammonia Process (KAAP). After the merger of Dresser and Halliburton in 1998, Kellogg and Brown & Root (KBR) was formed; combined Kellogg and Braun ammonia technologies. KBR now offers many different processes including Purifier, KAAP+Purifier, and KAAPlus with a Kellogg Reforming Exchanger System (KRES) and KAAP reactors.

The Purifier plants use mild primary reforming conditions, excess air in the secondary reformer, cryogenic purifier, horizontal synthesis converter and unitized refrigerant chiller. KBR claims the designs are now available to build large scale new plants up to 5000 tpd using their latest technologies.

Haldor Topsoe plants

Many plants were built over the years using this technology up to 2000 tpd. Various synthesis loop designs and converter arrangements such as S200, S250 and S300 have been employed in Topsoe plants.

ICI AMV process: has a feed gas saturator, milder reforming conditions, excess air in the secondary reformer, an electric driven syngas compressor, and a cryogenic purifier. Some plants are in operation using this technology in Canada and China.

Leading Concept Ammonia (LCA) process

Originally developed by ICI, LCA incorporates low temperature catalysts for pre-treatment, gas heated reforming, feed gas saturator, single isothermal shift reactor and syngas purification. The plants built in the UK with LCA process have been in operation for more than 20 years.

Ammonia Casale

Developed axial-radial baskets for ammonia synthesis converters and these were installed in all types of converters. This has helped many

ammonia plants to upgrade plant capacities and also to improve plant efficiencies.

Linde Ammonia Concept (LAC) This process has an air separation plant, primary reforming, isothermal high temperature (HT) shift reactor, and CO2 removal by Pressure Swing Absorption (PSA) and back-end with Ammonia Casale technology.

Uhde Dual Pressure process

Uhde and Synetix developed a new process for large capacity ammonia plants to overcome the bottlenecks of standard piping and to reduce the compressor demands.

This process employs a once through ammonia synthesis converter located at an intermediate pressure level, upstream of the main synthesis converter. The new flow sheet delivers a capacity of 4000 tpd using well-proven equipment.

Megammonia process

Lurgi developed this process with an Ammonia Casale back-end loop. The main features of the process are catalytic partial oxidation, a high temperature shift reactor, and CO2 removal using Rectisol solvent, liquid N2 wash unit and 200-bar synloop. Lurgi would offer 4000 tpd plants using this technology.

Process simulation

Computer simulation models were developed to investigate optimum operating conditions and evaluate potential projects for existing ammonia plants. The well known process simulation packages are AspenTech, HYSIS, and SIMSCI.

Training simulator

This is an advanced training tool with excellent capabilities for providing hands-on experience in a true-to-life environment. It’s useful for training new operators, for refresher training, and also for developing appropriate corrective strategies to minimise process upsets, thereby improving the reliability and safety of the plant. The dynamic simulator is also a significant tool in carrying out process studies to evaluate alternative process control schemes and operating parameters.

Training simulators can also be used to optimise the control strategy, to test the trip logic, and to develop detailed start up instructions.

PROCESS CONTROL

Over the years, ammonia plants have replaced the old pneumatic control systems with distributed computer control systems (DCS). They have

advantages like consistent and smoother operation; good response to unusual conditions, provide snap shots and trend charts, and generate process logs and management reports.

With the DCS systems, the process variables such as feed flow determination, catalyst tube temperature control, CH4 slip control, flue gas temperature control, S/G ratio control, H/N ratio control, purge flow and synthesis reactor control have improved significantly. DCS systems have increased productivity and improved plant efficiency.

In the 21st century, advanced process control systems came into place and increased yield, extended catalyst life and provided better on-stream time.

Some plants have installed multi-variable advanced control systems and have increased production rates by 0.6% and reduced energy consumption by 1.5%.

Another type of advanced process control system was known as Adaptive Technologies. This was originally based on neural networks and then encompassed fuzzy logic and non-linear multi-variable dynamic control.

HAZOP STUDIES

Hazard and operability (HAZOP) studies have been introduced in eighties to ammonia plants. The methodology can be applied in all plant modifications as well as to new plant design. The same studies have been used for DCS projects.

Some plants have installed stand-alone computerised emergency shutdown systems and this is widely used in the industry on modern ammonia plants.

AMMONIA STORAGE TANKS

Many surveys have been reported on ammonia storage tanks at AIChE symposiums.

There are essentially three different types of storage tanks, namely Horton spheres [design conditions of 413 kPa, 1.1 oC (60 psig, 34 oF)], high-pressure bullets [1723 kPa, 93 oC (250 psig, 200 oF)] and atmospheric storage tanks [6.9 kPa, -33 oC (1 psig, -28 oF)].

The atmospheric storage tanks are designed to three different types; single wall tanks with external insulation, double wall tanks with perlite insulation between the tanks and double integrity tanks with cup in tank and external insulation. The atmospheric storage tanks are built per the API 620 Code.

About 60% of installed tanks have flares to dispose of ammonia vapours in the event of pressure build up.

Different types of secondary containment systems are available - separate steel structure dikes combined with conventional earthen dikes, reinforced concrete dikes backed by earthen fill, and conventional earthen dike.

Many tanks have been decommissioned, inspected and recommissioned. There is a trend to using non-intrusive inspection methods for tank integrity utilising acoustic emission testing and risk based inspection techniques. Such methods can reduce the cost considerably versus intrusive inspection methods and have the advantage of keeping oxygen out of the system, which can contribute to stress corrosion cracking.

Studies have also shown that a small amount of water is effective as a corrosion inhibitor in ammonia service, and it prevents stress corrosion cracking.

COMBUSTION OF AMMONIA

In the symposium of 1961 the combustion properties of ammonia were first addressed. In that meeting combustion of ammonia had been of interest for a long period of time but the available combustion properties have been inadequate to explain fully the anomalous behaviour of ammonia or to permit satisfactory evaluation of the potential hazards of ammonia in industrial operations.

Historically W. Henry in the 1809 Philosophical Transactions first published the flammability limits of ammonia in oxygen and was apparently the oldest recorded for any combustibles.

By 1914 German investigators established definite flammable limits for ammonia in air.

A compilation of flammable-limit data shows seven additional published studies were presented between 1922 and 1949.The pressures developed by ammonia-air explosions were measured in 1923.

In spite of this evidence, and apparently as late as 1951 ammonia was indicated to be non-combustible and experiments were cited as “rough proof that ammonia does not support combustion or burn.”

In the 1961 AIChE proceedings it was reported this misconception was fairly wide spread, even among people associated with the ammonia operations in part because historical incidences of fires or explosions attributed to ammonia was low.

This fact could be explained by the observed difficulty of igniting ammonia, and by the low speed of flame propagation in ammonia-air mixtures.

The work by Buckley and Husa lead to confirmation of the combustion properties of ammonia and in defining the boundaries between flammable and non-flammable mixtures of ammonia and air at 16 to 27% at OoC and 15.5 to 28% at 100oC.

Even though ignition is difficult and flame propagation proceeds with little vigor the work is recognised and well respected in the ammonia industry today to ensure safety in operations.

COOLING WATER TREATMENT

Many plants have changed over their cooling water treatment from the heavy metal based chromate to a phosphate-based treatment. The non-chromate treatment program meets the new environmental standards and provided industry with protection approaching that of chromate based treatment.

BOILER WATER TREATMENT

Boiler water systems for the nitrogen industry mainly consists of make up water (demineralised water) preparation, handling of condensate returns, condensate polishing, and chemical treatment to prevent corrosion, strong alkali attack, and hydrogen damage.

Steam systems operating at 100 bar or higher require high purity make up and consistently uncontaminated condensate return.

There are mainly two types of treatments for high-pressure boiler water systems and these are coordinated phosphate (an internal treatment) and an all volatile zero solids treatment which requires precision control. Plants are using both the systems.

Periodic chemical cleaning of the steam generation equipment must be considered inevitable. Every possible step should be taken to maintain clean waterside surfaces in high-pressure boilers in order to minimise corrosion potential.

Depending on the contamination type, amount and frequency, the internal treatment prerequisite is a thorough examination of the system prior to choosing the program. Once the program is selected, meaningful testing and monitoring of the BFW and boiler water system is necessary.

METALLURGICAL IMPROVEMENTS

The reformer tube materials have changed over the years from HK-40, to HP Nb modified, to HP micro-alloys. Inlet pigtails have changed from 1-1/4Cr-1/2 Moly to stainless steel. Hot outlet manifolds and weldolets use Alloy 800H or 800HT materials and there is a trend towards using cast equivalent materials instead of wrought materials.

Many changes have been made to the mechanical design and fabrication of reformer tubes. Besides upgrades in metallurgy to improve creep rupture life, the new alloys have allowed thinner wall enabling higher rates and better heat transfer. Great strides have been made in welding technology for reformer tubes such that very few reformer tubes fail at the weld or heat affected zone areas.

New designs have been developed using internal refractory lining systems to solve problems of failures at outlet headers and transfer lines in reformer furnace service.

The reformer tube inspection and life assessment have also improved over the years. Various techniques are employed such as eddy current, ultrasonic, laser profilometry, tube thickness and tube diameter measurements. All these systems have their own merits, but the salient point is they have to be used on a frequent basis to monitor tube life. The inspection advances have proven highly beneficial to operators in delineating tube retirement schedules and removed the uncertainty of early or unexpected tube ruptures.

Brittle failure/rupture has been troublesome for the industry for years. Most will remember or read about the numerous instances of ships breaking in half during World War II. Great strides have been made in understanding the combined presence or actions of several factors, of which temperature is very important consideration in influencing the brittle fracture behaviour of ferritic steels. There are many interconnecting factors affecting brittle failure, namely alloy content, deoxidation practice, microstructure, thickness and heat treatment to name a few. Other issues, and much harder to define, include defect size and shape, fabrication methods, welding practices, post weld heat treatment, and rate of loading. Rigorous mathematical analytical methodologies have unfolded over the years in an attempt to quantify material load carrying capacity with known or perceived defects.

Many embarrassments have occurred to operators

on existing equipment and to fabricators for new equipment where catastrophic failure has occurred to fabricated vessels following repairs or during the final acceptance stage of hydro testing with media at low ambient temperatures.

Industry has taken heed of these incidents and now incorporates for the most part safe guards to mitigate against such embarrassing occasions.

Huge advances have been made in the inspection of serpentine piping coils in process heaters utilising intelligent pigs. Corrosion and/or erosion effects can be tracked on successive outages providing management with a tool for scheduling repairs and replacement, without forced outages.

Many advances have occurred in inspection and testing for ammonia and urea plant equipment. To name a few, automated ultrasonic, time of flight diffraction, advanced ultrasonic backscatter technique, electromagnetic acoustic transducers, acoustical emission, alternating current field measurement, laser profilometry, remote field eddy current, real time radiography, various tank inspection tools [tank climber and magnetic flux exclusion (MFE)], video imaging, real time radiography, and thermography to list a few. Likely there are others that are missed, but suffice to say, many tools have come to the assistance of plant operators to help improve plant reliability.

Many failures were reported on front-end waste heat boilers (WHB) downstream of the secondary reformer. Those were addressed by replacing them with alternative designs. However, failures are still reported for various reasons, such as overheating, lack of continuous water supply, loss of refractory, fabrication issues, metal dusting and improper operating conditions. Some designers have offered alternative WHB designs with removable bundles. The latter provide a means of removing the failed bundle in a controlled and scheduled manner permitting the plant to get back on stream without the uncertainty in repair time.

New designs with thin tube sheets for horizontal WHB and for a close coupling to the converter outlet have proved to be reliable.

Improvements to eliminate metal dusting have been made with a clear understanding of the mechanism and the development of materials to resist metal dusting. This new knowledge is being incorporated in newer plants and as retrofits in older operating plants.

Ammonia synthesis equipment is also prone to failures and design of such equipment must be done considering the possibilities of hydrogen

attack and nitriding. Major advances have been made in understanding the process of nitriding, and in materials to lessen this effect in operation.

More information is being developed on the understanding of high temperature hydrogen attack. The API recommended practice 941 is in its 6th revision since inception in 1970 due to new and continued damage cases found in industry. The ammonia industry, petroleum refining and petrochemical industry is indebted to George Nelson for first proposing the “Nelson Curves” on high temperature hydrogen attack at Shell in 1949. Complimenting API 941 is data incorporating time at operating temperature, operating temperature and hydrogen partial pressure in assessing risk to high temperature hydrogen attack.

Of particular concern is the issue with C + 0.5 Mo materials where serious damage has been cited in the past 20 years. With respect to Mn + 0.5 Mo materials API 941 6th edition reports no hydrogen attack history below the C + 0.5 Mo line, especially when normalised, quenched and tempered material is used. However the writer’s have first hand experience with hydrogen attack in Mn + 0.5 Mo in a horizontal ammonia converter below the C+ 0.5 Mo line.

Many older plants have considerable equipment made of C + 0.5 Mo with High Temperature Hydrogen Attack (HTHA) a major issue.

Thick section 2 ¼ Chrome + 1 Mo steel plates used in ammonia pressure vessel equipment at high operating temperatures experienced many temper embrittlement failures until the extensive research found ways to avoid such a phenomenon by controlling impurity levels and altering fabrication processes.

Stress corrosion cracking continues to be an issue in the ammonia industry and continues unabated. Failures occur due to lack of attention on hydro testing, wet insulating materials, and oxygen entrainment in the case of carbon steel ammonia storage tanks.

Thermal fatigue in the ammonia industry is a major concern. Thermal fatigue or thermal stress fatigue results in the deterioration of alloys due to temperature cycles in which stresses from expansion or contraction and from differential expansion of various phases without external loading eventually lead to cracking, resulting in premature failures and safety hazards. Many incidences of thermal fatigue have been discussed at various symposiums and failures continue even today in the industry.

Urea plant information started to be addressed by N.H Walton in the proceedings in 1964. Data first listed the many alloys that had been tested in urea carbamate mixtures. Material issues in the form of corrosion were interesting and unpredictable.

A listing materials examine ranged from austenitic stainless steels, nickel alloys all the way up to the more exotics like titanium, tantalum and zirconium. Samples of lead were included. 316SS was the workhorse alloy at the time. Many materials corroded away quite obviously. It is quite interesting to note the high nickel alloys did not due well in urea carbamate mixtures.

Such information was confirmed later in 1975 works of DSM in The Netherlands where nickel content was shown to have a negative influence on the corrosion resistance of austenitic stainless alloys and has lead to the work on developing the duplex stainless steel alloys for urea service. Much work continues on these alloys today.

Ferritic content was also broached at this time wherein lower ferritic was better, and upper limits are now imposed by all urea licensors.

Even in 1964 zirconium was noted to have a very low rate of corrosion in urea carbamate mixtures, although it was difficult to obtain components in zirconium at that time. Such is not the case today.

Titanium has been used for years in urea carbamate service and continues to be used today in some plants, although its major drawback is low erosion resistance.

Great strides have been made in alloy development for urea service and today the Moly modified 310SS is one of the main staples. As well, zirconium alone and in combination with stainless steel is used very extensively in urea service, but corrosion issues with this combination have surfaced in other locations.

New developments are considering combinations of Zr/Ti to overcome corrosion and erosion issues.

SUMMARY

1. All the incidents since the early years of the symposium were listed including the root causes and remedy actions taken.

2. Major safety incidents were discussed in brief.

3. Plant operational performance over the years was reviewed.

4. Major process technology developments were highlighted.

5. New process technologies for building large-scale new ammonia projects were briefed.

6. Various developments on ammonia storage tanks, desulphurisation and CO2 removal systems were described.

7. Maintenance or metallurgical improvements carried out over the years were elaborated.

Authors’ Acknowledgment

The paper is dedicated to all those of past and present who spared their valuable time in organising the symposiums, writing, reviewing and presenting papers.

Also thanks to all the current AIChE ammonia safety committee members and our friend Walter Benson for their very valuable input and suggestions to this paper.

REFERENCES

[1] Safety Performance in Ammonia, Methanol and Urea Plants, 1999-2001 Surveys Gerald P. Williams Vol 44 AIChE Symposium, 2003

[2] Failures of Secondary Waste Heat Boilers Jagmohan Singh, S.L.Verma and B.M.Patel Vol 44 AIChE Symposium, 2003

[3] Failure of a Molecular Sieve Vessel Resulting from a Defective Weld Repair Michael Picou Vol 43 AIChE Symposium, 2002

[4] Fire in Secondary Reformer Outlet Line to Wastle Heat Boiler Jagmohan Singh, P. Basu, and B.M. Rao Vol 42 AIChE Symposium, 2001

[5] Primary Reformer Failure D.H. Timbres and Mark McConnell Vol 42 AIChE Symposium, 2001

[6]Failure of Inner Shell of Double Walled Atmospheric Ammonia Tank K.A.Nair and N.V.Jagan Mohan Vol 42 AIChE Symposium, 2001

[7] Explosion of MDEA Storage Tank Russell R. Peterson, David C. Haring, Timothy G. Johnson, and James M. Senn Vol 41 AIChE Symposium, 2000

[8] Explosion of Hydrogen in a Pipeline for CO2

John Oscar Pande and JanTonheim Vol 41 AIChE Symposium, 2000

[9] Failure of Internals of Ammonia Converter Dadang Heru Kodri, Handiono, and Didiek P. Vol 41 AIChE Symposium, 2000

[10] Safety Performance in Ammonia Plants 1997-1998 Survey Gerald P. Williams Vol 41 AIChE Symposium, 2000

[11] Ammonia Converter: Weld Joint Failure C.P.Chhabra and Ashok J.Gupta Vol 40 AIChE Symposium, 1999

[12] Experience of Ammonia Converter with Catalyst Leakage and Repairs Muhammad Aleem Khan and Jorgen Juul Ramussen Vol 40 AIChE Symposium, 1999

[13] Safety Performance in Ammonia Plants: Survey VI Gerald P. Williams Vol 39 AIChE Symposium, 1998

[14] Ammonia Process Primary Waste Heat Boiler Shell Failure Experience Colin P.Jackson Vol 39 AIChE Symposium, 1998

[15] Inner Basket Failure of Ammonia Booster Reactor Kamarudin Zakaria and Lau Nai Tuang Vol 39 AIChE Symposium, 1998

[16] Cause of Damage and Repair of Reformed Gas Firetube Boiler Zeng Zhong Quan and Mark A. Holderman Vol 37 AIChE Symposium, 1996

[17] Catastrophic Failure of Tubesheet in Fire Tube Reformed Gas Waste Heat Boiler Harry van Praag, Bhaskar Rani and Harvey M. Herro Vol 37 AIChE Symposium, 1996

[18] Remedial Actions to Reformer Waste Heat Boilers M.Boumaza and M.El Ketroussi Vol 37 AIChE Symposium, 1996

[19] Failure, Repair and Replacement of Waste Heat Boiler Shahid Ahmed and Zaheer Anwar Vol 37 AIChE Symposium, 1996

[20] Dissimilar Weld Cracking and Repairs on Primary Reformer Exit Header Andrew Walker and Neil Mackenzie Vol 36 AIChE Symposium, 1995

[21] Failure and Repair of Two Primary Make Gas Boilers Philip Bailey and John MacDonald Vol 35 AIChE Symposium, 1994

[22] Tube Failure in a Waste Heat Boiler in Ammonia Synthesis Section Reinhard Michel and Hans-Dieter Marsch Vol 35 AIChE Symposium, 1994

[23] Failures in Waste Heat Boilers Helmut Thielsch, Florence Cone, and Jonathan Freeman Vol 35 AIChE Symposium, 1994

[24] Experience with Metal Dusting in Waste Heat Boilers R.J. Gommans and T.L. Huurdeman Vol 35 AIChE Symposium, 1994

[25] Repair and Retubing of Reformed Gas Boiler Anil Bhaskar Tipnis, Dilip Deshmukh, and Nirmal Chandra Bandopadhyay Vol 34 AIChE Symposium, 1993

[26] Repair of Waste Heat Boiler in Synloop of NH3-Plant Wolfgang Bickel, Maximilian Walter, and Konrad Nassauer Vol 34 AIChE Symposium, 1993

[27] Further Cracking in Converter Effluent/BFW Exchanger Philip J. Bailey and John G. MacDonald Vol 34 AIChE Symposium, 1993

[28] Failure of Waste-Heat Boiler after Debottlenecking Process Air Compressor Edgar Lebold, Joerg Reininghaus, and Roland Schober Vol 33 AIChE Symposium, 1992

[29] Causes and Prevention of Explosion and Fire in Synthesis Section A.K. Mukhopadhyay and P.P. Singh Vol 33 AIChE Symposium, 1992

[30] Failure of Waste Heat Boiler Downstream of Secondary Reformer S.K. Mukherjee, S.R. Ghosh, and S. Chatterjee Vol 32 AIChE Symposium, 1991

[31] Failure and Novel Repair of Thick-Wall Synthesis Converter Forgings James D.Campbell and Robert L. Rawlinson Keith C.Wilson Vol 32 AIChE Symposium, 1991

[32] Major Incident Following the Failure of an Ammonia Injector on a Urea Plant P.J. Nightingale Vol 31 AIChE Symposium, 1990

[33] March 20, 1989 Accident in Lithuanian Fertiliser Plant Bengt Orval Andersson Vol 31 AIChE Symposium, 1990

[34] Explosion of Synloop Ammonia Separator Hans-Dieter Marsch Vol 31 AIChE Symposium, 1990

[35] Stress Corrosion in a 12-ltonne Fully –Refrigerated Ammonia Storage Tank J.R.Byme and F.E.Moir R.D. Williams Vol 29 AIChE Symposium, 1988

[36] Failure and Repair of a Primary Waste Heat Boiler V. Sitaraman, Eko Santoso, and S. Sathe Vol 28 AIChE Symposium, 1987

[37] Damage to and Replacement of an Ammonia Storage Tank Foundation O.A.Martinez, S.Madhavan, D.J.Kellett and H.Hamrouni Vol 27 AIChE Symposium, 1986

[38] Failure of Ammonia Converter Start-Up Heater Tube R.J. Mack and J.T Shultz Vol 27 AIChE Symposium, 1986

[39] Failure of Ammonia Converter/Feed Exchanger S. Karkhanis and W.H. Van Moorsel Vol 27 AIChE Symposium, 1986

[40] Investigation of Damage and repair of a 1000 MTD Horizontal Ammonia Converter Subir Rao, R.C.A. Wiltzen and Wesley Jacobs Vol 26 AIChE Symposium, 1985

[41] Failure and Repair of the Shell of a Primary Waste Heat Boiler on a 1,100 ton/d Ammonia Plant A.F. Pariag, I.E. Welch, and G.E. Kerns Vol 26 AIChE Symposium, 1985

[42] Explosion of a Benfield Solution Storage Tank J.T. McDaniel Vol 26 AIChE Symposium, 1985

[43] Rupture of the Start-Up Heater Coil in the Synthesis Loop of the New Ammonia Plant Wolfgang Rall and Heinz Spaehn Vol 25 AIChE Symposium, 1984

[44] Stress Corrosion Cracking in Syngas Heat Exchangers H.G. Orbons and T.L. Huurdemann Vol 25 AIChE Symposium, 1984

[45] Failure of Dissimilar Metals Weld in Reformer Tubes Osama El Ganainy Vol 25 AIChE Symposium, 1984

[46] Waste Heat Boiler Failure and Modifications M. Lufti El-Migharbil and E.M. Hasaballah Vol 22 AIChE Symposium, 1979

[47] Partial Collapse of an Atmospheric Ammonia Storage Tank Bruce H.Winegar Vol 22 AIChE Symposium, 1979

[48] Synthesis Start-Up Heater Failure F.G. Kokemor Vol 22 AIChE Symposium, 1979

[49] Ammonia Loading Line Rupture R. Hakansson Vol 19 AIChE Symposium, 1976

[49] Ammonia Loading Line Rupture R. Hakansson Vol 19 AIChE Symposium, 1976

[50] Ammonia Plant Converter Basket Failure R.L. Thompson and J.B. Brooks Vol 19 AIChE Symposium, 1976

[51] Fatal Accident in CO2 Removal System T.R. Visvanathan Vol 18 AIChE Symposium, 1975

[52] Failure and Repair of Ammonia Converter Basket A.Kusha and D.Lloyd Vol 18 AIChE Symposium, 1975

[53] Failure in Start-Up Heater Tube J. Mitcalf Vol 17 AIChE Symposium, 1974

[54] Ammonia Tank Failure - South Africa H. Lonsdale Vol 17 AIChE Symposium, 1974

[55] Failure of a Boiler Pressure Shell W.W. Patterson Vol 15 AIChE Symposium, 1972

[56] Ammonia Storage Tank Repair J.G.MacArthur Vol 14 AIChE Symposium, 1971

[57] Brittle Fracture of an Ammonia Synthesis Heat Exchanger H.K. Karinen Vol 13 AIChE Symposium, 1970

[58] Suffocation of Workers in a CO Converter R.K. Simms Vol 7 AIChE Symposium, 1964

[59] Explosion During Breaking-in of a Compressor S. Strelzoff Vol 6 AIChE Symposium, 1963

[60] Compressor Explosion C.W. Gibbs Vol 2 AIChE Symposium, 1959

Tab

le –

1: I

ncid

ents

/ Fi

res /

Exp

losi

ons/

Fai

lure

s

All

of th

ese

are

cove

red

in p

aper

s prin

ted

in th

e A

IChE

Am

mon

ia T

echn

ical

Man

uals

and

usi

ng th

e “y

ear r

epor

ted”

the

sour

ce p

aper

can

be

loca

ted

in th

e “A

mm

onia

Tec

hnic

al M

anua

l.”

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

1.

1959

C

ompr

esso

r exp

losi

on d

urin

g a

rout

ine

shop

test

kill

ed 6

peo

ple

& in

jure

d 30

Igni

tion

of o

il ai

r moi

stur

e In

ert g

as u

sed

for t

estin

g co

mpr

esso

rs.

2.

1959

O

xyge

n pl

ant r

e-bo

iler

expl

osio

n, n

o in

jurie

s, no

ru

ptur

es

Co-

crys

tal f

orm

atio

n of

ace

tyle

ne &

ni

trous

oxi

de b

uilt

up a

t the

bot

tom

of r

e-bo

iler

New

des

ign,

whe

re so

lids d

o no

t acc

umul

ate

adop

ted.

3.

1960

O

xyge

n pl

ant v

apor

iser

ex

plos

ion

Acc

umul

atio

n of

hyd

roca

rbon

in th

e va

poris

er

Add

ition

al in

stru

men

tatio

n; si

mpl

ified

col

d bo

x de

sign

with

SS

pip

ing.

4.

19

60

Oxy

gen

plan

t exp

losi

on

Hyd

roca

rbon

con

cent

ratio

n in

mai

n co

nden

ser

Uni

t was

rebu

ilt w

ith a

reci

rcul

atio

n pu

mp

on m

ain

cond

ense

r &

silic

a ge

l tra

p.

5.

1960

H

eat e

xcha

nger

exp

losi

on a

t a

nitro

gen

was

h un

it A

ccum

ulat

ion

of n

itrou

s oxi

des

Syst

ems p

ut in

pla

ce to

redu

ce n

itrou

s oxi

de a

ccum

ulat

ions

.

6.

1960

R

uptu

re o

f car

bon

stee

l pip

ing

on

nitro

gen

was

h un

it H

eavy

ther

mal

shoc

k re

sulti

ng fr

om lo

w

tem

pera

ture

s C

arbo

n st

eel p

ipin

g re

plac

ed; p

rovi

ded

addi

tiona

l in

stru

men

tatio

n.

7.

19

61

Hyd

roge

n fir

e fr

om re

vers

e flo

w

on p

ump

Che

ck v

alve

on

pum

p di

scha

rge

faile

d Fl

ow c

ontro

l val

ve in

stal

led

on d

isch

arge

of e

ach

pum

p.

8.

1961

O

xyge

n tra

iler f

ire

Leak

ing

hose

on

the

traile

r Pr

oced

ure

to st

op li

quid

oxy

gen

trans

fer i

n ca

se o

f any

leak

s. R

emot

e is

olat

ion

on li

quid

dis

char

ge li

nes

9.

1961

A

ir fr

actio

natio

n pl

ant e

xplo

sion

W

oode

n st

ruct

ures

on

oxyg

en p

lant

W

oode

n eq

uipm

ent r

emov

ed fr

om th

e co

ld b

ox sh

ell a

fter

mai

nten

ance

wor

k.

10.

1962

O

il se

para

tor e

xplo

sion

in a

n A

ir Se

para

tion

plan

t. O

il m

ixed

with

O2 r

ich

was

te g

as

New

O2 a

naly

ser i

nsta

lled.

11.

1962

H

ydro

gen

com

pres

sor c

ylin

der

expl

osio

n In

terc

hang

eabl

e va

lves

on

com

pres

sor

Inst

alle

d no

n-in

terc

hang

eabl

e su

ctio

n &

dis

char

ge v

alve

s.

12.

1962

N

itrog

en c

ompr

essi

on sy

stem

ex

plos

ion

Elec

trica

l fai

lure

led

to h

ydro

carb

on

cont

amin

atio

n N

ew a

larm

s, sa

fety

inst

rum

ente

d sy

stem

, O2 a

naly

ser

Item

Y

ear

Rep

orte

d In

cide

nt

Roo

t Cau

se

Rem

edy

Act

ion

Take

n

13.

1963

Fa

ilure

of p

rimar

y re

form

er

outle

t pip

ing

Hig

h te

mpe

ratu

re st

ress

rupt

ure

in 3

04SS

pi

ping

resu

lted

in w

eld

seam

failu

re d

ue to

br

ittle

ness

at

787o C

Rep

lace

d ou

tlet p

ipin

g w

ith in

colo

y 80

0 m

ater

ial.

14.

1963

Ex

plos

ion

in a

fter c

oole

r of a

co

mpr

esso

r usi

ng sy

nthe

tic

lubr

ican

t

Com

bust

ion

on th

e co

mpr

essi

on c

ylin

der

crea

ted

shoc

k pr

essu

re w

ave

that

led

to

expl

osio

n

Cha

nged

the

cool

er d

esig

n.

15.

1963

Ex

plos

ion

durin

g br

eaki

ng o

f a

com

pres

sor i

ncid

ent k

illed

one

pe

rson

Air

used

to te

st sy

nthe

sis g

as c

ompr

esso

r at

hig

her p

ress

ures

that

incr

ease

d ai

r te

mpe

ratu

re.

Do

not u

se a

ir fo

r com

pres

sor t

estin

g at

hig

her p

ress

ures

, use

on

ly N

2 pre

ssur

es.

16.

1963

A

ir he

ater

exp

losi

on

Ove

rsiz

ed h

eatin

g el

emen

t ins

talle

d as

par

t of

ear

lier m

odifi

catio

n.

New

ther

moc

oupl

es in

stal

led

to m

onito

r tem

pera

ture

s on

air

heat

er. H

eate

rs p

rote

cted

by

circ

uit b

reak

ers.

17.

1963

A

ir se

para

tion

plan

t fire

Tr

appe

d oi

l acc

umul

atio

n on

liqu

id O

2 re

flux

pum

p El

imin

ated

liqu

id O

2 pum

p.

18.

1963

O

xidi

sing

salt

expl

osio

n M

ixin

g of

oxi

disi

ng &

redu

cing

mat

eria

ls

Seal

s/ga

sket

s mad

e of

non

-com

bust

ible

mat

eria

ls.

19.

1964

C

atas

troph

ic o

xida

tion

on

prim

ary

refo

rmer

out

let p

ipin

g Lo

calis

ed fo

rmat

ion

of m

olyb

denu

m o

xide

ric

h sl

ag.

Avo

id u

sing

316

SS

20.

1964

Su

ffoc

atio

n of

wor

kers

in a

CO

co

nver

ter,

3 pe

ople

kill

ed

Con

fined

spac

e en

try in

“C

O”

atm

osph

ere

Strin

gent

pro

cedu

res d

evel

oped

for c

onfin

ed sp

ace

entry

.

21.

1964

Ex

plos

ion

in N

2 ga

s com

pres

sor

O2 C

onta

min

atio

n of

N2 c

ompr

esso

r In

stal

led

dual

rang

e O

2 ana

lyse

r and

trip

syst

em to

S/D

O2

com

pres

sor.

22.

1964

Ex

plos

ion

of c

onde

nser

in a

n O

2 pl

ant

Hyd

roca

rbon

cau

sed

com

bust

ion

of

mat

eria

l in

cond

ense

r In

stal

led

a re

cycl

ing

abso

rber

. Ins

talle

d a

trap

to d

rain

liqu

id

O2.

23.

1965

Ex

plos

ion

in e

xpan

der d

isch

arge

pi

ping

O

il ac

cum

ulat

ion

in e

xpan

der p

ipin

g N

ew a

naly

tical

equ

ipm

ent i

nsta

lled.

24.

1965

Li

quid

O2 d

ispo

sal v

esse

l ex

plos

ion

Hyd

roca

rbon

con

tam

inat

ion

New

hea

ting

proc

edur

es in

corp

orat

ed.

25.

1965

N

itric

oxi

de e

xplo

sion

R

eact

ion

with

hyd

roca

rbon

s N

ew m

etho

d of

rem

ovin

g N

O fr

om th

e ga

s stre

am d

evel

oped

. 26

. 19

65

Oxy

gen

fire

HP

Oxy

gen

pum

p se

als f

aile

d D

erem

ing

and

repl

acem

ent o

f sili

ca g

el c

arrie

d ou

t. Se

al w

as

rede

sign

ed.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

27.

1965

A

mm

onia

Tan

k Le

ak

Mis

sing

wel

d on

tank

floo

r dur

ing

cons

truct

ion.

Ta

nk e

mpt

ied

out,

repa

ired

& p

ut b

ack

in se

rvic

e.

28.

1966

Li

quid

O2 p

ump

failu

re

Bea

ring

faile

d, Im

pelle

r of t

he p

ump

cam

e in

con

tact

with

the

pum

p ca

sing

, O2

boos

ter p

ump

expl

oded

Lock

ing

devi

ce in

stal

led

at th

e en

d of

the

shaf

t. Se

tscr

ew

mat

eria

l cha

nged

to S

S.

29.

1966

Lo

ss o

f ins

ulat

ion

on a

n am

mon

ia st

orag

e ta

nk

Expa

nsio

n jo

ints

inst

alle

d in

corr

ectly

in

orig

inal

inst

alla

tion

Tank

insu

latio

n re

built

com

plet

ely.

30.

1966

In

sula

tion

fire

on a

Sto

rage

Sp

here

Sp

ace

heat

ers u

sed

durin

g co

nstru

ctio

n V

esse

l san

dbla

sted

& re

insu

late

d.

31.

1966

B

rittle

frac

ture

of a

mm

onia

co

nver

ter d

urin

g hy

drot

est a

t the

sh

op

No

final

hea

t tre

atm

ent d

one

Ves

sel r

epla

ced.

32.

1966

R

efor

min

g sy

stem

failu

re

Stre

ss c

orro

sion

cra

ckin

g re

sulte

d fr

om

chlo

ride

in a

ctiv

ated

car

bon.

R

epai

r wor

k do

ne.

33.

1966

Tu

be &

pip

ing

failu

re

Loca

lised

ove

rhea

ting

resu

lted

in ru

ptur

e of

air

pipi

ng &

subs

eque

nt fi

re

Cha

nge

of p

ipin

g m

etal

lurg

y, p

erio

dic

insp

ectio

n &

ad

ditio

nal i

nstru

men

tatio

n 34

. 19

66

Dis

tanc

e pi

ece

expl

osio

n A

loos

e pi

ston

nut

& sl

ippe

r fai

lure

on

reci

proc

atin

g co

mpr

esso

r U

sing

onl

y tw

o bo

lts o

n th

e di

stan

ce p

iece

.

35.

1966

M

etha

nol p

lant

exp

losi

on

Rup

ture

of o

il bl

owdo

wn

line

allo

wed

co

mpr

esso

r syn

thes

is lo

op to

dep

ress

ure

in a

reve

rse

flow

dire

ctio

n

Cha

nges

mad

e to

con

trol r

oom

bui

ldin

g.

36.

1966

N

itric

aci

d pl

ant e

xplo

sion

A

ccum

ulat

ion

of a

mm

oniu

m n

itrite

dur

ing

a pr

olon

ged

star

tup.

C

hang

es m

ade

to p

lant

star

tup

proc

edur

es.

37.

1967

A

ir se

para

tion

plan

t inc

iden

t R

eact

ion

in h

ydro

carb

on

abso

rber

Li

quid

dum

p fr

om th

e co

lum

n se

para

ted.

Dea

d le

g el

imin

ated

. 38

. 19

67

Hig

h sp

eed

coup

ling

failu

re

Mis

alig

nmen

t, po

or c

ontro

l & a

ssem

bly

proc

edur

es.

Long

bol

ts, g

ood

tole

ranc

e &

ass

embl

y co

ntro

ls

39.

1968

R

efor

mer

man

ifold

cra

ckin

g O

xida

tion

& m

agne

tism

C

rack

s rep

aire

d.

40.

1969

R

uptu

re o

f am

mon

ia ta

nker

St

ress

cor

rosi

on c

rack

ing

Cea

sed

usin

g TI

bui

lt ta

nker

s. 41

. 19

69

Tran

sfer

line

failu

re

Hig

her w

ater

boi

l off

than

ant

icip

ated

Im

prov

ed in

sula

tion

on ja

cket

wat

er.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

42.

1969

Fa

ilure

of p

rimar

y w

aste

hea

t bo

iler

Silic

a ca

rry

over

from

refr

acto

ry

Ref

ract

ory

was

repl

aced

with

low

silic

a re

frac

tory

.

43.

1970

A

n am

mon

ia ta

nk c

ar

emer

genc

y H

ole

on th

e ta

nker

follo

win

g a

colli

sion

w

ith a

noth

er ta

nker

. Ta

nker

repa

ired,

new

pro

cedu

res p

ut in

pla

ce.

44.

1970

Fa

ilure

of l

ow te

mpe

ratu

re N

H3

line

Free

thaw

cyc

le b

etw

een

the

pipe

slee

ve

& th

e pi

pe

Seal

bet

wee

n th

e sl

eeve

and

the

pipe

mad

e m

ore

wat

ertig

ht.

Non

free

zing

solu

tion

adde

d to

the

slee

ved

porti

on o

f the

lin

e.

45.

1970

Ex

plos

ion

in fe

ed g

as se

ctio

n Ig

nitio

n of

a m

ixtu

re o

f O2,

H2 a

nd N

2 C

ontin

uous

on

stre

am a

naly

sis.

Trip

syst

em p

rovi

ded.

46

. 19

70

Brit

tle fr

actu

re o

f an

amm

onia

sy

nthe

sis h

eat e

xcha

nger

M

ater

ials

, lig

ht fo

rgin

g &

def

ectiv

e he

at

treat

men

t R

ight

mat

eria

ls h

eat e

xcha

nger

sele

cted

.

47.

1970

Ex

plos

ion

in th

e fe

ed g

as

sect

ion

Cra

cks d

evel

oped

dur

ing

wel

ding

, poo

r he

at tr

eatm

ent.

Preh

eat o

n w

eldi

ng a

ttach

men

ts c

ontro

lled

care

fully

w

hen

mak

ing

mai

n se

am.

48.

1971

A

mm

onia

tank

ove

rflo

w

Failu

re o

f hig

h le

vel a

larm

and

S/D

sy

stem

In

stal

led

relia

ble

addi

tiona

l hig

h-le

vel a

larm

s/tri

p sy

stem

s. 49

. 19

71

Cat

alys

t fus

ion

in se

cond

ary

refo

rmer

Lo

ss o

f nat

ural

gas

feed

and

con

tinue

d ai

rflo

w

Trip

syst

em c

heck

ed th

orou

ghly

.

50.

1971

Fa

ilure

of a

n ex

chan

ger

Cor

rosi

on in

hot

MEA

, flo

atin

g he

at

exch

ange

r. N

ew c

orro

sion

inhi

bito

r ins

talle

d.

51.

1971

Fa

ilure

of a

mm

onia

load

ing

hose

Su

dden

pre

ssur

e bu

ild u

p in

hos

e du

e to

fa

iled

switc

h on

ship

. D

o no

t dra

g ho

se o

ver d

ocks

or d

ecks

. Do

not r

oll h

ose

mor

e th

an o

ne re

volu

tion.

Avo

id sh

arpl

y be

nt, c

urve

d or

tw

iste

d ho

ses

52.

1971

Fa

ilure

of r

efor

mer

out

let h

eade

r C

reep

rupt

ure

resu

lted

from

ext

ensi

ve

inte

rgra

nula

r cra

ckin

g.

Bul

ge m

onito

ring

devi

ces i

nsta

lled

regu

lar o

ptic

al

pyro

met

er su

rvey

s of t

he tu

bes,

pigt

ails

, and

tube

su

ppor

ts.

53.

1971

H

ydro

gen

dam

age

to a

co

nver

ter.

Hyd

roge

n at

tack

on

amm

onia

con

verte

r R

epla

ced

carb

on st

eel f

orgi

ngs w

ith 2

-1/4

CR

. – 1

Mo

allo

y st

eel.

54.

1971

N

itrid

ing

in a

n am

mon

ia p

lant

N

itrid

ing

on sy

nloo

p W

HB

R

epai

rs m

ade

on c

rack

s.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

55.

1971

Le

ak o

f an

amm

onia

tank

st

orag

e ta

nk

Leak

age

on fl

oor o

f the

tank

thro

ugh

num

erou

s pin

hole

s, re

sulte

d fr

om

cons

truct

ion

& te

stin

g ac

tiviti

es in

col

d w

inte

r mon

ths.

Tank

em

ptie

d ou

t, re

pairs

car

ried

out.

56.

1971

Pr

imar

y re

form

er tr

ansf

er h

eade

r fa

ilure

C

reep

rupt

ure

caus

ed w

ith ra

pidl

y in

crea

sing

tem

pera

ture

due

to lo

w le

vel o

n w

ater

jack

et.

Tran

sfer

hea

der r

epai

red.

57.

1972

C

rack

ing

& b

liste

ring

in th

e sh

ift c

onve

rter

Mat

eria

ls o

f con

stru

ctio

n R

epai

red

vess

els,

stre

ss re

lieve

d, m

ater

ials

cha

nged

.

58.

1972

Fa

ilure

of b

oile

r pre

ssur

e sh

ell.

Det

erio

ratio

n of

the

refr

acto

ry w

all a

ided

by

ham

mer

ing

of th

e sh

roud

slip

join

ts.

Ves

sel r

epai

red,

repl

aced

wat

er ja

cket

.

59.

1972

Fa

ilure

of a

mm

onia

sepa

rato

r Em

erge

ncy

S/D

cau

sed

shoc

ks, r

esul

ting

in m

assi

ve fa

ilure

. V

esse

l rep

aire

d.

60.

1973

C

orro

sion

in C

O2 re

mov

al

tow

er

Stre

ss c

orro

sion

cra

ckin

g re

sulte

d fr

om

elec

tro c

hem

ical

reac

tion.

R

epai

red

dam

aged

ves

sels

by

wel

ding

an

exte

rnal

ban

d of

stee

l pla

tes.

61.

1973

Ex

plos

ion

in a

wat

er tr

eatm

ent

unit

Pres

sure

bui

ld u

p, d

ecom

posi

tion

of

amm

oniu

m n

itrat

e &

oxi

disa

tion

of re

sin.

St

anda

rd o

pera

ting

proc

edur

es m

odifi

ed. C

oppe

r su

lpha

te d

isco

ntin

ued

as a

lgic

ide.

62

. 19

73

Failu

re o

f am

mon

ia st

orag

e ta

nk

insu

latio

n Fr

eeze

thaw

cyc

le o

n fo

am g

lass

in

sula

tion

85%

of t

he in

sula

tion

repl

aced

with

ure

than

e.

63.

1973

St

eam

gen

erat

ing

tube

failu

re

Acc

umul

atio

n of

boi

ler c

hem

ical

s & lo

w

circ

ulat

ion

Incr

ease

d ci

rcul

atio

n ra

te, c

hang

e ov

er o

f wat

er

treat

men

t pro

gram

64

. 19

73

Stea

m re

form

er tu

be fa

ilure

W

ater

car

ry o

ver i

n st

eam

dru

m

Hor

izon

tal p

erfo

rate

d ba

ffle

pla

tes i

nsta

lled

abov

e st

eam

/wat

er in

lets

. Sec

onda

ry se

para

tor i

nsta

lled

betw

een

stea

m d

rum

& su

perh

eate

r. 65

. 19

73

Expa

nsio

n jo

int f

ailu

re

Hea

t tre

atm

ents

at w

rong

tem

pera

ture

s St

ringe

nt p

roce

dure

s ado

pted

at t

he sh

op.

66.

1973

Ex

plos

ion

in v

ent s

tack

R

ever

se fl

ow o

f bur

ning

gas

V

ent h

eate

r dra

in li

nes p

rovi

ded

with

wat

er se

als.

Con

tinuo

us N

2 pu

rge.

Rup

ture

d 24

” el

bow

repl

aced

. 67

. 19

73

Air

stea

m c

oil f

ailu

re

Rel

ief v

alve

faile

d to

lift.

PS

V re

loca

ted,

pro

perly

des

igne

d an

d br

aced

. 68

. 19

74

Seco

ndar

y re

form

er a

ir in

let

nozz

les f

ailu

re

Inte

rgra

nula

r cra

ckin

g of

wel

d jo

ints

R

epai

rs d

one

usin

g ne

w ty

pe o

f wel

ding

rods

.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

69.

1974

W

aste

hea

t boi

ler f

ailu

re

Dow

ncom

er d

rain

line

s rup

ture

d. L

oss o

f ci

rcul

atio

n in

WH

B

Letd

own

valv

es re

plac

ed w

ith h

igh-

pres

sure

ratin

g.

70.

1974

Ex

plos

ion

in U

rea

Plan

t Pr

esen

ce o

f oil

trace

s & H

2 ga

s in

CO

2 fe

ed

Ope

ratin

g pr

oced

ures

cha

nged

to k

eep

scru

bber

off

gas

ou

t of e

xplo

sion

lim

its.

71.

1974

A

mm

onia

Tan

k fa

ilure

in S

outh

A

fric

a, 1

8 pe

ople

kill

ed

Brit

tle fr

actu

re o

f dis

hed

end

of p

ress

ure

stor

age

bulle

t. Th

e ve

ssel

not

stre

ss

relie

ved

Und

efin

ed

72.

1974

A

mm

onia

refo

rmer

free

ze u

p R

ever

se fl

ow w

ater

from

leak

ing

WH

B

free

ze u

p on

refo

rmer

tube

s, re

sulte

d in

to

rupt

ure

of tu

bes

Avo

id c

old

wea

ther

shut

dow

ns. K

eep

refo

rmer

war

m

durin

g S/

D &

pay

atte

ntio

n to

dra

inin

g liq

uid

73.

1974

C

oupl

ing

failu

re b

etw

een

com

pres

sors

M

isal

ignm

ent o

f LP

case

of s

ynga

s co

mpr

esso

r. M

isal

ignm

ent c

orre

cted

usi

ng o

ptic

al a

lignm

ent.

Extre

me

care

take

n in

tigh

teni

ng c

oupl

ing

bolts

. 74

. 19

74

Expl

osio

n of

am

mon

ia li

quor

ta

nk

Inte

rnal

ove

rpre

ssur

e du

e to

com

bust

ion

of N

H3,

H2,

met

hane

gas

abo

ve th

e liq

uor

New

ope

ratin

g pr

oced

ures

/cod

es d

evel

oped

.

75.

1974

Fa

ilure

in se

cond

ary

refo

rmer

ve

ssel

. Fa

ilure

of r

efra

ctor

y lin

ing

on th

e ve

ssel

. M

onol

ith re

frac

tory

lini

ng re

plac

ed w

ith a

two-

phas

e sy

stem

. Ins

talle

d th

erm

al si

phon

s & w

ater

jack

et.

76.

1974

Fa

ilure

of s

tart

up h

eate

r tub

e.

Nitr

idin

g of

hea

ter c

oils

and

tem

pera

ture

im

bala

nce

on c

oils

U

ndef

ined

77.

1975

C

orro

sion

in th

e N

apht

ha

refo

rmer

W

rong

out

let m

ater

ials

of c

onst

ruct

ion

R

epai

red

outle

t pig

tails

.

78.

1975

Fa

ilure

& re

pair

of a

mm

onia

co

nver

ter b

aske

t C

hlor

ide

stre

ss c

orro

sion

cra

ckin

g fr

om

insu

latio

n V

esse

l rep

aire

d.

79.

1975

Fa

tal a

ccid

ent i

n C

O2 r

emov

al

syst

em, 9

peo

ple

kille

d.

Rup

ture

of C

S el

bow

in C

O2

rem

oval

syst

em c

ause

d by

ero

sion

with

im

ping

emen

t of h

igh

velo

city

stre

am o

f ho

t liq

uid.

CS

elbo

ws r

epla

ced

with

SS,

gla

ss p

anel

s red

uced

in th

e co

ntro

l roo

m.

80.

1975

R

uptu

re in

am

mon

ia sh

ift

conv

ersi

on u

nit

Cor

rosi

on re

sulte

d fr

om p

oor w

ater

di

strib

utio

n &

lack

of g

ood

pH c

ontro

l. D

istri

buto

r tra

y pr

ovid

ed, p

H m

easu

red

at m

ore

poin

ts.

Cor

rosi

on p

robe

s ins

talle

d in

the

loop

s. 81

. 19

76

Am

mon

ia c

onve

rter b

aske

t fa

ilure

St

ress

cor

rosi

on c

rack

ing

from

chl

orid

es

in h

ydro

test

wat

er, i

nsul

atio

n.

Con

verte

r bas

ket w

as re

plac

ed.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

82.

1976

N

H3 l

oadi

ng li

ne ru

ptur

ed.,

Two

peop

le k

illed

W

rong

hos

e sp

ecifi

ed.

Hos

e re

plac

ed a

nd n

ew p

roce

dure

s put

in p

lace

.

83.

1976

A

mm

onia

pip

elin

e ru

ptur

e Ex

tern

al c

orro

sion

of t

he p

ipel

ine

Line

repa

ired

by re

plac

ing

30 m

of t

he p

ipe.

84

. 19

76

Am

mon

ia sh

ift c

onve

rter f

ailu

re

Hyd

roge

n cr

acki

ng o

n th

e ve

ssel

wel

d re

sulte

d fr

om w

eld

elec

trode

s. A

smal

l rea

ctor

use

d as

a te

mpo

rary

HTS

con

verte

r.

85.

1976

A

mm

onia

tank

floo

r and

fo

unda

tion

failu

re.

Impr

oper

wel

ding

dur

ing

cons

truct

ion.

Fl

oor &

foun

datio

n re

paire

d.

86.

1976

C

atas

troph

ic fa

ilure

in p

roce

ss

gas l

ine.

C

arbo

nic

acid

cor

rosi

on o

n ca

rbon

stee

l. Li

ne re

plac

ed w

ith S

S pi

pe.

87.

1976

Ex

plos

ion

in a

mm

onia

co

nver

ter.

N

itrid

ing

of th

e au

sten

itic

mat

eria

ls.

Con

verte

r rep

aire

d.

88.

1976

Fa

ilure

of a

mm

onia

pla

nt a

ir co

mpr

esso

r. Po

or d

etai

l des

ign

& fa

bric

atio

n of

inte

r st

age

cool

ers.

Dam

age

to c

ompr

esso

r mot

or re

paire

d, in

ter s

tage

co

oler

s rep

aire

d.

89.

1976

Fa

ilure

of a

mm

onia

pla

nt

trans

fer l

ine

Seve

re c

orro

sion

dam

aged

rise

r cas

tabl

e co

atin

g Sh

roud

cha

nged

to S

S.

90.

1976

M

ajor

fiel

d re

pairs

to a

mm

onia

co

nver

ter

Hyd

roge

n da

mag

e on

low

er C

S ou

tlet

forg

ing

Ves

sel f

orgi

ng re

new

ed.

91.

1976

R

epla

cem

ent o

f am

mon

ia

conv

erte

r bas

ket

Chl

orid

e at

tack

resu

lted

from

insu

latio

n,

hydr

otes

t wat

er &

cat

alys

t. B

aske

t rep

lace

d.

92.

1977

C

orro

sion

of a

mm

onia

pla

nt

heat

exc

hang

er

Hyd

roge

n at

tack

. Ex

chan

ger w

as re

paire

d &

hea

t-tre

ated

per

pro

cedu

re.

93.

1977

C

O2 s

tripp

er e

xplo

sion

. H

2 gas

or n

atur

al g

as d

isso

lved

in so

lven

t. W

ash

trays

& d

emis

ting

pads

repl

aced

. 94

. 19

77

Tube

dam

age

in N

H3 p

lant

ex

chan

gers

V

ibra

tion

dam

age.

B

affle

des

ign

mod

ified

from

dou

ble-

segm

ente

d, b

affle

th

ickn

ess d

oubl

ed.

95.

1977

Pr

oble

ms w

ith w

aste

hea

t boi

ler.

Exce

ssiv

e fo

ulin

g re

sulte

d fr

om h

igh

silic

a su

ppor

t bal

ls.

Low

silic

a al

umin

a ba

lls in

stal

led.

Cat

alys

t cha

nged

in

seco

ndar

y re

form

er.

96.

1978

A

mm

onia

sepa

rato

r acc

iden

t. N

ozzl

e fa

ilure

on

mul

ti la

yer v

esse

l. V

esse

l was

repa

ired.

97

. 19

78

Am

mon

ia st

orag

e ve

nt a

ccid

ent

Ref

riger

atio

n co

mpr

esso

r trip

ped

out,

rele

ased

NH

3 vap

ours

, ign

ited

by th

e fla

re

on to

p of

the

tank

.

Flar

e w

as re

loca

ted;

em

erge

ncy

man

way

ven

t rep

lace

d w

ith a

stan

dard

relie

f vac

uum

bre

aker

.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

98.

1978

Fa

ilure

at t

he in

let n

ozzl

e of

am

mon

ia c

onve

rter.

Hyd

roge

n em

britt

lem

ent a

t the

loca

tion

of

forg

ing

LAP

A n

ew n

ozzl

e w

ith th

e up

grad

ed m

ater

ial i

nsta

lled

on

conv

erte

r inl

et.

99.

1978

R

efor

mer

rise

r pre

ssur

e sh

ell

leak

. G

as le

aks o

n tra

nsfe

r hea

der a

nd ri

ser

tube

. R

epla

ced

trans

fer h

eade

r, m

odifi

catio

n m

ade

to ri

sers

.

100.

19

78

Star

t up

dam

age

to a

CO

2 ab

sorb

er

Inte

rnal

exp

losi

on re

sulte

d fr

om

com

bust

ible

gas

mix

ture

. C

ontro

l circ

uits

for a

ir tri

p va

lve

mod

ified

.

101.

19

78

Stre

ss c

orro

sion

cra

cked

sy

nthe

sis g

as li

ne.

Cor

rosi

on b

y am

mon

ium

nitr

ate.

Th

e sy

ngas

line

was

repa

ired.

102.

19

78

Ure

a re

acto

r fai

lure

. Pl

ugge

d w

eep

hole

s & c

orro

ded

liner

sh

ell.

Wee

phol

es in

crea

sed,

aut

omat

ic a

nd re

liabl

e m

onito

ring

syst

em in

stal

led.

10

3.

1979

C

rack

ing

in a

mm

onia

con

verte

rs

Hig

h th

erm

al st

ress

from

man

y cy

cles

ca

used

cra

ckin

g on

mul

ti w

all c

onve

rter.

Cra

cks r

epai

red.

104.

19

79

Parti

al c

olla

pse

of a

n at

mos

pher

ic st

orag

e ta

nk

Failu

re o

f vac

uum

relie

f val

ves.

Tank

was

repa

ired.

105.

19

79

Stre

ss c

orro

sion

cra

ckin

g in

am

mon

ia st

orag

e.

Inad

equa

te p

urgi

ng o

f air

befo

re

intro

duci

ng li

quid

NH

3,

Wel

ding

repa

irs d

one

on ta

nk.

106.

19

79

Synt

hesi

s sta

rtup

heat

er fa

ilure

. Lo

calis

ed o

verh

eatin

g du

e to

low

flow

. N

ew in

terlo

cks p

rovi

ded

and

coil

mat

eria

l upg

rade

d.

107.

19

79

Ure

a re

acto

r bot

tom

failu

re.

Mic

ro c

rack

ing

in th

e la

p w

eld

join

t due

to

stre

ss fr

om th

erm

al e

xpan

sion

&

cont

ract

ing

of li

ning

slee

ves.

Wel

ding

repa

irs c

arrie

d ou

t.

108.

19

79

Was

te h

eat b

oile

r fai

lure

. Th

ick

tube

shee

ts a

nd lo

ng tu

bes,

sens

itive

to th

erm

al sh

ocks

. N

ew d

oubl

e co

mpa

rtmen

t des

ign

deve

lope

d.

109.

19

80

Failu

re o

f sup

erhe

ated

stea

m

head

er.

Ove

rhea

ting,

ove

rstre

ssin

g di

stor

tion.

W

eld

repa

irs d

one

on fa

iled

pipi

ng.

110.

19

80

Smal

l lea

k ca

used

a b

ig le

ak.

Igni

tion

of a

pig

tail

leak

initi

ated

cat

alys

t tu

be fl

ange

leak

s. Le

aks r

epai

red.

111.

19

80

Tem

pera

ture

s run

aw

ay o

f a

met

hana

tor.

Ther

mow

ell t

empe

ratu

res w

ere

low

er th

an

gas t

emp.

Gas

tem

p lo

wer

than

that

of

bulk

gas

.

All

ther

moc

oupl

es m

ade

horiz

onta

l.

112

1981

Fa

ilure

of p

roce

ss a

ir lin

e B

ack

flow

of p

roce

ss g

as in

to a

ir lin

e an

d fa

ilure

of c

heck

val

ve

Ope

ratin

g pr

oced

ures

cha

nged

and

mod

ified

surg

e co

ntro

l sys

tem

.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

113

1981

V

ent s

ilenc

er fa

ilure

W

ater

and

stea

m in

gres

s in

to v

ent h

eade

r du

e to

WH

B fa

ilure

Si

lenc

er a

nd ta

il pi

pe re

paire

d an

d in

stal

led.

114

1981

Pu

mp

and

mot

or fa

ilure

in h

ot

pota

ssiu

m c

arbo

nate

syst

em

Bac

k flo

w d

ue to

che

ck v

alve

failu

re

Impr

oved

inst

rum

enta

tion

on p

ump

disc

harg

e co

ntro

l va

lves

. 11

5 19

81

Am

mon

ia se

para

tor f

ailu

re

Met

allu

rgic

al fa

ilure

of t

he v

esse

l N

ew v

esse

l fab

ricat

ed.

116

1981

U

rea

auto

clav

e fa

ilure

C

orro

sion

of w

eld

over

lay

from

ca

rbam

ate

solu

tion

Perm

anen

t rep

airs

mad

e to

aut

ocla

ve.

117

1981

H

igh

pres

sure

hea

t exc

hang

er

igni

tion

Hyd

roge

n di

ffus

ion

thro

ugh

the

crys

tal

stru

ctur

e of

the

met

al

Wel

d re

pairs

on

tube

shee

t ret

aini

ng ri

ng.

118

1982

Su

dden

pre

ssur

e in

crea

se in

a

vent

hea

der

Nic

kel b

ased

foil

on v

ent s

ilenc

er h

oles

U

se o

f nat

ural

gas

for h

eatin

g up

LT

shift

con

verte

r.

119.

19

83

Failu

re o

f a 1

00 b

ar st

eam

line

. R

uptu

re fr

om h

igh

tem

pera

ture

& st

ress

, w

rong

mat

eria

l. Pi

ping

was

repl

aced

.

120.

19

83

Fire

in a

com

pres

sor h

ouse

V

ibra

tion

indu

ced

by th

e pu

mpi

ng sy

stem

. Lu

be o

il co

nsol

e w

as in

stal

led

outs

ide

the

build

ing.

12

1.

1983

Pr

imar

y re

form

er ri

ser l

iner

co

llaps

e D

epos

it of

car

bona

ceou

s mat

eria

l res

ulte

d fr

om h

igh

sulfu

r in

feed

gas

. R

efor

mer

ope

ratin

g pr

oced

ure

mod

ified

.

122.

19

83

Ref

orm

er p

igta

il cr

acks

. M

ovem

ent c

ause

d by

ther

mal

exp

ansi

on.

Bea

ring

rolle

rs in

stal

led

on p

roce

ss g

as li

ne to

pig

tails

. 12

3.

1983

Se

cond

ary

refo

rmer

cat

alys

t su

ppor

t dom

e fa

ilure

Ex

plos

ion

in se

cond

ary

refo

rmer

. N

ew te

mpo

rary

cat

alys

t sup

port

inst

alle

d.

124

1983

Sh

ell r

uptu

re o

f a se

cond

ary

refo

rmer

O

verh

eatin

g ne

ar th

e st

eam

wat

er

inte

rfac

e.

New

lini

ng a

nd re

frac

tory

inst

alle

d. R

epai

rs d

one

on th

e ve

ssel

. 12

5 19

84

Cra

cks i

n th

e ou

tlet s

ectio

n of

th

e st

eam

refo

rmer

tube

s Pr

esen

ce o

f wat

er in

con

dens

ed fo

rm.

Dam

aged

tube

s rep

lace

d.

126

1984

Fa

ilure

of d

issi

mila

r wel

ds in

re

form

er tu

bes

Hyd

roge

n in

duce

d cr

ack

form

atio

n.

Leak

ing

tube

s rep

aire

d. E

xter

nal i

nsul

atio

n ap

plie

d on

the

wel

d.

127.

19

84

Fire

in p

rimar

y re

form

er

pent

hous

e.

Ris

er ru

ptur

e &

gas

leak

. R

iser

tube

repa

ired.

128.

19

84

Rup

ture

of s

tartu

p he

ater

coi

l. H

ydro

gen

indu

ced

crac

ks; c

onde

nsin

g of

m

oist

ure

on th

e tu

be o

uter

surf

ace.

C

oil r

epai

red,

new

ther

moc

oupl

es in

stal

led

on th

e co

ils

129.

19

84

Stre

ss c

orro

sion

cra

ckin

g in

sy

ngas

hea

t exc

hang

er.

Cor

rosi

on fr

om c

onta

min

ated

wat

er o

f w

ettin

g th

e in

sula

ted

equi

pmen

t. Pr

otec

tive

pain

ting

unde

rnea

th in

sula

tion

mat

eria

l.

Item

Y

ear

Rep

orte

d In

cide

nt

Roo

t Cau

se

Rem

edy

Act

ion

Take

n

130.

19

84

NH

3, S

tora

ge ta

nk ro

of ru

ptur

e.

Def

icie

ncy

in th

e ro

of to

wal

l wel

d co

nnec

tion,

resu

lted

into

hig

h st

ress

low

fa

tigue

.

Wel

d w

as p

rope

rly re

paire

d.

131.

19

85

Cor

rosi

on in

CO

2 a

bsor

ptio

n to

wer

. C

arbo

nic

acid

impi

ngem

ent.

Rep

airs

don

e to

abs

orpt

ion

tow

er.

132.

19

85

Dam

age

at sy

ngas

turb

ine

by

exce

ssiv

e st

eam

supe

rhea

ting

Def

ect i

n co

ntro

l sys

tem

, los

s of p

roce

ss

air.

New

trip

syst

em o

n st

eam

supe

rhea

t con

trol.

133.

19

85

Expl

osio

n of

a B

enfie

ld so

lutio

n st

orag

e ta

nk

Hyd

roge

n ga

s ing

ress

into

stor

age

tank

, ig

nitio

n by

stat

ic c

harg

e.

New

tank

des

igne

d w

ith n

o in

gres

s of H

2. N

ew o

pera

tiona

l pr

oced

ures

ado

pted

. 13

4.

1985

Ex

plos

ion

in c

old

stor

age

kills

fir

e fig

hter

Ig

nitio

n of

a h

azar

dous

acc

umul

atio

n of

N

H3 g

as

Und

efin

ed

135.

19

85

Extra

low

S/C

ratio

cau

sed

over

re

duct

ion

of H

TS c

atal

yst.

Mal

func

tion

of st

eam

flow

con

trol.

Tigh

t shu

t off

val

ves w

ere

prov

ided

on

impu

lse

line

drai

n va

lves

. 13

6.

1985

Fa

ilure

& re

pair

of p

rimar

y w

aste

hea

t boi

ler.

Ther

mal

ly in

duce

d st

ress

es d

ue to

liqu

id

leve

l flu

ctua

tion.

C

oatin

g th

e up

per e

xpos

ed a

rea

of th

e sh

ell a

nd u

se o

f ox

ygen

scav

enge

rs in

BFW

. 13

7.

1985

Fa

ilure

of h

igh-

pres

sure

sy

nthe

sis p

ipe.

Se

vere

hyd

roge

n at

tack

. C

onve

rter i

nlet

pip

ing

chan

ged

to ri

ght m

ater

ial.

138.

19

85

Fire

box

expl

osio

n in

a p

rimar

y re

form

er

Leak

ing

refo

rmer

tube

. R

efor

mer

tube

repl

aced

.

139.

19

85

Dam

age

& re

pair

of a

hor

izon

tal

amm

onia

con

verte

r.

Rev

erse

flow

from

syng

as c

ompr

esso

r due

to

dia

phra

gm fa

ilure

. In

tern

al re

pairs

mad

e to

bas

ket.

140.

19

85

Leak

in a

mm

onia

pla

nt re

form

er

conv

ectio

n se

ctio

n na

tura

l gas

pr

ehea

t coi

l.

Ove

rhea

ting

of p

re-h

eat c

oils

. Pa

rt of

pre

-hea

t coi

l rep

lace

d

141.

19

85

Maj

or fi

re in

a st

eam

met

hane

re

form

er fu

rnac

e.

Wel

d qu

ality

, sho

rteni

ng o

f pig

tails

. Fu

rnac

e re

built

with

new

tube

s.

142.

19

85

Mul

tiple

cra

ckin

g &

leak

age

of

hot s

ynth

esis

gas

pip

e In

corr

ect h

eat t

reat

men

t, an

d ni

tridi

ng

All

crac

ks w

ere

repa

ired.

143.

19

85

Seve

re c

arry

ove

r phe

nom

ena

in

met

hano

l pla

nt

Inco

mpl

ete

seal

wel

ds a

nd c

rack

ed w

elds

du

e to

stra

in a

nd h

igh

tem

pera

ture

s. St

eam

dru

m in

tern

als m

odifi

ed.

144.

19

85

Tube

failu

re o

n th

e sy

nthe

sis g

as

com

pres

sor a

fter c

oole

r. Fl

ow in

duce

d tu

be v

ibra

tion.

C

ross

baf

fle d

esig

n m

odifi

ed.

Item

Y

ear

Rep

orte

d In

cide

nt

Roo

t Cau

se

Rem

edy

Act

ion

Take

n

145.

19

86

Dam

age

of sy

ngas

com

pres

sor.

Failu

re o

f ant

i-sur

ge c

ontro

l val

ve d

ue to

fa

ulty

flow

mea

sure

men

t. C

hang

ed z

ero

poin

t dis

loca

tion

of th

e flo

w m

easu

rem

ent.

146.

19

86

Dam

age

of a

mm

onia

stor

age

tank

foun

datio

n.

Gro

und

mov

emen

t fro

m e

arth

quak

e.

Tank

foun

datio

n re

plac

ed.

147.

19

86

Failu

re o

f the

feed

gal

lery

&

pres

sure

shel

l of C

O2

rege

nera

tor.

Impi

ngem

ent p

late

bre

akin

g aw

ay fr

om

the

wal

l, su

rge

of g

as.

Rep

air w

ork

perf

orm

ed o

n fe

ed g

alle

ry.

148.

19

86

Failu

re o

f am

mon

ia c

onve

rter

feed

exc

hang

er.

Stiff

enin

g ef

fect

cau

sed

by th

e re

pair

ring

adde

d to

the

orig

inal

kit.

R

epai

rs m

ade

to tu

besh

eet.

149.

19

86

Failu

re o

f am

mon

ia st

artu

p he

ater

. N

itrid

ing

& st

ress

es in

duce

d by

ther

mal

cy

clin

g.

Tube

mat

eria

l cha

nged

.

150.

19

86

Fire

at S

emile

an p

ump

by

reve

rse

mot

ion.

D

efec

tive

chec

k va

lve.

Pu

mp

disc

harg

e ga

te v

alve

s rep

lace

d by

mot

or o

pera

ted

valv

es –

che

ck v

alve

repl

aced

with

a re

liabl

e on

e.

151.

19

86

Aux

iliar

y bo

iler e

xplo

sion

G

as le

aks t

hrou

gh le

akin

g fu

el v

alve

s. Pr

ovid

ed d

oubl

e bl

ock

& b

leed

val

ves o

n fu

el g

as h

eade

r. 15

2.

1986

Sy

ngas

com

pres

sor t

rain

failu

re.

Loca

lised

hig

h st

ress

resu

lting

in h

igh

cycl

e fa

tigue

failu

re.

New

des

ign

coup

ling

inst

alle

d.

153.

19

86

Ove

rhea

ting

of sy

ngas

co

mpr

esso

r. R

ag in

com

pres

sor s

uctio

n lin

e.

Rem

oved

rag.

154.

19

87

Pipi

ng fa

ilure

in a

hig

h pr

essu

re

stea

m sy

stem

Lo

calis

ed th

erm

al st

rain

due

to

accu

mul

atio

n of

con

dens

atio

n.

Pipi

ng d

esig

n m

odifi

ed to

hol

d te

mpe

ratu

re a

nd e

limin

ate

cond

ensa

tion.

15

5.

1987

Fa

ilure

and

repa

ir of

a p

rimar

y w

aste

hea

t boi

ler

Loca

lised

refr

acto

ry fa

ilure

, sub

sequ

ent

over

heat

ing,

and

hig

h te

mpe

ratu

re st

ress

ru

ptur

e.

The

botto

m h

ead

was

repl

aced

.

156.

19

87

Pipe

rupt

ure

caus

ed b

y vi

brat

ions

of a

safe

ty v

alve

Im

prop

er sa

fety

val

ve, p

ipin

g la

yout

and

su

ppor

ts.

Safe

ty v

alve

insp

ectio

n pr

ogra

m e

nfor

ced

to m

inim

ise

futu

re

risks

. 15

7.

1987

W

eld

crac

king

in re

form

er o

utle

t pa

rts

Diff

eren

ce in

mec

hani

cal a

nd p

hysi

cal

prop

ertie

s of b

ase

and

wel

d m

etal

. R

epai

rs c

arrie

d ou

t on

wel

d fa

ilure

s.

158.

19

87

Synt

hesi

s gas

com

pres

sor f

ailu

re

Unc

onve

ntio

nal r

epai

rs, d

ue to

lack

of

spar

e di

aphr

agm

ass

embl

y.

Dia

met

er o

f bal

anci

ng d

rum

redu

ced.

Qui

ck c

losi

ng N

RV

w

as m

odifi

ed.

159.

19

87

Failu

re o

f sec

onda

ry re

form

er

cata

lyst

and

air

burn

er

Insu

ffic

ient

com

bust

ion

zone

. C

atal

yst h

old-

dow

n la

yer o

f alu

min

a ba

lls w

as re

duce

d.

Item

Y

ear

Rep

orte

d In

cide

nt

Roo

t Cau

se

Rem

edy

Act

ion

Take

n

160

1987

C

orro

sion

in h

ot p

otas

sium

CO

2 ab

sorb

er

Failu

re o

f cor

rosi

on in

hibi

tion

syst

em.

Bot

tom

sect

ion

of th

e sh

ell w

as S

S ov

erla

id, s

tress

relie

ved

and

pass

ivat

ed.

161.

19

87

Stre

ss c

orro

sion

cra

ckin

g in

fie

ld a

mm

onia

stor

age

tank

s Pr

esen

ce o

f oxy

gen.

Po

st w

eld

heat

trea

tmen

t car

ried

out.

162.

19

88

Rup

ture

of H

TS e

xit p

roce

ss g

as

line

Rap

id te

mpe

ratu

re ri

se.

Prov

ided

hig

h te

mpe

ratu

re a

larm

s and

seco

nd g

as fl

ow

met

er.

163.

19

88

Expl

osio

n th

at o

ccur

red

durin

g a

wel

ding

ope

ratio

n In

adeq

uate

isol

atio

n pr

oced

ures

and

m

onito

ring

tech

niqu

es.

Proc

ess i

sola

tion

proc

edur

es m

odifi

ed.

164.

19

88

Synt

hesi

s gas

com

pres

sor

coup

ling

corr

osio

n fa

tigue

fa

ilure

s

Fatig

ue in

itiat

ion.

C

lean

lubr

icat

ion

syst

em.

165.

19

88

Seve

re c

rack

ing

of C

O2

abs

orbe

r exi

t lin

e St

ress

cor

rosi

on c

rack

ing.

C

rack

s rep

aire

d.

166.

19

88

Stre

ss c

orro

sion

in a

12,

000

tonn

e am

mon

ia st

orag

e ta

nk

Mat

eria

l use

d an

d w

eld

proc

edur

es

adop

ted

susc

eptib

le to

SC

C a

nd H

2 cr

acki

ng.

All

defe

cts r

epai

red.

167.

19

88

Prob

lem

s in

a pr

oces

s gas

coo

ler

Poor

BFW

qua

lity.

C

oole

r lea

ks w

ere

repa

ired.

16

8.

1988

Ex

plos

ion

in a

nitr

ic a

cid

tail

gas

duct

D

iffic

ulty

in o

btai

ning

eve

n H

2 d

istri

butio

n, le

akag

e of

gas

com

pres

sor

disc

harg

e va

lves

.

Two

bello

ws r

epla

ced.

Pip

ing

mod

ifica

tions

car

ried

out.

169.

19

89

Anh

ydro

us a

mm

onia

rele

ase

Buc

klin

g of

tank

floo

r due

to d

eter

iora

tion

of fo

am g

lass

insu

latio

n.

Stor

age

tank

dec

omm

issi

oned

, mot

hbal

led.

170.

19

89

New

cas

es o

f SC

C in

am

mon

ia

stor

age

tank

SC

C in

O2 a

tmos

pher

e.

Cat

hodi

c po

laris

atio

n.

171.

19

89

Nea

r fai

lure

of 5

0 ba

r nitr

ogen

su

pply

line

B

rittle

frac

ture

failu

re d

ue to

reve

rse

flow

. In

stal

led

an in

verte

d ‘U

’ tub

e in

N2 l

ine.

172.

19

89

Expl

osio

n in

synt

hesi

s gas

co

mpr

esso

r B

ackf

low

of s

ynth

esis

gas

thro

ugh

com

pres

sor r

ecyc

le li

nes.

Add

ition

al sa

fety

val

ves w

ere

inst

alle

d.

173.

19

89

Stru

ctur

al in

tegr

ity o

f 12,

000

tonn

e am

mon

ia ta

nk in

the

pres

ence

of S

CC

Sign

s of s

tress

cor

rosi

on c

rack

ing.

Ta

nk in

tegr

ity m

onito

ring

put i

n pl

ace.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

174.

19

89

Cra

ckin

g in

HP

syng

as p

ipe

Ther

mal

cyc

ling

resu

lted

from

mix

ing

of

wet

and

dry

stea

m.

Con

dens

ate

rebo

iler s

hell

size

was

incr

ease

d.

175.

19

89

Mag

netit

e la

yer i

n pr

imar

y W

HB

and

aux

iliar

y bo

iler

Boi

ler l

eake

d du

e to

cor

rosi

on.

Boi

ler w

ater

pH

low

ered

, blo

wdo

wn

rate

s inc

reas

ed.

176.

19

89

Seve

re d

amag

e to

the

roto

r of a

sy

ngas

com

pres

sor

Col

lisio

n be

twee

n st

atio

nery

and

rota

ting

parts

. V

ario

us p

arts

of c

ompr

esso

r wer

e m

odifi

ed o

r re

desi

gned

. 17

7.

1990

A

ccid

ent i

n Li

thua

nian

ferti

liser

pl

ant,

7 pe

ople

kill

ed

Am

mon

ia st

orag

e ta

nk ro

llove

r. U

ndef

ined

178.

19

90

Expl

osio

n of

synl

oop

amm

onia

se

para

tor

Mer

cury

aff

ecte

d st

eel p

rope

rties

, for

med

ex

plos

ive

com

poun

ds.

Mer

cury

rem

oval

syst

em in

stal

led.

179.

19

90

Effe

ct o

f mer

cury

in a

mm

onia

pl

ants

C

orro

sion

and

form

ing

of e

xplo

sive

m

ixtu

re.

Mon

itor m

ercu

ry le

vels

in fe

edga

s.

180.

19

90

Leak

in a

mm

onia

stor

age

tank

C

rack

on

over

lapp

ing

plat

es.

Tank

dec

omm

issi

oned

, lea

ks re

paire

d.

181.

19

90

Maj

or in

cide

nt fo

llow

ing

the

failu

re o

f am

mon

ia in

ject

or in

ur

ea p

lant

, 2 p

eopl

e ki

lled

Cra

nk sh

aft f

ailu

re o

n am

mon

ia in

ject

ion

pum

p du

e to

a fa

tigue

cra

ck.

Equi

pmen

t iso

latio

n pr

oced

ures

impr

oved

.

182.

19

90

Failu

re o

f syn

gas c

ompr

esso

r Im

prop

er d

esig

n an

d op

erat

ion

of a

nti-

surg

e sy

stem

. Su

rge

cont

rol s

yste

m w

as re

desi

gned

.

183.

19

90

Failu

re o

f LTS

exi

t pro

cess

gas

lin

e SS

line

rupt

ured

and

exp

lode

d du

e to

th

erm

al c

ycle

stre

ss fa

tigue

alo

ng se

am

wel

d.

Pipi

ng w

as re

plac

ed w

ith n

ew li

ner a

nd n

ozzl

e.

184.

19

90

Failu

re o

f pro

cess

air

preh

eat

coil

Coi

l def

orm

ed d

ue to

ther

mal

exp

ansi

on.

Coi

l red

esig

ned

with

a tw

o-pi

ece

tube

supp

ort s

yste

m.

185.

19

90

Cra

ckin

g in

am

mon

ia c

onve

rter

efflu

ent B

FW e

xcha

nger

H

ydro

gen

embr

ittle

men

t. C

rack

s wer

e gr

ound

ed a

nd re

paire

d.

186.

19

91

Failu

re a

nd n

ovel

repa

ir of

thic

k w

all s

ynth

esis

con

verte

r for

ging

Lo

w c

ycle

ther

mal

fatig

ue in

itiat

ed

crac

king

. M

odifi

ed d

esig

n fo

r con

verte

r for

ging

.

187.

19

91

Cra

ck fo

rmat

ion

in w

elds

in th

e ou

tlet l

ines

of a

n am

mon

ia

conv

erte

r.

Hyd

roge

n in

duce

d st

atic

fatig

ue.

Sect

ions

of p

ipin

g re

plac

ed.

Item

Y

ear

Rep

orte

d In

cide

nt

Roo

t Cau

se

Rem

edy

Act

ion

Take

n

188.

19

91

Cat

alys

t tub

es fa

ilure

follo

win

g fu

rnac

e fir

e H

igh

tem

pera

ture

stre

ss, t

herm

al sh

ock,

in

side

surf

ace

carb

onis

atio

n O

pera

ting

tem

pera

ture

s low

ered

. Edd

y cu

rren

t ins

pect

ion

empl

oyed

. 18

9.

1991

Fa

ilure

of s

econ

dary

refo

rmer

w

aste

hea

t boi

ler

Hig

h th

erm

al st

ress

bet

wee

n tu

be to

tube

sh

eet j

oint

s. R

outin

e in

term

itten

t blo

w d

own

rest

ored

.

190.

19

91

Failu

re o

f tw

o 10

0 ba

r BFW

lin

es

Hig

h flo

w v

eloc

ities

cau

sed

eros

ion

in

BFW

pip

ing.

B

FW p

ipin

g w

as re

paire

d.

191.

19

91

Failu

re o

f tw

o C

O2 r

egen

erat

ors

Vac

uum

form

atio

n.

Ope

ratin

g pr

oced

ures

cha

nged

. 19

2.

1991

Ex

plos

ion

in P

urge

Gas

R

ecov

ery

(PG

R) u

nit c

old

box

Mis

sing

of g

aske

t dur

ing

orig

inal

in

stal

latio

n.

Dam

aged

tail

gas l

ine

was

repl

aced

alo

ng w

ith th

e ja

cket

w

ater

line

. 19

3.

1991

W

eld

failu

re in

2 -1

/4 C

r- 1

Mo

amm

onia

con

verte

r U

se o

f agg

lom

erat

ed fl

ux in

con

junc

tion

with

a L

TPLH

T.

Und

efin

ed

194.

19

91

Stea

m sy

stem

con

tam

inat

ed b

y C

atac

arb

solu

tion

Usi

ng st

eam

con

dens

ate

as p

ump

seal

flu

sh w

ater

C

atac

arb

pum

p se

al fl

ush

syst

em m

odifi

ed.

195.

19

91

Leak

in th

ick

wal

led

synt

hesi

s co

nver

ter

Und

efin

ed

Cra

cked

wel

d se

am w

as c

ut o

ut a

nd c

ompl

etel

y re

-w

elde

d.

196

1991

H

ydro

gen

atta

ck in

2-2

5 C

r –

1Mo

stee

ls b

elow

Nel

son

curv

e Fo

rmat

ion

of n

itrid

es/c

arbo

nitri

des o

ut o

f th

e pr

e-ex

istin

g ca

rbid

es, l

ed to

hyd

roge

n at

tack

.

Und

efin

ed

197.

19

92

Tim

ely

dete

ctio

n of

dam

aged

ga

s dis

tribu

tor a

void

ed fa

ilure

s C

arbu

risat

ion

and

plas

tic d

efor

mat

ion

due

to o

verh

eatin

g.

New

gas

dis

tribu

tor i

nsta

lled.

198.

19

92

Impe

ller f

ailu

re o

f a p

roce

ss a

ir co

mpr

esso

r Fa

tigue

failu

re.

Impr

ovem

ents

mad

e on

ant

i-sur

ge c

ontro

l sys

tem

.

199.

19

92

Failu

re o

f WH

B a

fter

debo

ttlen

ecki

ng a

ir co

mpr

esso

r M

alfu

nctio

n of

wat

er c

ircul

atio

n in

boi

ler

tube

s, re

sulte

d tw

o-ph

ase

flow

. W

HB

repa

ired.

200.

19

92

Expl

osio

n an

d fir

e in

synt

hesi

s se

ctio

n Ex

plos

ive

mix

ture

in v

ent t

ail p

ipe

from

pa

ssin

g dr

ain

valv

es a

nd li

fting

of P

SV.

Ven

t hea

der d

rain

syst

em m

odifi

ed. P

SV’s

relo

cate

d.

Prov

ided

con

tinuo

us p

urgi

ng o

f N2 ai

r ven

ts

201.

19

92

Inci

dent

on

mot

ive

stea

m ra

isin

g ga

s coo

ler

Cre

vice

cor

rosi

on p

rom

oted

by

chlo

rides

. N

ew d

esig

n co

oler

inst

alle

d.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

202.

19

92

Foun

datio

n fa

ilure

on

20,0

00

tonn

e am

mon

ia st

orag

e ta

nk

Cyc

lic fr

eezi

ng d

amag

e.

Rep

airs

don

e on

tank

foun

datio

n.

203

1993

C

rack

ing

of st

eam

refo

rmer

bo

ttom

man

ifold

St

rain

ass

iste

d in

ter-

gran

ular

oxi

datio

n.

Use

of c

entri

fuga

l cas

t 20/

32+N

b w

ith m

atch

ing

fille

rs.

204.

19

93

Failu

re o

f syn

thes

is w

aste

hea

t bo

iler b

y ro

tatin

g fe

rrul

es

Nitr

idin

g, w

rong

mat

eria

l for

the

ferr

ules

. U

ndef

ined

205.

19

93

Failu

re o

f WH

B in

synl

oop

Failu

re o

f hea

t pro

tect

ion

shie

ld in

let t

o th

e bo

iler.

71 tu

bes r

emov

ed, r

epai

red

and

rein

stal

led.

206.

19

93

Furth

er c

rack

ing

in c

onve

rter

efflu

ent B

FW e

xcha

nger

H

ydro

gen

embr

ittle

men

t. C

rack

s wer

e re

paire

d.

207.

19

93

Proc

ess g

as e

xit t

empe

ratu

re

fluct

uatio

ns in

prim

ary

refo

rmer

Tr

appe

d st

eam

bet

wee

n lin

er a

nd

refr

acto

ry le

d to

buc

klin

g of

out

let h

eade

r. Tr

ansi

tion

asse

mbl

y of

8th ro

w ri

ser w

as re

plac

ed

com

plet

ely.

20

8.

1993

In

effic

ient

moi

stur

e se

para

tor

dam

ages

air

com

pres

sor

Moi

stur

e er

oded

inte

rsta

ge la

byrin

ths.

New

pee

rless

in li

ne se

para

tor i

nsta

lled.

209.

19

93

Seco

ndar

y re

form

er a

ir m

ixer

fa

ilure

Lo

ss o

f ste

am fl

ow c

ause

d bu

rner

tip

failu

re.

New

bur

ner i

nsta

lled,

cat

alys

t rep

lace

d.

210.

19

93

Ret

ubin

g of

refo

rmed

gas

boi

ler

Boi

ler w

ater

dep

osits

cau

sed

build

-up

on

tube

s. In

situ

repl

acem

ent d

one

of a

ll tu

bes.

211

1994

St

ress

cor

rosi

on in

am

mon

ia

stor

age

tank

s H

igh

O2 c

onte

nt o

f 10

ppm

. M

aint

ain

wat

er c

onte

nt o

f abo

ut 0

.2%

.

212

1994

Tu

be fa

ilure

in S

ynlo

op W

HB

La

ck o

f wat

er c

ircul

atio

n.

Leak

ing

tube

s plu

gged

, rep

aire

d.

213.

19

94

Cre

ep d

amag

es in

out

let

man

ifold

s and

prim

ary

refo

rmer

C

reep

cra

ckin

g af

ter 2

5 ye

ars i

n op

erat

ion.

Fu

ll m

anifo

ld w

as re

plac

ed.

214.

19

94

Failu

re o

f tw

o pr

imar

y m

ake

gas

boile

rs

Loss

of B

FW fl

ow, b

rittle

frac

ture

of

ferr

ules

. B

oile

r tub

es re

paire

d, re

plac

ed, p

lugg

ed.

215.

19

94

Failu

res i

n w

aste

hea

t boi

lers

D

esig

n de

ficie

ncie

s, de

fect

s dur

ing

fabr

icat

ion,

pla

nt u

pset

s. R

epai

rs c

arrie

d ou

t on

WH

B’s

.

216.

19

94

Am

mon

ia w

aste

hea

t boi

ler

repl

acem

ent

Boi

ler r

an d

ry.

New

boi

ler o

f flo

atin

g he

ad ty

pe w

as in

stal

led.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

217.

19

94

Wel

d zo

ne c

rack

s in

repa

ired

2-1/

4-1

Mo

amm

onia

con

verte

r M

anuf

actu

ring

defe

cts,

hydr

ogen

atta

ck.

Cra

cks r

epai

red.

218.

19

94

Met

al d

ustin

g in

was

te h

eat

boile

rs

Car

bon

depo

sitio

n, w

rong

mat

eria

ls.

Avo

id c

arbo

n fo

rmat

ion,

use

refr

acto

ry li

ners

.

219

1994

H

eavy

cor

rosi

on p

robl

em in

B

enfie

ld C

O2 re

mov

al sy

stem

Fa

ilure

of B

enfie

ld so

lutio

n qu

ality

. Th

e sy

stem

was

shut

dow

n, c

lean

ed, p

assi

vate

d an

d re

star

ted.

22

0.

1994

Se

vere

leak

age

in C

O2 s

tripp

er

rebo

iler

Failu

re o

f flo

atin

g he

ad g

aske

t. G

aske

t rep

lace

d an

d ne

w sh

ell o

f SS

orde

red.

221.

19

94

Failu

res i

n ur

ea st

rippe

rs

Stre

ss c

orro

sion

cra

ckin

g in

am

mon

iaca

l so

lutio

n.

Bot

tom

cha

nnel

hea

ds re

plac

ed.

222

1995

D

issi

mila

r wel

d cr

acki

ng &

re

pairs

on

prim

ary

refo

rmer

ou

tlet h

eade

r

Low

tem

pera

ture

cre

ated

agg

ress

ive

envi

ronm

ent w

ith c

arbo

nic

acid

. A

hea

ter i

nsta

lled

on d

issi

mila

r met

al w

eld

(DM

W) j

oint

fo

r S/D

pur

pose

- ne

w te

mpe

ratu

re m

onito

ring

syst

em

inst

alle

d.

223.

19

95

Vib

ratio

n pr

oble

ms w

ith

reva

mpe

d ai

r com

pres

sor

Con

tam

inat

ion

of th

e co

mpr

esso

r with

co

rros

ion

prod

ucts

. C

S su

ctio

n lin

es re

plac

ed w

ith S

S.

224.

19

95

Cat

astro

phic

failu

re o

f am

mon

ia/a

ir m

ixer

Pr

e-ig

nitio

n of

air/

amm

onia

mix

ture

by

cata

lyst

, rus

t. M

ixer

pip

e w

as re

plac

ed.

225.

19

95

Failu

re o

f CW

circ

ulat

ion

pum

p M

alfu

nctio

n of

ove

rspe

ed tr

ip d

evic

e an

d go

vern

or o

f tur

bine

. N

ew v

ibra

tion

mon

itors

inst

alle

d. T

hrus

t wea

r trip

pr

ovid

ed.

226.

19

95

Prob

lem

atic

LTS

cat

alys

t re

duct

ion

Inco

rrec

t ope

ratio

n of

ven

t val

ve o

n co

rner

gas

line

. C

aref

ul p

lann

ing

impr

oved

cat

alys

t red

uctio

n sy

stem

s.

227.

19

95

Nitr

idin

g in

am

mon

ia re

acto

r N

itrid

ing

caus

ed b

y fa

iled

prot

ectio

n tu

bing

. M

ater

ials

resi

stan

t nitr

idin

g in

stal

led.

228.

19

95

Fatig

ue c

rack

ing

of a

bsor

ber o

n hy

drog

en p

lant

PSA

uni

t D

efec

t fro

m h

ydra

tion

prop

agat

ion.

C

rack

was

repa

ired.

229.

19

95

Rep

airs

on

CO

2 ab

sorb

er.

Cor

rosi

on b

y C

O2 a

ttack

on

MEA

syst

em.

Org

anic

coa

ting

empl

oyed

on

MEA

abs

orbe

r. 23

0.

1995

Fa

ilure

s in

urea

reac

tors

D

efec

ts d

urin

g fa

bric

atio

n, p

lant

ups

ets,

oper

atin

g co

nditi

on.

Rep

airs

car

ried

out o

n lin

ers

231.

19

95

Cra

ck fo

rmat

ion

in w

elds

in

conv

erte

r out

let l

ines

Lo

w c

ycle

ther

mal

fatig

ue.

Wel

ds w

ere

repa

ired.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

232.

19

95

Am

mon

ia re

leas

e du

ring

barg

e un

load

ing

Vac

uum

bui

ld-u

p in

the

tank

, fai

lure

of

vacu

um b

reak

er.

Und

efin

ed

233.

19

95

Synt

hesi

s gas

cou

plin

g fa

ilure

To

rsio

nal i

mpa

ct o

n th

e co

uplin

g to

roto

r sh

aft.

Cou

plin

g w

as re

plac

ed.

234

1996

D

amag

e of

refo

rmed

gas

fire

tu

be b

oile

r H

igh

pH b

oile

r wat

er.

Boi

ler w

as re

paire

d.

235.

19

96

Cat

astro

phic

failu

re o

f tub

e sh

eet i

n fir

e tu

be w

aste

hea

t bo

iler

Hig

h he

at fl

ux a

nd d

epar

ture

from

nu

clea

te b

oilin

g.

Boi

ler f

ront

sect

ion

repl

aced

.

236.

1996

Fa

ilure

of B

FW p

ump

turb

ine

follo

win

g si

te p

ower

failu

re

Pum

p ra

n w

ithou

t lub

ricat

ion.

A

seco

nd n

on-r

etur

n va

lve

inst

alle

d.

237.

19

96

Failu

re o

f was

te h

eat b

oile

r Lo

calis

ed re

frac

tory

failu

res a

nd

subs

eque

nt o

verh

eatin

g.

Boi

ler h

ead

was

repl

aced

.

238.

19

96

Failu

re o

f exp

ansi

on b

ello

ws o

f sy

nloo

p ho

t hea

t exc

hang

er

Hyd

roge

n at

tack

, fat

igue

load

ing

Expa

nsio

n be

llow

s rep

aire

d by

inst

allin

g a

slee

ve w

ith

pack

ing

rings

and

gla

nd.

239.

19

96

Failu

re a

nd re

pair

of w

aste

hea

t bo

ilers

Lo

ss o

f wat

er le

vel i

n st

eam

dru

m.

Des

ign

impr

ovem

ents

mad

e, re

pairs

don

e on

WH

B.

240.

19

96

Rep

lace

men

t of N

H3 s

tora

ge

tank

D

id n

ot m

eet a

ny st

anda

rds f

or ta

nks.

A n

ew ta

nk w

as b

uilt.

241.

19

96

Cor

rosi

on a

ssis

ted

crac

king

in

CS

wal

l of u

rea

reac

tor

SCC

, stre

ss, m

edia

V

esse

l scr

appe

d.

242.

19

96

Con

tam

inat

ion

of B

enfie

ld C

O2

rem

oval

syst

em

Org

anic

aci

ds p

rodu

ced

in ‘C

O’ s

hift

reac

tor.

Proc

ess c

onde

nsat

e tre

atm

ent s

yste

m in

stal

led.

243.

19

97

Rep

air o

f CO

2 st

rippe

r col

umn

Chl

orid

e st

ress

cor

rosi

on c

ause

d by

wet

in

sula

tion.

R

epai

red

CO

2 stri

pper

- re

vise

d op

erat

ing

cont

rols

.

244.

19

97

Wel

d cr

acks

in N

H3

conv

erte

r H

ydro

gen

indu

ced

crac

ks

Wel

ds re

paire

d.

245.

19

97

Def

ects

with

NH

3 pla

nt st

acks

Lo

calis

ed in

tern

al c

ombu

stio

n ov

erhe

ated

ba

se o

f the

stac

k.

Def

orm

ed b

end

was

cut

out

and

repl

aced

.

246.

19

98

Shro

ud fa

ilure

s of p

roce

ss a

ir co

mpr

esso

r tur

bine

H

igh

stre

ss le

vels

on

the

shro

uds.

Shro

uds a

nd b

ladi

ng m

odifi

ed.

Ite

m

Yea

r R

epor

ted

Inci

dent

R

oot C

ause

R

emed

y A

ctio

n Ta

ken

247.

19

98

Expl

osio

n in

prim

ary

refo

rmer

Ex

plos

ive

gas m

ixtu

re in

refo

rmer

fu

rnac

e.

Bur

ner m

anag

emen

t sys

tem

mod

ified

.

248.

19

98

Pres

sure

relie

f val

ve p

ipin

g fa

ilure

s and

fire

in sy

nthe

sis

loop

Inad

equa

te su

ppor

t for

pre

ssur

e re

lief

pipi

ng.

Dev

elop

ed n

ew p

ipin

g su

ppor

t crit

eria

.

249.

19

97

Stre

ss c

orro

sion

of N

b co

ntai

ning

cas

t allo

ys

Cau

stic

pro

duce

d fr

om h

ydro

lysi

s re

actio

n.

Spar

e pa

rts sh

ould

be

kept

in d

ry c

ondi

tion.

250

1998

Pl

uggi

ng o

f bay

onet

/sca

bbar

d tu

be W

HB

Po

wer

failu

re c

ause

d da

mag

e to

boi

lers

. Le

akin

g tu

bes p

lugg

ed.

251.

19

98

Inne

r bas

ket f

ailu

re o

f NH

3 bo

oste

r rea

ctor

N

umer

ous p

lant

trip

s. Fa

ilure

of b

olts

and

tri

p va

lves

/che

ck v

alve

s. B

aske

t int

erna

ls w

ere

repa

ired.

252.

19

98

Dam

age

of e

lect

ric m

otor

of

Ben

field

solu

tion

pum

p R

ever

se ro

tatio

n of

pum

ps fr

om fa

iled

Non

Ret

urn

Val

ves’

(NR

V).

NR

V p

ipin

g si

zing

incr

ease

d to

min

imis

e flo

w in

duce

d vi

brat

ions

. 25

3 19

98

Prim

ary

WH

B sh

ell f

ailu

re

Hyd

roge

n at

tack

, cre

ep ru

ptur

e,

mec

hani

cal,

ther

mal

cyc

lical

stre

ss.

Use

of 1

¼C

r-½

Mo

for W

HB

shel

ls.

254.

19

99

Stra

in-a

ge c

rack

ing

of A

lloy

601

tube

s at 6

00o C

. St

ress

rela

xatio

n cr

acki

ng.

Exte

nsiv

e re

pairs

mad

e to

refo

rmer

out

let p

ipin

g.

255.

19

99

Cat

alys

t lea

kage

in a

mm

onia

co

nver

ter

Res

trict

ion

in th

erm

al e

xpan

sion

of s

cree

n w

ires c

ause

d ex

cess

ive

com

pres

sor s

tress

. C

entre

scre

en w

as re

paire

d.

256.

19

99

Failu

re o

f aM

DEA

line

In

stru

men

t fai

lure

led

to fl

ow in

duce

d vi

brat

ions

of p

ipin

g.

Faile

d pi

ping

was

repl

aced

.

257.

19

99

Nat

ural

gas

feed

pre

heat

er fi

re

Flam

e im

ping

emen

t led

to o

verh

eatin

g.

Trip

syst

em w

as m

odifi

ed.

258.

19

99

Am

mon

ia c

onve

rter j

oint

failu

re

Hyd

roge

n in

duce

d cr

acki

ng d

ue to

poo

r PW

HT.

C

onve

rter w

as re

paire

d.

259.

19

99

Failu

re o

f Ben

field

flas

h dr

um

Fatig

ue fa

ilure

of u

pper

baf

fles.

Rep

airs

mad

e to

flas

h dr

um, P

WH

T al

so d

one.

26

0.

1999

C

orro

sion

in C

O2 re

mov

al

sect

ion

Ars

enic

bas

ed v

etro

coke

syst

em.

Solv

ent s

yste

m re

plac

ed w

ith a

new

one

.

261.

19

99

Air

and

refr

iger

atio

n m

achi

ne

oil c

onso

le fi

re

Failu

re o

f ref

riger

atio

n co

mpr

esso

r sea

ls -

resu

lted

to th

e br

eaka

ge o

f oil

line.

M

any

hard

war

e m

odifi

catio

ns im

plem

ente

d.

262.

19

99

Air

com

pres

sor i

nter

coo

ler

leak

age

Vib

ratio

ns o

f tub

es o

n ‘U

’ tub

e de

sign

. U

tube

s pro

vide

d w

ith su

ppor

ts. V

eloc

ity in

crea

sed

in

tube

s.

Item

Y

ear

Rep

orte

d In

cide

nt

Roo

t Cau

se

Rem

edy

Act

ion

Take

n

263.

19

98

Failu

res i

n C

O2 re

mov

al sy

stem

In

adeq

uate

mec

hani

cal d

esig

n, fa

bric

atio

n de

fect

s. A

new

dis

tribu

tor a

nd su

ppor

t arr

ange

men

t pro

vide

d.

264.

20

00

Seco

ndar

y re

form

er b

urne

r fa

ilure

W

rong

mod

ifica

tions

, ope

ratio

n at

hig

her

rate

s. B

urne

r des

ign

mod

ified

.

265

2000

Fa

ilure

of s

ynth

esis

loop

BFW

ex

chan

ger (

123C

) inl

et n

ozzl

e

Inco

mpl

ete

fusi

on o

n in

terf

ace

butte

ring,

hy

drog

en e

mbr

ittle

men

t.

Noz

zle

was

repa

ired.

266.

20

00

Expl

osio

n of

aM

DEA

stor

age

tank

R

ever

se fl

ow o

f gas

from

abs

orbe

r. C

heck

val

ve in

stal

led;

Pro

cess

Haz

ard

Ana

lysi

s (PH

A)

and

Stan

dard

Ope

ratin

g Pr

oced

ures

(SO

P) re

view

ed.

267.

20

00

Inte

rnal

failu

res o

f am

mon

ia

conv

erte

r Ex

pans

ion

join

t did

not

abs

orb

ther

mal

ex

pans

ion.

D

esig

n im

prov

ed fo

r con

verte

r int

erna

ls.

268.

20

00

Expl

osio

n of

hyd

roge

n in

a C

O2

pipe

line

H

2 en

riche

d ga

s ent

ered

the

pipe

line,

fo

rmed

exp

losi

ve m

ixtu

re.

Trip

syst

em m

odifi

ed. S

epar

ate

sam

plin

g sy

stem

in

stal

led.

26

9.

2001

Fa

ilure

of n

atur

al g

as

com

pres

sor

Stic

king

of m

ain

trip

valv

e an

d no

zzle

va

lves

. Tr

ip v

alve

s rep

lace

d. T

rip m

atrix

mod

ified

.

270.

20

01

Failu

re o

f inn

er sh

ell o

f dou

ble

wal

led

stor

age

tank

H

ydro

stat

ic h

ead

of a

mm

onia

in th

e an

nulu

s act

ed o

n bo

ttom

pla

te le

d to

pl

astic

def

orm

atio

n.

Inst

rum

enta

tion

was

impr

oved

on

the

tank

, rep

airs

don

e on

tank

bot

tom

.

271.

20

01

Nat

ural

gas

line

failu

re

Cor

rosi

on re

sulte

d fr

om c

arbo

nic

acid

. G

as li

ne re

plac

ed w

ith u

pgra

ded

mat

eria

l. 27

2.

2001

Fi

re in

seco

ndar

y re

form

er

outle

t lin

e to

WH

B

Hyd

roge

n at

tack

, the

rmal

cyc

ling.

D

amag

ed p

ortio

n of

pip

ing

repl

aced

with

Inco

nel 6

01.

273.

20

01

Prim

ary

refo

rmer

failu

re

Ove

rhea

ting

at n

o st

eam

flow

con

ditio

n.

New

trip

syst

em in

stal

led

for s

tart-

up o

pera

tion.

27

4.

2002

A

uxili

ary

boile

r fai

lure

s Po

or w

ater

qua

lity.

Not

pro

perly

cle

aned

st

eam

syst

em.

All

the

BFW

and

stea

m sy

stem

che

mic

ally

cle

aned

.

275.

20

02

Failu

re a

nd re

pair

of se

cond

ary

refo

rmer

H

ydro

gen

assi

sted

cra

ckin

g.

Rep

airs

mad

e on

all

crac

ks.

276.

20

02

Bur

st b

efor

e le

ak fa

ilure

of H

igh

tem

pera

ture

shift

eff

luen

t WH

B

Stra

in a

gein

g.

Leak

s wer

e re

paire

d.

277.

20

02

Failu

re o

f mol

ecul

ar si

eve

drye

r D

elay

ed h

ydro

gen

atta

ck.

Und

efin

ed

278

2002

Fa

ilure

and

dam

age

of H

igh

tem

pera

ture

shift

con

verte

r Ex

cess

ive

heat

gen

erat

ed fr

om a

ir ox

idat

ion

of c

atal

yst

Cat

alys

t was

repl

aced

. Air

valv

e re

paire

d.

279.

20

02

Hot

spot

and

ruby

form

atio

n in

se

cond

ary

refo

rmer

D

ehyd

ratio

n an

d de

posi

tion

of ru

by.

Upp

er p

art o

f cat

alys

t rep

lace

d - a

lum

ina

tiles

repl

aced

w

ith h

exag

onal

bric

ks.

Item

Y

ear

Rep

orte

d In

cide

nt

Roo

t Cau

se

Rem

edy

Act

ion

Take

n

280.

20

02

Expl

osio

n in

air

line

to

seco

ndar

y re

form

er

Con

tam

inat

ion

in p

roce

ss a

ir lin

e du

e to

ba

ckflo

w.

Star

t-up

proc

edur

es m

odifi

ed. T

rip v

alve

repl

aced

with

ba

ll ty

pe.

281.

20

02

Line

r cra

cks i

n a

gas p

hase

are

a of

ure

a re

acto

r C

yclic

ther

mal

stre

sses

. R

elin

ing

done

.

282.

20

02

Cra

cks i

n am

mon

ia c

onve

rter

Hyd

roge

n em

britt

lem

ent,

poor

wel

d re

pair

durin

g fa

bric

atio

n.

Cra

cks r

epai

red.

283.

20

03

Synl

oop

was

te h

eat b

oile

r exi

t lin

e fa

ilure

H

igh

trans

ient

stre

ss a

nd st

rain

. R

epai

rs d

one

on fa

ilure

s.

284.

20

03

Expl

osio

n of

aux

iliar

y bo

iler

Leak

ing

fuel

gas

val

ves.

Rel

iabi

lity

of sa

fety

trip

syst

em im

prov

ed.

285.

20

03

Seco

ndar

y re

form

er W

HB

fa

ilure

Sl

udge

dep

osits

and

cor

rosi

on u

nder

sl

udge

. Ex

chan

ger d

esig

n m

odifi

ed to

allo

w in

term

itten

t bl

owdo

wn.

28

6.

2003

Em

britt

lem

ent i

n ca

st re

form

er

outle

t man

ifold

com

pone

nts

Form

atio

n of

nio

bium

rich

silc

ide

inte

rmet

allic

s. U

ndef

ined

287.

20

03

Lifti

ng o

f inn

er c

up o

f NH

3 st

orag

e ta

nk

Earth

quak

e.

Inne

r cup

was

lifte

d, le

velle

d th

e cu

p.

288.

20

03

Axi

al fl

ow a

ir co

mpr

esso

r fa

ilure

Lo

ose

blad

e in

inne

r rin

g.

Seco

nd ro

w b

lade

s mad

e st

rong

er.

289.

20

04

Stea

m e

xplo

sion

in a

mm

onia

pl

ant

Ove

rfill

ing

of st

eam

dru

m, p

assi

ng v

alve

s in

BFW

line

s. R

epai

rs m

ade

to w

aste

hea

t boi

ler.

290.

20

04

Failu

re o

f Cat

acar

b so

lutio

n pu

mp

Rev

erse

rota

tion

of p

ump,

faile

d ch

eck

valv

es.

Cha

nged

che

ck v

alve

des

ign.

Inst

alle

d re

mot

e op

erat

ed

disc

harg

e va

lves

.

Tab

le –

2 H

isto

ry o

f Am

mon

ia P

lant

Ben

chm

arki

ng S

urve

ys

Surv

ey

No.

N

o.

Yea

rs

Surv

ey P

erio

d N

o.

Plan

ts

Ope

ratin

g Fa

ctor

%

O

pera

ting

Fact

or d

py

Tota

l sp

y

Serv

ice

Fact

or

%

1

2 19

69 -

1970

22

86

.3%

50

.09.

52

2 19

71 -

1972

27

87

.5%

45

.58.

53

4 19

73 -

1976

30

86

.4%

49

.510

.84

5 19

77 -

1981

88

84

.9%

55

.29.

387

.2%

5 4

1982

- 19

85

93

80.8

%

70.1

8.3

89.4

%6

3 19

94 -

1996

82

91

.9%

29

.55.

792

.4%

7 2

1997

- 19

98

95

91.5

%

31.1

6.0

92.7

%8

2 20

00 -

2001

55

89

.6%

37

.85.

791

.5%

Ave

rage

87

.4%

46

.18.

090

.6%

Ope

ratin

g fa

ctor

(On

stre

am fa

ctor

) = U

ptim

e/To

tal t

ime;

Ser

vice

fact

or =

Upt

ime/

Dem

and

time;

O

pera

ting

fact

or, d

ays p

er y

ear,

dpy

= A

ll do

wn

time

days

/No.

of y

ears

(sur

vey

perio

d); s

py =

shut

dow

ns p

er y

ear

Pl

ant S

urve

ys In

tern

atio

nal,

Inc.

(PSI

) was

est

ablis

hed

in 1

996

and

cond

ucte

d Su

rvey

s 6, 7

, and

8. T

hese

wer

e fe

e-ba

sed

mul

ti-cl

ient

ben

chm

arki

ng st

udie

s.