View
13
Download
1
Category
Preview:
Citation preview
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.
Recommended