Fire Leak Final

8/2/2019 Fire Leak Final

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EMEREGNCY HANDLING PROCEDURES FOR

HCU/DHT-IV

MAJOR LEAK/FIRE IN HP REACTION SECTION

BY

D I L I P


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December 10, 1991

North Rhine, Westphalia, Germany

A pipe failure in the T-junctions area of an air cooler in thehigh pressure section of the HCU resulted in a release of HC

and H2, which subsequently ignited.

Reason

-severe corrosion/erosion in pipeline

Result

- A substantial part of unit was destroyed by the

explosion and subsequent fire.

-HCU was shut down for approx. seven months with

loss of nearly $90,000,000

WHY TO BE DISCUSSED?

Reference-The 100 Largest Losses 1972-2001

Large Property Damage Losses in the Hydrocarbon-Chemical Industries.MARSH-Property Risk Consulting


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This may be the result


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This may be the result


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Corrosion

Erosion

Mechanical failure of equipment/instrument/

lines

De chocking of Low Point Drains (LPDs)

Leaks may take place by


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WHY TO BE DISCUSSED?

A leak in the HP system-A serious emergency ,

requires immediate action to prevent harm topersonnel and equipment.

The first moves- Dont panic ,Be decisive and actpromptly.

In case of leak in the HP reaction system, theentire high pressure system will start todepressurise through the leak. These escapinggases can provide fuel for a serious fire.


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Normal Operation Fire/leak

Reactor Heater Fires Watch Stop

Make-up H2 Rate Watch Stop

Oil Feed Rate Watch Stop

System Pressure Watch Depressurize

Recycle Compressor Watch Maximum

Reactor Quench Watch Maximum

F/E Bypass Rate Watch MaximumSeparator CTL Valves Watch Watch

Injection Water Watch Stop

Action items...


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Immediate Actions

1. Depressurize the reactor loop by opening the

emergency depressuring valve.

2. Trip (extinguish) all furnace fires (main

burners and pilots).

3. Maximize quench to the reactor beds.

4. Stop all make-up hydrogen flow to the unit.

5. Maximize feed/effluent exchanger bypassrate.

Call Refinery Fire Dept. to respond to fire


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Immediate Actions

6. Continue recycle gas as long as possible to assist

cooling.

A. If recycle gas compressor is the source of the leak,

trip the machine and close the isolation valves.

Follow the procedure for loss of recycle gascompressor.

7. Close the feed control valves to the 1st,2nd stage

HCR & DHT reactors. Verify the chopper valvestrip closed.

8. Trip the reactor feed pumps -16-PA-CF-101/201A/B/301A/B


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Secondary Actions

9. Manually block in the fuel gas supply (pilot and

main burners),

Open air resister fully of each burners,

Stack damper to be kept full open

10. If possible (depending on the location of the emergency),

preparations should be made to operate one of

the MUG compressors on nitrogen.

11. If safe to do so, start emergency nitrogen to

the discharge of the RGC


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12. Monitor the liquid oil levels in the separators and carefully

control liquid levels to prevent blowing high pressure gasinto the low pressure system. Manually close level valveswhen levels go low.

13. Stop and secure water injection and amine systems.

14. Block in the fuel gas supply (pilot and main burners) to allfurnaces and admit snuffing steam into the fireboxes. (Incase of fire inside firebox)

15. If the leak has not been contained, maintain a nitrogenflow out of the leak to prevent pulling air into the system.

Secondary Actions


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ACCIDENTS IN HCU- CASE STUDIES-1

1-Major Reactor Runaway-Fatality at a U.S. Refining

Company

Background-Incident occurred in a

2ndstage reactor at a HCU

Refinery throughput -140 KBPD.

Reference-CLG seminar on hydro cracker
http://videos/OISD%20WORK%20SHOP.ppt


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Incident Summary

Temperature excursion began with a hot spot

in Bed 4 of a 5-bed reactor.

Hot spot most likely caused by poor flow andmisdistribution (cause unidentified).

Confusion was due to a variety of factors including:

Fluctuating temperature readings

Stopping of make-up flow to second stage

Misleading recycle H2 purity analysis

Absence of audible high temperature alarms after the

first high temperature occurrence


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Penal officers did not depressurize reactor when

temperatures exceeded maximum levels because theywere confused about whether an excursion was actually

occurring.

Penal officers were attempting to verify temperaturesin the reactor by having an person obtain temperaturereadings from the field panels under the reactors

Poor radio communications hampered relaying thesereadings to the control room.

Incident Summary (Contd)


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Even after reactor inlet temperatures were >

800F (4270

C), they did not depressurize. They didbegin to take steps to cool the reactor by increasingquench and reducing the heater outlet temperature.

Temperatures continued to rise out of control

while field person continued to verify fieldinstrumentation at the panel located at the bottomof the reactor

Unit was still not depressured!!Once temperature were in excess of 1400F(7600C), the reactor outlet piping ruptured causing amassive explosion and fire



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The person checking the field panel was killed.

46 Company and contract personnel were injured.

13 injured personnel were taken to the hospital,treated, and released.

Rx 3 4th and 5th bed

0

200

400

600800

1000

1200

1400

1600

7:33

:00

7:33

:40

7:34

:20

7:35

:00

7:35

:40

7:36

:20

7:37

:00

7:37

:40

7:38

:20

7:39

:00

7:39

:40

7:40:20

7:41:00

7:41:40

deg

F

Bed 4

outletBed 5

inletBed 5

outlet

Bed 5

OutletBed 5

outletBed 5

outletRx 3


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Incident Causes and Contributing Factors

Conditions to support and encourage employees to

operate reactors in a safe manner were inadequate.

Human factors were poorly considered in the design andoperation of the reactor temperature monitoring system.

Supervisory management was inadequate.Operational readiness and maintenance was inadequate.

Training and support was inadequate.

Procedures were outdated and incomplete.

Process Hazard Analysis was flawed.


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2.Major Incident InvolvingPiping Failure and Fire at a

HCU.

Unit Overview

2 Stage Hydrocracker Unit

Running at maximum rate (~25KBPD)

Sequence of EventsInvestigation Findings

Lesson Learned


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Sequence of Events

Plant running normally at maximum feed and

ascending reactor profile.

Hydrogen make-up system started to sag.

Only token feed cuts made (1000 bbl and 500 bbl).

Recycle loop starts to sag.

Increased quenching robbed recycle hydrogen.

Reactors start to overheat, temperature waves start.Field team did opening and closing the F/E exchangerB/P


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Sequence of Events (Contd)

Furnace TCV going fully closed off

Reactor temperatures reached as high as 1200F(649C).

A small flange fire found and extinguished with a

steam ring on the reactor bottom.A second small fire was observed under the reactorat the bottom head.

Flame impingement on the quench piping causedthe piping to fail.

A large fire erupted and the unit was subsequentlyshutdown.


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Lessons Learned

The Panel officers should have moved more

aggressively in decreasing feed to stay within theavailable hydrogen make-up.

Operator moves were reactive rather thanproactive,

Once quenching proved ineffective to control bedtemperatures, temperature excursion proceduresshould have been executed.


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Unit Overview

60 KBPD 2-StageHydro cracking Unit

Running atmoderate rate (~45KBPD)

http://videos/OISD%20WORK%20SHOP.ppt


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Sequence of Events

Plant running normally at moderate rates

2:25- H2S monitor alarmed

Vapor release observed

Called Refinery Fire Dept. to respond topotential fire

Sounded local evacuation in plant

Field team used SCBAs and set fire monitor onway out of unit

Plant emergency shutdown activated


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Sequence of Events (Contd)

2:28 - Deflagration of vapor cloud.

2:28 - Called in fire to Refinery Fire Dept.

Plant Protection and First Response Teamvolunteers respond.

2:30 - Refinery Fire Dept. called City Fire Dept. torespond.

~2:43 -Instrumentation lost to unit.


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First-StageLow Pressure

Separator

Second-Stage

Low Pressure

Separator

Power Recovery Turbine

(Was Out of Service at the Time)

To

Distillation

Section

Pressure Drop

Control Valve

Level Controller

Level Controller

- Valve That Failed

Simplified Flow Diagram of Immediate Area


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Isolation Block Valve on Pressure Drop Control ValveFrom Combined First-Stage and Second-StageEffluent Stream (From Low Pressure Separators) tothe Distillation Section Failed

Isolation Block Valve Bonnet


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Second-Stage Air Coolers

Location of Valve That Failed


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Damage at Field Work Center

Most of the crew was located in this building at the time of the

release


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Conduit runs for instrumentation and other electrical

equipment lasted approximately 15 minutes before collapse.


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Lessons Learned

Key items that led to safe shutdown and evacuation of

unit:

Training, Training, Training

Utilization of emergency shutdown devices

Sequential dump system utilized to depressure units

Make-up hydrogen choppers activated

Remote shutdowns of all feed pumps.

Site specific training of ALL personnel working in theunit, which included evacuation training.


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Lessons Learned (Contd)

One key item found is that this units EDS was set up to

fail closed on loss of electrical signal.

This caused the EDV system to close once the conduitrun failed.

Fireproofing needs to be evaluated on all emergencyshutdown devices (EBVs, EDVs, choppers, etc.)

ACCIDENTS IN HCU CASE STUDIES 4


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A 2-inch line carrying hydrogen gas at 3,000 psi failed at aweld, resulting in a high pressure hydrogen fire.

The fire resulted in flame impingement on the calcium

silicate insulation of the skirt for a 100-foot high reactor in aHCU.

The steel skirt for this reactor, which was 10 to 12 feet in

diameter and had a wall thickness of seven inches,subsequently failed.

The falling reactor damaged air coolers and other process

equipment, greatly increasing the size of the loss

April 10, 1989

Richmond, California, United States



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At the time of the loss, the HCU was being shut down

for maintenance and the reactor was in a hydrogen

purge cycle.

Approx. 25 percent of the refinery throughput capacity,including the complete HCU production, was lost for a

period offive months.

Restoration of the hydro cracker itself required nearlytwo years.




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The explosion was caused by the failure of a valve bonnetin a HP section of a 60,000 barrels-per-day HCU

A vapor cloud formed from the release, ignited, and was

followed by a large fire fed by escaping hydrocarbons athigh pressure.

The explosion resulted in the collapse of a large section of

pipe rack and destruction of a large fin fan cooler mounted

above the rack.

March 25, 1999

Richmond, California, United States




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Many pumps were destroyed and a separator was

badly damaged.

Approximately 300 fire-fighters and 33 fire trucksparticipated in the two and a half hour effort to

control the fire.

Foam concentrate consumed totalled 3,200 gallons.

The hydro cracker was out of service for 12 months.




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January 27, 1997

Martinez, California, United States

At 7:41 p.m. an effluent line from a reactor in the HCUfailed , resulting in an explosion and fire.

Observation:Seconds before the explosion, a section of

the pipe was reported as glowing red.

Reason:The line apparently ruptured due to excessively

high temperatures, & the failure to depressurize the unit

upon detection of high temperature.

The hydrocarbons apparently auto-ignited shortly after

the initial release.



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The rupture of the 12-inch effluent line was discovered on

a straight run of pipe, not at a weld.

Analysis of the failed section of pipe, at the point of

failure, indicated that the pipe had expanded in

circumference by approximately 5 inches. This caused a

localized bulge in the pipe prior to rupture

Loss:Approx.$80,000,000



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October 8, 1992

Wilmington, California, United States

An explosion originating in the HCU occurred at 9:43 p.m.in this 75,000 barrels-per-day refinery

The explosion resulted from the rupture of a six-inch

carbon steel 90-degree elbow (outside radius) and releaseof a hydrocarbon/hydrogen mixture to the atmosphere.

The vapour cloud ignited within seconds after the rupture

at an undetermined point in the plant



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This explosion, which damaged nearby buildings &

shattered windows several miles away, was recorded as asonic boom at the California Institute of Technology

in Pasadena, approximately 20 miles from this 350-acre

refinery.

An inspection after the failure found the line at

nearly full design thickness a short distance away from the

failure.




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On these facts, it was concluded that the line failure wasthe result of the thinning of the Schedule 120 carbon steel

elbow due to long term erosion/corrosion.

The fire was finally extinguished at 2:00 a.m. on October11.(Approx.52 hrs.)

Loss: $96,000,000



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