Lessons: Operating Procedures

An explosion, caused by sodium metal reacting with water, occurred in a chemical plant in Mohekou Bengbu City Industrial Park. The fire was put off in 1 h.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

A leakage of Carbon disulfide cooling pipe occurred in Ruixing company. 8 killed and 6 injured in the following rescue process.

Proximate causes:
• Inadequate tools, equipment & vehicles (pipe leaking)

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

On Wednesday 23 May 1984, a group of 44 people was assembled in a valve house set into a hillside at the outfall end of the Lune/Wyre Transfer Scheme at Abbeystead. The visitors were attending a presentation to allay anxieties on the effects of the installation on the winter flooding of the lower Wyre Valley.

As part of this presentation, water was to be pumped over the weir regulating the flow of water into the Wyre. Shortly after pumping commenced there was an intense flash, followed immediately by an explosion causing severe damage to the valve house.

Sixteen people were killed; no one escaped without injury from the valve house.

The explosion was caused by the ignition of a mixture of methane and air, which had accumulated in the valve house. The methane had been displaced from a void, which had formed in the end of the Wyresdale Tunnel during a period of 17 days before the explosion when no water was pumped through the system.

No source of ignition for the explosion has been positively identified. Thorough examination and testing of the electrical equipment has not revealed any faults likely to have caused ignition and there is insufficient evidence to confirm any of the other explanations which have been considered. Smoking in the Valve House was not prohibited because the likelihood of a flammable atmosphere arising there had not been envisaged.

KEY ISSUES:
• DESIGN CODES – PLANT
• LEAK / GAS DETECTION
• OPERATING PROCEDURES
• TRAINING

Report: https://www.icheme.org/media/13697/the-abbeystead-explosion.pdf

Image Credit: HSE

At about 16:53 hours on Saturday 1 June 1974 the Nypro (UK) site at Flixborough was severely damaged by a large explosion. Twenty-eight workers were killed and a further 36 suffered injuries. It is recognised that the number of casualties would have been more if the incident had occurred on a weekday, as the main office block was not occupied. Offsite consequences resulted in fifty-three reported injuries. Property in the surrounding area was damaged to a varying degree.

Prior to the explosion, on 27 March 1974, it was discovered that a vertical crack in reactor No.5 was leaking cyclohexane. The plant was subsequently shutdown for an investigation. The investigation that followed identified a serious problem with the reactor and the decision was taken to remove it and install a bypass assembly to connect reactors No.4 and No.6 so that the plant could continue production.

During the late afternoon on 1 June 1974 a 20 inch bypass system ruptured, which may have been caused by a fire on a nearby 8 inch pipe. This resulted in the escape of a large quantity of cyclohexane. The cyclohexane formed a flammable mixture and subsequently found a source of ignition. At about 16:53 hours there was a massive vapour cloud explosion which caused extensive damage and started numerous fires on the site.

Eighteen fatalities occurred in the control room as a result of the windows shattering and the collapse of the roof. No one escaped from the control room. The fires burned for several days and after ten days those that still raged were hampering the rescue work.

KEY ISSUES:
• PLANT MODIFICATION / CHANGE PROCEDURES
• DESIGN CODES – PIPEWORK
• MAINTENANCE PROCEDURES
• PLANT LAYOUT
• CONTROL ROOM DESIGN
• OPERATING PROCEDURES
• INERTING

Report: https://www.icheme.org/media/13689/the-flixborough-disaster-report-of-the-court-of-inquiry_repaired.pdf

Image Credit: Scunthorpe Telegraph (George Schofield)

Shortly after 6pm, on 2 June 2011, an atmospheric storage tank within the amine regeneration unit at the Chevron Pembroke Refinery exploded. A fireball split the tank open and killed four workers: Robert Broome, Julie Jones, Dennis Riley and Andrew Jenkins. The sole survivor, Andrew Phillips, sustained severe burns and suffered life-changing injuries.

The force of the explosion ejected the five-tonne steel tank roof over 55 metres through the air. After narrowly missing a multi-fuel pipe track, the roof crashed onto a pressurised storage sphere containing extremely flammable butane. Good fortune prevented the airborne roof from puncturing the butane storage vessel, which would have led to an uncontrolled release of liquified petroleum gas (LPG).

The explosion was caused by the unintended ignition of a flammable atmosphere within the tank (17T302), during what should have been a routine cleaning operation conducted in preparation for maintenance.

KEY ISSUES:
• OPERATING PROCEDURES
• PERMIT SYSTEM
• CONTROL OF CONTRACTORS
• RISK ASSESSMENT
• COMPETENCE

Image Credit: HSE

A contractor died after entering a confined space at Dow Chemical’s plant in Oyster Creek.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Unidentified

On June 9, 2009, a major natural gas explosion heavily damaged the ConAgra Slim Jim meat processing factory in Garner, North Carolina, just south of Raleigh. Three workers were crushed to death when a large section of the building collapsed. The explosion critically burned four others and sent a total of 71 people to the hospital including three firefighters who were exposed to toxic anhydrous ammonia from the plant’s refrigeration system. Approximately 18,000 pounds of ammonia were released to the environment and 100,000 square feet of the plant were damaged. Due to the severity of the structural collapse, there was the potential for numerous additional deaths or serious injuries.

KEY ISSUES:
• DIRECTLY VENT PURGED GASES TO A SAFE LOCATION OUTDOORS, AWAY FROM PEOPLE AND IGNITION SOURCES.
• USE COMBUSTIBLE GAS DETECTORS TO MONITOR THE GAS CONCENTRATION DURING PURGING OPERATIONS.
• ENSURE PERSONNEL INVOLVED IN GAS PURGING OPERATIONS ARE FULLY TRAINED.

ROOT CAUSES:
1. Purging into equipment vicinity is common practice

Image credit: CSB

An epoxyethane device got exploded and then triggered a fire. The fire spread to three of six chemical tanks nearby. Each tank has a storage capacity of 1000 cubic meters. More than 200 fire fighters arrived at the site to put out the fire.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

The June 13, 2013 catastrophic equipment rupture, explosion, and fire at the Williams Olefins Plant in Geismar, Louisiana, which killed two Williams employees. The incident occurred during nonroutine operational activities that introduced heat to a type of heat exchanger called a ‘reboiler’ which was offline, creating an overpressure event while the vessel was isolated from its pressure relief device. The introduced heat increased the temperature of the liquid propane mixture confined within the reboiler shell, resulting in a dramatic pressure rise within the vessel due to liquid thermal expansion. The reboiler shell catastrophically ruptured, causing a boiling liquid expanding vapor explosion (BLEVE) and fire.

Process safety management program weaknesses at the Williams Geismar facility during the 12 years leading to the incident caused the reboiler to be unprotected from overpressure.

KEY ISSUES:
• OVERPRESSURE PROTECTION
• PROCESS HAZARD ANALYSIS
• MANAGEMENT OF CHANGE
• PRE-STARTUP SAFETY REVIEW
• OPERATING PROCEDURES
• HIERARCHY OF CONTROLS
• PROCESS SAFETY CULTURE

ROOT CAUSES:
1. Williams did not perform the 2001 MOC until after the plant was operating with the valves installed, and the associated PSSR was incomplete. These actions did not comply with facility (and regulatory) safety management system requirements; however, Williams management accepted both of these practices;
2. Car seals are low-level, administrative controls, but they were the favored safeguard in the 2006 PHA recommendation to prevent overpressure events. Williams Geismar did not have a policy requiring the effectiveness of safeguards to be analyzed;
3. Williams Geismar did not follow OSHA PSM regulatory requirements that operations activities have an associated procedure to safely conduct the work. For example, Williams did not create a procedure specifically for switching the propylene fractionator reboilers Such a procedure should have alerted the operations personnel of the overpressure hazard;
4. The Williams PHA policy did not require effective action item resolution and verification, resulting in incorrect action item implementation in the field;
5. The Williams PHA policy did not require PHA teams to effectively evaluate and control risk; and
6. Operations personnel had informal authorization to manipulate field equipment as part of assessing process deviations without first conducting a hazard evaluation and developing a procedure.

Image & AcciMap Credit: CSB

Three killed when feeding additives bnaphthalene sulfonate to a reaction pool at a chemical fertilizer company.

Proximate causes:
• Failure in following procedure (Improper operation)

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

An explosion occurred in a thermal power generation company preparation plant

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Photojournalist

A gas explosion occurred in confined space in coal mine industry

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

4 killed in a gas explosion happened in the coal mine in Enshi city.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

Ethanol vapors leaked from piping caught fire and caused an explosion at the Poet Ethanol Plant in Glenville. Two out of four employees that were in the plant were injured. Significant damage to the facility

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Albert Lea Tribune

A tank containing chlorine exploded at the Olin Chlor Alkali Products plant in Becancour. Workers in nearby buildings were evacuated, but employees at Olin Chlor Alkali were told to remain at the chemical plant.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Sebastien Lacroix

A natural gas pipeline explosion and fire occurred at a gas booster station as a crew worked on a 4-inch gas line. The workers were replacing some gas lines, repairing a ruptured line.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: News Channel 10 Amarillo

On the morning of Sunday 27 June 1982 two explosions occurred at the premises of Staveley Chemicals Limited. The source of the explosions was a pit containing drums of sulphur trioxide and of oleum. The drums of sulphur trioxide had been returned from customers more than 10 years previously and had then been stored in the open. Over the following years minor leaks developed through corrosion, and sulphur trioxide vapour began to escape as a visible fume. In November 1981 the company decided to overcome the problem by surrounding the drums with an absorbent solid. A pit was dug out on some open land within the works site, the drums placed within the pit, then covered over with a proprietary absorbent material and topped with crushed blast furnace slag. No special provision was made for drainage of the pit, nor to prevent ingress of ground water or rain. Drums of oleum were included together with the drums of sulphur trioxide in the pit.

The first explosion occurred at 10:45 hours on June 27th. Two drums were blown out of the site, over a public highway, to fall into open ground outside the works boundary and about 300 metres from the containment pit. Fortunately no injury to persons or damage to property was caused by these events. Further, but less intense explosions continued until the following day. A cloud of white acid mist billowed up from the site.

The Fire Brigade could not use water hoses because of the possibility of causing a violent reaction with any escaping oleum or liquid sulphur trioxide within the containment pit. It was decided that the best immediate course of action would be to put anhydrous sodium sulphate powder into the open pit in order to absorb liquid and suppress fuming. Several bags of this powder were thrown in and by 12:00 hours the mist emission was lessening. However, a second explosion occurred at 12:30 hours with a large release of acid mist but without ejecting any drums. There was a third explosion at about 14.30 hours. Tarpaulins were put over the pit to prevent the ingress of rain. The last explosion was at about 03:00 hours, the following morning. This explosion was minor compared with those on the previous day.

On Monday 28 June, a heavy steel grid was placed over the pit to reduce the risk of further drums being ejected. Temperature measurements were made in the pit, and found to be as high as 90°C in places. Subsequently the drums were all taken out of the pit and put on to open ground nearby. There were 32 sound drums remaining, and 25 corroded and empty or nearly empty.

KEY ISSUES:
• DRUM / CYLINDER HANDLING

Image Credit: YouTube (Hollingwood Lad)

Flammable color powder exploded in at a recreational water park in Taiwan

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: CNN

An explosion and fire was caused by the failure of ammonia synthesis equipment

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

An explosion occurred in a petrochemical company in Xiangtan Jiuhua Industrial Zone. There was huge smoke

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

Gas leakage and explosions happened in the Mao Dongsheng industrial zone. It was reported that the spill affected 56 primary schools students and a teacher, and they were then sent to the hospital.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

Leak from a container of hydrochloric acid when being moved. Firefighters deposited a neutralizing agent on the ground.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Loughborough Echo

Several main roads closed after a tanker carrying potentially hazardous chemicals spilled some of its load.

Proximate causes:
• Improperly prepared equipment
• Inadequate engineering/design
• Improper handling of materials (the chemical had leaked from the tanks which were not properly secured)

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Dave Himelfield

A single-tank car carrying 24,000 gallons of acrylonitrile, derailed and caught on fire. After burning for hours, the fire was extinguished. Thousands evacuated

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Wade Payne / Reuters

An explosion occurred at a chemical plant. Before the explosion, some workers were welding the interior of waste water storage. The blast tore out the upper structure of the storage facility, which subsequently collapsed

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: BBC

At approximately 12:37 on Saturday 10th July 1976 a bursting disc on a chemical reactor ruptured. Maintenance staff heard a whistling sound and a cloud of vapour was seen to issue from a vent on the roof. A dense white cloud, of considerable altitude drifted offsite.
Among the substances in the white cloud was a small deposit of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (‘TCDD’ or ‘dioxin’), a highly toxic material.

The release lasted for some twenty minutes. Over the next few days following the release there was much confusion due to the lack of communication between the company and the authorities in dealing with this type of situation.

The nearby town of Seveso, located 15 miles from Milan, had some 17,000 inhabitants. No human deaths were attributed to TCDD but many individuals fell ill. 26 pregnant women who had been exposed to the release had abortions. Thousands of animals in the contaminated area died and many thousands more were slaughtered to prevent TCDD entering the food chain.

KEY ISSUES:
• OPERATING PROCEDURES
• RELIEF SYSTEMS / VENT SYSTEMS
• CONTROL SYSTEMS
• ALARMS / TRIPS / INTERLOCKS
• REACTION / PRODUCT TESTING
• DESIGN CODES – PLANT
• SECONDARY CONTAINMENT
• EMERGENCY RESPONSE / SPILL CONTROL

Image Credit: ICMESA
Report: https://www.aria.developpement-durable.gouv.fr/fiche_detaillee/5620_en/?lang=en

Explosion as a result of a build-up of toxic fumes with ignition causing a fire ball. The men were killed while working in a confined unit. Damaged buildings

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Ashley Cashfield

A massive explosion occurred in a chemical plant. 130 firefighters came to control the blaze. The explosion occurred after a large-size tank containing liquid hydrogen caught fire

Proximate causes:
• Inadequate tools, equipment & vehicles (leak of a 1000 square meters tank containing petrochemical product)

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Reuters

On July 17, 2007, at about 9 a.m., an explosion and fire occurred at the Barton Solvents Wichita facility in Valley Center, Kansas. Eleven residents and one firefighter received medical treatment. The incident triggered an evacuation of Valley Center (approximately 6,000 residents); destroyed the tank farm; and significantly interrupted Barton’s business. An investigation by the U.S. Chemical Safety and Hazard Investigation Board (CSB) has concluded that the initial explosion occurred inside a vertical above-ground storage tank that was being filled with Varnish Makers’ and Painters’ (VM&P) naphtha. VM&P naphtha is a National Fire Protection Association (NFPA) Class IB flammable liquid that can produce ignitable vapor-air mixtures inside tanks and, because of its low electrical conductivity, can accumulate dangerous levels of static electricity.

KEY ISSUES:
• NONCONDUCTIVE FLAMMABLE LIQUIDS CAN ACCUMULATE STATIC ELECTRICITY DURING TRANSFER & STORAGE.
• STATIC SPARKS CAN READILY IGNITE FLAMMABLE VAPOR-AIR MIXTURES INSIDE STORAGE TANKS.
• MATERIAL SAFETY DATA SHEETS (MSDSS) OFTEN DO NOT ADEQUATELY COMMUNICATE HAZARD DATA AND PRECAUTIONS.

ROOT CAUSES:
1. Stop-start filling, air in the transfer piping, and sediment and water (likely present in the tank) caused a rapid static charge accumulation inside the VM&P naphtha tank.
2. The tank had a liquid level gauging system float with a loose linkage that likely separated and created a spark during filling.
3. The MSDS for the VM&P naphtha involved in this incident did not adequately communicate the explosive hazard.

Image credit: CSB

Explosion at a fertilizer factory from a gas entrapment in a steam boiler. The stairway where the steam boilers were located had collapsed along with the lift instalments. Facility damage

Proximate causes:
• Inadequate work plan
• Inadequate engineering design
• Inadequate assessment of needs and risk

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Unidentified

On July 20, a chlorine cooler at the Baton Rouge plant failed, leaking chlorine into the Genetron 143a refrigerant (G-143a) coolant system. The coolant system itself then failed, releasing chlorine to the atmosphere, which overwhelmed operators located both inside and outside the control room and caused them to leave the area. Seven plant workers were injured. The entire plant was evacuated, and authorities were notified. Because chlorine had been released to the atmosphere, the East Baton Rouge OHSEP initiated its community notification system and issued a shelter-in-place advisory for residents within a 0.5-mile radius. The release lasted approximately 3.5 hours, largely because:
• Operators were forced to evacuate the area before they could diagnose the problem and isolate the source of the leak.
• Chlorine entered the control room and damaged process control equipment.
• Unit emergency shutdown procedures did not completely isolate the chlorine supply.

During the July 20 chlorine release, all units at the Baton Rouge plant were shut down. Chlorine had corroded the process control system, which needed to be replaced. Work at the facility during the days that followed consisted mainly of maintenance, shipping activities, and the return of process equipment to a safe, normal state. On July 29, an operator working in the ton-cylinder area of the plant was preparing empty 1-ton refrigerant cylinders for offsite testing. During this procedure, he removed a plug from a 1-ton cylinder he likely believed to be empty. The cylinder was actually full, and its contents were released. The operator was engulfed in a cloud later determined to be contaminated antimony pentachloride; he died the following day, July 30.

Following the July 20 and 29 incidents at the Baton Rouge facility, the president of the Honeywell Specialty Materials group ordered a review of all facility operations prior to restarting operations. While Honeywell was investigating the two incidents and reviewing overall plant safety systems, plant activities were limited to maintenance and inspection. During the July 20 chlorine release, the plant’s G-22 unit was rapidly shut down using emergency procedures. Some equipment, such as an HF vaporizer, was left in an abnormal shutdown state (i.e., it contained liquid hydrogen fluoride). For the next few weeks, operations personnel started returning equipment to normal conditions. On August 12, operators began using a venturi stick to remove liquid hydrogen fluoride from a vaporizer in the G-22 process. This activity resulted in an HF release on August 13 that injured one employee and exposed one operator.

KEY ISSUES:
• HAZARD ANALYSIS
• NONROUTINE SITUATIONS
• OPERATING PROCEDURES

ROOT CAUSES:
1. The Honeywell Baton Rouge plant management systems did not protect against failures in the chlorine cooler.
2. The consequences of chlorine entering the coolant system were not fully evaluated.

1. Honeywell had no program to identify and address potential hazards in the ton-cylinder area.
2. Honeywell and C&MI have no systematic processes for positively verifying the contents of cylinders rejected by C&MI.
3. The Honeywell systems for segregating and storing 1-ton cylinders did not include procedures for identifying and handling abnormal cylinders.

1. Honeywell had no procedures for identifying and planning for nonroutine job situations.

Image Credit: CSB

Explosion of chlorine cylinder at the Lamingo Water Board Treatment Plant. The explosion happened at 4 a.m. caused an excess chlorine inhalation by the nearby residents.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Channels Television

A leak and explosion occurred in a distillation unit with a 3 million ton annual capacity in China National Petroleum corporation Qin Yang Location. This incident happened after a 9 days inspection and maintenance

Proximate causes:
• Inadequate tools, equipment & vehicles (mechanical failure of a small component caused the leak of oil)

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

A fire and explosion occurred to the storage tanks containing raw material

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

A nitrogen tank exploded and a building collapsed at a chemical plant. Explosion caused a leakage of titanium dioxide and nitrogen, but no high levels of chemicals were detected in the area. Damaged buildings

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Twitter / Kani_West

Two methylbenzene storage tanks exploded

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)

Fire in a chemical factory in Chakeri area of Kanpur, Uttar Pradesh, India. It took more than 5 h for 15 fire fighting vehicles to extinguish the fire. A large portion of the factory and a storehouse adjacent to it were destroyed.

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: Unidentified

Fire broke out at 10:50 pm at the site of a logistics company, operating since 2011 in the Tianjin port sector with a floor area covering 46,000 m². At the time of the accident, the company had been storing on-site several types of hazardous substances: calcium carbide, toluene diisocyanate, ammonium nitrates, potassium and sodium, as well as 700 tonnes of sodium cyanide.

As fire-fighters were attacking the blaze with water, 2 explosions occurred around 11:30 pm. The first had the equivalent force of 3 tonnes of TNT, while the second was more powerful at 21 tonnes. A tremendous plume of smoke formed, followed by a massive fire. The resultant emergency response comprised several thousand fire-fighters, soldiers and police officers.

On 21st August, a full 9 days later, 4 new fire outbreaks occurred adjacent to the sites of the explosions.

Investigation Report (LEARN MORE): ARIA

There was a chlorine release at Pacific Steel recycling plant. The gas came from a cylinder that workers were crushing for scrap metal. Evacuation of 17 buildings inside an industrial park

Proximate causes:
• Lack of knowledge of hazards present
• Inadequate training effort
• Lack of policies/standards/procedures for the task

Source: A web-based collection and analysis of process safety incidents (https://www.sciencedirect.com/science/article/abs/pii/S0950423016302285)
Image Credit: The Spokesman-Review

A short interruption in the supply of cooling water to a separation column downstream of a steam cracker resulted in the need to open relief valves from the column to flare. Subsequent manual choking back of the relief line to flare resulted in the pressure relief valves opening. These valves vibrated excessively, resulting in the failure of the bolted flanges and the release of the propylene-rich column overhead line into the atmosphere. The resultant explosion led to the failure of utility lines to the cracker requiring a crash shutdown. The lack of process steam due to the interruption to the utility supply resulted in the failure of furnace tubes and the release of quench oil. There was subsequently a pool fire from the released quench oil under the cracker, resulting in damage to four of the 10 cracker furnaces.

[ Property Damage $180 Million. Estimated Current Value $187 Million ]

Image credit: Unipetrol