Country: United Kingdom

The International Biosynthetics (IBIS) plant was, at the time of the accident, a wholly owned subsidiary of Shell UK Ltd. and employed some 250 people in the manufacture of fine chemicals.

The release occurred on the phosgene plant at 11:27 hours on 7 December 1991. The batch reaction involved the phosgenation of dimethyl aniline (DMA) in a toluene solution. The process involved the addition of 1 tonne of recycled toluene to the reactor, then as no more recycled toluene was available fresh toluene was to be added. Attempts were made to fill the reactor with 2 tonnes of fresh toluene. The flow indicator showed that the required amount of toluene had been added to the reactor, however a control valve between the pump and the vessel was closed and none of the toluene had been added. A level measurement was available for the vessel but as the process appeared to be proceeding normally this was not checked.

The next stage was to add 20 kg of phosgene to check if any water was present in the reactor. This would have resulted in a temperature rise of the solution. Because there was insufficient toluene in the vessel, the temperature indicator was not in the solution and therefore showed no temperature rise. As there appeared to be no water in the reactor, 0.8 tonnes of phosgene were then added to the vessel. After a shift changeover the next steps in the process were carried out. These were to add 1.6 tonnes of DMA and heat to 65°C. The operating temperature was reached but the temperature continued to rise to well above 100°C. As the pressure increased the pressure control valve, pressure relief valve and bursting disc all operated as designed and relieved the vessel to a scrubbing column. The reaction was more violent than had been predicted and the relief system had insufficient capacity to deal with the pressure rise. This resulted in a connection on the condenser line failing and releasing the contents of the vessel to atmosphere. Fortunately the phosgene had been consumed in the reaction. However, the vapour cloud drifted for 4 km affecting about 60 people and staining some property blue.

KEY ISSUES:
• CONTROL SYSTEMS
• REACTION / PRODUCT TESTING
• RELIEF SYSTEMS / VENT SYSTEMS

Report: https://www.icheme.org/media/13702/release-of-chemicals-from-international-biosynthetics-ltd.pdf

Image Credit: HSE

In the early hours of Sunday 11th December 2005, a number of explosions occurred at Buncefield Oil Storage Depot, Hemel Hempstead, Hertfordshire. At least one of the initial explosions was of massive proportions and there was a large fire, which engulfed a high proportion of the site.

Over 40 people were injured; fortunately there were no fatalities. Significant damage occurred to both commercial and residential properties in the vicinity and a large area around the site was evacuated on emergency service advice. The fire burned for several days, destroying most of the site and emitting large clouds of black smoke into the atmosphere.

KEY ISSUES:
• SYSTEMATIC ASSESSMENT OF SAFETY INTEGRITY LEVEL REQUIREMENTS
• PROTECTING AGAINST LOSS OF PRIMARY CONTAINMENT
• ENGINEERING AGAINST ESCALATION OF LOSS OF PRIMARY CONTAINMENT
• ENGINEERING AGAINST THE LOSS OF SECONDARY AND TERTIARY CONTAINMENT
• OPERATING WITH HIGH RELIABILITY ORGANISATIONS
• DELIVERING HIGH PERFORMANCE THROUGH CULTURE AND LEADERSHIP

HSE Reports:
MIIB Final Report Vol 1: https://www.icheme.org/media/13707/buncefield-miib-final-report-volume-1.pdf
MIIB Final Report Vol 2a: https://www.icheme.org/media/13923/buncefield-miib-final-report-volume-2a.pdf
MIIB Final Report Vol 3a: https://www.icheme.org/media/13923/buncefield-miib-final-report-volume-2a.pdf
Land Use Planning – Recommendations: https://www.icheme.org/media/10694/recommendations-on-land-use-planning.pdf
Land Use Planning – Model: https://www.icheme.org/media/13709/illustrative-model-of-a-risk-based-lup-system_repaired.pdf
Explosion Mechanism: https://www.icheme.org/media/10696/buncefield-explosion-mechanism-advisory-group-report.pdf
BSTG Final Report: https://www.icheme.org/media/10697/safety-and-environmental-standards-for-fuel-storage-sites.pdf
Emergency Preparedness: https://www.icheme.org/media/10698/recommendations-on-emergency-preparedness.pdf
Design & Operation: https://www.icheme.org/media/10699/recommendations-on-the-design-and-operation-of-fuel-storage-sites.pdf
Initial Report: https://www.icheme.org/media/10700/buncefield-initial-report.pdf
Investigation – Progress Report: https://www.icheme.org/media/10705/buncefield-first-progress-report.pdf
Investigation – 2nd Progress Report: https://www.icheme.org/media/10703/buncefield-second-progress-report.pdf
Investigation – 3rd Progress Report: https://www.icheme.org/media/10702/buncefield-third-progress-report.pdf
Why did it happen?: https://www.icheme.org/media/10706/buncefield-report.pdf

Image Credit: Hertfordshire County Council

On 14 December 1984 fire broke out in a furniture repository in Sheffield which formed part of a very large warehouse and transit shed building occupied by the National Freight Consortium plc. In two days the fire destroyed the whole warehouse, with the exception of one protection section. It involved the attendance of several hundred fireman over a total period of six days.

Among the wide variety of goods stored in the building was a relatively small tonnage of chemicals. Concern was expressed during and after the fire about the difficulty experienced by the Fire Brigade in identifying the possible risks from the materials stored, followed by allegations by the Fire Brigades’ Union that firemen had been unnecessarily exposed to harmful fumes without the benefit of breathing apparatus.

The fire also led to expressions of concern about a number of aspects, including the delay in summoning the Fire Brigade and possible exposure of member of the public to harmful fumes and asbestos material evolved in the fire.

Report: https://www.icheme.org/media/13698/the-brightside-lane-warehouse-fire.pdf

Image Credit: HSE

Failure of seabed components caused 210,000 metric tonnes of FSU to break free in bad weather. Three out of four latch plates fractured. About 210,000 bbl-per-day of crude was lost, equating to about 10% of UK production.

[ Property Damage $60 Million. Estimated Current Value $138 Million ]

Image credit: ShipSpotting.com

On 4 January 1977, a serious fire and explosion occurred at the Braehead Container Clearance Depot at Renfrew in Scotland.

The fire and explosion, which originated at a warehouse occupied by James Kelman Transport and Storage, completely wrecked that warehouse and the adjacent whisky bonded warehouse occupied by Clyde Container Services Ltd and also caused widespread window and roof damage to domestic, commercial, industrial and public property within a radius of a mile of the premises. The cost of the damage is estimated at some £6 000 000.

It was fortunate that, despite the extent of the damage, only twelve members of the public and one watchman were treated for shock and minor injuries. After investigation had eliminated one cause of fire after another it was discovered that it had accidently been started by three boys who had lit a fire to warm themselves at a den which they had made, during the New Year holiday, from cardboard cartons stacked beside the warehouse.

Subsequent experimental work tended to suggest that explosions of this nature and severity can be caused by the involvement of commercially pure sodium chlorate under the intense heat conditions of an industrial fire.

Report: https://www.icheme.org/media/13693/the-fire-and-explosion-at-braehead-container-depot-renfrew.pdf

Image Credit: HSE

On 10 January 1985 an explosion destroyed the central section of a three-storey block of luxury flats in South London, killing eight of the residents. Preliminary investigations indicated a gas leak as a probable cause.

It was found that the explosion was caused by gas leaking into the building from a crack in the gas main, a 150mm (6 inch) diameter cast iron pipe buried at the rear of the building, which carried gas at low pressure. The crack was primarily due to loading on the pipe caused by differential settlement. The loading could not be evenly distributed along the pipe, as it was held rigidly near the point of failure by the concrete encasement of a drain, which acted as a fulcrum.

Report: https://www.icheme.org/media/13699/the-putney-explosion.pdf

Image Credit: HSE

Refinery and local fire fighters spent more than six hours battling a fire on a large oil refinery. A warning was issued to local residents because of thick nontoxic smoke generated from a stack on the site. The fire is thought to have broken out in a furnace. No injuries were reported.

[ Property Damage $150 Million. Estimated Current Value $162 Million ]

Image credit: Essar

On 17 January 1981 at approximately 00:07 hours operators on the plant observed an explosion followed by a fire. They immediately evacuated the area. On-site security initiated the on-site emergency procedures and called both the works fire brigade and the local authority fire brigade. Staff in a nearby control room initiated shut down procedures.

On arrival at the site the fire service set up two cooling sprays onto LPG pipelines within the plant. The deployment of additional water sprays was advised to protect unaffected pipelines (carrying kerosene, white spirit, petrol, fuel gas, high pressure steam, low pressure steam and lubricating oil) from the heat of the burning propane.

Residual propane in the plant was permitted to burn off and the severity of the fire gradually diminished. By 07:58 hours the fire was under control. Isolated pockets of oil residues continued to burn for some hours later.

Propane gas, contained in two 20 tonne storage vessels, was consumed by fire, and the area around the vessels was severely damaged.

The incident investigation believed that the release of gas occurred as the result of a damaged seal on a propane recirculating pump. Fire damage of control cables made process isolation difficult.

Fire severely damaged the de-asphalting plant and pipe work, the supporting structures and the feedstock storage tanks

KEY ISSUES:
• INSPECTION / NON-DESTRUCTIVE TESTING (NDT)
• ACTIVE / PASSIVE FIRE PROTECTION

Image Credit: Ben Brooksbank

A series of explosions which occurred at a chemical storage depot at 27 River Road, Barking on 21 January 1980 was probably caused by the rapid thermal decomposition of sodium chlorate in an intense fire.

About 4000 people were temporarily evacuated from nearby housing estates when large quantities of smoke were blown in their direction.

The storage of sodium chlorate in quantities as low as 2-45 tonnes was not considered, prior to this incident, to be potentially dangerous. All previously recorded incidents involved quantities of 20 or more tonnes of the material.

This report emphasises the need for occupiers of similar premises to pay attention to:
– segregating various chemicals into different categories with regard to their relevant properties;
– obtaining advice on fire precautions from authoritative sources;
– preparing adequate emergency procedures in conjunction with the emergency services.

Report: https://www.icheme.org/media/13693/the-fire-and-explosion-at-braehead-container-depot-renfrew.pdf

Image Credit: HSE

The Bermuda registered LPG tanker Havkong, berthed at the Braefoot Bay Marine Terminal in the River Forth in fine weather on 23 January 1993. The ship moored alongside, in compliance with the terminal’s Jetty Regulations, including those related to moorings. However the winch and fairlead positions aboard Havkong were such that, despite deploying lines in excess of those required, the final mooring pattern geometry resulted in only two lines contributing restraint against westerly winds.

At 18:50 hours, when Havkong had loaded approximately 6000 tonnes of a nominated 15 000 tonne cargo of butane, the Braefoot Bay area was subjected to an unusually violent squall. This squall produced a veering westerly wind with gusts in the order of 80 knots (92 mph) superimposed on a mean wind speed that reached 62 knots. The resulting additional loading on the mooring system was resisted only by the forward backsprings. The winch brakes for these were overcome and the ship began to move ahead along the berth driven by the wind. As she gathered momentum the loading arms reached their envelope limits and successfully disconnected with no spillage of cargo. The remainder of the mooring lines failed one by one as the load came upon them sequentially.

Havkong began to swing under the influence of both the wind and the last of the moorings and drifted eastwards, broadside to the wind. She cleared a ship on the other berth, which was loading ethylene, by approximately 20 metres. About eight minutes after breaking away her engine was ready for use and this was used to keep the ship in the deep-water channel as she drifted downwind while the anchors were prepared. She was eventually brought to anchor approximately one mile east of the berth. A pilot boarded her to assist and tugs arrived. With tug assistance the ship was manoeuvred out into the main channel and then to a designated anchorage. The incident was declared over at 22:55 hours when Havkong anchored in Kirkcaldy Bay.

The available evidence leads to a conclusion that Havkong grounded lightly, probably on two occasions, during the incident. However, no damage was done to the hull and her cargo containment remained intact. There were no injuries on board and no spillage of cargo. Damage to the ship was limited to some deformed rails near the manifold and minor damage to one manifold line. As a result of the ship’s movement there was minor damage to the access gantry, loading arms and navigation light on the jetty.

The inadequacies in Shell Expro’s system for dealing with high wind speeds did not in themselves contribute to the incident. However, they led to the highly unsatisfactory situation that when the Havkong broke free from its moorings, terminal staff were caught by surprise with the ship still loading normally, despite wind speeds above the limits specified for stopping loading and disconnecting.

KEY ISSUES:
• EMERGENCY RESPONSE / SPILL CONTROL
• CONTROL ROOM DESIGN
• OPERATING PROCEDURES
• DESIGN CODES – JETTIES

Image Credit: ShipSpotting.com

At about 8.23 pm on 1 February 1994 there was a release of reactor solution from a recirculating pump near the base of a 25 tonne ethyl chloride (EC) reactor vessel at the factory of The Associated Octel Company Ltd, Ellesmere Port, Cheshire. The reactor solution was highly flammable, corrosive and toxic, mainly consisting of ethyl chloride, a liquefied flammable gas, mixed with hydrogen chloride a toxic and corrosive gas, and small quantities of solid catalyst, aluminium chloride. A dense, white cloud soon enveloped the plant and began to move off-site.

The on-site and external emergency services were called in accordance with pre-arranged procedures for major incidents involving chemical release. Over the next one and a half hours action was taken to isolate the leak, to suppress the further release of vapour and to prevent the cloud spreading.

In spite of these attempts a pool of liquid continued to collect and at 10.08 pm the flammable vapours of ethyl chloride ignited, causing a major pool fire which was most intense at the base of the reactor. As the incident developed there were also fires at flanges damaged in the fire, including jet flames at the top of two large process vessels on the plant. Although these vessels and the reactor were protected by a fire resistant coating, there was concern at one stage that the vessels might explode and the damage extend to chlorine storage vessels on the adjacent plant.

The leak occurred at a point between fixed pipework and the discharge port of a pump recirculating liquids to the reactor, as a direct consequence of either (a) the failure of a corroded securing flange on the pump working loose; or (b) the failure of a PTFE flexible connection (‘bellows’) connecting the pump discharge to the pipe. The HSE believes the first of these possible causes was the more likely. The most likely source of ignition was an electrical control box to a compressor nearby.

KEY ISSUES:
• CORROSION / SELECTION OF MATERIALS
• DESIGN CODES – PIPEWORK
• MAINTENANCE PROCEDURES
• ISOLATION

Report: https://www.icheme.org/media/13705/the-chemical-release-and-fire-at-the-associated-octel-company-limited.pdf

Image Credit: HSE

Heavy storm conditions in the North Sea caused four of this floating production, storage, and offloading’s (FPSO) 10 anchor chains to break resulting in the vessel moving off its position. It is estimated that the FPSO was subject to 53-knot winds and nine meter waves. Normally, a complex piping system runs from the wells on the seabed up to the FPSO, however, this infrastructure was damaged in the incident. Following the vessel moving off its position, all of the wells were immediately shut in. Subsequent surveys showed that no oil had been lost. The 74 non-essential crew were evacuated to near-by platforms and 43 essential crew members remained onboard. Two members of crew received minor injuries. The facility was projected to be producing an average of 18,400 bbl-per-day of oil prior to the loss.

[ Property Damage $450 Million. Estimated Current Value $497 Million ]

Image credit: Maersk

On the 11 February 1980 a fire and a series of explosions occurred at a warehouse in a factory at Trubshaw Cross, Longport, Stoke-on-Trent. On the morning of the fire the warehouse contained some 49 tonnes of liquefied petroleum gas (LPG) in cartridges and aerosol containers as well as about 1 tonne of petroleum mixtures in small containers, raw materials, and packaging materials. It is almost certain that the source of ignition was the electrical system of a battery operated fork lift truck.

LPG is a well known fire and explosion hazard; the circumstances of the fire emphasise the need for occupiers of premises containing LPG to be adequately informed, by obtaining information and advice from authoritative sources, on the hazards of LPG and the precautions to be observed in its storage.

Report: https://www.icheme.org/media/13695/the-fire-and-explosions-at-permaflex-trubshaw-cross-stoke.pdf

Image Credit: Stoke Sentinel

At approximately 10:00 hours workers on site noticed the electrical lights flickering and saw smoke coming from the warehouse. On opening the warehouse door to investigate, a wall of thick smoke confronted an employee. Shutting the door he raised the alarm and called the fire brigade. The warehouse was used for storing large quantities of ICI herbicides in plastic bottles and drums with plastic liners and octyl phenol in paper sacks.

The fire brigade responded promptly and was automatically issued with TREM cards (Transport Emergency Cards) relating to the herbicides and Octyl Phenol. However, by this time the fire had become established and had broken through the roof of the warehouse. The intensity and speed at which the fire developed surprised the fire fighters, as they believed the warehouse contents to be largely incombustible.

Some of the drums/bottles had burst in the fire and their contents were washed down the road and into Hey Beck, a small stream that drains from the site. This resulted in a major pollution incident. Because of the large volumes involved the decision was taken to allow the material to continue to flow into the drains, washed down by the fire brigade. This washing down activity continued for over two days after the incident. The diluted herbicides turned the stream into a brown foaming torrent for several miles. The River Calder was affected by this pollution. The fire fighters were faced with additional problems because of the physical properties of octyl phenol. This substance floats on water producing a flowing pool of burning liquid.

The seriousness of the pollution prompted action to be taken to contact police, the water authority, local radio stations and the press to warn the general public of the dangers of coming into contact with the contaminated water. Farmers were warned to keep livestock away from riverbanks.

The exact cause of this accident is unknown. A worker had been shrink-wrapping paper sacks of octyl phenol onto wooden pallets using a plastic film and a hand held cylinder heat gun, shortly before the incident occurred. It is feasible that the flame from the gun passing too close overheated one of the pallets, causing one or more bags, or the pallet to smoulder, eventually bursting in flames.

KEY ISSUES:
• EMERGENCY RESPONSE / SPILL CONTROL
• REACTION / PRODUCT TESTING

Image Credit: West Yorkshire Fire & Rescue Service

Fifteen months before the incident occurred it had been noticed that the flare line isolation valve V17 was passing. It was decided however to wait for a scheduled shutdown of the catalytic cracker unit and No 1 flare before commencing work on the valve. Gases from the remaining operating units were re-routed to No 2 and No 3 flares. This flare arrangement would allow the pipelines at V17 to be isolated.

When senior refinery staff prepared a plan for the isolation of the flare system, they concentrated on the operational and safety requirements of the flare system, making sure that no operational areas of the plant were inadvertently isolated. The details of the removal of V17 were not considered and left to those who would be responsible for the work.

Four workers were involved with the removal of the valve. When the majority of the bolts were undone the joint opened slightly and liquid dripped from a small gap between the flanges. The workers sought advice. The valve was checked and it was concluded that it was safe to carry on. Non ferrous hammers were provided before continuing with the removal. All the bolts were removed and the crane took the weight of a spacer and started to remove it, at which point gallons of liquid poured from the valve. A flammable vapour cloud formed from the rapidly spreading pool. The cloud reached the nearby air compressor, ignited and flashed back around the working area.

Two workers managed to escape the fire but a fitter and a rigger were engulfed by the flames and killed. The fire was allowed to burn in a controlled manner for almost two days while the rest of the refinery was shut down and the flare system purged with nitrogen

KEY ISSUES:
• DESIGN CODES – PIPEWORK
• MAINTENANCE PROCEDURES
• ISOLATION

Report: https://www.icheme.org/media/13700/the-fires-and-explosion-at-bp-oil-grangemouth-refinery-ltd.pdf

Image Credit: HSE

On 20 March 1990 the halogen exchange reactor on the Fluoroaromatics plant was ruptured by the pressure generated by a runaway reaction. The plant was partially destroyed and missiles were projected over 500m. Six employees were injured and one subsequently died from post-operative complications.

A batch had been charged into the vessel and was being heated up as normal. When it reached 165oC, the temperature continued to rise and the operators adjusted the jacket temperature. The display screen in use did not display pressure and they were unaware of a corresponding rise in pressure. By the time they were alerted to the rise in pressure the pressure relief valves had lifted. Before any other corrective action could be taken, the reactor exploded. The pressure in the vessel reached a value of about 60-80 barg compared with the relief valve set pressure of 5 barg.

The resulting blast was enhanced by the formation of a fireball, which occurred when the contents of the reactor ignited within the plant structure. This started local fires and initiated what became a major conflagration in an adjacent unit where vessels containing xylene were damaged by the blast/missile effects. The ensuing fires were brought under control in four hours by the Shell fire team and Cheshire fire service.

The initial cause of the incident was the ingress of excessive water into the process leading to the formation of acetic acid which, upon recycle to the reactor, reacted vigorously with the reactor contents initiating the explosion. Water was present as a part of the process, however a massive incursion led to the formation of a separate layer in the process vessel which was not removed but recycled back into reactor.

KEY ISSUES:
• CONTROL ROOM DESIGN
• RAW MATERIALS CONTROL / SAMPLING
• REACTION / PRODUCT TESTING
• RELIEF SYSTEMS / VENT SYSTEMS

Image Credit: The Leader

On Saturday 21 March 1987 the hydrocracker unit was being recommissioned following a routine shut down. During the recommissioning a plant trip occurred. This was thought to be a spurious trip and the plant operators started to bring up the unit to normal operating conditions. From then on until the time of the incident the plant was held in stand by condition with no fresh feed.

At 07:00 hours the following morning there was a violent explosion and subsequent fire. The explosion could be heard and felt up to 30km away. The explosion centred on a low pressure (LP) separator vessel, V306, which was fabricated from 18mm steel plate and weighed 20 tonnes.

The investigation of the accident suggested that an air operated control valve on the high pressure (HP) separator had been opened and closed on manual control at least three times. Liquid level in the LP separator fell and the valve was opened. This action allowed the remaining liquid in the HP separator to drain away and for high pressure gas to break through into the LP separator. As the pressure relief on the LP separator had been designed for a fire relief case, not gas breakthrough the vessel subsequently exploded.

The control valve did not close automatically because the low low level trip on the HP separator had been disconnected several years earlier. The operators did not trust the main level control reading and referred to a chart recorder for a back up level reading. There was an offset on this chart recorder which led them to assume that the level in the HP separator was normal.

KEY ISSUES:
• MAINTENANCE PROCEDURES
• CONTROL SYSTEMS
• OPERATING PROCEDURES
• PLANT MODIFICATION / CHANGE PROCEDURES
• ALARM / TRIPS / INTERLOCKS
• RELIEF SYSTEMS / VENT SYSTEMS
• ISOLATION

Report: https://www.icheme.org/media/13700/the-fires-and-explosion-at-bp-oil-grangemouth-refinery-ltd.pdf

Image Credit: HSE

At 09.45 on 22 March 1989 a vehicle carrying approximately 800 kg of mixed explosives exploded at the premises of Vibroplant Ltd on the Fengate Industrial Estate, Peterborough. The explosion caused the death of a fireman and injuries to at least 107 other people, 84 of whom received hospital treatment. Two of the injured were admitted to intensive care.

The vehicle was a standard commercial model specially modified to carry explosives, operated by Nobels Explosives Company (NEC), a subsidiary of ICI. It had entered the Vibroplant yard, in order to turn round off the road, when a minor explosion occurred inside the load compartment, causing a fire. The fire brigade was called and took up position. The fire increased and after approximately 12 minutes the entire load, apart from a small number of detonators, detonated en masse.

The vehicle did not carry any external placarding to tell emergency services that it contained explosives, but this did not contravene the legislation in force at the time. The fire brigade was told that the vehicle was carrying commercial explosives before firemen arrived on the scene.

Report: https://www.icheme.org/media/13701/the-peterborough-explosion.pdf

Image Credit: HSE