 A view of the Longford plant | |
  Longford  Melbourne Location of Longford in the state of Victoria, around 216 km (134 mi) east of Melbourne | |
| Date | 25 September 1998 (1998-09-25) |
|---|---|
| Time | 12:26 pm (AEST) |
| Duration | 20 days until normal gas supply resumed |
| Venue | Esso Australia Resources Ltd. Longford Gas Plant 1 (GP1) |
| Location | Longford,Victoria,Australia |
| Coordinates | 38°13′26″S147°10′01″E / 38.224°S 147.167°E /-38.224; 147.167 |
| Type | Jet fire andconflagration |
| Cause | Low temperature embrittlement andthermal stress of aheat exchanger |
| Outcome | - Fires lasting more than two days - Gas supplies to Victoria resumed on 14 October 1998 |
| Deaths | 2 |
| Non-fatal injuries | 8 |
| Property damage | US$443 million (US$987 million in 2021) |
| Inquiries | Byroyal commission, 12 November 1998 – 15 April 1999 |
| Coroner | Graeme Johnstone |
On 25 September 1998 a catastrophic accident occurred at theEssonatural gas plant inLongford,Victoria,Australia.[1] A pressure vessel ruptured resulting in a seriousjet fire, which escalated to aconflagration extending to a large part of the plant. Fires lasted two days before they were finally extinguished.
Two workers were killed and eight others injured.[1]Natural gas supply to the state of Victoria was severely disrupted and were not fully restored until 14 October.[2] Total estimated property costs amounted to US$443 million (US$987 million in 2021),[3] while financial losses to the companies affected by the gas shortage were estimated at aroundA$1.3 billion.[4]
The Victorian state government established the Longford Royal Commission to publicly investigate the causes of the accident.
In 1998, the Longford gas plant was owned by a joint partnership betweenEsso andBHP. Esso was responsible for the operation of the plant. Esso was a wholly owned subsidiary of US-based company Exxon, which has since merged withMobil, becomingExxonMobil.[5]
Built in 1969, the plant at Longford is the onshore receiving point for raw natural gas output from the Marlin, Barracouta and Snapper fields in theBass Strait, as well ascrude oil from further offshoreoil platforms. The plant complex consisted of threegas processing plants (Gas Plants 1, 2 and 3 or GP1, GP2 and GP3) and onecrude oil stabilisation plant (CSP).[6] It was the primary provider of natural gas to Victoria and provided some supply toNew South Wales.
The gas feed from the Bass Strait consisted of liquid and gaseous raw natural gas, containingmethane,ethane,propane andbutane, together with water vapours andhydrogen sulfide (H2S). In order to produce natural gas of commercial specifications, it was necessary to separate nearly all non-methane content. Water and hydrogen sulfide were first removed from the gas. The resulting stream still contained both liquidcondensate and gaseous components.[7]
Gas Plant 1 was a lean-oilabsorption plant separating methane fromliquefied petroleum gas (LPG) bystripping the gas using a liquid hydrocarbon stream called "lean oil" (a light oil similar toaviation kerosene).[7] This occurred in two absorbers (working in a parallel configuration), large verticalpressure vessels in which chilled raw natural gas rose up from the bottom, on its way up shed heavier components (ethane, propane and butane) against the falling stream of lean oil and finally left the vessel at the top as methane. Lean oil, on the other hand, absorbed heavy gas components on its way down and thereby left the absorber having become "rich oil". Most of the heavier gas components left at the bottom of the absorbers in the form of LPG.[8]
Coupled with the absorbers was a system ofcolumns,pumps andheat exchangers used to regenerate the lean oil from the rich oil stream by separating from it heavier gas components the oil had stripped from the natural gas in the absorbers.[9][10]
Gas Plants 2 and 3, which were built in 1976 and 1983 respectively, used cryogenic technology, rather than absorption, to produce commercial-grade natural gas.[7] At the time of the accident, Longford was able to process in excess of 530 MMscfd of sales gas, 37,700 barrels per day of LPG, and 188,500 barrels per day of crude oil.[11]
There were several precursors to the breach of containment that escalated to the fire. Post-event analysis was difficult due to the complex interconnections and interactions between different plant streams. This complexity was probably also a factor that made the diagnosis of the plant upset very challenging for the operators and may have contributed to causing the accident.[12]
During the morning of Friday 25 September 1998,[a] a pump supplying heated lean oil toshell-and-tube heat exchanger GP905 in Gas Plant 1 tripped. This was likely due to high level of liquid in one of the process drums, which in turn was caused by excess liquid overflowing from the demethaniser column.[14] This chain of events was probably initiated by an increase in flow from the Marlin gas field.[14]
A heat exchanger is a vessel that allows thetransfer of heat from a hot stream to a cold one. It does not operate at a singletemperature, but experiences a range of temperatures throughout the vessel. Temperatures through GP905 normally ranged from 60 to 230 °C (140 to 446 °F). Due to the stoppage in the flow of the heating medium and the continued inflow of cold process fluid on the shell side of the exchanger, parts of GP905 experienced temperatures as low as −48 °C (−54 °F). Ice from condensed atmospheric humidity formed on the unit shell. The same occurred elsewhere in the plant (for example on heat exchanger GP922), where cryogenic fluid was present which, under normal circumstances, would have been hot. A decision was taken to shut down the entire Gas Plant 1.[15]
Once the faulty pump was restarted, hot lean oil was pumped into the heat exchanger at 230 °C (446 °F). At 12:26 pm the steel of the exchanger outer shell,embrittled due to exposure to temperatures far below its safe design envelope, gave way due tothermal stress.
About 10 tonnes of hydrocarbon were immediately vented from the rupture andflashed.[16] A vapour cloud formed and drifted downwind. It ignited 60–90 seconds later,[17] when it reached a set offired heaters 170 m (560 ft) away. This caused adeflagration which quickly burnt its way back to the leak source. When the flame front reached the rupture in the heat exchanger, a fierce jet fire developed. There was however noblast wave and the nearbycontrol room was undamaged.[16][18][b] The plant supervisor and a maintenance supervisor were killed in the initial fire.[17]
The jet fire burnt beneath a criticalpipe rack section colloquially known to the operators as "King's Cross". In a case ofdomino effect accident, over a 30-minute period from 13:00 to 13:32, impinging flames led to three other releases of large flammable inventories. A full-blown plantconflagration ensued.[17][21]
Complete isolation of the pipes feeding the fire required nearly two and a half days, as a result of the interconnections between the three gas plants.[21] Consequently, it was not possible to extinguish the fire until 17:30 on 27 September.[1] ManyCountry Fire Authority brigades were involved in fire-fighting operations.[22] Gas production, however, had been shut down immediately, and the state of Victoria was left without its primary gas supplier. Within days,VENCorp shut down the state's entire gas supply. The resulting gas supply shortage was devastating to Victoria's economy, crippling industry and the commercial sector. 1.4 million households and 89,000 businesses were affected.[1] Thehospitality industry, which relied on natural gas for cooking, was heavily damaged. Loss to industry during the crisis was estimated at aroundA$1.3 billion.[4] As natural gas was also widely used in houses in Victoria for cooking, water heating and home heating, many Victorians endured 20 days without these facilities.
Gas supplies to Victoria resumed on 14 October. Many Victorians were outraged and upset to discover only minor compensation on their next gas bill, with the average compensation figure being only around $10.
Aroyal commission was called on 12 October 1998,[1] headed by formerHigh Court judgeDaryl Dawson. This was the first time a royal commission was called for an industrial accident in the state of Victoria since thecollapse of the West Gate Bridge in Melbourne in 1970.[23] The Longford Royal Commission sat for 53 days, commencing with a preliminary hearing on 12 November 1998 and concluding with a closing address by Counsel Assisting the Royal Commission on 15 April 1999.[24]
Esso blamed the accident on plant operators negligence, even producing the training records of one particular operator in an attempt to show he should have known how to manage the plant upset.[25] The findings of the Longford Royal Commission, however, focused on Esso's safety practices rather than on actions by individual operators:
The causes of the accident on 25 September 1998 amounted to a failure to provide and maintain so far as practicable a working environment that was safe and without risks to health. This constituted a breach or breaches of section 21 of the [Victorian] Occupational Health and Safety Act 1985.[26]
The Longford Royal Commission's findings became key lessons learned in the domain ofprocess safety.[27][28] Andrew Hopkins, who was an expert witness at the royal commission,[29] based his 2000 book onLessons from Longford on the results of the commission.[30][25] Points of interest and lessons learned from Longford include aspects such as:
Certain managerial shortcomings were also identified:
It has been argued that Esso's safety culture was too focused onlost-time incidents of an eminentlyoccupational safety nature and was less concerned about safe plant maintenance and operations, an attitude that may ultimately have led to the major fire.[40] The relocation of key engineers to the Melbourne office without a proper risk assessment has been indicated as a failure to carry out proper organizationalmanagement of change, a fundamental element ofprocess safety management.[41][32] Another aspect that may have warranted a formal change management process was the increase in heavy gas components in the feed from the offshore gas fields. While it is normal for fields like those feeding the Longford gas plants to yield heavier gas in later lifecycle phases, the creeping change should have been nonetheless assessed, and procedural or design provisions put in place accordingly. Instead, plant operators were obliged to manage the increase in condensate liquids reactively and working with what facilities they already had available.[42][32] Other elements of process safety management that failed at Longford include leadership and culture, process safety information, hazard identification and risk analysis, operating procedures, training,incident investigation, and emergency preparedness, despite Esso "Operations Integrity Management System" nominally meeting process safety management requirements.[43][44]
Esso was taken to theSupreme Court of Victoria by theVictorian WorkCover Authority. The jury found the company guilty of eleven breaches of the Occupational Health and Safety Act 1985, and JusticePhilip Cummins imposed a record fine of A$2 million in July 2001.[45][46][47]
In addition, aclass action was taken on behalf of businesses, industries and domestic users who were financially affected by the gas crisis. The class action went to trial in the Supreme Court on 4 September 2002, and was eventually settled in December 2004 when Esso was ordered to pay A$32 million to businesses which suffered property damage as a result of the incident.[48]
Following the Longford accident, Victoria introduced theMajor Hazard Facilities Regulations to regulate safety at plants that present major process hazards (revoked in 2007).[49] The regulations imposed a non-prescriptive regime on facility operators, requiring them to demonstrate control of major hazards via the use of asafety management system and asafety case. As a result, about fifty major-hazard facilities had to develop and submit a safety case by 30 June 2002 to the regulator WorkSafe, a division of the Victorian Workcover Authority.[50] Other Australian states have also implemented similar regulatory regimes.[51]
