PROCESS SAFETY MANAGEMENT AND RISK HAZARD ANALYSIS. GORDON MCKAY PhD, DSc

Transcription

1 PROCESS SAFETY MANAGEMENT AND RISK HAZARD ANALYSIS BY GORDON MCKAY PhD, DSc 2.1 Analysis of Major Accidents 1

2 2.1 Analysis of Major Accidents PROCESS SAFETY MANAGEMENT WHY PROCESS SAFETY MANAGEMENT INTRODUCTION Both large and small businesses are involved with processes containing hazardous substances. These businesses include manufacturers, contractors, warehouses, distributors, end-users, and waste disposers. As a result of many catastrophes caused by the release of such materials over the past several years, many different interest groups have begun to narrow their focus to the job being done to manage processes involving hazardous materials. These groups include employees, labour, stockholders, the media, neighbours, law makers, and regulators It is imperative that management at all levels in the organisations handling these materials be skilled in understanding and applying certain proven principles to achieve excellence in managing the safety of their operations. ACCIDENTS COST MONEY AND LIVES Industrial Losses (i) Louisville, Kentucky Serious accidents within industry take lives and cost the businesses and other individuals affected close to a billion dollars each year. The following examples of accidents in recent year illustrate the need for improved process safety management, including process hazards reviews (PHRs). A11 dollars are 1994 dollars. Louisville, Kentucky Year: 1965 Chemical Plant Destructive Force: Explosion and Fire - 12 deaths - 61 injuries - $51 million in damages Two standard units and an experimental unit that processed vinyl acetylene exploded. Investigators identified high temperatures that resulted from a mechanical failure in the, vinyl acetylene compressor. The high temperature initiated a chemical decomposition that spread to adjoining units. This tragic event led to major changes in the company programmes to eliminate process related incidents. 2

3 (ii) Flixborough, England Flixborough, England Year: 1974 Caprolactam Manufacturing Plant Destructive Force: Explosion and Fire - 28 deaths - $167 million in damages The failure of a temporary 20 inch dogleg pipe containing two expansion bellows by-passing a reactor caused this explosion. A cloud of cyclohexane vapour was released after an expansion bellows failure; this cloud reached a nearby hydrogen plant - the most likely source of ignition. The installation of the temporary pipe had not been considered a potential hazard, but instead was considered a routine plumbing job. The incident is one of the most highly publicised process safety accidents in history and its consequences led to improved knowledge of WCE (Unconfined Vapour Cloud Explosions). (iii) Seveso, Italy Seveso, Italy Year: 1976 Agricultural Chemical Plant Destructive Force: Release of dioxin - Animals and vegetation ki31ed - Individuals exposed suffered a higher than normal cancer rate High pressure developed in a batch reactor and released high-temperature by-products from the reactor to the atmosphere through the relief valve. The contents included about two kilograms of dioxin. The material caused extensive vegetation destruction, animal deaths, and human skin infections. The Italian government declared a state of emergency, evacuated rural communities in the plant area, and sought international assistance to stabilise the area and to define cleanup techniques. A study covering the ten year period following the dioxin release indicates a higher than norma1 occurrence of leukaemia, lymphoma, and liver cancer in people exposed. 3

4 (iv) Tacao, Venezuela Tacoa, Venezuela Year: 1982 Power Station Destructive Force: Explosion and Fire deaths injuries - $ 70 million in damages A half-filled storage tank containing 20,000 tons of fuel oil exploded and caught fire. A second blast ore the roof off the tank, showered emergency workers with burning oil, and blew up a small hydrogen storage tank nearby. Two additional tanks exploded hours later. Flames leaping hundreds of feed knocked a helicopter out of the sky. Escaping oil polluted the sea. Four million people in nearby Caracas were forced to self-ration their power consumption after the blast. Although the safety equipment at the plant was believed to have been modern and in working condition, local fire brigades stated that they did not have the resources necessary to cope adequately with a fire of this magnitude. (v) Mexico City, Mexico Mexico City Year: 1984 LPG Storage Terminal Destructive Force: Explosions and Fires of LPG deaths - $ 25 million in damages An 8-inch pipeline from a refinery 25 miles away ruptured while filling one of six storage spheres at a terminal. The refinery sensed the loss of pressure but only terminal personnel could stop the flow, and they could not be reached by phone. The release formed a vapour cloud which ignited by a flame. Fire continued for several hours, causing numerous explosions of other storage tanks. The fire water system was destroyed in the initial blast. (vi) Bhopal, India 1984 Bhopal, India Year: 1984 Insecticide Production Plant Destructive Force: Release of Methyl Isocyanate - about 3,000 deaths - over 10,000 people injured; many of these people were blinded An overpressured storage tank containing acutely toxic methyl isocyanate caused a large, sustained release of the chemical. The toxic gas cloud drifted to densely populated areas, resulting in many deaths. Several safety systems installed to prevent such an incident were not functioning at the time of release. 4

5 (vii) Chernobyl, Russia Chernobyl, Russia Year: 1986 Graphite-Moderated Nuclear Power Reactor Destructive Force: Release of Radioactive Fission Products - 31 deaths (reported) - 50,000 people permanently evacuated square miles unfit for habitation As the No. 4 1,000-megawatt nuclear reactor was being shut down, a test was undertaken to determine if residual heat could be used to generate electric power. Several safety systems were bypassed to allow the test to be performed and many control rods and safety rods were withdrawn. The nuclear reaction ran away, and a hydrogen/carbon monoxide/air explosion occurred which released large quantities of radioactive materials. (viii) Pasadena, Texas Pasadena, Texas Year: 1989 Polyethylene Plant Destructive Force: Ethylene and Isobutane Vapour Cloud Explosion and Fire - 23 deaths injuries - $ 744 million in damages During contractor employee cleanout of polyethylene from a settling leg in a continuous polyethylene reactor operating at elevated pressures and temperatures, an error was made in positioning a valve that isolated the reactor from the settling leg. About 85,000 pounds of ethylene and isobutane escaped in less than 2 minutes from the reactor, formed a vapour cloud, and was ignited. After about 10 minutes, two isobutane tanks exploded and fires spread from each of these explosions. 5

6 (viii) Stirlington, Louisana Sterlington, Louisiana Year: 1991 Petrochemical Plant Destructive Force: Fire and Explosion - $ 107 million in damages - 8 fatalities - 30 families temporarily homeless injuries Workers were preparing to check a compressor in the nitroparaffin unit when they noticed a small fire and sounded the plant fire alarm. Approximately 30 seconds later, an explosion occurred which was followed by a series of smaller explosions. The effects of the, initial explosion were reported as far away as eight miles from this 15-acre plant. Additionally, the initial explosion completely destroyed an area of the plant approximately the size of a city block. Subsequent fires were reported to have burned for more than seven hours. Although the incident did not damage the two ammonia units on-site, the entire plant was temporarily shut down for precautionary measures. 6