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Wednesday, 23 February 2011 00:43

Case Studies in Technological Change

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Changes in plant technologies production pressures and the need for continually training workers are essential to the safe and healthful environment. The following three examples occurred in the United States. Technological change affects all workers around the world.

Production versus Safety

Production pressures can severely compromise safety and health unless management is careful to analyse the potential consequences of decisions designed to increase productivity. One example comes from a 1994 accident in a small steel plant in the United States.

At about 4:00 a.m. several workers were preparing to tap molten steel from an electric arc furnace. The steel market was good and the enterprise was selling all the steel it could produce. Workers were on heavy overtime schedules and the plant was working at full capacity. The furnace had been scheduled for a shutdown in order to replace its refractory lining, which had worn dangerously thin. Hot spots had already developed in the furnace shell, but the company wanted a couple of final batches of steel.

As the tap began, the lining of the vessel burned through. Steel and slag poured from the break and quickly melted through a water line supplying the cooling system for the furnace. The water exploded into steam with tremendous force. Two workers were in the path. Both were severely burned. One of them died three days later.

One obvious cause of the accident was operating the furnace beyond the safe life of its refractory lining. In addition, electric furnaces are generally designed to keep the main cooling water lines above the height of the molten steel and slag at all times, in order to prevent exactly this kind of accident. However, this furnace had been modified in the recent past to increase its capacity by raising the level of the molten material, and the engineers overlooked the water line. A simple breakout of molten metal and slag would have been serious, but without the water line it would not have caused a steam explosion, and the injuries would not have been as severe. Both factors resulted from the demand for productivity without sufficient concern for safety.

Training

Worker training should include more than a set of specific safety rules. The best safety training conveys a comprehensive understanding of the process, equipment and potential hazards. It is important that workers understand the reason for each safety rule and can respond to unforeseen situations not covered by the rules.

The importance of comprehensive training is illustrated by a 1986 accident in a North American steel plant. Two workers entered a furnace vessel in order to remove scaffolding that had been used to reline the vessel with new refractory brick. The workers followed a detailed “job safety analysis”, which outlined each step in the operation. However, the job safety analysis was defective. The vessel had been refitted two years previously with a system for blowing argon gas through the molten metal, in order to stir it more effectively, and the job safety analysis had never been updated to account for the new argon system.

Another work crew reconnected the argon system shortly before the two workers entered the vessel. The valves were leaking, and the lines had not been blanked out. The atmospheric test required for confined space entry was not properly done and the workers who entered the vessel were not present to observe the test.

Both workers died from oxygen deficiency. A third worker entered the vessel in a rescue effort, but was himself overcome. His life was saved by a fourth worker, who cut the end from a compressed air hose and threw the hose in the vessel, thus providing oxygen to the unconscious victim.

One obvious cause of the accident was the failure of the enterprise to update the job safety analysis. However, comprehensive training in the process, equipment and hazards might have enabled the workers to identify the deficiencies in the job analysis and take steps to ensure that they could enter the vessel safely.

Technological Change

The importance of analysing new or changed technology is illustrated by a 1978 accident in a North American chemical plant. The enterprise was reacting toluene and other organic chemicals in a closed vessel. The reaction was driven by heat, which was supplied to the vessel through a heating coil with circulating hot water. The plant engineering department decided to replace the water with molten sodium nitrate, in order to speed the reaction. However, the coil had been repaired with braising compounds which melted at a temperature lower than the temperature of the sodium nitrate. As a result, sodium nitrate began to leak into the vessel, where it reacted with the organic compounds to form unstable organic nitrates.

The subsequent explosion injured several workers, destroyed the reactor vessel, and damaged the building. However, the consequences could have been much worse. The accident happened late at night, when no workers were near the vessel. In addition, hot shrapnel entered a nearby process unit containing large amounts of diethyl ether. Fortunately, none of those vessels or lines were hit. An explosion on the day shift, or one which released a vapour cloud of diethyl ether, could have caused multiple deaths.

 

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Contents

Preface
Part I. The Body
Part II. Health Care
Part III. Management & Policy
Part IV. Tools and Approaches
Part V. Psychosocial and Organizational Factors
Part VI. General Hazards
Part VII. The Environment
Part VIII. Accidents and Safety Management
Part IX. Chemicals
Part X. Industries Based on Biological Resources
Part XI. Industries Based on Natural Resources
Part XII. Chemical Industries
Part XIII. Manufacturing Industries
Part XIV. Textile and Apparel Industries
Part XV. Transport Industries
Part XVI. Construction
Part XVII. Services and Trade
Part XVIII. Guides