Fatal US incidents prompt numerous safety investigations

Paul Boughton

Following a series of fatal incidents across the country, the US Chemical Safety Board (CSB) has initiated a number of in-depth investigations.

Most recent is the announcement that it has started investigations at the Bayer CropScience plant in Kanawha County, West Virginia, following an explosion in August that left one man dead and another injured.

According to local newspaper “The State Journal”, the explosion occurred in a new tank primarily containing methyl isobutyl ketone, a by-product of methomyl. Methomyl is used in Larvin, a pesticide and the main product in that section of the plant. The tank had been operational for about a week before the explosion. It was in the west carbamoylation center on the west side of the plant.

“It just came out of some extensive maintenance work, but it was all normal work,” company spokesman Tom Dover told the newspaper.

Some equipment had been replaced and upgraded, and the unit had been restarted. The tank typically ran four to seven months a year, so the restart was normal, he said.

“We were not aware of any problems that first week, but that’s the sort of thing that will come out as a result of the investigation,” he said. “It will take days and weeks, not hours, to understand this. Something happened last night in this equipment, and that’s going to be the focus of ongoing investigations.”

The process was one that had been used at the plant for years. As part of an environmental programme, the solvent was burned in the plant’s boiler system, producing steam, which was then used as an alternative fuel. The plant then burned off various gases, as well as natural gas, so the plant did not need to purchase natural gas or have to dispose of waste product.

Bayer purchased the plant in 2002 from Aventis CropSciences.

Meanwhile, on 20 August, the CSB announced that it is proceeding with an investigation of the causes of a recent accident at the Goodyear rubber manufacturing facility in southeast Houston, in which one employee was killed and approximately seven others were injured, including several contract workers who were exposed to hazardous anhydrous ammonia.

CSB investigators have completed two week-long visits to the plant, conducting interviews and gathering other evidence.

The accident occurred on 11 June during a maintenance operation on a heat exchanger, which used pressurised, liquid ammonia to cool chemicals that are later processed to make synthetic rubber. The rubber-making chemicals were pumped through steel tubes inside the heat exchanger, while ammonia flowed through a cylindrical steel shell that surrounded the tubes.

The day prior to the accident, the process was shut down for cleaning. During the shutdown, an isolation valve was closed between the heat exchanger and a pressure-relief device designed to protect the heat exchanger from possible over-pressure. On the morning of the accident, an operator used steam to clean out process piping; the steam also flowed through the heat exchanger tubes. The steam heated the liquid ammonia remaining in the exchanger shell that caused the pressure to build. With the path to the pressure-relief device blocked, the heat exchanger ruptured catastrophically.

An operations supervisor, who was not involved in the maintenance work but was working in the area, was killed by the explosion. Her body, which was covered with explosion debris, was not discovered until several hours after the emergency had been declared over.

"This tragic accident is but the latest example of the destruction that can result from a lack of effective pressure relief systems and practices," said CSB chairman John Bresland, who personally visited the accident site on 12 June. "Companies should be vigilant to ensure that pressure-relief systems are adequate and are properly maintained and operated to continuously protect equipment from over-pressure."

Bresland said the CSB investigation would likely focus on the company's practices for managing, inspecting, and maintaining relief systems; training operators; and accounting for workers during emergencies. A case study report is expected at the end of 2008.

Five days before the Goodyear announcement, on 15 August, the CSB also announced that it is to conduct a full investigation of the storage tank explosion that killed three workers and injured a fourth at the Packaging Corporation of America corrugated cardboard mill in Tomahawk, Wisconsin, on 29 July.

The accident occurred as workers were performing welding to repair a flange fitting on top of an 80-foot-tall storage tank, which contained recycled water and paper fibre. The three workers were standing on a catwalk above the domed, cylindrical tank performing welding when an internal explosion ripped open the tank lid. All three workers died of traumatic injuries, including two who were found on the ground beneath the tank. A fourth, who had been observing the work from a further distance, survived with minor injuries.

Among the issues the investigation will examine is whether anaerobic microbes, which grow in the absence of oxygen and feed on organic matter, produced flammable gas to fuel the explosion.

Large storage tanks at paper mills – especially those that are stagnant, poorly mixed, or have long material retention times – are at an elevated risk for the growth of anaerobic bacteria. Recycled process water, known in the industry as “white water,” contains nutrients that promote growth of the organisms, producing hydrogen or other flammable gases that can be ignited by hot work or other sources of ignition. The cause of the explosion remains to be determined; the CSB plans to conduct microbiological and chemical testing to understand what fuelled the blast.

“The CSB has noted that there have been previous tank explosions at paper mills during hot work and we will be closely examining the tragedy in Wisconsin to determine if there are similarities,” said Bresland.

This investigation is expected to take approximately a year to complete, says the CSB.

Sugar refinery fine

Meanwhile, the US Occupational Safety and Health Administration (OSHA) has issued citations proposing penalties totalling US$8,777,500 against Imperial Sugar and its two affiliates alleging violations at their plants in Port Wentworth and Gramercy.

OSHA initiated the inspections following an explosion and fire on 7 February at the Port Wentworth refinery that claimed the lives of 13 employees and hospitalised 40 others. Three employees still remain hospitalised. The proposed penalties against Imperial Sugar represent the third largest fine in the history of OSHA.

OSHA's inspections of both facilities found that there were large accumulations of combustible sugar dust in workrooms, on electrical motors and on other equipment. The investigation also determined that officials at the company were well aware of these conditions, but they took no action reasonably directed at reducing the obvious hazards.

"I am outraged that this company would show a complete disregard for its employees' safety by knowingly placing them in an extremely dangerous work environment," said OSHA assistant secretary of labour for occupational safety and health Edwin G Foulke Jr. He added, "What is even worse is that a month after the devastating catastrophe in Port Wentworth that claimed the lives of 13 people, this company had done little to ensure abatement of the combustible dust hazards at its other plant. If OSHA investigators had not inspected and posted an imminent danger notice regarding areas at the second plant, the same thing could have happened again."

OSHA proposed US$5,062,000 in penalties for safety violations at the Port Wentworth refinery and US$3,715,500 for safety violations found at the Gramercy refinery. The citations include 108 instances of willful violations related to the combustible dust hazard, including the failure to clean up dust and not using appropriate equipment or safeguards where combustible dust is present. OSHA also has issued ten citations for other willful violations, 100 citations for serious violations and four citations for other-than-serious safety and health violations.

OSHA officials are also involved in an investigation into an explosion at Luling in West Texas. Here a 36-inch natural gas line exploded, sending flames hundreds of feet into the air. Pipeline owner Energy Transfer Company (ETC) said the problem occurred in an isolated, ten-mile long section of the pipeline. Local firefighters said the flames could be seen seven miles away, rising to over 400 feet in height at one point during the incident.

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