The CSB (Chemical Safety Board) recently released its investigation report into three accidents that occurred over a 33-hour period in January 2010 at the DuPont Corporation‘s Belle, West Virginia, chemical facility.
The final incident involved a deadly release of the World-War One era chemical weapon - phosgene gas.
The incident is noteworthy because it contains lessons for any individual or organization with process hazards that could result in Major Accident Events (MAEs). So please read on...
When releasing the report, CSB Chairperson Rafael Moure-Eraso said, "our final report shows in detail how a series of preventable safety shortcomings - including failure to maintain the mechanical integrity of a critical phosgene hose - led to the accidents. That this happened at a company with DuPont‘s reputation for safety should indicate the need for every chemical plant to redouble their efforts to analyze potential hazards and take steps to prevent tragedy".
The accidents began when an alarm sounded leading operators to discover that 2,000 pounds of methyl chloride, a toxic and extremely flammable gas, had been escaping to air for five days.
The next day, workers discovered a separate leak in a pipe carrying oleum, producing a toxic cloud of sulfur trioxide.
The phosgene gas release occurred later the same day, and the exposed worker died the next evening.
Dr. Moure-Eraso said, "DuPont has had a stated focus on accident prevention since its early days. DuPont became recognized across industry as a safety innovator and leader. We at the CSB were therefore quite surprised and alarmed to learn that the DuPont Belle plant had not just one, but three accidents that occurred over a 33-hour period in January 2010".
The CSB investigation found deficiencies in the DuPont Belle facility HSE-MS common across all three accidents.
DuPont's deficiencies are worth noting because they may apply to virtually any Major Hazard Facility, and were said by the CSB to include:
1. Maintenance and inspections;
2. Alarm recognition and management;
3. Accident investigation;
4. Emergency response and communications; and
5. Hazard recognition.
CSB board member and former chairman John Bresland noted the CSB finding that the phosgene hose that burst was supposed to be changed out at least once a month. But the hose that failed had been in service for seven months. Furthermore, the CSB found the type of hose involved in the accident was susceptible to corrosion from phosgene.
Team Lead Johnnie Banks said, "Documents obtained during the CSB investigation showed that as far back as 1987, DuPont officials realized the hazards of using braided stainless steel hoses lined with Teflon,
or polytetrafluoroethylene".
A DuPont internal expert had even recommended the use of hoses lined with Monel, a metal alloy used in corrosive applications. The DuPont official stated: "Admittedly, the Monel hose will cost more than its stainless counterpart. However, with proper construction and design so that stresses are minimized…useful life should be much greater than 3 months. Costs will be less in the long run and safety will also be improved." Unfortunately for the dead worker, the Monel hose was never used.
Other DuPont documents also showed that DuPont officials had considered increasing the safety of the area of the plant where phosgene was handled by enclosing the area and venting the enclosure through a scrubber system to destroy any toxic phosgene gas before it entered the atmosphere.
However, the documents indicate the company was concerned with containing costs and decided not to make the safety improvements.
CSB investigators concluded that an enclosure, scrubber system, and routine requirement for protective breathing equipment before personnel entered the enclosure would have prevented any personnel exposures or injuries.
The CSB recommended that OSHA revise the General Industry Standard for Compressed Gases to be at least as effective as the relevant National Fire Protection Association (NFPA) Code 55 (the Compressed Gases and Cryogenics Fluids Code).
This would require secondary enclosures for highly toxic gases such as phosgene and provide for ventilation and treatment systems, interlocked failsafe shutdown valves, gas detection and alarm systems, piping system components, and similar layers of protection.