Jun 14, 2007
CSB Issues Safety Bulletin on Dangers of a Major Chlorine Release During Railcar Unloading; Agency Calls on U.S. Department of Transportation to Expand Regulatory Coverage to Require Emergency Shutdown Systems
Washington, DC, June 14, 2007 - The U.S. Chemical Safety Board (CSB) today released a safety bulletin warning that some chlorine railcar transfer systems lack effective detection and emergency shutdown devices, leaving the public vulnerable to potential large-scale toxic releases.
The Board formally recommended that the U.S. Department of Transportation (DOT) expand its regulatory coverage to require facilities that unload chlorine railcars to install remotely operated emergency isolation devices to quickly shut down the flow of chlorine in the event of a hose rupture or other failure in the unloading equipment. The safety bulletin cites two previous incidents of accidental chlorine releases that occurred as a result of ruptured transfer hoses.
Chlorine railcars are equipped with an internal excess flow valve (EFV) that is designed to stop the flow of chlorine if an external valve breaks off while the railcar is in transit. However, these EFVs are not designed to stop leaks during railcar unloading, and the failure of a transfer hose may not activate the EFV and the toxic chlorine will continue to escape. Companies should install emergency shutdown systems that can quickly stop the flow of chlorine if a hose ruptures during the unloading operation, the bulletin said.
In August 2002 a hose ruptured at a DPC Enterprises plant near Festus, Missouri. The emergency shutdown valves did not close as designed due to poor maintenance, and the EFV did not close. The only way to stop the release of chlorine from the railcar was to send emergency responders through a four-foot deep yellowish-green fog of chlorine vapor to manually close shutdown valves located on top of the railcar. Incidents such as the one at DPC demonstrate why EFVs should not be relied upon to stop hazardous material releases during unloading operations.
However, in a survey of drinking water and wastewater treatment facilities conducted by the CSB, investigators found that approximately 30 percent of the bulk chlorine users contacted continue to rely solely on the EFV to stop chlorine flow in the event of a transfer hose rupture.
The DOT Hazardous Materials Regulations (HMR) regulate transportation of hazardous materials by rail, aircraft, vessel, and motor vehicle tank truck and currently require emergency shutdown equipment for motor vehicle tank truck chlorine transfer systems but not for railcar chlorine transfer systems.
CSB Board Member John Bresland said, "Chlorine is a very useful but a highly toxic substance that needs appropriate safeguards to prevent releases and protect the public. Our safety bulletin reveals the importance of expanding current regulatory coverage to chlorine railcar unloading operations."
The safety bulletin compares two chlorine releases from railcars that were investigated by the CSB. The first incident, discussed briefly above, involved a 48,000 pound release of chlorine at DPC Enterprises due to a ruptured transfer hose. As a result hundreds of residents were evacuated or were required to shelter in place, 63 residents sought medical attention and three were admitted to the hospital. The second incident occurred in August 2005 at Honeywell International's Baton Rouge chemical plant when chlorine began to escape from a railcar due to a transfer hose failure. There, the emergency shutdown system functioned properly and the release lasted less than one minute. There was no impact to the surrounding community.
Investigator Lisa Long said, "In contrast to the 2002 incident at DPC, the rapid and successful activation of the emergency shutdown system at Honeywell prevented a major release and limited off-site impacts to the surrounding community."
The CSB recommendation calls on DOT to expand regulatory coverage to require railcar unloading operations to have the following safeguards:
- Remotely operated isolation devices that will quickly isolate a leak in any of the flexible hoses used to unload a chlorine car - The shutdown system must be capable of stopping a chlorine release from both the railcar and the equipment at the facility receiving the chlorine - Periodic maintenance and operational testing of the emergency isolation system to ensure it will function in the event of an unloading system chlorine leak
ADDITIONAL CHLORINE INCIDENTS:
Although the incidents described below do not directly deal with chlorine railcar unloading operations they do indicate the severe hazards to the public in the event of a chlorine railcar leak and the importance of transporting and transfer of this deadly but useful chemical safely. These transportation incidents have been investigated by the National Transportation Safety Board (NTSB).
- June 28, 2004 - The collision of two trains near Macdona, Texas caused a release of liquefied chlorine from one of the train's tank cars. The chlorine vaporized, engulfed the area and led to the deaths of the train conductor and two local residents.
- January 6, 2005 - In Graniteville, South Carolina, a Norfolk Southern train collided with a stationary train, leading to a derailment, and the release of an estimated 120,000 pounds of chlorine. The derailment and resulting chlorine release caused 9 deaths, led to over 500 persons seeking medical treatment for possible chlorine exposure and the mandatory evacuation of over 5,000 residents.
The CSB is an independent federal agency charged with investigating industrial chemical accidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.
The Board does not issue citations or fines but does make safety recommendations to plants, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website, www.csb.gov. For further information contact:
Sandy Gilmour 202.261.7614 or cell 202.251.5496, Public Affairs Specialist Jennifer Jones 202.261.3603 or cell 202.577.8448.