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Safer chlorine transfer

June 25, 2007 | A version of this story appeared in Volume 85, Issue 26

Emergency protective equipment at facilities that unload chlorine from tanker railcars is inadequate and should be changed, says the Chemical Safety & Hazard Investigation Board (CSB) in a recently released safety bulletin. On the basis of its investigations, the board is also recommending that the Department of Transportation 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 when a hose ruptures or another failure of unloading equipment occurs. The board notes that rail tankers are equipped with internal valves that stop flow when an accident occurs during transit, but these systems are not designed to stop leaks during unloading. Also, failure of a transfer hose may not activate these emergency valves. A CSB investigation of a 2002 accident at DPC Enterprises, Festus, Mo., found that when a hose ruptured, the emergency shutdown valve also failed and emergency responders were forced to walk though a 4-foot-deep fog of chlorine vapor to manually close the shutdown valve on top of the railcar. The board notes that a survey of bulk chlorine users found that 30% relied solely on emergency valves without remote shutoffs to stop chlorine flow when a hose ruptures. The bulletin is available at


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