USA

On Saturday May 26th, a man refueling his compressed natural gas (CNG) SuperShuttle van was killed when a storage tank on the vehicle ruptured in California.  This is the first known US incident where a failure of the natural gas fuel system contributed to a fatality.  An investigation was carried out by the California Department of Occupational Safety and Health (DOSH), with the cooperation and assistance of the Clean Vehicle Education Foundation.

An evaluation of the failed cylinder for DOSH, conducted by SEAL Laboratories in El Segundo, CA, concluded that "...the failure of the CNG cylinder was due to stress corrosion cracking..." of the fiberglass over-wrap.  The cause of the stress corrosion cracking was "consistent with the exposure of the CNG cylinder to the car battery acid...." most likely when it was rear-ended in an accident three weeks prior to the tank failure.  A copy of the SEAL Laboratories report can be found here.

The cylinder that ruptured was an older cylinder manufactured by Comdyne.  These cylinders are known to be sensitive to acid exposure.  CVEF and NGVAmerica recommend that Comdyne cylinders exposed to acid in a collision or other mishap should be depressurized as soon as possible to prevent rupture.  They should then be removed from service, rendered unusable, and disposed of.  Other fiberglass wrapped CNG cylinders may also be damaged by battery acid.  NGV owners should contact the cylinder manufacturer if other cylinders have been exposed to acid. 

This accident also points out the importance of inspecting cylinders after an accident or fire and every three years or 36,000 miles, whichever comes first.  For more information on cylinder inspection, as well as where to find a certified inspector or how to become certified as a cylinder inspector, go to the Clean Vehicle Education Foundation website.