USA, Philadelphia
On June 9, 2008, a Type 2 Lucas Aerospace CNG tank ruptured on a Ford E350 natural gas powered truck at a Philadelphia Gas Works facility in the Port Richmond area of Philadelphia. Type 2 CNG cylinders are designed so that the liner alone will withstand at least 1.25 times the system service pressure. The cylinder composite overwrap adds to the overall cylinder strength of at least 2.5 times service pressure. In this case both the overwrap and the liner failed. The fiberglass overwrap failure was the result of stress corrosion cracking, probably from an unidentified corrosive agent. The liner appears to have failed from being over-pressurized during fueling.
Amongst the lessons summarised last month to NGVAmerica members are:
* Inspect or immediately defuel and destroy cylinders exposed to strong corrosive agents(contact your vehicle or cylinder manufacturer for information on whether cylinders need to be defueled and destroyed)
* Assure that dispensers do not dispense CNG at pressures higher than the service pressure of your vehicles (or 1.25 times the service pressure for temperature compensated systems). Check dispenser pressure controls and/or relief valves for proper operation. Assure that proper periodic maintenance is performed per the dispenser manufacturer’s recommendations.
For more information contact the Clean Vehicle Education Foundation by emailing John Lapetz at jlapetz@cleanvehicle.org.
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