NGVi Highlights Dangerous CNG Equipment Issue That Is Often Overlooked


The Natural Gas Vehicle Institute (NGVi) is alerting fleet managers about an important requirement under NFPA 52, the installation code for natural gas vehicles, that is often overlooked.

It states that any fuel cylinder with a shut-off valve must also provide technicians with a way to determine whether pressure is still present in that container. This is vital to the safety of CNG technicians involved in the inspection and maintenance of heavy-duty NGVs. Otherwise, they leave themselves open to potential injury and death.

“This requirement has been a part of NFPA 52 since the version released back in 2016,” says NGVi Executive Director Leo Thomason. “Yet it’s been my experience that virtually no CNG-powered heavy-duty vehicles that I or our other instructors at NGVi have seen during our live, in-person training have had the capability to visually determine the presence of pressure inside their cylinders.”

Cylinder valves may fail while in the closed position, giving technicians the false sense that these cylinders have been defueled. Thomason says he knows of at least two vehicle technicians who have lost their lives in this type of situation. Each one attempted to remove a valve from a cylinder they thought was empty, only to be struck and killed by the valve due to the pressure that was released.

How can these dangers be avoided? Thomason offers three solutions: “One, have a pressure gauge in the PRD port on the cylinder valve. Two, have a transducer installed in the high-pressure portion of the fuel system that’s connected to a pressure-indicating device. Three, have a written procedure for determining cylinder pressure prepared by the CNG fuel system manufacturer or installer.”

For more information about how to ensure natural gas vehicle safety for your fleet vehicles, technicians, drivers and the general public, reach out to NGVi.

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