Lately, I have come across LP powered forklifts with power lacking issues, no other issues were found - the trucks would idle just fine, step on the accelerator and the engine would die. With no issues found engine side, it was time to check the LP tank itself. Picking up the tank from the truck cradle, it felt like there should be about a half tank left, you could even feel the liquid slosh inside the tank.
After a "quick pressure test" I was able to determine that the ratio of gas to liquid had reached a point where it was no longer effectively supplying the engine with liquid fuel. For comparison, think of an aerosol can turned upside down, the liquid dribbles out - turn it right side up and attempt to use - and only the propellant gas comes out. LP engines require the pressurized liquid to run, the gas when combined with air going into the engine is too "lean" for the engine to run.
As this happened several times at one particular customer with a large fleet, I began to make a connection in regard to the questionable tanks. They use the typical DOT tanks for forklifts, and the tanks in question were past their recertification date!
DOT PROPANE TANKS ARE REQUIRED TO BE RECERTIFIED 12 YEARS AFTER THEIR INITIAL DATE - WHICH IS STAMPED ON THE COLLAR.
So, if you own your own LP tanks, ask your local propane dealer if they can recertify your tanks for you, or if you use a provider, ask of service tags to mark which tanks you believe are questionable.
For more information in regard to certification, here is a blog entry I found while researching for this blog, as well as the picture above: http://blog.hyundaiforkliftsocal.com/2011/09/be-safe-use-propane-tanks-that-are.html
Tom Kassen
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