What Happens To Expired CNG Tanks?
While the benefits of CNG vehicles are well documented – what do owners of CNG vehicles or fleets do when their tanks reach their expiration date?
NGVAmerica estimates approximately 110,000 NGVs (natural gas vehicles) are in use in the United States today, displacing about 360 million gasoline-gallon equivalents (GGE) per year.
Standards For CNG Cylinder Life
There have been a couple revisions in standards for lifetime of a CNG cylinder. The latest one came in 2007 that raised the lifespan to 25 years. After this time, tanks can not be recertified and must be taken out of service. The owners then have two choices – to replace by cylinders (very expensive), or retire the vehicle.
The idea of developing a process for recertifying older tanks was considered and then discarded for both technical and liability reasons.
Stephe Yborra from the Clean Vehicle Education Foundation, says that with the expansion of cylinder lifetime, the problem of not being ready to retire a vehicle at the end of life shouldn’t really be a problem.
Right now, there are no national standards in place for inspecting cylinders. Notices are placed on cylinders stating they should be inspected for damage or deterioration every 36 months or 36,000 miles, whichever comes first, or after a fire or accident.
Cylinders can appear safe, but there can be unseen corrosion that could compromise a cylinder. Many people don’t consider that road spill that contains battery acid or other corrosives could also harm cylinders.
Standards for Cylinder Tracking
States have their car, truck and NGV registration databases. Not all of them record fuel types. There is a lack of a national database of all CNG vehicles. Some urge the building of a nation-wide database of these types of vehicles. This would depend on each state to participate.
Be Proactive About Expiration Dates
Fleet owners should be tracking their vehicles and flagging those coming up for expiration in order to have time to plan either the retirement of the truck or replacement of the tank. If CNG tanks are used after the expiration date, the liability is on the fleet owner or individual, not on the maker of the cylinder.
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