Gary68 said:
underbody is what i wanted info on,thanks
Found this information at several sites.
In fact it is against the law for sellers of Propane to fill a DOT propane tank that is 12 years or older that has not been re-certified. The propane tank must be recertified by a facility that is certified to do DOT Tank recertification. Some large Propane suppliers and some RV repair facilities are certified to do the DOT Tank recertification.
When the DOT Tank is inspected and passes it is recertified for 5 years and must be re-inspected and recertified every 5 years thereafter. Every time it is recertified a new re-certification label is affixed to the DOT Propane Tank.
There are 2 types of propane storage vessels, an ASME TANK and the DOT CYLINDER. NFPA pamphlet 58 states that the DOT CYLINDER needs to be recertified after 12 years from the manufacturing date. Depending on the certifying method used, they are recertified every 5,7,12 years thereafter. The recertification involves an inspection and testing of the cylinder to confirm that the cylinder is still safe and legal to remain in service.
ASME TANKS that are found on an RV do not get recertified. They should have the relief valve replaced every 10 years.
Vertical (BBQ) portable propane storage vessels are typically called a DOT "cylinder" while horizontal ASME storage vessels are typically called a "tank" in the literature I've seen.
There were changes in the law around 2002 requiring new valve types to be installed at recertification.