The tests and inspections required for tank trailers are: external visual inspection (V), internal visual inspection (I), lining test (L), pressure retest (P), leakage test (K), and thickness test (T). Requirements for these six tests and inspections can be found in 49 CFR 180.407( §180.407.
Prior to any test or inspection, the cargo tank should be professionally cleaned. Cleaning has safety and practical implications. A clean tank will ensure that inspectors are not exposed to any dangerous materials. It is important prior to starting the tests to double check to make sure to purge all liquid and vapor lines and any void areas on the cargo tank. Additionally, a clean tank ensures that no defects in the tank are overlooked because they were obscured by residue, dirt, or debris.
Each specification cargo tank must be tested and inspected by an inspector meeting the qualifications in 49 CFR 180.407.
