ACOUSTIC-EMISSION TESTING OF STEEL CYLINDERS FOR THE STORAGE OF NATURAL-GAS ON VEHICLES

Acoustic emission testing for the periodic inspection of steel cylinde rs used for the storage of natural gas on vehicles was investigated. N ormal refuelling pressurization does not produce adequate emission to enable structural integrity assessment. Detection of cracks through 15 % or more of the side wall is feasible using overpressurization to 33% above the nominal refuelling pressure. A methodology was developed to distinguish between general corrosion product signals and those prima rily associated with cracks. The effects of test interruption and the rate of cylinder pressurization on acoustic emissions were examined. T he test method involves the application of one conditioning pressure c ycle followed by one overpressure cycle. The sensitivity of the test m ethod is adequate to permit an inspection interval of five years in se rvice.