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

Acoustic emission testing for the periodic inspection of steel cylinders used for the storage of natural gas on vehicles was investigated. Normal 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 primarily associated with cracks. The effects of test interruption and the rate of cylinder pressurization on acoustic emissions were examined. The test method involves the application of one conditioning pressure cycle followed by one overpressure cycle. The sensitivity of the test method is adequate to permit an inspection interval of five years in service.