Understanding Acoustic Emission Testing- Reading 1 Part B-A

■ Gas Trailer Tubes
Acoustic emission testing on pressurized jumbo tube trailers was authorized
by the Department of Transportation in 1983. Instead of using hydrostatic
retesting, where tubes must be removed from service and disassembled, AET
allows for in situ testing. A 10% over-pressurization is performed at a normal
filling station with AE sensors attached to the tubes at each end. A
multichannel acoustic system is used to detection and mapped source
locations. Suspect locations are further evaluated using ultrasonic inspection,
and when defects are confirmed the tube is removed from use. AET can
detect subcritical flaws whereas hydrostatic testing cannot detect cracks until
they cause rupture of the tube. Because of the high stresses in the
circumferential direction of the tubes, tests are geared toward finding
longitudinal fatigue cracks.
Charlie Chong/ Fion Zhang