Acoustic emissions testing of air storage vessels at APTU is cost-savings effort

  • Published
  • By Deidre Ortiz
  • AEDC/PA
ARNOLD AIR FORCE BASE, TENN. --  In an effort to save money and have less facility down-time, a new technique was used at the AEDC Aerodynamic and Propulsion Test Unit (APTU) at Arnold Air Force Base to inspect the high pressure air storage vessels.

Adam Fanning, Air Force Asset manager for the von Kármán Gas Dynamics Facility, explained that high pressure acoustic emissions testing is being implemented to inspect the large bottles at APTU for cracks.

“We haven’t done this at Arnold before, but the inspection technique has been used since the 1970s at other places,” he said. “This technique has been identified as a replacement for volumetric testing.”
Fanning added that this technique also prevents the bottles from being taken physically out of the system.

“There is less down time, because previously you’d have to take the 90 bottles and X-ray them,” he said. “With this, you pump the bottles to 105 to 110 percent pressure and listen for a flaw or crack growth.”
As part of the inspection, an outside contractor was hired and its ropes crew hung sensors on the bottles, which will detect flaws.

“We used the JM3 compressors to pump the bottles to their max pressure capacity to stress them and see if there were any cracks or flaws,” he said. “Whenever a crack grows, a sensor sounds letting us know there’s something there.”

Fanning also mentioned the process took several hours and the weather conditions to perform the inspection had to be just right.
“We couldn’t do it in the rain because it’s so sensitive to any noise outside.”

Fanning said it’s estimated that cost savings of using this technique is more than $300,000, and the inspection is part of the system’s 20 year recertification effort.

“It’s a less labor intensive way to do the job that requires less down time and overall less man power,” he said.