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Helium Leak Testing
Vacuum Testing - Helium Spray - Bag Testing
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Helium leak testing is required for all cryogenic equipment and vacuum vessels we build. Final leak tests are performed once the vessel is fabricated through various methods, including helium leak test chambers, bag testing and helium leak check protocols. Numerous intermediate helium leak checks are also performed on subassembly weldments during different stages of the production process. In some cases, welds cannot be repaired once subassemblies are attached to the main vessel, so it becomes imperative to ensure that individual welds are leak-tight. It speeds up production time in the big picture since it dramatically reduces the time required to pinpoint a leak.
Helium leak detection is performed with a self-calibrated leak detector. A vacuum of 10-6 Torr or lower is pulled on either the interior or exterior of the assembly that is being tested. A wand blows a small amount of Helium around each questionable weld zone. If there is a leak in a weld, the Helium will be drawn into the vacuum, and the detector will sound an alarm. Sometimes the entire part can be enclosed in a bag filled with Helium. The bagging process is a conservative method used to prove that no leaks are present in the vessel. The leak detector will specify the leak rate that is detected. For cryogenic and vacuum equipment, leak rate acceptance criteria would commonly require a system sensitivity of 1x10-9 to 1x10-8 atm.cc/sec, (mbar.l/s), for a valid helium leak check. |
