Non-Destructive Testing Methods: Helium Leak Test

A helium leak test can be used to find through-wall leaks in pressure equipment and welds. A vessel or exchanger is first filled with 5-10 psi of helium and sealed. A helium mass spectrometer is then used on the exterior and passed near any welds or other areas to be tested, to ‘sniff’ or search for any helium above normal background levels. If helium is detected, a leak is likely nearby.

This test is commonly used to check for leaks in tube-to-tubesheet welds on a heat exchanger. The test should be performed after all tube end welding but before tube expansion so that only the welds are being tested. A hood (usually a plastic bag) is used to enclose the end of the exchanger so that any leaking helium is collected in the bag and all tube end welds on one side can be tested at once.

Due to the smaller size of the helium atom, this test has the potential of finding leaks that water would not pass through during a hydrostatic test. Helium is also non-toxic and chemically inert, making it an ideal safe testing medium. Ward can perform this test with in-house equipment, so contact us if you have any questions about helium leak testing.