Our full clean room services include a range of testing including leak testing, for helium and positive pressure testing. Macfab’s focus on providing a low total cost of ownership through quality work is added through our leak testing of prototype and production parts.
Leak testing is a form of Non-destructive Testing (NDT). This form of testing allows validation of the part and process while not requiring it to be a sacrificial (scrap) part. Using our Agilent vacuum and leak detectors combined with our innovative custom testing systems, your parts will arrive as expected.
Macfab practices these leak testing methods in order of sensitivity:
Air Pressure (Vacuum) Decay
Air Pressure (Vacuum) Decay utilizes air at a vacuum up to 80 pounds per square inch (PSI). This process reduces the variation caused by temperature, has a higher throughput compared to other methods, and can detect multiple defects if present.
The Bubble Immersion method is used to test welds and sealing of assemblies. The test piece can be pressurized at 3 to 40 PSI with a maximum of 125 PSI and submerged in a tank of water. The inspector then looks for bubbles indicating a defect.
Helium Mass Spectrometry
At nearly double the sensitivity of the bubble test method is Helium Mass Spectrometry 100x to 1,000,000x. This method requires being able to develop a negative pressure difference between the test part and the atmosphere. Using this method, a quantitative measurement volume of cubic centimeters per second (atm cc/sec) of the leak rate can be recorded. Depending on the configuration of the part/assembly, the precision with which this testing is done, the location of the leak(s) can often be identified on the part.
Highlighted in yellow are the testing methods Macfab performs, additional information in the table are other testing methods and their comparison for reference.
|Method||Quantifiable Result||Locate Leak||Global 1||Go/ No Go||Test Media||Test Volume Dept.2||Relative Cost|
|Air Pressure (Vacuum) Decay||Yes||No||Yes||Yes||Air||Yes||Medium|
|Dye Liquid Tracers||No||Yes||No||No||Liquid||No||Low|
|Thermal Conductivity Sniffing||Limited||Yes||No||Yes3||Helium||No||Low|
|Sulfur Hexafluoride (SF6) Sniffing||Limited||Yes||No||Yes3||SF6||No||Low-Med|
|Helium Mass Spec Sniffing||Limited||Yes||No||Yes3||Helium||No||Med-High|
|Helium Mass spec Atmosphere Accumulation||Yes||No||Yes||Yes||Helium||Yes||High|
|Helium Mass Spec Hard Vacuum||Yes||Yes||Yes||Yes||Helium||No||High|
|Trace Gas Mass Spec Hard Vacuum||Yes||Yes||Yes||Yes||R134a, SF6, Air, H2, NO2, CO2||No||High|
1. The test method measure the global leak rate of the part, versus individual leaks.
2. The test volume significantly affects the test cycle time and/or sensitivity.
3. Result may vary based on skill of operator.
While no process is error free, our investment in multiple methods and a range of leak testing sensitivities provides us with options to meet a customer’s range of expectations from engineering specifications, quality verifications, and supply chain requirements.