There is a difference between the price of a part and the cost of the part – quality.  Macfab’s focus on providing a low total cost of ownership is added through our leak testing of a prototype. 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.

As a supply chain partner, focusing on mutual success, Macfab conducts leak testing on all prototype type parts that require it. If a crack or hole is found, we careful review our internal process and retest the part. Our engineering team has developed fixturing to allow our testing to be done in both static (stationary) and dynamic (moving) conditions painting a more realistic

As a part moves into production, so too does our leak testing. The focus remains to identify defects that can only be found using this testing method. Our engineering and quality teams develop sampling plans based on consistency of the process and experience, to conduct periodic inspection of the parts validating the process remains in control. A stable process generates steady a flow of products to our customers.

Macfab practices these leak testing methods in order of sensitivity: Air Pressure (Vacuum) Decay, Bubble Immersion, and Helium Mass Spectrometry.  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.

Finally, 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.

Method Quantifiable Result Locate Leak Global1 Go/ No Go Test Media Test Volume Dep.2 Relative Cost Typical Sensitivity (atmcc/sec)
Air Pressure (Vacuum) Decay Yes No Yes Yes Air Yes Medium 0.01
Mass Flow Yes No Yes Yes Air Yes Medium 0.01
Dye Liquid Tracers No Yes No No Liquid No Low 0.001
Bubble Immersion No Yes No No Air No Low 10-4
Thermal Conductivity Sniffing Limited Yes No Yes3 Helium No Low 10-5
Sulfur Hexafluoride (SF6) Sniffing Limited Yes No Yes3 SF6 No Low-Med 10-5to 10-9
Helium Mass Spec Sniffing Limited Yes No Yes3 Helium No Med-High 10-7
Helium Mass spec Atmosphere Accumulation Yes No Yes Yes Helium Yes High Approx. 10-4
Helium Mass Spec Hard Vacuum Yes Yes Yes Yes Helium No High 10-9
Trace Gas Mass Spec Hard Vacuum Yes Yes Yes Yes R134a, SF6, Air, H2, NO2, CO2 No High 10-7 dependent on test media gas
  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 sensitivities provides us with options to meet a customer’s range of expectations from engineering specifications, quality verifications, and supply chain requirements.  Let’s discuss the option best suited for your part and the total cost of ownership.