When it comes to meeting quality measures, manufacturers have a variety of standards from the ASTM, FDA and other organizations that they must meet. Often, these requirements include a leak testing component. Leak testing methods are recommended for everything from automotive parts to medical devices and pharmaceutical products. However, because there are a variety of different leak testing options, it can be difficult to decide which method is right for you and your product. Below is a brief explanation of one of the most common methods, helium leak testing, which can help determine whether or not this option is right for you.
The Tracer Gas
Helium leak testing is extremely popular because of how effectively helium works as a tracer gas: it is non-toxic, nonflammable, inert, and also one of the most abundant elements in the universe. Additionally, it has an extremely small atomic size, allowing it to pass easily through leaks in a product at vacuum condition. One misconception is that at pressure condition helium leaks more than air. The truth is that air leaks first, followed by helium, as air is less viscous then helium.
The Leak Testing Equipment
Helium leak testing uses a mass spectrometer leak detector, also called a helium leak detector, to locate and measure leaks in a product. To do this, a test part is connected to the leak detector and the tracer gas, helium, is introduced to the test part. Any helium leaking through the test part is then measured and correlated to maximum allowed leakage (flow rate). The helium can be introduced using three different methods: vacuum testing, pressure testing, and pressure/vacuum testing.
In vacuum testing the test part is placed in a hermetically sealed vacuum chamber. The part and chamber are evacuated to create a vacuum and helium is applied to the part. Helium gas concentration is measured at the vacuum chamber outside the part. Since the chamber is in hard vacuum, any helium leakage will change gas concentration significantly. While in pressure testing, the part is pressurized with helium and potential leak sites are sniffed with a probe. Finally, with pressure/vacuum testing, a combination of the two previous methods is achieved by pressurizing the test part and placing it into a vacuum. This method tests a product’s overall leak rate. The vacuum method is by far the most sensitive and reliable method for helium leak testing. The sniffer method should be used to locate the point of leak, not to measure leakage.
While helium leak testing is one of the more common forms of leak detection, it has become increasingly expensive due to a shortage of the tracer gas. Helium is one of the most common elements in the universe, but not as abundant on Earth. Experts believe this limited supply will not be able to sustain increased demands worldwide. Even with the United States, along with Qatar and Russia, increasing helium production the inevitable future shortages will still be felt. Because of this, helium has become more expensive with supply disruptions, and many companies are finding it more difficult to justify the cost when other leak testing solutions like ATC’s Mass Extraction exist.