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Leak Testing: Helium Testing Versus Hydrostatic Testing

by Nov 14, 2017Weld Testing

Estimated Reading Time: 4 minutes

The chemical, medical device, semiconductor, and alternative energy industries rely on a range of components and manufacturing equipment during the course of their business. They regularly utilize components including stainless steel cylinders and canisters, metal pipes and plastic tubes that hold or move chemical materials and compressed gasses. These cylinders and pipes can experience extreme pressures that can degrade the interior cylinder tank system as well as the piping components.

When any cylinder or pipe is repaired or replaced, it needs to undergo testing before placed into operation. Leak testing is vital to preventing chemicals and gases from escaping the chamber, as that could cause equipment failure, workplace damage, flammable environments, and work injuries. There are two testing methods performed by Axenics to search for leaks: helium leak testing and hydrostatic testing.

Helium Leak Testing

Helium leak testing is a common method that OEMs rely on when testing systems that will be a part of high pressure or vacuum processes. This type of testing searches for the smallest of leaks using helium in a hermetically sealed testing chamber.

There are two ways that the helium leak testing is performed. The product can be tested from the outside-in using a vacuum pressure method. In this use case, the product is placed into a hermetically-sealed chamber and both the chamber and product are evacuated of air. Then, helium is pumped into the chamber and the gas concentration is monitored. If there is a leak in the product, the concentration of gas in the chamber will change.

The other method of helium leak testing involves using the pressure method to check for leaks from the inside-out. The product is pressurized with helium or a mixture of helium and nitrogen. Then, a sniffer probe device is used along connections and places that would normally leak to check for concentrations of escaped helium.

Hydrostatic Testing

Hydrostatic testing is one of the top methods used to confirm cylinders and components are free of leaks. This test relies on water pressure to identify leaks.

The cylinder or device is filled with water or another liquid that has a dye applied to it. Once the water reaches a pressure that is above the working pressure for the equipment, it is held there for a set timeframe. Then, the device or cylinder is checked for leaks.

There are several different methods to hydrostatic testing. There is a water jacket method where the cylinder is filled with water and placed into a sealed chamber that also has water. The cylinder is then pressurized as it expands and forces the chamber’s water into a tube. Then, the cylinder pressure is relieved to test how much it shrinks.

The proof pressure method tests for wall thinning in the cylinder. The cylinder will undergo pressures that are three times to six times above its normal operating pressure.

The third test method is direct expansion. The cylinder is filled with a certain amount of water and then pressurized. Then the pressure is released as the amount of water that is ejected from the cylinder is measured and compared to the amount of water that was placed into the container.

When to Use Hydrostatic Testing and Helium Leak Testing

Helium leak testing is often used when also performing a high pressure gas proof test since it can be done on the same equipment. Many manufacturers that are using refrigeration equipment and components will rely on helium leak testing. It can also be used on equipment that is completely dry and will be used in environments that won’t experience moisture.

We often use hydrostatic testing to check the strength of our welds for low pressure stainless steel canisters. It can also be used to check fire extinguishers, chemical pipelines, and storage tanks. It is an ideal testing method when equipment has been repaired or has been rebuilt.

At Axenics, we perform both hydrostatic testing and helium leak testing, both as a part of our manufacturing quality control, and as a stand-alone service. If you wish to have leak testing performed on your equipment and need to identify the right method to use, please contact our expert technicians so we can provide you with additional information.

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