Why Use Volumetric Fill Testing for Sealed Parts?

March 8, 2016 | By CTS Admin
There are many leak testing methods, some are more general or multi-purpose, some are highly specialized. This variety of leak testing options makes it possible to use several different processes to test the same part or product. However, not all tests are created equal—one method may return a positive result, while a different test performed on the same test part may yield a different outcome. As such, it is important to use the right leak test method for the job at hand. A prime example of a specialized test is sealed part testing. Though these parts can be leak-tested in various ways, volumetric fill testing is the only way to ensure accurate and reliable results.

Effective Volumetric Fill Testing from CTS

Because sealed parts are, well, sealed, they cannot be directly tested for leaks. Instead, we use volumetric fill testing to determine if these parts are, in fact, sealed. Volumetric fill testing is effective in detecting gross leaks. By detecting gross leaks, the need for the more time-consuming process of fine leak testing can be eliminated—if a part has a gross leak, there’s no need to check it for fine leaks. Sentinel I28 leak test instruments from Cincinnati Test Systems (CTS) feature special manifolds with two test ports for volumetric fill testing. Through one port, the test instrument is connected to an external reservoir tank of any size, either directly or via tubing. The other test port is connected to a part testing chamber that contains the sealed test part. Prior to volumetric testing, the reservoir tank is filled through a regulator; when testing begins, the regulator is isolated from the tank and only the pressure stored in the tank is used. The fill valve on the I28’s manifold, allowing air to pass from the reservoir tank, through the manifold, and into the test chamber. If a part leaks, it will fill with air, resulting in a lower pressure in the chamber, as the same amount of air is occupying more space (i.e., the volume of the chamber and the part combined, rather than just the volume of the chamber). Low pressure limits during the test chamber fill cycle will result in a Reject due to the presence of a severe leak. Using a fixed volume of air or vacuum in the reservoir tank to “fill” the test chamber enables the instrument to calculate the volume of the test chamber. Test results are presented on the instrument’s screen, showing the volume of air that has entered the leaking test chamber as a percent value referenced to the size of the reservoir tank volume. For example, if a leaking test part holds a quarter of the volume of your reservoir tank, the test results will be displayed as 25%.  Volume limits set above the expected volume will result in a Reject due to a leaking sealed part. For more information on our volumetric fill testing instruments, contact CTS today. We have the leak detection solution you need.

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