Vacuum leak testing

Perform the vacuum leak test with an empty freeze drier and condenser. After reaching the maximum available vacuum, the vacuum pump is switched off after a delay time and the valves are closed. Monitor the vacuum decrease for a period of 24 h. Let the condenser cool to avoid water evaporation and vacuum decrease. 

Testing on an assembled container closure system is usually performed by the applicant (or a testing laboratory commissioned by the applicant), and the test results are provided in the application. Such tests may include vacuum-leak testing, moisture permeation, and weight loss or media fill. Testing on an individual packaging component is typically performed by the manufacturer of the component and is reported via a DMF (see Section V). 

Vacuum Leak Testing ASTM D-3078—Leaks in Heat Sealed Flexible Packages... 

C.C. Minter, Vacuum Leak Testing with Liquids, Rev. Sci. Inst., 31, 458-459... 

In vacuum columns, it is best to first perform the leak test described above at just below the maximum permissible pressure (23). Leaks are generally easier to detect and repair when the column is under pressure. Next, the normal operating vacuum is pulled on the column. The vacuum equipment is then turned off and isolated from the column, and the rate of pressime rise is monitored. The air leakage rate can be inferred from the rate of pressime rise. Purging often needs to be repeated following a vacuum leak test in order to remove air that leaked in during the test. 

The leak detection methods described above for pressure leak testing also apply for vacuum leak testing. More sensitive methods use an easily detectable tracer gas. Excellent detailed reviews of leak testing and leak detection techniques are available elsewhere (315, 345). 

Water or other liquids should be adequately removed from the column prior to a vacuum leak test. Evaporation of liquids may cause a rise in pressiire during the test. 

Vacuum Leak Test. The vacuum leak test is similar in concept to the internal pressure leak test in that the result is a pass/fail for the detection of bubbles emanating from the package while submersed in a water bath. The method is described in ASTM D3078, Standard Test Method for Leaks in Heat-Sealed Flexible Packages. The pressure differential is obtained by evacuating the chamber, causing the package to expand. 

To realize such a vacuum leak test, a vacuum set-up similar to the one used for the actual part manufacture is installed (described below), but without the part lay-up itself. Instead, only one or two plies of a glass fibre prepreg material are used. This dummy set-up is then evacuated and cured. Air leaks in the mould will cause porosities in the cured matrix. Thanks to the transparency of the glass fibres and the low thickness of the dummy... 

It is worth mentioning that in some cases, sonrces of pressure leaks cannot be easily repaired. This is especially the case if the leak occurs in the mould structure, which is why vacuum leak tests on the empty mould, as described before, are so important. 

Mould vacuum leak test Leak test method pass/no pass criteria... 

A-9.1.3 Slip-On Flanges. The need for venting the space between the welds in double-welded, slip-on flanges should be considered for fluid services (including vacuum) that require leak testing of the inner fillet weld, or when fluid handled can diffuse into the enclosed space, resulting in possible failure. 

Strobel, M. L., Strobel, C. J., and Delin, G. N., 1998, Design for a Packer/Vacuum Slug Test System for Estimating Hydraulic Conductivity in Wells with LNAPLs, Casing Leaks, or Water Tables Intersecting the Screens GroundWater Monitoring Remediation, Fall, pp. 77-80. 

A total of four Co and Fe based alloys were procured from a commercial source. Disks were punched from the foil and mounted into VCR vacuum fittings, with a nickel gasket on one surface and the sample in direct contact with the VCR sealing surface on the other. The sample assemblies were leak tested and verified leak tight to 2x10 7 sscm He prior to intallation in the permeation test apparatus. 

Leak Testing Location of through wall defects and flaws while under pressure or vacuum. Various fluids and gases are used for pressure testing several types of leak detectors are used to locate a leak. 

Today leak tests for vacuum systems are usually carried out with helium leak detectors and the vacuum method (see Section 5.7.1). The apparatus is evacuated and a test gas is sprayed around the outside. In this case it must be possible to detect (on the basis of samplings inside the apparatus) the test gas which has passed through leaks and into the apparatus. Another option is to use the positive-pressure leak test. A test gas (helium) is used to fill the apparatus being inspected and to build up a slight positive pressure the test gas will pass to the outside through the leaks and will be detected outside the device. The leaks are located with leak sprays (or soap suds, 5.4.5) or - when using He or H2 as the test gas - with a leak detector and sniffer unit (5.7.2). 

Vacuum envelope test (integral leak test)... 

Document that the reservoir conforms to purchase specification and invoice. Verify and document that the vessel meets or exceeds the pressure rating (vacuum) specified in the purchase specifications. Perform vacuum hold tests on the tank and document. Acceptance ID tests will vary with the size of the system. A positive pressure test is often done in order to find leaks. Perform and document cleaning procedures used prior to placing the vessel in service. This completes the normal testing done on the tank prior to joining it to the vacuum system. 

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