Slide Test for leaks in a water bath or with trace gas? Find the right solution for your packaging

LEAK TESTING IN A WATER BATH

Leak testing in a water bath is a visual test method. The test item is completely immersed in water. If there are leaks, visible air bubbles rise.

LEAK TESTING WITH TRACE GAS

The leak testing with trace gas is done using gas sensors. The test item must contain the defined trace gas. If leaks are present, the escaping gas is detected by the sensors.

HOW IS THE TESTING DONE?

Bubble test systems consist of a transparent water bath into which a test specimen is completely immersed, and can be inspected from all sides for any rising air bubbles, i.e. leaks. Ideally, grippers are available to hold the test specimen under water during this process.

The bubble test works best the higher the pressure in the test item is compared to the ambient pressure. Then notable streams of air bubbles rise from the leaks to the water surface. At a pressure difference of a few mbar, the surface tension of the water delays or prevents the formation of bubbles. Solid items or components are therefore pressurised with compressed air for water leak testing. Conversely, it is also possible to reduce the ambient pressure in the water chamber: In the sealable water chamber, the air space above the water is evacuated for this purpose.

For a controlled testing process, an always consitent pressurisation or evacuation as well as testing time under water must be defined and adhered to. The visual checking and attention of the tester is crucial: he/she must notice the rising air bubbles and can thus determine the position of the leak on the test item.

Systems for leak testing with trace gas are available for random sample testing and as fully automated inline machines for checking the entire production. One or more test items are positioned in a chamber, a vacuum is created and the trace gas escaping from leaks is detected by sensors.

Food or medical products packaged with a modified atmosphere are mainly tested for escaping CO2. It is already present in many packages as part of the modified gas atmosphere. This is different for items or component groups that must have trace gas applied to them. In the most strenuous of leak-tightness requirements, helium or hydrogen serve as trace gases which, with their small molecular size, can pass through even the smallest gaps. For food packaging, such a fine test is rarely necessary. Moreover, the additionally introduced hydrogen makes it difficult to analyse the modified atmosphere for residual oxygen.

Leak tests with trace gas can be automated very easily and thus can also include digital documentation of the testing process. The quality checking is carried out independent of any human inspector and is absolutely standardised. The sensors provide measured values from which an exact leakage rate can be derived.

TIGHTNESS CLASSIFICATIONS

All packaging materials and conjoined components have tiny openings that can be understood as leaks. Technically, there is no such thing as absolute leak-tightness. Whether a test item is “leak-tight” or “leaky” can only be said with reference to the predefined leakage rate. It sets the limit between a tolerable leak and a leak that endangers the function or safety of the product.

Each leak test method has its advantages and disadvantages. It depends on what you want to test, how you define leak-tightness, and how you intend to integrate the testing into your production.

LEAK TEST IN A WATER BATH

Pro

  • precise localisation of leaks
  • weak point analysis, to optimise the production process (e.g. seams, sealing points, material condition, assembly faults, etc.)
  • expensive items can be selectively reworked

Contra

  • visual inspection by human without exact leakage rate
  • the tested item may not be able to be returned into production (food)
  • regular cleaning of the chamber, or water changes required

Especially suitable

  • for medium to large components with low mould complexity, e.g. stainless steel fittings, fuel tanks, plastic parts, etc.
  • for modified atmosphere packages
  • for flow bags, thermoformed trays, stand-up pouches, tetrapaks, blisters, vials, sachets, capsules, cans, bottles
  • for sample testing

Not suitable

  • for complex geometries
  • for the detection of microleaks (leakage rates below 10-4 mbar l/s)

LEAK TEST WITH TRACE GAS

Pro

  • determination of a leakage rate
  • short testing time
  • automated testing & digital documentation
  • can be integrated into a production line

Contra

  • trace gas may have to be additionally introduced into the product
  • disproportionately large leaks, from which the trace gas escapes too quickly, can falsify the test

Especially suitable

  • for modified atmosphere packages that already contain the trace gas CO2
  • for the detection of microleaks (leakage rates below 10-4 mbar l/s)
  • for 100% testing of the production

Not suitable

  • for locating a leak (possible with probe)

ARE YOUR PACKAGES REALLY TIGHT?

Do not compromise, rely on certified quality systems from WITT for industrial leak testing.

With the LEAK-MASTER® model series from WITT, you have the choice: leak testing in a water bath or with CO2 as the trace gas.

LEAK-MASTER®
EASY


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Optimise your packaging process by detecting leaks with pinpoint accuracy. Leak testing in a water bath is simple and effective with the LEAK-MASTER® EASY leak tester.

LEAK-MASTER®
PRO 2


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Non-destructive sample testing and intuitive operation. The LEAK-MASTER® PRO2 detects escaping CO2. Quality inspection for advanced users with automatic documentation.

LEAK-MASTER®
MAPMAX


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Leak detection on an industrial scale using trace gas CO2. With LEAK-MASTER® MAPMAX you test your entire production: fully automated and integrated into your packaging line.

DO YOU PACK WITH MODIFIED ATMOSPHERE?

Longer shelf life and freshness. This is what packaging of foods, pharmaceutical and cosmetic products is all about. WITT is expert in packaging technology with modified gases and offers gas mixers, gas analysers and leak detectors especially for MAP.

Contact

WITT-GASETECHNIK GmbH & Co KG

Salinger Feld 4-8
58454 Witten
Germany
Tel. +49 (0)2302 8901- 0

We are experts in customised solutions in gas process engineering and gas safety technology. We supply gas mixers, leak testers, gas analysers and gas safety technology to the food and beverage industry, the steel industry, the glass industry, the laser industries and many others industries and applications. From product selection and planning to installation, maintenance and repairs, you can rely on our technical support every step of the way.

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