Comparing Leak-Testing Methods

Should you use water or CO₂?

Published: Tuesday, November 16, 2021 - 12:02

Many industrial products must be leak-tight. For example, food, cosmetics, or pharmaceutical packaging, but also products such as lights in the automotive industry, electronics, or plastic components. But how can manufacturers test the leak-tightness of their products?

The entry-level solution is to test in a water bath. This is a simple yet effective method. The test specimen is held under water, and the tester watches for rising air bubbles. Very intuitive. In principle, it’s much like patching a bicycle tube, except that the product is not inflated but tested in a vacuum chamber. The product inflates itself, and bubbles escape from leaks. The important thing is that you not only know that the packaging is leaking, but you also immediately recognize where. This allows weak points in the process to be detected and eliminated. The LEAK-MASTER EASY makes this process economical and uncomplicated.

Practically everything that must be leak-proof can be tested using this method. Often it’s packaging. Tubular bags, stand-up pouches or thermoformed trays, even vacuum packaging can be tested. For food products the testing is usually for meat or sausage products, salad, bread, snacks, dairy products, pet food, or medical products. Even testing the popular coffee capsules is possible. Lights, bubble wrap, or plastic parts must also be leak-tight.

Although the testing can be done in a water bath, it depends on the requirements. If it’s just a matter of checking for leaks and finding their sources, these testing devices are good. But there are limitations: Testing in water usually means the product can no longer be sold. In addition, the test is performed manually. This places quite high demands on personnel and may have an influence on the result.

A more standardized approach is to leak-test using specific test gas and sensor technology. The LEAK-MASTER PRO 2, determines the leak tightness of relevant products using CO₂ sensors. Here, too, a vacuum is created in a test chamber to draw gas out of the leaking packaging. Parameters, such as vacuum and measurement time, are defined in advance by the customer, which allows the test to be performed automatically. At the end of the measurement, the PRO 2 displays the result by means of a light signal. If the device lights up red, for example, CO₂ has been detected, and the product is leaking. The test is therefore completely independent of the inspector and is standardized and reproducible. Everything is documented digitally, and the data can also be exported.

In terms of the test speed, the more CO₂ in the packaging, the faster you can find a leak. As a rule, 8–10 seconds are often sufficient. In principle, leaks of 10 micrometers or more can be reliably detected. These microleaks are the ones that cause the most problems for manufacturers. A major advantage of CO₂ testing is that it’s nondestructive. After testing, the leak-proof packages can be put on sale without any problems. This saves waste and costs.

Just to restate: Water bath devices provide the cheapest method; they’ve been proven over many years and work reliably. If I want to find out where my product is leaking, I need a water bath in any case. And if I don’t have CO₂ in the product, or I have a vacuum pack, the water bath is the best option. For more standardization and automation, CO₂ units are a good choice. This is because they don’t need to be inspected by a human. The result is still reliable even after the umpteenth test at the end of a long working day.

Second point: With a CO₂ test, you can check for leak-tightness without destroying the product. And finally, testing without water is cleaner and less complicated. Changing the water regularly and cleaning the bath aren’t necessary. Using both devices as needed is ideal. With the CO₂ device, you can perform all spot checks safely and nondestructively. In the case of a leaking package, you can use the water bath to find the location of the leak.

If 100-percent inspection is needed, usually an in-line solution is required. Here, too, machines with CO₂ sensors have become well established in practice. The LEAK-MASTER MAPMAX, for example, is used by food producers to ensure perfect packaging and thus the quality of their products. As with the PRO 2, the MAPMAX receives all the packages from the packaging machine. A vacuum is created in a chamber. Sensors detect escaping CO₂. If a leak is detected, an alarm triggers on the device. In addition, leaking packages can be physically rejected. Everything is fully automatic. What’s more, it’s fast and reliable; the MAPMAX manages up to 15 cycles per minute.

Keep in mind that in most cases, the MAPMAX is used to test whole batches or cartons directly, rather than individual items. There are faster machines on the market where pressure is applied to the package via a roller. However, this method finds only very large leaks, which isn’t as useful for most producers. In fact, testing outer packaging is the safest because the testing is done at the very end of the process.

Whether random testing or in-line testing is required depends on the product, the packaging, the process, the expiration date, as well as the distribution channels. But in any case, in-line offers the maximum confidence that customers will receive their products in leak-proof packages.

About The Author

Geert Elie

Geert Elie is a food technologist, born and educated in the Netherlands. In the course of his career he has worked for an industrial gas company, and for food machinery manufacturers. For over ten years he was working for the distributor of WITT Products in the Netherlands, and has now joined WITT.based at their headquarters in Witten, Germany.