Mechanical Engineering Wiki / Tightness
Tightness
Tightness or impermeability is the property of material structures to be impermeable to certain substances, gases, liquids or even radiation. This is a relative concept, as there is no such thing as absolute impermeability. Instead, impermeability must always be assessed in relation to the material being tested, the structure and the "substance" penetrating it. For example, a water pipe proves to be leak-proof until the pressure inside becomes too high - then the pipe may crack and water will leak through. On the other hand, the water pipe is probably not impermeable to radiation from the outset. A leak test is used to determine whether and to what extent a material structure is leak-proof. Tightness tests are part of everyday life, especially in production.
Why is tightness so important?
In production, leak tests are indispensable as part of quality control. The non-destructive test method is sometimes also referred to as a leak test and is used for systems and components in a wide range of industries. Testing the tightness of a component or complex system can be important for various reasons: for example, a leak test during the production process can prevent cost-intensive reworking of components at a later date. In addition, the use of components and systems that are not sufficiently tight can result in repair costs later on. Furthermore, many industries have specific standards and legal guidelines for the tightness of components - a leak test is also essential in order to comply with these. The best example: If, for example, pipe systems in a refrigeration system are not sufficiently tight, gas or water can leak out. This can not only cause considerable damage, but may also lead to accidents or personal injury.
How do you test for leaks?
Leak tests are used in a wide variety of production processes - which is why there are specific leak test methods depending on the application, which are usually implemented as vacuum or overpressure methods. The relevant specifications can be found in DIN EN 1779. Typical examples are
- Worker water bath test (bubble test)
- Water bath test with ultrasonic sensor
- Differential pressure test
- Ultrasonic detection
- Leak test with test gases
It is crucial that the leak test of a test specimen is already integrated into the production process. This prevents expensive reworking in series production from the outset. However, to ensure that the test methods actually deliver reliable results, the devices used for this purpose should be regularly maintained and readjusted if necessary.
In which industries does the tightness of components and systems play a role?
Nowadays, leak testing can be recommended for (almost) every serial production process. Industries that require leak-tight components and systems include the automotive sector, shipbuilding, medical and laboratory technology, the aerospace industry, mechanical engineering, electrical engineering and many more. Other measurement technologies used in industrial series production include torque, X-ray and radar.