LEAK DETECTION
Another problem with this method is if the leak detection spray does not adhere suffi ciently to the test specimen and drips off again or if, in the case of gross leaks, it is blown away as a result of the high pressure of the escaping air. Foam testing is understandably not suitable at all for places that are diffi cult to access or cannot be seen. After using leak detection spray, parts must be cleaned again. This cleaning eff ort is, of course, always required, even if the component was able to meet the leak tightness requirements.
4. The refrigerant as tracer gas A practice which is occasionally used is to fi ll refrigerant into the refrigerant circuit after a pressure decay test in order to then determine the location of the leakage with a refrigerant leak detector. However, many standards stipulate that the refrigerant circuit must not be fi lled with refrigerant until the leak tightness of the system has been ensured. In these cases, the use of refrigerant to localize leakages is prohibited from the outset.
leakages even when they are in hard-to-reach locations.
The device is characterized by particularly good gross leak tolerance and very high availability. A robust, highly resistant mass spectrometer virtually eliminates contamination-related downtime due to the ability to quickly restore measurement readiness. The mass spectrometer also has excellent measurement sensitivity, even at large distances. Both helium and the less expensive forming gas – a mixture of 95% nitrogen and 5% hydrogen – are suitable as tracer gases.
match the performance of leak detectors that are intended for production purposes. In addition, their sensors frequently also respond to other substances, which leads to detection interference.
In tests where refrigerant is permitted to be used to localize leakages, refrigerant is deliberately fi lled into a leaky system. Following the test, the refrigerant must then be removed from the testing circuit and recycled – which takes time and causes additional costs.
5. Simple, mobile leak detectors A variety of simple, compact handheld leak detectors are available on the market. All of these devices are optimized for on-site service on construction sites. They are compact, easy to transport and equipped with simple, low-cost sensor technology.
However, these service devices are hardly able
to fulfi l the requirements in production settings. For example, they cannot determine the size of leakages because they cannot be calibrated – even though the displays of some devices suggest the opposite with their numerical values. Neither the detection sensitivity nor the response behaviour of these service devices can
www.acr-news.com February 2020 19
Modern tracer gas methods The equipment that is actually suitable for carrying out leak testing in a production setting of the refrigeration and air conditioning industry is testing equipment that works with mass spectrometers or other highly sensitive sensor technologies, such as Wise technology. The newly developed XL3000fl ex sniff er leak detector, for example, is specially designed to meet the requirements of the refrigeration and air conditioning industry and off ers the maximum level of process reliability. The device draws in the tracer gas at a very high volumetric fl ow rate of up to 3000 standard cubic centimetres per minute (sccm). This is up to 50 times the value of conventional devices. Leaking tracer gas clouds are always reliably detected and leakages can be reliably detected even from large distances. This makes the testing far less operator-dependent and detects
The device is equipped for networking and automation due to its many communication interfaces that correspond to the latest industry standards. In the near future even a robot - or a two-armed cobot (collaborative robot) - will be able to perform leak testing with the device in combination with an optical system. The advantages of automation: even greater effi ciency, less operator-dependent errors and extremely reliable leak detection.
In refrigeration and air conditioning technology, leak tightness requirements are particularly high because environmentally harmful and climate- damaging refrigerant is not allowed to escape. In this context, we are looking at the smallest of leaks, causing an undesired refrigerant loss of only a few grams per year. However, such small leaks can neither be detected nor pinpointed with many of
the leak testing methods that remain in common use.
Tracer gas methods are therefore recommended for the manufacturing of refrigeration and air conditioning systems. Ideally, the tracer gas leak detectors that are used for this purpose should work with a high suction fl ow rate. This signifi cantly reduces the operator dependency of the testing and signifi cantly increases process reliability.
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