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Leak Detection And Testing In Air-conditioners And Refrigerators. by SunFlow(m): 1:54pm On Sep 28, 2016
Refrigerators, Heating systems and gas burner assemblies have several things in common: they all face leakage challenges and they operate with components that may pose a health or environmental risk if the gas or refrigerant leaks.



Leaks

A leak also known as leakage enables fluids either liquids or gases to flow from a machine’s high-pressure side to the low-pressure side. Leak detection systems replicate this action.



Leak Detection Testing Methods



Bubble testing, which is also known as dunking or water immersion, is an old but efficient technique for leak detection. Pressurized parts are submerged in water and observed for escaping bubbles. Larger bubbles mean a larger leak and they are easily detected. Small bubbles mean small leaks, which are not as easy to detect. A type of this test is called the soap solution bubble test, a tried and true technology, but one that has its shortfalls. It is a slow process, requiring training and experience



Pressure decay

Pressure decay is a two-way test that determines whether there is a leak. The process is straightforward. The part is pressurized with high pressure air or dry nitrogen, isolated from the pressure source and monitored for pressure changes over time. The data on pressure changes is then converted into measures of leakage rates. If there is a fast pressure drop, a large leak is present. Furthermore, a slow pressure drop means a small leak. Sensitivity is based on testing time, the pressure transducer and volume. Pressure-decay testing is prone to distraction by changes in the temperature of the air inside the test object. Temperature rises as air is compressed and the test processes must wait until the temperature stabilizes. Some pressure decay systems now employ softwares and thermometers that balances for temperature distortion to a limited pace, but it is not possible to fully eliminate this problem.



Tracer gases

Helium is a very accurate method that can measure leaks below 0.001 standard cubic centimeters per second (cc/sec). In the most common helium testing method, test parts are pressurized with helium and leakage flow is detected with mass spectrometry sampling of the testing chambers.

In another method, the chamber is not evacuated, but instead is left alone for a set amount of time to allow escaping helium to accumulate in the chamber. Another technique is to pressurize the chamber and draw the helium into the component. Lastly, the chamber can also be pressurized. Helium also is used in sniff tests in which the assembly is pressurized with helium and a sniffer searches for samples of air around suspected leak points. Equipment costs, maintenance and helium costs make this method expensive. Helium gas is one such gas that has been used effectively in many applications. It requires pumps and vacuums that may be open to dust and may result in higher maintenance costs. Helium also is a non-regenerative resource, and is more expensive than hydrogen, he says. Another tracer gas is hydrogen. Hydrogen gas, or more accurately a mixture of 5% nitrogen and 95% hydrogen gases, has been used since the mid-1980s. Its use was on a limited basis because of flammability issues until detectors were developed that could detect small hydrogen in low concentrations. Today, diluted hydrogen is now considered a green gas; it is non-flammable and now considered environmentally safe.

source: http://xtrimlaughs.com/2016/09/leak-detection-and-testing-in-air-conditioners-and-refrigerators/
Re: Leak Detection And Testing In Air-conditioners And Refrigerators. by SunFlow(m): 1:55pm On Sep 28, 2016

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