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Tuesday, November 21, 2017

The Use Of Hydro Testing

By Nancy Morgan


Hydro test is a process where different pipe systems or other pressure devices are tested for their strength and possible leaks. This is usually done after more significant repairs, or simply to check out the equipment before continuing to use it. Hydro testing is usually required to validate the system and it is the only way of finding out if it will work properly.

For performing this procedure, the system has to be shut down, and none of these methods can be used when the system is running. It is a nondestructive way of finding out if everything is in order, and if it is working properly. Testing is usually required after repairs or for issuing various operating licenses. It is performed to find possible leaks and other failures.

When it comes to different pipelines, the system should be first totally emptied, and all natural gas, oil or other substances removed. After that, the pipeline should be mechanically cleaned and vented. The whole system is then filled with water, and this process removes all the remains of air held within. After that, the pressure that exceeds the designed pressure limit of this pipeline is applied.

In this particular process, the pressure used for testing should be approximately 50 percent higher than the pressure this pipeline is designed for. This pressure should remain for some time, until the official persons visually check the unit for cracks or leakages. In some cases, fluorescent dyes may also be used, to ease the procedure and to make it possible to find the origin of leaks.

Since these pipes may be used for different types of fluids, and different types of fluids may have different characteristics, this must be taken into consideration when running this test. These characteristics may have significance foe making the final evaluation.

For pressure vessels and similar units another technique is applied. Depending on the purpose, you can use one of three most common methods. The first one is used mostly for testing pressure vessels, and this is the method of direct expansion. The vessel is first filled with previously set amount of water. After that, it's put under pressure, for calculated time. During that time, some amount of water gets expelled from the vessel, and this should be measured.

Another method is called water jacket method, because the unit should be filled with water first, and then loaded into a sealed chamber. This chamber, called the test jacket, is also filled with water. Pressurizing vessel inside this sealed chamber results in expansion of the vessel, and this forces water out of the sealed chamber. This is how you can measure total expansion.

After the pressure is removed, tested vessel should slowly shrink back to its original size. Sometimes it does, and sometimes it doesn't. If it does, everything is in order, but if it doesn't, depending of the shrink-back percentage, it might require a service. When it's not important to have these numbers, it's easier to use so called pressure method. It will be enough to check the unit for leaks or other issues that can cause failures, for example, wall thinning.




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