Principle
The bubble test is a simple and intuitive method for testing the sealing performance of valves, based on the surface tension of liquids and the solubility of gases in liquids. When the valve is immersed in water or water is applied to its sealing part, if there is pressure inside the valve and the seal is not tight, the gas will escape from the leak into the water to form bubbles. By observing whether there are bubbles in the water, it can be judged whether the valve is leaking.
Operation steps
Immersion method (applicable to small valves)
For small valves, they can be completely immersed in a container filled with water. The container should be large enough to accommodate the valve and ensure that the valve can move freely in the water, and the depth of the water should be able to cover all possible leakage parts of the valve.
Before putting the valve into the water, make sure the valve is in the closed state, and check whether there is oil or other impurities on the surface of the valve. If necessary, clean it to ensure that the water can adhere well to the surface of the valve to facilitate the observation of bubbles.
Slowly put the valve into the water and observe whether there are bubbles around the valve. The valve can be gently shaken or a certain pressure can be applied to it to simulate the state of the valve in actual work, so as to expose potential leakage points. If continuous bubbles are observed in a certain part, it means that there is a leak in that part.
For example, when testing a small faucet valve, immerse it in a transparent glass container filled with water, and the operator can clearly see whether there are bubbles in various parts of the faucet. If bubbles are found to be constantly coming out at the connection between the valve core and the valve body of the faucet, it can be judged that the connection is poorly sealed and there is a leakage problem.
Smearing method (applicable to large valves or valves that are inconvenient to immerse in water)
For large valves or valves that cannot be immersed in water as a whole, a layer of water or soapy water can be applied to key parts such as the sealing surface of the valve and the connection between the valve stem and the valve body. The application should be uniform and meticulous to ensure that all areas that may leak are covered.
To put the inside of the valve in a certain pressure state, a certain pressure of gas can be filled into the valve by connecting a pressure source (such as compressed air or nitrogen), or the pressure conditions of the valve in actual operation can be simulated. For example, for a stop valve installed on a large pipeline, after the valve is closed, a certain pressure of gas can be introduced into the valve from one end of the pipeline.
Observe whether bubbles are generated in the part where water or soapy water is applied. If bubbles appear, it means that the valve is leaking at that part. The size and number of bubbles can initially reflect the extent of the leak. Generally speaking, the larger the bubbles and the more they are, the more serious the leak.
For example, when testing a large gate valve, the operator applies soapy water on the sealing surface of the gate and the valve body, and then fills the valve with gas at a pressure of 0.3 bar through a pipe. If large bubbles are found in a certain part of the sealing surface, and the number of bubbles increases over time, it indicates that the sealing surface of the gate valve has a more obvious leakage problem, and it needs to be repaired or the seal replaced.
Application scenario
The bubble test method is simple and easy to operate, with low cost. It is often used for preliminary inspection of valves that do not require particularly high sealing, or for quick inspection of valves on site to see if there is obvious leakage. For example, at a construction site, for some temporarily installed water supply and drainage valves, a bubble test can be used for rapid inspection to promptly detect whether the valves are improperly installed or have damaged seals, and ensure the normal operation of the water system during construction. In some small repair workshops or home repairs, this method can also be used to perform simple sealing checks on common valves, such as faucets and heating valves. Although the detection accuracy of the bubble test is relatively low and cannot detect tiny leaks, for some general application scenarios, it can quickly and effectively determine whether the valve has a larger leakage problem, providing a reference for further inspection and maintenance.
