Common faults and preventive measures of automatic valves

One of the faults, the valve is blocked. The reasons are: ① The control channel is blocked by debris (the channel is small and easy to block); ② The piston is stuck in the highest position due to rust stains; although the upper part is stressed, it cannot move downwards, and the main channel cannot be opened. Therefore, the filter must be installed before the piston pressure reducing valve; for the newly installed or long-term out of service pressure reducing valve, it must be disassembled for inspection and cleaning. The second fault is that the valve is directly connected and cannot reduce pressure. The reasons are: ① the piston is stuck in a certain position (not the highest position); ② the main valve handle is stuck in a certain position (not the close position) of the cylinder plate guide hole; ③ the spring under the main valve disc is broken or invalid; ④The valve handle of the pulse valve is stuck at a certain position (not the close position) in the seat hole, so that the piston is always under pressure; ⑤There is dirt stuck or there is between the two sealing surfaces of the main valve disc and the main valve seat Notches; ⑥ The diaphragm fails due to fatigue or damage. For pressure reducing valves, special emphasis should be placed on regular inspections. If dirt and rust stains are found, they should be removed in time; the piston ring should be replaced if damaged; the spring should be replaced with a usable spring; if the sealing surface is not tight, it should be reground; the diaphragm should be replaced if it is not working well; Coarse, use sandpaper to polish. Third, the pressure behind the valve cannot be adjusted. In addition to the above-mentioned various reasons, there are: ① the adjustment spring fails; ② the cap joint leaks and cannot maintain the pressure. Imported metering pump
This must be prevented by timely inspection and treatment. In addition, there is a phenomenon that the pressure pulse after the valve fluctuates, which is extremely unstable. This is because the difference between the input medium and the output medium is too large, and a valve with the same valve diameter should be reselected. Another reason for the unstable pressure behind the valve is improper selection of the adjusting spring; for a pressure reducing valve with a nominal pressure, there are several types of adjusting springs. For example, if the nominal pressure is 16 kg/cm², the adjusting spring has 1-3 There are three kinds of kg/cm2, 2-8kg/cm2, and 7-11kg/cm2. If the pressure behind the valve is only 1-3kg/cm2, the spring is 7-11kg/cm2.

In this way, the pressure after the valve cannot be adjusted correctly. 2. One of the failures of the spring type safety valve is leakage of the sealing surface. The reasons are: ①There is debris between the sealing surfaces; ②The sealing surfaces are damaged. Such failures must be prevented by regular maintenance. The second fault is that the sensitivity is not high. The reasons are: ① spring fatigue; ② improper use of the spring. The spring is fatigued and should undoubtedly be replaced. Improper use of the spring is a spring-type safety valve with a nominal pressure that the user does not pay attention to. There are several pressure sections, and each pressure section has a corresponding spring. For example, a safety valve with a nominal pressure of 16 kg/cm² uses a pressure range of 2.5-4 kg/cm² and a spring of 10-16 kg/cm² is installed. Although it can be opened easily, it fluctuates high and low. , Very insensitive. 6.2.3 The common faults of check valve or check valve are: ①The disc is broken; ②The medium flows back. The reason for the disc breaking is that the pressure of the medium before and after the check valve is close to equilibrium and they are “see-saw” each other. The disc is often beaten with the valve seat, and it is made of some brittle materials (such as cast iron, brass, etc.)

The disc is broken. The preventive method is to use a check valve whose disc is a flexible material. The reasons for the backflow of the medium are: ①The sealing surface is damaged; ②The impurities are caught. Repairing the sealing surface and cleaning impurities can prevent backflow. The above description of common failures and prevention methods can only serve as inspiration. In actual use, other failures will be encountered. To actively and flexibly prevent valve failures, the most fundamental thing is to be familiar with its structure and material. And the principle of action.