Reasons for internal leakage in valves

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In actual production, there are many reasons for internal leakage in valves, mainly including the following: 1. Poor quality of the valve leads to internal leakage. Unqualified valve products end up in the production area, or the material used for the valve’s internal components is of poor quality and the heat treatment is inadequate, resulting in insufficient hardness; such valves are prone to being damaged by high-speed fluids, which causes internal leakage during use. 　　2. Poor valve tuning causes internal leakage. Affected by the processing and assembly techniques, electric valves often fail to open properly even after being manually closed. If the travel distance of the electric valve is reduced by adjusting the operating positions of the upper and lower limit switches, it results in an undesirable situation where the valve cannot be closed tightly or does not open fully ； Increasing the travel distance of the electric valve causes the overload torque switch to activate as a protection measure ； If the operating value of the over-torque switch is set too high, it can lead to damage to the reduction gearing or to the valve, and in severe cases, even burnout of the motor. To address this issue, during the adjustment of the electric door, the electric valve is usually manually closed completely and then turned back one full turn in the opening direction; this sets the position of the lower limit switch for the electric door. Afterwards, the electric valve is opened to its fully open position to determine the position of the upper limit switch. In this way, the electric valve will not fail to open after being manually closed tightly, allowing the door to open and close smoothly. However, this approach inadvertently leads to internal leakage of the electric door. Even if the electric valve is adjusted ideally, since the operating position of the limit switch is relatively fixed, the continuous erosion and wear of the valve caused by the flow of the medium can result in poor sealing of the valve, leading to internal leakage. 　　3. The water quality in the thermal system is substandard, and inadequate pipe flushing leads to internal leakage in the valves. During the startup of the unit, especially during commissioning, as the system has been out of use for a long time, rust and scale accumulate in the pipes. At such times, the system’s drain valves should be opened fully to carry out flushing. If the flushing is not thorough, impurities such as rust will accumulate between the valve core and the valve seat, causing the valve to get stuck at the bottom of the valve core when it is closed. This results in poor sealing and internal leakage. 　　4. Improper operation by the operator caused internal leakage of the valve. When starting or stopping the unit, the appropriate timing for operating the switches and valves should be selected. If it is turned off too late or turned on too early during shutdown, the high steam parameters will cause severe erosion of the valve. When closing the valve, it is necessary to confirm that it has been closed properly.