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Cause analysis and treatment measures of electric gate valve leakage

by:Sino Valves     2021-02-25
The electric gate valve produced is the most common type of industrial electric valve, which is widely used in petroleum, petrochemical, power stations, long-distance pipelines, shipbuilding and other industrial fields. As a kind of fluid control equipment, the gate valve opening and closing part is a gate. Through the up and down movement of the gate, the open and closed states are switched to realize the function of cutting off or connecting the medium in the pipeline. If the electric gate valve leaks, it is easy to bring hidden dangers to pipelines and equipment and facilities, and even affect the safety of personnel and equipment. Understanding the structure and operating principle of the gate valve can help us operate the gate valve correctly and better grasp the operating status of the gate valve. Once the electric gate valve leaks, the correct disposal method can be taken the first time to reduce economic losses and reduce the probability of accidents. Gate valve leakage is generally divided into internal leakage and external leakage. There are many reasons for the leakage of electric gate valves. In-depth analysis and research are required before corresponding treatment measures can be taken. 1. Reasons for leakage of electric gate valve 1.1 The processing accuracy of the wedge-shaped sealing ring is low, which causes the valve to have internal leakage. The wedge-shaped seal can be divided into two categories. The first is a hard seal, also called a metal wedge ring; the second is a soft seal. Also called composite graphite wedge ring. If the accuracy of the wedge-shaped sealing ring is low, it is easy to cause internal leakage of the gate valve. 1.2 The unstable operating conditions of the production and operation cause the internal leakage of the gate valve. The operating conditions of the electric valve during the production operation are unstable, and its pressure and ambient temperature may vary greatly, which makes the sealing ring bear greater impact pressure, scouring force and Deformation causes the gap between the sealing ring and the valve body to become larger and larger, causing internal leakage of the electric valve. 1.3 The quality of valve maintenance is not enough to cause the internal leakage of the gate valve. In the process of disassembling the valve for maintenance, when installing the wedge seal ring, the sealing surface was not cleaned, and some fine particles and impurities remained. These fine impurities were in the valve operation process. It may scratch the sealing surface, and once a penetrating scratch is formed on the sealing surface, it will cause the electric valve to leak. 1.4 Medium corrosion of the wedge seal ring causes internal leakage of the gate valve. When designing the wedge seal ring, it is necessary to pay more attention to the strength and corrosion resistance of the seal ring. The surface hardness of the seal ring is smaller than the hardness of the bonnet sealing layer, and it must conform to the external force. Under the action of conditions, plastic deformation can occur, and the medium may also corrode the wedge seal ring during long-term operation, which will cause the gate valve to leak. 1.5 The switch of the electric actuator of the gate valve is not in place, causing the leakage of the gate valve to be controlled by the actuator. The actuator relies on liquid, gas, electricity or other energy sources and converts it into a driving function through a motor, cylinder or other device, driving the valve to fully open Or fully closed position. If the electric actuator is not opened or closed in place, the gate valve cannot be fully opened or closed, resulting in internal leakage of the electric valve. 1.6 Valve body defects cause leakage of electric valves. Casting defects often appear in valve bodies, such as: pores, slag inclusions, cracks, sand holes, etc. If these defects are not found in the factory, or if correct repair measures have not been taken, Valve leakage will occur during on-site use. 2. Treatment measures for electric gate valve leakage 2.1 Fix the valve body pressure plate and increase the bolt pre-tightening force. When there is leakage or a small amount of leakage inside the electric gate valve, the first job is to tighten and fix the valve body pressure plate, and increase the bolt to Strengthen the pre-tightening force between the pressure plate and the wedge-shaped sealing ring, which can help the plastic deformation of the sealing ring, thereby better reducing the size of the gap between the valve body, the pressure plate and the sealing ring, and avoiding leakage of the valve self-sealing. If there is no major change in the leakage when tightening and fixing the bolts, the tightening measures should be stopped immediately and other measures should be taken instead. 2.2 Inject the sealant through the grease injection hole. When the electric valve has a small internal leakage, the sealing surface or packing can be injected through the grease hole to temporarily relieve the internal leakage of the valve. When it is convenient for inspection and maintenance, the electric valve can be disassembled and returned to the factory for repair. 2.3 Welding and strengthening the gap between the end face of the valve body, the stuffing box and the pressure plate. To deal with the self-sealing leakage of the electric valve, it is necessary to do a good job of dismantling the valve handwheel and valve frame. First, we must cooperate with the technicians to grasp and adjust the on-site working conditions. Then, after opening the valve fully, disassemble the bolts fixed on the electric valve bracket, rotate the valve bracket to make sure that the valve stem does not rise and fall, and then start to disassemble the valve bracket. After disassembling the valve frame, the valve body should be exposed at the pressure plate of the valve, and the gap between the pressure plate and the valve body should be sealed and welded. In consideration of the sealing of the leakage position, the valve frame is reassembled and welded. The size of the gap should be between 5 mm and 8 mm, and the position of the welding angle and the pressure plate is a forty-five degree angle, and it should be polished according to the actual assembly situation. 2.4 Check the zero position of the actuator    The zero position setting of the actuator is inaccurate, and the valve has not reached the fully closed position. Manually open and close the valve fully, and then adjust the zero position of the actuator to ensure that the actuator can accurately fully open or close the valve. 2.5 Repair welding of valve body or return to factory for repair     When there is leakage of valve body, electric valve manufacturer can repair the defect of valve body by welding, or return to factory for repair and replacement of valve body.
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