What is the cause of gate Valve leakage?How should it be handled?

2022-04-23 0 By

Gate valve is one of the most common industrial valves, widely used in petroleum, petrochemical, power station, long-distance pipeline and shipbuilding industries.As a fluid control device, the opening and closing part of the gate valve is a gate plate. Through the up-down movement of the gate plate, the state of opening and closing is switched, so as to realize the function of cutting off or connecting the pipeline intermediary.If the gate valve leaks, it is easy to bring hidden trouble to the pipeline and equipment and facilities, and even affect the safety of personnel and equipment.Understanding the structure and operating principle of gate valve can help us operate gate valve correctly and better grasp the running state of gate valve.Once the gate valve leakage, the first time to take the right way to reduce economic loss, reduce the probability of accident.Gate valve leakage is generally divided into internal leakage and external leakage. There are many reasons leading to gate valve leakage, which need in-depth analysis and research before taking corresponding disposal measures.1. The low machining accuracy of the wedge sealing ring causes the leakage of the valve wedge sealing can be divided into two categories. The first kind of hard seal, also known as the metal wedge ring;The second is a soft seal, also known as a composite graphite wedge ring.If the accuracy of the wedge sealing ring is low, it is easy to cause leakage in the gate valve.2, the production operation condition is not stable in the process of production operation of the gate valve leakage valve, the pressure and environmental temperature may have a large range of changes, which makes the sealing ring to bear larger impact pressure, scouring force and deformation, resulting in the gap between the sealing ring and the valve body is bigger and bigger, resulting in the valve leakage.Within 3 gate valves, valve repair quality closes nevertheless, causing leakage staff to open the valve for maintenance in the process of installation, didn’t the wedge ring seal face is clean, some tiny particles and impurities, these small impurities in the valve during operation may scratch sealing surface, once the sealing surface to form themselves a scratch, the result will be a valve leakage.4, medium corrosion wedge ring the gate valve leakage at the time of design wedge ring need more pay attention to the strength and corrosion resistance of sealing ring, sealing ring surface hardness than the bonnet seal layer hardness smaller, but also conform to the conditions in the external force can occur under the action of plastic deformation, the long time running in the process of corrosion medium can also wedge ring,This causes the gate valve to leak.5, the gate valve actuator switch is not in place so that the leakage gate valve switch in the gate valve is controlled by the actuator. The actuator relies on liquid, gas, electricity or other energy and converts it into a driving effect through the motor, cylinder or other devices to drive the valve to the fully open or fully closed position.If the actuator is not opened or closed properly, the gate valve cannot be opened or closed completely, resulting in internal leakage of the valve.6, valve body defects resulting in leakage casting valve body often appear casting defects, such as: porosity, slag, cracks, trachomere, etc., if these defects are not found in the factory, or found not to take the correct repair measures, there will be valve leakage in the process of field use.2, 1, gate leakage treatment measures fixed clamp body and improve bolt pre-tightening force of gate valves when leakage or a small amount of leakage occurs, the first job is to step up and take hold of the clamp of the body, and to strengthen the platen and by increasing bolt pre-tightening force between wedge ring, it can help to seal plastic deformation,So as to better reduce the size of the gap between the valve body, the pressure plate and the sealing ring, to avoid the leakage phenomenon of the valve self-sealing.If there is no significant change in leakage when tightening and fixing bolts, fastening measures should be stopped immediately and other treatment measures should be taken instead.2, inject sealant through the grease injection hole when the valve appears small internal leakage, you can grease the sealing surface or packing through the grease injection hole, temporarily relieve the valve internal leakage.When it is easy to repair and maintain, the valve can be removed and returned to the factory for repair.3, welding reinforcement valve end face, the gap between the packing box and the pressure plate of the valve sealing leakage treatment needs to do a good job of disassembly valve handwheel and valve frame work, first of all to cooperate with the staff to grasp and adjust the working condition of the site, and then open the valve, and then remove the bolt fixed on the valve bracket,After rotating the valve rack ensures that the stem does not rise or fall, the valve rack is removed.Removed after valve, the valve of the pressure plate parts above the valve body, and to carry on seal the gap between clamp and body and the welding work, out of consideration of leak location after valve frame of back pack process, welding gap size should be between 5 mm to 8 mm advisable, and welding Angle and positions of the platen is the state of the 45 degree Angle,And according to the actual assembly situation for grinding.4, check the actuator zero actuator zero setting is not accurate, did not reach the valve fully closed position.Fully open and close the valve manually, and then adjust the actuator zero position to ensure that the actuator can accurately fully open or fully close the valve.5, valve body repair welding or back to the factory maintenance when there is leakage of valve body, valve manufacturers can repair the defects of valve body, or back to the factory to repair and replace the valve body.First of all, to judge the defects of the valve body, there are penetrating cracks, penetrating defects, and more than a certain area of shrinkage is not allowed to repair, in this case, can only be returned to the factory to replace the valve body.For the valve body defects that can be repaired, appropriate welding process should be developed to determine the welding method, electrode material, post-welding stress relief method, and appropriate non-destructive testing of the welding position to ensure that the repair meets the requirements.By analyzing the causes and treatment measures of gate valve leakage, the valve leakage can be alleviated or eliminated by improving bolt pretightening force, sealing with pressure on line and injecting sealant.With pressure sealing to professional solid foundation of the staff to operate, through welding reinforcement sealing valve end face, stuffing box and pressure plate clearance, injection sealant and other ways can better avoid the occurrence of leakage accidents, so as to solve similar valve leakage problems brought reference and guidance.