A certain oil management office product pipeline length of 540 km long, consists of 6 oil stations to download oil and increase pipeline delivery pressure of refined oil, pipeline with high pressure, large diameter characteristics. As the delivery of oil flammable, explosive, plumbing and mechanical pipelines appear not easy to handle, so the valve selection, taking into account the economy and practicality, in the oil pipeline and gas station, and more to take the import ball valve And domestic electric flat gate valve used in conjunction. At present, the Z9B43WbFPN2.5DN200 electric flat gate valve (parallel gate valve) used by the oil station is mainly composed of an electric actuator, a valve body, a valve cover, a valve stem, a valve plate and a floating valve seat. The valve seat and the valve plate are Two-way seal, high requirements on pipeline media cleanliness. Z9B43WbFPN2.5DN200 electric flat gate valve pressure level is not high, but the failure rate is higher, affecting the normal control center of the oil delivery plan implementation. And if the valve can not be operated in time, it is possible for pipeline pressure to over-pressure to cause other equipment failure and run oil, which has a big potential safety hazard. One valve seat and the valve plate surface, valve seat and valve body surface with two locations is the point of failure. (1) The joint surface of the valve seat and the valve plate is machined with a sealing groove of Φ200mm × 8mm, the sealing material of which is PTFE (reinforced polytetrafluoroethylene) sealing ring, which can be effectively fitted with the valve plate working face to make the valve seat Seal with the valve plate, the oil does not leak. (2) The joint surface of the valve seat and the valve body is sealed with an O-ring rubber. The arc length between the two inlet and outlet valve seats and the valve body is equipped with a spring. When the valve is assembled, a compression spring is applied to apply a certain pre-tightening force to the valve seat, Valve inlet and outlet valves and valve plate to achieve two-way sealing effect. 2. Faults and Analysis General For electric flat gate valve failure, after excluding the electrical wiring and electric head mechanical problems, it is usually the first to open the valve drain plug for sewage treatment, valve cavity by observing the internal blockage of impurities, internal failure of the valve preliminary Analysis, based on experience, the phenomenon of fault valve plate and valve seat displacement. Example 1 When the electric flat gate valve with valve number 512 (flow meter back valve in gas station) is closed, it will not be able to continue to the limit stroke of 11%. Analysis of the failure to observe the valve electric head indicates normal, no alarm display screen, remote control valve in the dispatch room can be 100% fully open. The electric head control switch to remote control by the local control, the use of manual off, the handwheel torque is larger, no significant effect, no longer forced to pull. According to the valve plate is stuck position, initially determine the valve cavity with foreign body stuck in the valve plate stroke 11% position. Valve No. 512 before the pipeline is not installed filters, in accordance with process requirements, the valve must be open during operation. Long-term operation of pipeline oil rust, oil sands precipitated in the valve cavity through the valve, the valve needs to be closed, the operator is not timely sewage (valve cavity impurities to determine how much the site is not good, and the sewage pipe plug should not be disassembled) , Resulting in the accumulation of impurities more. In the operation of the valve is closed, the valve plate at the bottom of the stopper (guide block) gradually compressed impurities, some of the impurities in the valve cavity is compressed into a cake-like no longer flow. When the valve can not be closed, the electric head travel indicator indicates that the position of the valve plate is between 1% and 99% (full-closed state is 00% and fully open is 100%). When the valve chamber space is filled with impurities such as rust, the closed valve cavity impurities and sewage oil will be expanded under high temperature, the pressure increases. During the lifting process of the valve plate, the spring between the valve seat and the valve body will slightly expand and contract. The impurities gradually penetrate between the springs in contact with the valve seat and adhere to the valve body and the valve seat. As the seat pressure by the media, relative to the valve plate will do self-sealing adjustment, the valve plate raised to fully open state, the valve plate limit about 1/2 of the seat diameter, seat sealing spring by the valve plate Move, showing uneven force, the gap between the valve seat and the body increases. The impurities adhering to the valve seat and the valve body surface gradually fill the gap between the valve seat and the valve body during the telescopic movement of the spring. The amount of spring expansion and contraction is reduced, and the valve seat can not be reset after being ejected. The two seats in the valve body was V-shaped state, above the large, below the small. When the valve plate is closed to the minimum position of the PTFE seal, the seal ring on the valve seat is scratched, causing the valve to close in place. Example 2 valve 521 electric flat gate valve (gas station in the flow meter pre-valve), manual and remote control can not open and close, electric head indicates limit travel 4% ~ 6% swimming. Fault Analysis Observing the valve electric head indicates normal, the judgment is firmly stuck in the slide plate in the slide, the electric head only when the electric head within the worm 4% ~ 6% idling, the actual valve stem is not moving. Electric flat gate valve can not open and close the case, indicating that the internal damage to the valve has been more serious, we must disintegrate the valve for a comprehensive inspection and maintenance. Valve cavity more impurities, the seat in the valve body position displacement into a V-shaped state. The operator does not know the internal situation, repeated action valve, resulting in the valve plate guide part of the large chrome layer scratched, the valve plate is scratched groove damage, damaged PTFE ring seal, metal surface nap. The impurities adhere to the valve plate and enter the slide plate of the valve plate to increase the friction between the slide plate and the valve plate. The electric head drives the valve rod and the valve plate to move up and down. After the load increases, the worm gear of the electric head obviously emits hard rotating sound. Friction within the slide on both sides of the unbalanced, the small friction plate on the side of the slight upward tilt, the stem in the normal tilt or sloshing force, and the valve cover and seal pressure Lan friction, it is easy to scratch the valve Rod. Stem lift force exceeds the set value, the electric head torque protection to open to stop running, the valve plate is stuck in the slide does not move. 3. Action on the fault electric flat gate valve for sewage inspection, cleaning valve cavity impurities, remove minor faults, to restore normal use of the function. If the valve appears to be closed or unable to open and close the phenomenon, you need to schedule scheduling maintenance time. Valve really needs disintegration inspection, maintenance personnel need to contact the factory before the disintegration to prepare spare parts, mainly floating seat O-ring, spring, PTFE ring and valve cover in the open combination pad to understand the same type of valve repair technical requirements . Maintenance personnel will lift the valve lines and interlocks, disassembly pipeline flange bolts, install the blind after the electric flat gate valve to the maintenance area for disintegration inspection. First electric head and the valve detachment, the valve on the operating table, clean the stem leakage screw part and the sealing surface position, spray a little lubricating oil on the stem to prevent the valve stem seals are removed hurt. Loosen the gland bolts so that the seal is no longer under pressure, loosen the flange bolts of the electric flat gate valve cover, lift the valve cover and seal together slowly from the top of the valve stem with the lifting chain, open the valve blowdown Plug the wire, rinse the inside of the valve with clean water, check the cleanliness of the slide in the valve plate and the tilt of the valve plate. After cleaning the valve cavity, tap the valve plate with a copper rod and adjust the valve plate to the middle of the slide. Prefabricate a pair of Z-shaped brackets welded with steel plates, install two Z-shaped lifting brackets at the valve plate dovetail groove and the stem connecting block, one end of which attaches the valve stem connecting block, and the position of the flange sealing surface in the valve Do a good job of protection, to prevent scratches), each placed a 3t jack, supporting the other end of the Z-shaped bracket. (1) Check the displacement of the floating valve seat, measure the width of the valve seat installation process groove (8mm) and the straight distance (240mm) from the process tank to the inlet and outlet flanges. M24 machined special cylindrical nut, a thickness of 6mm, with M24 × 400mm lead screw, made into a stretch. In the import and export of the valve seat of the process of installing four tensioners, compressed valve seat and valve clearance, reducing the seat on the valve plate thrust. At this time both of them operate the jack at the same time, and put the Z-shaped bracket together with the valve plate and the valve rod out of the valve cavity to remove the valve plate. (2) Loosen the tensioner, remove the valve seat, clean the bonding surface impurities, check the valve seat part of the damage. (3) Clean the valve seat, valve plate and valve chamber. (4) As long as the installation of the four tensioner seat evenly tightened to measure the gap between the two seat ring seal, and valve plate to confirm the thickness of the tolerance with the transition fit, the valve plate sealing surface lubrication Oil can be easily re-installed. The reverse order of loading and disassembly. On-site maintenance of electric flat gate valve chrome layer off a large area, the valve plate is drawn about 3mm two scratches, extending to the bottom of the valve plate, protruding iron filings, resulting in the valve can not be opened. Seat and valve body due to the presence of impurities, the valve seat displacement occurs in the valve seat and valve body surface below the nozzle, the spring around the adhesion of about 2mm thick sludge, and the top is relatively clean, indicating the O-valve seat Seal has been squeezed to form a leakage of impurities, the effect of losing a comprehensive seal. V-shaped seat firmly clamped valve plate, resulting in the valve can not be closed. Two valve seat inlaid seal serious defect can not be used, the lower part of the seat metal surface scratches, grinding and repair can continue to use. Maintenance personnel site on the valve plate scratches adhesive repair, grinding treatment. The protruding part is repaired with a file and is ground to bring it close to its original finish. However, the chrome plate can not be repaired by hand, the chrome plating area is small and the conditions are not allowed. In order to get the valve put into operation as soon as possible, grinding and repairing the valve plate and the valve seat can reach the conditions of use. The reinforced polytetrafluoroethylene sealing ring of the valve seat has been worn and scrapped, and new PTFE material needs to be replaced. The machined sealing surface protrudes out of the valve seat by 0.25mm. After the processing is completed, the sealing surface is lapped and leveled by the grinding table. After maintenance treatment, the manual test operation, switch the valve reset after the reset limit, many times the operation is normal. Reasonable to improve, the sewage plug to replace the wire - small ball valve - draft tube - plug the structure, in line with the pressure level requirements and conditions of use, both economical and convenient, you can operate the valve before the operation of the sewage, to avoid serious blockage After processing.