Opening and closing fault treatment of electric flat gate valve in oil pipeline
2023-09-14 08:08:53
1. Overview The oil pipeline of a certain oil pipeline has a total length of more than 540 kilometers. There are 6 oil stations for downloading oil and increasing the pressure for pipeline product oil delivery. The pipeline has the characteristics of high pressure and large diameter. Because the transported oil is flammable and explosive, the pipeline is not easy to handle when it leaks or malfunctions. Therefore, considering the economy and practicality in the selection of the valve, the imported ball valve is often used in the oil pipeline and the oil delivery station. Used with domestic electric flat gate valve. At present, the Z9B43WbFPN2.5DN200 electric plate gate valve (parallel gate valve) is mainly used in the oil station. It consists 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 bidirectional. Sealing requires high cleanliness of the pipeline medium. Z9B43WbFPN2.5DN200 type electric flat gate valve is not high pressure level but the failure rate is high, affecting the normal control of the center's oil delivery plan. In addition, if the valve cannot be operated in time during operation, the pipeline pressure may overpressure and cause other equipment to malfunction and run out of oil, resulting in greater safety risks. One of the joints of the valve seat and the valve plate, and the joint surface of the valve seat and the valve body are fault multiple points.
(1) Sealing groove of Φ200mm×8mm is machined on the joint surface of the valve seat and the valve plate, and the mounting material is a PTFE (enhanced polytetrafluoroethylene) seal ring, which can be effectively attached to the valve plate working face to make the valve seat Sealed with valve plate, oil does not leak.
(2) The joint surface of the valve seat and the valve body is sealed with an O-type apron. The arc length between the two inlet and outlet valve seats and the valve body is equipped with a spring. When assembling, the spring is compressed, and a certain preload is applied to the valve seat. Make the valve inlet and outlet valve seat and the valve plate achieve two-way sealing effect.
2. Faults and Analysis Generally, for the failure of the electric flat gate valve, after eliminating the mechanical problems of the electric line and the electric head, it is usually the first time to open the valve drain plug to discharge the sewage. By observing the internal clogging of the valve chamber, the internal fault of the valve is preliminary. According to the analysis, according to experience, the fault phenomenon is mostly caused by the displacement of the valve plate and the valve seat.
Example 1 When the electric flat gate valve with valve position No. 512 is closed (the flow meter rear valve in the fuel delivery station) is closed, it is not possible to continue down to 11% of the limit stroke.
The fault analysis observes that the electric head of the valve indicates normal and there is no alarm symbol on the display screen. When the dispatching room remotely operates the valve, it can be fully opened 100%. After the power head control switch was changed from remote control to local control, the manual switch was turned off. The torque of the handwheel was large, there was no obvious effect, and no further forced movement was performed. According to the stuck position of the valve plate, it is preliminarily judged that foreign matter in the valve chamber is stuck at the 11% position of the valve plate. The No. 512 valve has no filter in front of the valve. According to the process requirements, the valve must be open during operation. The rust and oil sand in the long-term operation of the pipeline oil are precipitated in the valve chamber after passing through the valve. When the valve needs to be closed, the operator does not discharge the pollutants in time (the number of impurities in the valve cavity is not good at the site, and the drain plug is not suitable for disassembly). , resulting in more and more impurities. When the operation valve is closed, the limit block (guide block) at the bottom of the valve plate gradually compresses the impurities, and some of the impurities are compressed into a cake shape in the valve cavity and no longer flow. When the valve cannot be closed, the electric head stroke indicator indicates that the position of the valve plate is between 1% and 99% (the fully closed state is 00% and the full open is 100%). When the valve chamber space is filled with impurities such as rust, impurities and dirt in the closed valve chamber will expand due to high temperature and the pressure will increase. During lifting of the valve plate, the spring between the valve seat and the valve body will slightly expand and contract. Impurities will gradually infiltrate between the springs that are in contact with the valve seat and adhere to the joint surfaces of the valve body and the valve seat. Because the valve seat is affected by the medium pressure, self-sealing adjustment will be made relative to the valve plate. When the valve plate is lifted to the fully open state, the valve plate limit is approximately 1/2 of the valve seat diameter, and the valve seat sealing spring is covered by the valve plate. Moving, showing an uneven force state, the gap between the valve seat and the valve body increases. Impurities adhering to the joint surfaces of the valve seat and the valve body gradually fill up the gap between the valve seat and the valve body during the telescopic movement of the spring, and the amount of expansion and contraction of the spring is reduced, and the valve seat cannot be reset after being ejected. The two valve seats are V-shaped in the valve body, and the upper and lower surfaces are small. When the valve plate is closed to the minimum position of the PTFE sealing ring, it is stuck, and the sealing ring inserted in the valve seat is scratched, causing the valve to close in place.
Example 2 The electric flat valve valve with valve position number 521 (meter valve in the delivery station) can neither be opened nor closed by manual or remote control. The electric head indicates that the limit stroke is 4% to 6%.
Fault analysis observes that the electric head of the valve indicates normal, and it is judged that the valve plate is firmly stuck in the slide. When the electric head is operated, only the internal head of the electric head is idling at 4% to 6%, and the actual valve stem does not move. Electric flat gate valve can not open and close, indicating that the internal damage of the valve has been more serious, must disassemble the valve, conduct a comprehensive inspection and maintenance. When there is a lot of impurities in the valve cavity, the valve seat is displaced into a V-shaped state in the valve body. The operator was not aware of the internal conditions. Repeated operation of the valve resulted in scratches on the chrome plated layer of the large area of ​​the valve plate guide. The valve plate was scratched out of the groove and damaged. The PTFE seal of the valve seat was damaged, and the metal surface was pulled. Impurities adhere to the valve plate and enter the valve plate slide, increasing the friction between the slide and the valve plate. The electric head drives the valve stem and the valve plate to move up and down. After the load is increased, the worm wheel of the electric head obviously emits a strenuous sound. After the friction in both sides of the slideway is out of balance, the side with small friction on the valve plate tilts slightly upwards, and the valve stem is tilted or shaken under abnormal force, causing friction with the valve cover and the sealing pressure blue, and it is easy to scratch the valve. Rod. The lift force of the stem exceeds the set value, the torque protection of the electric head starts and stops, and the valve plate is stuck in the slide and does not move.
3. Handling measures Check the fault of the electric flat gate valve, clean up the impurities in the valve cavity, and eliminate minor faults so that they can return to normal use. If the valve does not close or does not open or close, you need to contact the dispatcher to schedule the repair. If the valve does require disassembly inspection, the maintenance personnel must contact the manufacturer to prepare spare parts before dismantling. The main components are floating seat O-rings, springs, PTFE seals, and bonnet-open combination pad to understand the technical requirements for the same type of valves. .
The maintenance personnel will release the valve line and interlock, disassemble the pipeline flange bolts, install the blind plate and transport the electric flat gate valve to the maintenance area for disassembly inspection. First disassemble the electric head from the valve, place the valve on the operating table, clean the position of the leakage screw part and the sealing surface of the stem, and spray a little lubricant on the stem to prevent the stem seal from being scratched when it is removed. hurt. Loosen the sealing gland bolt so that the seal no longer bears pressure. Loosen the middle flange bolt of the valve cover of the electric flat gate valve. Use the chain to slowly remove the valve cap and seal from the top of the valve stem and open the valve to drain Plug the plug and flush the inside of the valve with clean water to check the cleanliness of the valve slide and the inclination of the valve plate.
After cleaning the valve chamber, strike the valve plate with a copper rod and adjust the valve plate to the middle of the slide. A pair of prefabricated zigzag brackets welded with steel plates are installed. Two zigzag lifting brackets are installed at the valve plate dovetail grooves and stem connecting blocks. One end of the valve rod connecting block is attached to the flange sealing surface position in the valve (seal surface Do a good job of protection against scratches. Place a 3t jack each to support the other end of the zigzag support.
(1) Check the displacement of the floating seat. Measure the width (8mm) of the seating groove of the valve seat and the straight distance (240mm) from the groove to the inlet and outlet flanges. The special round nut of M24 is machined to a thickness of 6mm, and it is made into a set of tensioner with M24×400mm screw. Four tensioners are installed in the inlet and outlet valve seat process tanks to reduce the clearance between the valve seat and the valve body and reduce the thrust of the valve seat on the valve plate. At this time, both of them operate the jacks at the same time. The Z-shaped bracket is pushed out of the valve chamber together with the valve plate and the valve stem, and the valve plate can be taken out for inspection.
(2) Loosen the tensioner, remove the valve seat, clean the joint surface impurities, and check the damage of the valve seat part.
(3) Clean the seat, valve plate, and valve chamber interior.
(4) As long as the four tensioners of the valve seat are tightened evenly during installation, the clearance between the two valve seat sealing rings shall be measured to ensure that the valve plate sealing surface is lubricated when the matching tolerance with the valve plate thickness is a transitional fit. Oil can be easily reloaded. The reloading sequence is the reverse of disassembly.
On-site maintenance of the electric flat gate valve plate chrome plated layer off a large area, the valve plate is drawn out of about 3mm two scratches, extending to the bottom of the valve plate, there is protruding iron, so that the valve can not be opened. Due to the presence of impurities between the valve seat and the valve body, the valve seat is displaced. Below the nozzle of the valve seat and the valve body's joint surface, about 2 mm thick sludge is adhered around the spring, and the upper part is relatively clean, indicating the O type of the valve seat. The seal ring has been squeezed by impurities to form a leak and lose its full seal effect. The valve seat holds the valve plate in a V-shape, so that the valve cannot be closed. The defect of the sealing ring inlaid on the two valve seats is severely unusable, and the metal surface on the lower part of the valve seat is scratched and can be used after grinding and repair. The maintenance personnel performed adhesive repair and grinding on the scratches on the valve plate in the field. The bulge is repaired with a guillotine and ground to an original finish. However, the chromium plating on the valve plate cannot be repaired by hand, and the cost and conditions of chrome plating in a small area are not allowed. In order to achieve early production, grinding and repair of the valve plate and valve seat can meet the conditions of use. The seated reinforced PTFE sealing ring has been worn out and need to be replaced with new PTFE material. The machined sealing surface protrudes from the seat 0.25mm. After the machining is completed, the sealing surface is polished and leveled with a grinding table.
After the overhaul, a manual test operation is performed. After the switch is smooth, the switch limit of the valve is reset, and the multiple operations are normal. The rationalization and improvement will replace the blowdown plug with the wire-ball valve-drainage pipe-plugging structure. It meets the pressure level requirements and the conditions of use. It is economical and convenient. It can discharge pollutants before the operator operates the valve to avoid serious jamming. After processing.
(1) Sealing groove of Φ200mm×8mm is machined on the joint surface of the valve seat and the valve plate, and the mounting material is a PTFE (enhanced polytetrafluoroethylene) seal ring, which can be effectively attached to the valve plate working face to make the valve seat Sealed with valve plate, oil does not leak.
(2) The joint surface of the valve seat and the valve body is sealed with an O-type apron. The arc length between the two inlet and outlet valve seats and the valve body is equipped with a spring. When assembling, the spring is compressed, and a certain preload is applied to the valve seat. Make the valve inlet and outlet valve seat and the valve plate achieve two-way sealing effect.
2. Faults and Analysis Generally, for the failure of the electric flat gate valve, after eliminating the mechanical problems of the electric line and the electric head, it is usually the first time to open the valve drain plug to discharge the sewage. By observing the internal clogging of the valve chamber, the internal fault of the valve is preliminary. According to the analysis, according to experience, the fault phenomenon is mostly caused by the displacement of the valve plate and the valve seat.
Example 1 When the electric flat gate valve with valve position No. 512 is closed (the flow meter rear valve in the fuel delivery station) is closed, it is not possible to continue down to 11% of the limit stroke.
The fault analysis observes that the electric head of the valve indicates normal and there is no alarm symbol on the display screen. When the dispatching room remotely operates the valve, it can be fully opened 100%. After the power head control switch was changed from remote control to local control, the manual switch was turned off. The torque of the handwheel was large, there was no obvious effect, and no further forced movement was performed. According to the stuck position of the valve plate, it is preliminarily judged that foreign matter in the valve chamber is stuck at the 11% position of the valve plate. The No. 512 valve has no filter in front of the valve. According to the process requirements, the valve must be open during operation. The rust and oil sand in the long-term operation of the pipeline oil are precipitated in the valve chamber after passing through the valve. When the valve needs to be closed, the operator does not discharge the pollutants in time (the number of impurities in the valve cavity is not good at the site, and the drain plug is not suitable for disassembly). , resulting in more and more impurities. When the operation valve is closed, the limit block (guide block) at the bottom of the valve plate gradually compresses the impurities, and some of the impurities are compressed into a cake shape in the valve cavity and no longer flow. When the valve cannot be closed, the electric head stroke indicator indicates that the position of the valve plate is between 1% and 99% (the fully closed state is 00% and the full open is 100%). When the valve chamber space is filled with impurities such as rust, impurities and dirt in the closed valve chamber will expand due to high temperature and the pressure will increase. During lifting of the valve plate, the spring between the valve seat and the valve body will slightly expand and contract. Impurities will gradually infiltrate between the springs that are in contact with the valve seat and adhere to the joint surfaces of the valve body and the valve seat. Because the valve seat is affected by the medium pressure, self-sealing adjustment will be made relative to the valve plate. When the valve plate is lifted to the fully open state, the valve plate limit is approximately 1/2 of the valve seat diameter, and the valve seat sealing spring is covered by the valve plate. Moving, showing an uneven force state, the gap between the valve seat and the valve body increases. Impurities adhering to the joint surfaces of the valve seat and the valve body gradually fill up the gap between the valve seat and the valve body during the telescopic movement of the spring, and the amount of expansion and contraction of the spring is reduced, and the valve seat cannot be reset after being ejected. The two valve seats are V-shaped in the valve body, and the upper and lower surfaces are small. When the valve plate is closed to the minimum position of the PTFE sealing ring, it is stuck, and the sealing ring inserted in the valve seat is scratched, causing the valve to close in place.
Example 2 The electric flat valve valve with valve position number 521 (meter valve in the delivery station) can neither be opened nor closed by manual or remote control. The electric head indicates that the limit stroke is 4% to 6%.
Fault analysis observes that the electric head of the valve indicates normal, and it is judged that the valve plate is firmly stuck in the slide. When the electric head is operated, only the internal head of the electric head is idling at 4% to 6%, and the actual valve stem does not move. Electric flat gate valve can not open and close, indicating that the internal damage of the valve has been more serious, must disassemble the valve, conduct a comprehensive inspection and maintenance. When there is a lot of impurities in the valve cavity, the valve seat is displaced into a V-shaped state in the valve body. The operator was not aware of the internal conditions. Repeated operation of the valve resulted in scratches on the chrome plated layer of the large area of ​​the valve plate guide. The valve plate was scratched out of the groove and damaged. The PTFE seal of the valve seat was damaged, and the metal surface was pulled. Impurities adhere to the valve plate and enter the valve plate slide, increasing the friction between the slide and the valve plate. The electric head drives the valve stem and the valve plate to move up and down. After the load is increased, the worm wheel of the electric head obviously emits a strenuous sound. After the friction in both sides of the slideway is out of balance, the side with small friction on the valve plate tilts slightly upwards, and the valve stem is tilted or shaken under abnormal force, causing friction with the valve cover and the sealing pressure blue, and it is easy to scratch the valve. Rod. The lift force of the stem exceeds the set value, the torque protection of the electric head starts and stops, and the valve plate is stuck in the slide and does not move.
3. Handling measures Check the fault of the electric flat gate valve, clean up the impurities in the valve cavity, and eliminate minor faults so that they can return to normal use. If the valve does not close or does not open or close, you need to contact the dispatcher to schedule the repair. If the valve does require disassembly inspection, the maintenance personnel must contact the manufacturer to prepare spare parts before dismantling. The main components are floating seat O-rings, springs, PTFE seals, and bonnet-open combination pad to understand the technical requirements for the same type of valves. .
The maintenance personnel will release the valve line and interlock, disassemble the pipeline flange bolts, install the blind plate and transport the electric flat gate valve to the maintenance area for disassembly inspection. First disassemble the electric head from the valve, place the valve on the operating table, clean the position of the leakage screw part and the sealing surface of the stem, and spray a little lubricant on the stem to prevent the stem seal from being scratched when it is removed. hurt. Loosen the sealing gland bolt so that the seal no longer bears pressure. Loosen the middle flange bolt of the valve cover of the electric flat gate valve. Use the chain to slowly remove the valve cap and seal from the top of the valve stem and open the valve to drain Plug the plug and flush the inside of the valve with clean water to check the cleanliness of the valve slide and the inclination of the valve plate.
After cleaning the valve chamber, strike the valve plate with a copper rod and adjust the valve plate to the middle of the slide. A pair of prefabricated zigzag brackets welded with steel plates are installed. Two zigzag lifting brackets are installed at the valve plate dovetail grooves and stem connecting blocks. One end of the valve rod connecting block is attached to the flange sealing surface position in the valve (seal surface Do a good job of protection against scratches. Place a 3t jack each to support the other end of the zigzag support.
(1) Check the displacement of the floating seat. Measure the width (8mm) of the seating groove of the valve seat and the straight distance (240mm) from the groove to the inlet and outlet flanges. The special round nut of M24 is machined to a thickness of 6mm, and it is made into a set of tensioner with M24×400mm screw. Four tensioners are installed in the inlet and outlet valve seat process tanks to reduce the clearance between the valve seat and the valve body and reduce the thrust of the valve seat on the valve plate. At this time, both of them operate the jacks at the same time. The Z-shaped bracket is pushed out of the valve chamber together with the valve plate and the valve stem, and the valve plate can be taken out for inspection.
(2) Loosen the tensioner, remove the valve seat, clean the joint surface impurities, and check the damage of the valve seat part.
(3) Clean the seat, valve plate, and valve chamber interior.
(4) As long as the four tensioners of the valve seat are tightened evenly during installation, the clearance between the two valve seat sealing rings shall be measured to ensure that the valve plate sealing surface is lubricated when the matching tolerance with the valve plate thickness is a transitional fit. Oil can be easily reloaded. The reloading sequence is the reverse of disassembly.
On-site maintenance of the electric flat gate valve plate chrome plated layer off a large area, the valve plate is drawn out of about 3mm two scratches, extending to the bottom of the valve plate, there is protruding iron, so that the valve can not be opened. Due to the presence of impurities between the valve seat and the valve body, the valve seat is displaced. Below the nozzle of the valve seat and the valve body's joint surface, about 2 mm thick sludge is adhered around the spring, and the upper part is relatively clean, indicating the O type of the valve seat. The seal ring has been squeezed by impurities to form a leak and lose its full seal effect. The valve seat holds the valve plate in a V-shape, so that the valve cannot be closed. The defect of the sealing ring inlaid on the two valve seats is severely unusable, and the metal surface on the lower part of the valve seat is scratched and can be used after grinding and repair. The maintenance personnel performed adhesive repair and grinding on the scratches on the valve plate in the field. The bulge is repaired with a guillotine and ground to an original finish. However, the chromium plating on the valve plate cannot be repaired by hand, and the cost and conditions of chrome plating in a small area are not allowed. In order to achieve early production, grinding and repair of the valve plate and valve seat can meet the conditions of use. The seated reinforced PTFE sealing ring has been worn out and need to be replaced with new PTFE material. The machined sealing surface protrudes from the seat 0.25mm. After the machining is completed, the sealing surface is polished and leveled with a grinding table.
After the overhaul, a manual test operation is performed. After the switch is smooth, the switch limit of the valve is reset, and the multiple operations are normal. The rationalization and improvement will replace the blowdown plug with the wire-ball valve-drainage pipe-plugging structure. It meets the pressure level requirements and the conditions of use. It is economical and convenient. It can discharge pollutants before the operator operates the valve to avoid serious jamming. After processing.
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