A Kind of Repair Technology for Check Valves
Abstract
During the use of traditional horizontal lift check valves, problems such as damage to the sealing surface and breakage of the spool guide rod will occur due to the influence of liquid corrosion and impurities, which leads to a lot of disassembly and assembly, fast failure, and short service life of the check valve. Change the traditional horizontal lift check valve's structure and sealing method; add a valve sleeve assembly in the cavity of the check valve body, including valve sleeves, valve cores and valve sleeve covers, and change the end face seal to "O" type seals and cone seals. The improved check valve can not only ensure single flow, but also facilitate the disassembly and cleaning of valve components, which can effectively reduce labor intensity and production costs.
A check valve refers to a valve whose opening and closing part is a circular valve plate and is operated by its own weight and medium pressure to block the back flow of the medium. There are many types of check valves. According to the internal structure of check valves, they are mainly divided into lift check valves and swing check valves. Among them, the lift check valve is divided into two types: horizontal lift check valves and vertical lift check valves. In the gathering and transportation system of the oilfield, the traditional horizontal lift check valve is commonly used. This kind of check valve is mainly installed in the outlet of the oil pump and the metering room of the oil well. In the use process, the sealing surface is damaged and the valve core guide rod is broken due to the influence of liquid corrosion and impurities, which causes a lot of disassembly and assembly, fast failure, and short service life of the check valve. Find out a repair technology of check valves to facilitate the maintenance and cleaning of the check valve, improve the performance of the check valve, and extend the service life of the check valve.
1. Traditional horizontal lift check valves
1.1 The structure and working principle of the traditional horizontal lift check valve
The traditional horizontal lift check valve is mainly composed of the valve body, bonnet, valve core, guide cylinder and guide rod (Figure 1). The guide cylinder is welded to the center of the valve bonnet, and the guide rod is welded to the center of the valve core. The guide rod is sleeved in the guide cylinder to drive the valve core to move vertically up and down under the movement of the fluid medium. When the inlet pressure of the check valve is greater than the outlet pressure, the fluid medium lifts the valve core to form a channel for liquid; when the outlet pressure of the check valve is greater than the inlet pressure, the fluid medium at the outlet side makes the valve core move downward under the action of the pressure difference. At this time, the sealing surface of the lower end of the valve core is in contact with that of the valve body to quickly seal the fluid channel, thereby cutting off the fluid flow and achieving the purpose of preventing the medium from flowing back.
Figure 1 Traditional horizontal check valves
1.2 Problems existing in the traditional horizontal lift check valve
(1) Easily damaged sealing surfaces: The sealing of the traditional horizontal lift check valve is end face sealing. In the oil and gas gathering and transportation system, the flowing medium is mostly a mixture of oil, gas, and water. When the inlet pressure of the check valve is greater than its outlet pressure, the oil, gas, and water mixture will lift the valve core to form a liquid outlet channel. At this time, the oil flow is discontinuous due to the gas and liquid in the medium, resulting in a small pressure difference. At this moment, although the valve core can move up and down under the restriction of the guide rod and guide cylinder, the passage of the check valve which fluid passes through is relatively narrow and the pressure drop is great, causing uneven force on the valve core's surface. The valve core's surface constantly knocks on the valve body's sealing surface, damaging the sealing surface, causing the check valve to fail and affecting the service life of the check valve.
(2) Easy broken spool guide rods: When the oil flow in the pipeline is discontinuous, the valve core surface swings left and right in the valve body cavity under the condition of the uneven force, causing stress concentration at the welding seam of the guide rod and valve core; the guide rod will fall over time, causing the check valve to fail (Figure 2).
Figure 2 The spool and the guide rod being disconnected
(3) Difficult maintenance and repair of check valves: In the oil and gas gathering and transportation, the inner cavity of the check valve and its accessories need to be maintained and cleaned frequently due to the corrosion and scaling of the conveying medium.
When the inner sealing surface of the check valve is corroded, the check valve can only be replaced as a whole, because the inner sealing surface of the valve is integrated with the valve body. The check valve needs to be replaced. (Figure 3)
Figure 3 Corrosion of the inner sealing surface of the valve
1.3 The harm caused by the failure of the check valve
When the oil transportation equipment stops running for some reasons, if the check valve fails, the oil flow in the oil pipeline quickly flows back, from the oil transportation equipment-the inlet of the mixed transportation pump to the buffer tank or the air distribution bag. If the workers do not notice in time, it will cause leakages of crude oil.
2. The repair technology of the check valve
2.1 Technical Principles
Change the traditional horizontal lift check valve's structure and sealing method; add valve sleeve assembly in the cavity of the check valve body, and the valve sleeve assembly includes valve sleeves, valve cores and valve sleeve cover plates and other components (Figure 4). The valve sleeve and sealing surface of the valve body are compressed and sealed with an "O" type sealing ring, and the valve core and valve sleeve are sealed with an "O" type sealing ring on a certain angle conical surface. The improved check valve can not only ensure single flow, but also facilitate the disassembly and cleaning of valve components.
Figure 4 The schematic diagram of valve covers, valve cores and valve sleeves
2.2 Technical schemes and working methods of sleeve components of check valves
2.2.1 Technical solutions
The valve sleeve components provided in the check valve mainly include the valve sleeve cover plate, guide tube, guide rod, valve sleeve, valve core and other parts (Figure 5). Valve sleeves(7) are set in the valve body of the check valve, and the sealing surface between the bottom end of the valve sleeve and the valve body is an "O" type sealing ring (9); square notches are symmetrically provided at the two sides of the valve sleeve to make enough channels for the flow. A cone surface with a certain angle is designed for the valve sleeve, and the cone surface cooperates with the valve core to realize the sealing. The center of the upper plane of the valve core (8) is welded with the guide rod (6) and the guide tube(5) to move up and down; the lower end of the valve core is slotted to place an "O" seal ring (10), and the bottom surface of the valve core is a cone. When the valve core drops, the cone surface of the valve core and the "O" ring acts as a seal to achieve the purpose of single flows. The center of the lower end surface of the valve bonnet(4) is welded with a guide cylinder(5) to move up and down with a guide rod(6). Two small round holes are provided on the valve bonnet to facilitate the removal of the valve bonnet for internal maintenance. The valve bonnet is on the valve sleeve. When the check valve bonnet plate (3) is tightened, the bonnet and valve sleeve are simultaneously pressed. At this time, the "O" sealing ring at the bottom of the valve sleeve is compacted with the sealing surface of the valve body to achieve the purpose of a seal.
Figure 5 The assembly diagram of the valve sleeve lift check valve
2.2.2 Working modes
When the oil conveying equipment is operating normally, the flowing medium enters the check valve from the pump outlet to the inlet(1) of the check valve, and the pressure at the inlet of the check valve is greater than that at the outlet of the check valve and the weight of the valve core (8). The liquid flow jacks the valve core (8), and the guide rod (6) on the valve core surface moves upwards under the restriction of the guide cylinder (5). A channel is formed at this time. The liquid flows from the square notches on both sides of the valve sleeve (7) to the check valve's outlet (11). When the oil transportation equipment stops operating for some reason, the flowing medium in the pipeline quickly reverses, and the pressure at the outlet end (11) of the check valve is greater than that at the inlet end (1) of the check valve. Under the action of the pressure difference, the liquid flow reversely flows from the square grooves on both sides of the sleeve (7) to the valve sleeve, and the valve core (8) is forced by the downward force of the liquid flow at this time. The guide rod (6) on the valve core surface moves up and down under the restriction of the guide cylinder (5). When the spool moves downwards, the tapered surface of the spool and the "O" sealing ring act as a seal to close the channel and realize a single flow.
2.3 Maintenance methods
1) Stop the pump. Close the pump's inlet and outlet valves, and remove the large cover plate of the check valve.
2) Take the valve cover plate, valve core and other valve sleeve components out.
3) Check and clean the valve sleeve components, and replace the "O" sealing ring. If the component is damaged, replace it.
4) Put the valve sleeve, valve core, and valve bonnet in sequence, and tighten the large cover of the check valve.
5) Open the pump's inlet and outlet valves and start the pump.
2.4 Technical advantages and installation or operation requirements
2.4.1 Technical advantages
1) After using the new technology for maintenance, the daily maintenance of the check valve is convenient and the operation is simple. When the check valve fails and needs maintenance, only the accessories need to be removed and replaced, which is convenient, effectively reducing manual operation costs, material costs, labor intensity of workers.
2) The single flow effect of the check valve after the maintenance of the new technology is outstanding, and the sealing method is changed from flat sealing to cone angle sealing, which has more reliable sealing performance.
3) When the spool moves up and down, it is restricted by the guide cylinder and the valve sleeve, and the spool moves up and down more smoothly.
4) The sealing surface of the valve sleeve and the valve body adopts an "O" type sealing ring, which does not damage the original valve body's sealing surface.
5) Realize safe production and reduce equipment failures and pollution caused by the leakage of crude oil.
2.4.2 Requirements for installation and operation
The valve sleeve lifting check valve is suitable for the oil pump outlet at the horizontal pipeline. The following aspects of installation and operation should be paid attention to: ①The valve sleeve lift check valve should be installed horizontally with the pipeline. ② Pay attention to bumping when installing the components in the valve body to prevent damage to the valve parts. ③ According to the characteristics of the conveying fluid, regularly open the valve for cleaning and inspection.
3. The application effect
During the field test, test the device's tightness before and after installation, and the valve's inlet and outlet should not leak. After installation, the operation of the check valve should be dynamically observed and tracked. The check valve should operate normally and smoothly. At the same time, the problem of the knocking sound on the original check valve spool and valve body's sealing surface is solved. The output pressure of the hybrid pump is displayed normally. During routine maintenance, one operator can complete the maintenance and cleaning of the components of the valve sleeve within 15 minutes, which reduces the labor intensity of the workers and ensures the normal operation of the equipment.
4. Conclusion
The repair technology of the check valve by providing a valve sleeve assembly in the original check valve cavity effectively solves the problems of rapid failures and short service life of the original check valve, making the daily maintenance of the check valve more convenient. This repair technology also provides technical references for other types of repairs of valve bodies.
During the use of traditional horizontal lift check valves, problems such as damage to the sealing surface and breakage of the spool guide rod will occur due to the influence of liquid corrosion and impurities, which leads to a lot of disassembly and assembly, fast failure, and short service life of the check valve. Change the traditional horizontal lift check valve's structure and sealing method; add a valve sleeve assembly in the cavity of the check valve body, including valve sleeves, valve cores and valve sleeve covers, and change the end face seal to "O" type seals and cone seals. The improved check valve can not only ensure single flow, but also facilitate the disassembly and cleaning of valve components, which can effectively reduce labor intensity and production costs.
A check valve refers to a valve whose opening and closing part is a circular valve plate and is operated by its own weight and medium pressure to block the back flow of the medium. There are many types of check valves. According to the internal structure of check valves, they are mainly divided into lift check valves and swing check valves. Among them, the lift check valve is divided into two types: horizontal lift check valves and vertical lift check valves. In the gathering and transportation system of the oilfield, the traditional horizontal lift check valve is commonly used. This kind of check valve is mainly installed in the outlet of the oil pump and the metering room of the oil well. In the use process, the sealing surface is damaged and the valve core guide rod is broken due to the influence of liquid corrosion and impurities, which causes a lot of disassembly and assembly, fast failure, and short service life of the check valve. Find out a repair technology of check valves to facilitate the maintenance and cleaning of the check valve, improve the performance of the check valve, and extend the service life of the check valve.
1. Traditional horizontal lift check valves
1.1 The structure and working principle of the traditional horizontal lift check valve
The traditional horizontal lift check valve is mainly composed of the valve body, bonnet, valve core, guide cylinder and guide rod (Figure 1). The guide cylinder is welded to the center of the valve bonnet, and the guide rod is welded to the center of the valve core. The guide rod is sleeved in the guide cylinder to drive the valve core to move vertically up and down under the movement of the fluid medium. When the inlet pressure of the check valve is greater than the outlet pressure, the fluid medium lifts the valve core to form a channel for liquid; when the outlet pressure of the check valve is greater than the inlet pressure, the fluid medium at the outlet side makes the valve core move downward under the action of the pressure difference. At this time, the sealing surface of the lower end of the valve core is in contact with that of the valve body to quickly seal the fluid channel, thereby cutting off the fluid flow and achieving the purpose of preventing the medium from flowing back.
Figure 1 Traditional horizontal check valves
1.2 Problems existing in the traditional horizontal lift check valve
(1) Easily damaged sealing surfaces: The sealing of the traditional horizontal lift check valve is end face sealing. In the oil and gas gathering and transportation system, the flowing medium is mostly a mixture of oil, gas, and water. When the inlet pressure of the check valve is greater than its outlet pressure, the oil, gas, and water mixture will lift the valve core to form a liquid outlet channel. At this time, the oil flow is discontinuous due to the gas and liquid in the medium, resulting in a small pressure difference. At this moment, although the valve core can move up and down under the restriction of the guide rod and guide cylinder, the passage of the check valve which fluid passes through is relatively narrow and the pressure drop is great, causing uneven force on the valve core's surface. The valve core's surface constantly knocks on the valve body's sealing surface, damaging the sealing surface, causing the check valve to fail and affecting the service life of the check valve.
(2) Easy broken spool guide rods: When the oil flow in the pipeline is discontinuous, the valve core surface swings left and right in the valve body cavity under the condition of the uneven force, causing stress concentration at the welding seam of the guide rod and valve core; the guide rod will fall over time, causing the check valve to fail (Figure 2).
Figure 2 The spool and the guide rod being disconnected
(3) Difficult maintenance and repair of check valves: In the oil and gas gathering and transportation, the inner cavity of the check valve and its accessories need to be maintained and cleaned frequently due to the corrosion and scaling of the conveying medium.
When the inner sealing surface of the check valve is corroded, the check valve can only be replaced as a whole, because the inner sealing surface of the valve is integrated with the valve body. The check valve needs to be replaced. (Figure 3)
Figure 3 Corrosion of the inner sealing surface of the valve
1.3 The harm caused by the failure of the check valve
When the oil transportation equipment stops running for some reasons, if the check valve fails, the oil flow in the oil pipeline quickly flows back, from the oil transportation equipment-the inlet of the mixed transportation pump to the buffer tank or the air distribution bag. If the workers do not notice in time, it will cause leakages of crude oil.
2. The repair technology of the check valve
2.1 Technical Principles
Change the traditional horizontal lift check valve's structure and sealing method; add valve sleeve assembly in the cavity of the check valve body, and the valve sleeve assembly includes valve sleeves, valve cores and valve sleeve cover plates and other components (Figure 4). The valve sleeve and sealing surface of the valve body are compressed and sealed with an "O" type sealing ring, and the valve core and valve sleeve are sealed with an "O" type sealing ring on a certain angle conical surface. The improved check valve can not only ensure single flow, but also facilitate the disassembly and cleaning of valve components.
Figure 4 The schematic diagram of valve covers, valve cores and valve sleeves
2.2 Technical schemes and working methods of sleeve components of check valves
2.2.1 Technical solutions
The valve sleeve components provided in the check valve mainly include the valve sleeve cover plate, guide tube, guide rod, valve sleeve, valve core and other parts (Figure 5). Valve sleeves(7) are set in the valve body of the check valve, and the sealing surface between the bottom end of the valve sleeve and the valve body is an "O" type sealing ring (9); square notches are symmetrically provided at the two sides of the valve sleeve to make enough channels for the flow. A cone surface with a certain angle is designed for the valve sleeve, and the cone surface cooperates with the valve core to realize the sealing. The center of the upper plane of the valve core (8) is welded with the guide rod (6) and the guide tube(5) to move up and down; the lower end of the valve core is slotted to place an "O" seal ring (10), and the bottom surface of the valve core is a cone. When the valve core drops, the cone surface of the valve core and the "O" ring acts as a seal to achieve the purpose of single flows. The center of the lower end surface of the valve bonnet(4) is welded with a guide cylinder(5) to move up and down with a guide rod(6). Two small round holes are provided on the valve bonnet to facilitate the removal of the valve bonnet for internal maintenance. The valve bonnet is on the valve sleeve. When the check valve bonnet plate (3) is tightened, the bonnet and valve sleeve are simultaneously pressed. At this time, the "O" sealing ring at the bottom of the valve sleeve is compacted with the sealing surface of the valve body to achieve the purpose of a seal.
Figure 5 The assembly diagram of the valve sleeve lift check valve
2.2.2 Working modes
When the oil conveying equipment is operating normally, the flowing medium enters the check valve from the pump outlet to the inlet(1) of the check valve, and the pressure at the inlet of the check valve is greater than that at the outlet of the check valve and the weight of the valve core (8). The liquid flow jacks the valve core (8), and the guide rod (6) on the valve core surface moves upwards under the restriction of the guide cylinder (5). A channel is formed at this time. The liquid flows from the square notches on both sides of the valve sleeve (7) to the check valve's outlet (11). When the oil transportation equipment stops operating for some reason, the flowing medium in the pipeline quickly reverses, and the pressure at the outlet end (11) of the check valve is greater than that at the inlet end (1) of the check valve. Under the action of the pressure difference, the liquid flow reversely flows from the square grooves on both sides of the sleeve (7) to the valve sleeve, and the valve core (8) is forced by the downward force of the liquid flow at this time. The guide rod (6) on the valve core surface moves up and down under the restriction of the guide cylinder (5). When the spool moves downwards, the tapered surface of the spool and the "O" sealing ring act as a seal to close the channel and realize a single flow.
2.3 Maintenance methods
1) Stop the pump. Close the pump's inlet and outlet valves, and remove the large cover plate of the check valve.
2) Take the valve cover plate, valve core and other valve sleeve components out.
3) Check and clean the valve sleeve components, and replace the "O" sealing ring. If the component is damaged, replace it.
4) Put the valve sleeve, valve core, and valve bonnet in sequence, and tighten the large cover of the check valve.
5) Open the pump's inlet and outlet valves and start the pump.
2.4 Technical advantages and installation or operation requirements
2.4.1 Technical advantages
1) After using the new technology for maintenance, the daily maintenance of the check valve is convenient and the operation is simple. When the check valve fails and needs maintenance, only the accessories need to be removed and replaced, which is convenient, effectively reducing manual operation costs, material costs, labor intensity of workers.
2) The single flow effect of the check valve after the maintenance of the new technology is outstanding, and the sealing method is changed from flat sealing to cone angle sealing, which has more reliable sealing performance.
3) When the spool moves up and down, it is restricted by the guide cylinder and the valve sleeve, and the spool moves up and down more smoothly.
4) The sealing surface of the valve sleeve and the valve body adopts an "O" type sealing ring, which does not damage the original valve body's sealing surface.
5) Realize safe production and reduce equipment failures and pollution caused by the leakage of crude oil.
2.4.2 Requirements for installation and operation
The valve sleeve lifting check valve is suitable for the oil pump outlet at the horizontal pipeline. The following aspects of installation and operation should be paid attention to: ①The valve sleeve lift check valve should be installed horizontally with the pipeline. ② Pay attention to bumping when installing the components in the valve body to prevent damage to the valve parts. ③ According to the characteristics of the conveying fluid, regularly open the valve for cleaning and inspection.
3. The application effect
During the field test, test the device's tightness before and after installation, and the valve's inlet and outlet should not leak. After installation, the operation of the check valve should be dynamically observed and tracked. The check valve should operate normally and smoothly. At the same time, the problem of the knocking sound on the original check valve spool and valve body's sealing surface is solved. The output pressure of the hybrid pump is displayed normally. During routine maintenance, one operator can complete the maintenance and cleaning of the components of the valve sleeve within 15 minutes, which reduces the labor intensity of the workers and ensures the normal operation of the equipment.
4. Conclusion
The repair technology of the check valve by providing a valve sleeve assembly in the original check valve cavity effectively solves the problems of rapid failures and short service life of the original check valve, making the daily maintenance of the check valve more convenient. This repair technology also provides technical references for other types of repairs of valve bodies.
