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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.