An ultra-high pressure sand-proof plug valve with easy core replacement

Abstract

An ultra-high pressure sand-proof plug valve with easy core replacement has the following features: the small end of the truncated cone of the plug faces downwards and contacts and seals with the conical surface of the truncated cone hole in the center of the wear-resistant bushing; the wear-resistant bushing is installed in the valve cavity of the valve body, and its periphery is matched with the cylindrical hole of the valve cavity and two symmetrical axial keyways without clearance; the center of the valve cover is equipped with a valve stem, a combined seal, a thrust bearing and an O-ring, and the valve cavity of the valve body is sealed with a sealing gasket and uniformly distributed screws; the upper end face of the plug is connected with the flat key protruding at the lower end of the valve stem by a recessed keyway; a one-way valve is installed between the upper end face of the plug and the flow channel hole, and an axial through hole is drilled between the upper and lower end faces of the plug and at the entity on one side of the flow channel hole; a grease injection valve communicating with the upper and lower ends of the valve cavity is installed outside one side of the valve body and the valve cover respectively; after the valve cavity is filled with hydraulic oil, the automatic sealing of the plug valve is realized. It has the advantages of simple structure, easy processing, reliable performance, long service life, and easy maintenance.

Description

Technical Field

[0001] The invention relates to a plug valve used in the industries of oil and natural gas drilling and production. Background Art

[0002] In the pipeline of oil and gas drilling or fracturing operation, plug valves are used to replace flat gate valves for fluid switch control, which has the advantages of simple operation, rapid switch, and less safety risks. However, due to the small amount of ultra-high pressure and large diameter plug valves in the past, the relevant parties did not pay enough attention to research, resulting in poor performance and many failures of such domestic plug valve products. According to the investigation, the main problems are: first, the rubber seals used to seal between the valve body, arc sheet and plug are very easy to be damaged in high pressure, corrosive and sand-containing fluids above 70MPa; second, different fluid pressures cause the active gaps of the existing plug valves with multiple sealing structures to be compressed after the seals are compressed, which is very easy to be sand-included, abraded and leaked; third, the existing plug valve products imitated from foreign countries have complex structures, many parts and high precision, and it is difficult for general enterprises to guarantee their manufacturing quality; fourth, due to the complex structure and difficult processing of existing plug valve products, the product cost price remains high, the quality and efficiency of use are poor, and the enthusiasm and quantity of production and use of both supply and demand sides are suppressed. Summary of the invention

[0003] Aiming at the problems existing in the existing plug valves, the present invention conducts in-depth research and innovative design to provide a plug valve product which is suitable for use in high pressure or ultra-high pressure above 70MPa, corrosive and sand-containing fluids, is easy to replace worn plugs and bushings, and is inexpensive and of good quality.

[0004] The present invention is composed of a valve body, a plug, a wear-resistant bushing, a one-way valve, a valve cover, a valve stem, a thrust bearing, a washer, a grease injection valve and matching seals and connectors. The characteristics of the present invention are as follows: the small end of the truncated cone of the plug faces downwards and contacts and seals with the conical surface of the truncated cone hole in the center of the wear-resistant bushing; the wear-resistant bushing is installed in the valve cavity of the valve body, and its periphery is matched with the cylindrical hole of the valve cavity and two symmetrical axial keyways without clearance; the valve stem, a combined seal, a thrust bearing and an O-ring are installed in the center of the valve cover. The valve cavity of the valve body is sealed with a sealing gasket and uniformly spaced screws; the upper end face of the plug is connected with the protruding flat key at the lower end of the valve stem by a recessed keyway; a one-way valve is installed between the upper end face of the plug and the flow channel hole, and an axial through hole is drilled between the upper and lower end faces of the plug and at the solid part on one side of the flow channel hole; a grease injection valve connected to the upper and lower ends of the valve cavity is installed on the outside of one side of the valve body and the valve cover respectively; after the valve cavity is filled with hydraulic oil, the automatic sealing of the plug valve is realized.

[0005] Since the present invention adopts gapless metal seals between the valve body, wear-resistant bushing and the plug, and there are no complicated multiple arc pieces and other seals in the middle; therefore, there will be no problems such as high-pressure deformation, chemical corrosion, gap leakage and sand inclusion wear of the elastic seal, and it has the advantages of simple structure, easy processing, low cost and reliable performance. At the upper end of the plug, the recessed keyway is connected with the protruding flat key at the lower end of the valve stem to transmit the switching torque; due to the gap between the key and the groove, the plug can float freely to improve the sealing effect and prevent the valve stem from generating offset torque. A one-way valve is installed between the upper end face of the plug and the flow channel hole, and an axial through hole is drilled between the upper and lower end faces of the plug and on one side of the flow channel hole to exchange and balance the pressure between the valve cavity and the flow channel hole, and between the upper and lower ends of the valve cavity; it can prevent the sealing cone surface between the plug and the wear-resistant bushing from generating gaps and leakage due to the difference in internal and external pressures; and it can also reduce the valve switching resistance generated by the ultra-high pressure of the flow channel hole. On the outside of one side of the valve body and the valve cover, there is a grease injection valve connected to the upper and lower ends of the valve cavity. After the valve cavity is filled with hydraulic oil, it can keep the pressure at the upper and lower ends of the plug consistent and use the difference in area to always press the wear-resistant bushing; secondly, it can fill the space and gap in the valve cavity to prevent the fluid from entering the valve cavity; thirdly, it can provide lubrication for the sealing cone surface of the plug and the wear-resistant bushing to reduce friction resistance. The above structural elements cooperate with each other to ensure the long-term stable operation of the plug valve and ensure that its performance is not affected by the pressure changes, chemical properties, and sand content of the fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 This is a schematic cross-sectional view of the overall structure of the present invention when the valve is opened;

[0007] Figure 2 For the present invention Figure 1 Schematic diagram of the cross-section at AA in the middle;

[0008] Figure 3 For the present invention Figure 2 Schematic diagram of the bottom of the middle valve cavity in direction B.

[0009] The names of the parts indicated by the numbers in the figure are as follows:

[0010] 1. Valve body, 2. Plug, 3. Wear-resistant bushing, 4. Special-shaped sealing ring, 5. Check valve, 6. Sealing gasket, 7. Valve cover, 8. Valve stem, 9. Combined seal, 10. Thrust bearing, 11. O-ring, 12. Cylindrical head screw, 13. Union joint, 14. Washer, 15. Grease injection valve. DETAILED DESCRIPTION

[0011] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0012] The main parts of the present invention include: a valve body 1, a plug 2, a wear-resistant bushing 3, a one-way valve 5, a valve cover 7, a valve stem 8, a thrust bearing 10, a washer 14 and a grease injection valve 15; the sealing parts used include: a special-shaped sealing ring 4, a sealing gasket 6, a combined sealing part 9 and an O-ring 11; the connecting parts used include: a cylindrical head screw 12 and a union 13; except that the special-shaped sealing ring 4, the combined sealing part 9 and the O-ring 11 are non-metallic sealing parts, the rest are metal parts.

[0013] The valve body 1 is a three-way part, with a column in the middle and a blind hole valve cavity in the column; the left and right ends extend out with neck joints, and the left and right flow channels intersecting the blind hole valve cavity vertically are in the neck joints; among them: the neck joint at the short end is a female joint processed with external threads, and a special-shaped sealing ring 4 is installed in the mouth; the neck joint at the long end is a male joint equipped with a union 13, both of which are used to connect external pipes. The blind hole valve cavity in the middle of the valve body 1 is a stepped hole with two different diameters, one larger at the top and one smaller at the bottom, and a deeper backing groove is processed at the bottom of the small diameter stepped hole; at the edge of the small diameter stepped hole in the direction perpendicular to the axis of the left and right flow channels, two axial open keyways are symmetrically processed to prevent the wear-resistant bushing 3 from rotating with the plug 2. On the upper annular plane of the middle column of the valve body 1, a gasket groove and evenly distributed threaded blind holes are processed, so that the valve cover 7 and other parts can be connected with a sealing gasket 6 and a cylindrical head screw 12. A threaded reducing hole at the inlet communicating with the back cutter groove in the valve cavity is drilled on the side wall of the lower end of the intermediate column of the valve body 1 away from the neck joint, and a grease injection valve 15 is installed in the hole.

[0014] The plug 2 is a truncated cone-shaped part with a cylindrical short handle. The waist of the truncated cone is processed with a through flow hole; the upper end face of the cylindrical short handle is processed with a keyway perpendicular to the axis of the flow hole, an axial hole communicating with the lower end face, and a stepped hole with a thread at the upper opening communicating with the flow hole, which are respectively used to connect the flat key at the lower end of the valve stem 8, communicate the pressure of the upper and lower valve chambers, and install the one-way valve 5 for balancing the pressure. The axial through holes on the upper and lower end faces of the plug 2 are located on one side of the flow hole; the outlet of its upper end face is located in the keyway. The two center holes located on the axis of the two ends of the plug 2 are processed with internal threads in the center holes at the upper end to facilitate its processing and disassembly. On the conical sealing surface of the truncated cone of the plug 2, a layer of tungsten carbide cemented carbide material is evenly sprayed and welded to improve its high pressure resistance, wear resistance and corrosion resistance. The one-way valve 5 is composed of a steel ball, a compression spring and a hollow screw. The plug 2 is used as the valve body and is installed from bottom to top in a threaded step hole at the upper end of the plug 2 that communicates with the flow channel hole. It can prevent hydraulic oil leakage and sense the pressure changes of the flow channel hole to maintain the pressure balance inside and outside the valve.

[0015] The wear-resistant bushing 3 is a hollow cylindrical part, which is molded and sintered with YG8 tungsten-cobalt hard alloy material; the center of the cylinder is a smooth truncated cone hole, the middle of the cylinder is the left and right flow channel holes that penetrate perpendicularly to the truncated cone hole, and the edge of the surface of the cylinder perpendicular to the axis of the left and right flow channel holes is two full-length symmetrical raised axial flat keys. The diameter of the cylinder of the wear-resistant bushing 3 is the same as the diameter of the small-diameter step hole in the valve cavity, the size of the two raised flat keys is the same as the size of the two axial open keyways in the valve cavity, the diameter of the left and right flow channel holes is the same as the diameter of the left and right flow channel holes of the valve body 1, and the thermal expansion and contraction process is adopted during assembly, and there is no gap fit. The truncated cone hole in the center of the wear-resistant bushing 3 can contain the truncated cone of the plug 2, and the taper is the same, and sealing is achieved through matching grinding.

[0016] The valve cover 7 is a flat flange part, with a cylindrical step hole in the middle that expands step by step from bottom to top, and is equipped with a valve stem 8, a combined seal 9, a thrust bearing 10 and an O-ring 11 in sequence; a sealing groove for installing a sealing gasket 6 is cut on the lower plane to prevent leakage between the valve body 1 and the valve cover 7; a plurality of evenly distributed step holes are machined between the upper and lower planes so as to connect with the valve body 1 with cylindrical head screws 12; a reducing hole with a thread at the inlet communicating with the upper end of the valve cavity is drilled on the circumferential side wall of the valve cover 7, and a grease injection valve 15 is installed in the hole; on the upper plane and circumferential edge of the valve cover 7, according to the matching requirements of the drive mechanism, structural elements such as positioning threaded blind holes and valve switch indicator marks are also machined.

[0017] The valve stem 8 is a four-layer cylindrical part from large to small; the bottom surface of the bottom large cylinder is processed with a full-length flat key for transmitting the switch torque to the plug 2; the second cylinder is used to install the combined seal 9 to seal the gap between the valve cover 7; the third cylinder is used to install the thrust bearing 10 to reduce the friction resistance of the valve switch; the top small cylinder should be processed according to the connection requirements of the matching drive mechanism, such as processing into a "shuttle column, spline column, cylinder plus flat key" structure. The present invention shows an embodiment of "four shuttle columns plus top threaded holes" connected to the manual turntable lever drive mechanism.

[0018] The washer 14 is a square-section columnar part with both ends flush and a long recess in the middle. Both ends and the lower edge are all chamfered. Its length is equal to the distance between the bottom surfaces of two symmetrically distributed axial keyways in the valve cavity of the valve body 1, its width is the same as the width of the axial keyway, and its height is the same as the height of the backing groove in the valve cavity of the valve body 1. All its dimensions adopt negative tolerances and are placed at the bottom of the valve cavity through the two axial keyways in the valve cavity to limit the axial position of the wear-resistant bushing 3 in the valve cavity.

[0019] The thrust bearing 10, O-ring 11 and cylindrical head screw 12 of the present invention are all standard parts, and the special-shaped sealing ring 4, sealing gasket 6, union 13 and grease injection valve 15 are all common parts in oil drilling equipment; its combined seal 9 should be selected according to different working pressures, and the valve stem combined seal of different material composition and structure form should be selected to achieve high sealing, low resistance, moderate price and long life.

[0020] The present invention adopts the wear-resistant bushing 3 made of YG8 tungsten-cobalt hard alloy material, and spray-welds a layer of tungsten carbide hard alloy material on the conical sealing surface of the truncated cone of the plug 2, so that it has an ultra-long service life. After being worn by the sand-containing fluid after long-term operation, first discharge the hydraulic oil through the grease injection valve 15, unscrew the cylindrical head screw 12, open the valve cover 7, and hang it out through the threaded center hole on the plug 2; then use the disassembly tool to penetrate into the bottom of the valve cavity, hook the bottom edge of the wear-resistant bushing 3 from both sides of the washer 14 and pull it out; reinstall the new wear-resistant bushing 3 and the plug 2, and inject the hydraulic oil, and it can work for a long time again.

Claims

1. An ultra-high pressure sand-proof plug valve with easily replaceable core, comprising a valve body, a plug, a wear-resistant bushing, a one-way valve, a valve cover, a valve stem, a thrust bearing, a washer and a grease injection valve, characterized in that: The small end of the truncated cone of the plug faces downward and contacts and seals with the conical surface of the truncated cone hole in the center of the wear-resistant bushing; the wear-resistant bushing is installed in the valve cavity of the valve body, and its periphery is matched with the cylindrical hole of the valve cavity and two symmetrical axial keyways without clearance; the center of the valve cover is equipped with a valve stem, a combined seal, a thrust bearing and an O-ring, and the valve cavity of the valve body is sealed with a sealing gasket and uniformly distributed screws; the upper end face of the plug is connected with the protruding flat key at the lower end of the valve stem by a recessed keyway; a one-way valve is installed between the upper end face of the plug and the flow channel hole, and an axial through hole is drilled between the upper and lower end faces of the plug and at the entity on one side of the flow channel hole; a grease injection valve connected to the upper and lower ends of the valve cavity is installed on the outside of one side of the valve body and the valve cover respectively; after the valve cavity is filled with hydraulic oil, the automatic sealing of the plug valve is realized; The one-way valve is composed of a steel ball, a compression spring and a hollow screw, with a plug as the valve body, and is installed from bottom to top in a threaded step hole at the upper end of the plug that communicates with the flow channel hole; The valve stem is a four-layer cylindrical part from large to small: the bottom surface of the bottom large cylinder is processed with a full-length flat key, the second cylinder is used to install the combined seal, the third cylinder is used to install the thrust bearing, and the top small cylinder should be processed according to the connection requirements of the matching drive mechanism; The washer is a square-section columnar part with high and flat ends and a long depression in the middle. Both ends and the lower edge are chamfered. It is placed at the bottom of the valve cavity through two axial keyways in the valve cavity to limit the axial position of the wear-resistant bushing in the valve cavity.

2. The ultra-high pressure sand-proof plug valve with easy-to-replace core according to claim 1 is characterized by: The plug is a truncated cone-shaped part with a short cylindrical handle. A through flow hole is processed on the waist of the truncated cone; the upper end face of the short cylindrical handle is processed with a keyway perpendicular to the axis of the flow hole, an axial hole communicating with the lower end face, and a stepped hole with a thread at the upper opening communicating with the flow hole.

3. The ultra-high pressure sand-proof plug valve with easy-to-replace core according to claim 1 is characterized by: Two center holes are located on the axis lines at both ends of the plug, and internal threads are processed in the center holes at the upper ends; a layer of tungsten carbide hard alloy material is evenly sprayed and welded on the conical sealing surface of the plug cone.

4. The ultra-high pressure sand-proof plug valve with easily replaceable core according to claim 1 is characterized by: The wear-resistant bushing is a hollow cylindrical part, which is made of YG8 tungsten-cobalt hard alloy material molded and sintered; the center of the cylinder is a smooth truncated cone hole, the middle of the cylinder is the left and right flow channel holes that penetrate perpendicularly to the truncated cone hole, and the edge of the surface of the cylinder at a direction perpendicular to the axis of the left and right flow channel holes is two full-length symmetrical raised axial flat keys.

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