High pressure plug valve with floating seal assembly with self-pressing system and insert for this valve

Abstract

FIELD: pipeline fittings.SUBSTANCE: designs of sealing units of plug valves with a floating cylindrical plug, operating under high pressure. The plug valve comprises a body, a floating sealing unit consisting of a cylindrical plug and two inserts installed on opposite sides of the cylindrical plug between the cylindrical plug and the body. Each of the inserts is made in the form of a cylinder sector containing a central through hole and a curved groove on the outer cylindrical surface for installing an elastic sealing element. The outer cylindrical surface of each insert in the area located between the through hole and the curved groove is made with a local thickening that forms a support surface for contact with the housing and a gap (h) between the main outer cylindrical surface of the insert and the housing. Elastic sealing elements installed in the curved grooves of the inserts are designed with the possibility of providing preliminary pressing of the inserts to the cylindrical plug, the presence of locally thickened support surfaces on the inserts with the formation of a gap (h) between the main outer cylindrical surface of the inserts and the body ensures, when the working medium under pressure is supplied to the closed plug valve, the penetration of the working medium under pressure into the gap (h) and its effect on the sealing elements, creating an additional pressing force of the inserts to the cylindrical plug, proportional to the working pressure, and providing a self-pressure effect.EFFECT: increasing the tightness of the tap in the closed position by creating an additional radial force pressing the inserts against the plug, the magnitude of which is directly proportional to the operating pressure.2 cl, 5 dwg

Description

[0001] Field of technology to which the invention relates

[0002] The group of inventions relates to the field of pipeline fittings, in particular to the designs of sealing units of plug valves with a floating cylindrical plug, operating under high pressure.

[0003] Technology Level

[0004] Plug valves with a floating cylindrical plug and sector-shaped liners positioned between the plug and body are known. The seal between the liners and body is often provided by a rubber ring installed in a groove on the outer surface of the liners. In such designs, the liners are pressed against the plug by pre-deformation of the elastic ring and / or by the pressure of a buffer lubricant. The main drawback of such designs is that the force exerted by the liners against the plug is either constant or weakly dependent on the operating pressure in the pipeline. With significant increases in operating pressure, this can lead to insufficient sealing of the metal-to-metal (plug-liner) pair and leaks.

[0005] A rotary valve is known from the prior art, comprising a valve body with inlet and outlet channels and an opening located transversely relative to said channels, an elastically deformable, detachable, radially expanding sleeve rigidly located in said opening, wherein said sleeve has inlet and outlet channels that are in hydraulic communication with said inlet and outlet channels in the valve body, and an opening located transversely relative to said channels, a valve rotationally located inside said opening of said sleeve, wherein the corresponding dimensions of said valve and said opening in said sleeve are such that said sleeve is held in an elastically deformed state by said valve, and a strong gripping action is maintained between them, regardless of any limiting action of said valve body (see US 3346002 A, 1967-10-10).

[0006] The closest analogue (prototype) is known from the prior art, which is a high-pressure plug valve of large diameter, including a plug valve body (1), a rotating shaft (6) mounted on the upper part of the plug valve body (1) through a reducer (4), characterized in that the plug rod (7) is mounted on the valve body below the rotating shaft (6) through a bearing (27), wherein the plug rod (7) is connected to the rotating shaft (6), one end of the plug rod (7) protrudes into the plug valve body (1), the plug body (9) is mounted on the plug rod (7) protruding into the plug valve body (1), a combined sealing disk (11) is located on the circumference of the plug rod (7) between the bearing (27) and the plug body (9), wherein the combined sealing disk (11) contacts the inner wall of the plug body (9) and is connected to it, a sealing element located between the plug body (9) and the plug valve body (1),The lower cover (24) is mounted on the lower end of the plug valve body (1) by means of a screw and a nut, wherein the valve cover assembly is located between the lower cover (24) and the plug body (9), and the valve cover assembly is movably connected to the plug body (9). Between the plug body 9 and the inner wall of the shut-off valve body 1, a sealing element is provided, including a sealing arc 14 and a side arc 15. The sealing arc 14 is made in the form of a tile. The sealing arcs 14 are located at both ends of the through hole 10 of the plug body 9. The inner side surface of the sealing arc 14 is in sliding contact with the plug body 9. On the outer side of the plug body 9, between the two sealing arcs 14, a side arc 15 is located. The side arc 15 is made in the form of an arched plate. In the sealing arc 14, corresponding to the through hole 10 of the body of the plug 9,there are sealing holes 16. The sealing arc 14 on the outer side of the sealing hole 16 is provided with a multi-stage groove for a sealing ring. The multi-stage groove for a sealing ring consists of an inner groove 17 and an outer groove 18. A sealing ring is installed in each groove. The purpose of such an installation is to improve the sealing effect of the outer side of the sealing hole 16 of the sealing arc 14. The sealing arc plates 14 on both sides of the sealing ring groove are provided with mounting grooves. The mounting groove has the shape of a long strip. A spring element 19 is installed in the mounting groove. The spring element 19 contacts the inner wall of the plug valve body 1. During operation, the elastic force of the spring element 19 effectively ensures a constant hermetic seal of the sealing arc plate 14 and the plug body 9.

[0007] The disadvantage of the prototype is the lack of a mechanism for automatic (spontaneous) increase in the force of pressing the inserts to the plug when the pressure of the working medium increases, which limits the reliability and operating pressure of the tap.

[0008] Disclosure of the essence of the invention

[0009] The problem that the invention is aimed at solving is the creation of a design for a sealing unit for a plug valve that ensures the effect of self-compression of the inserts to the plug when the pressure of the working medium on the buffer lubricant inside the plug valve increases, thereby increasing the reliability and tightness of the valve.

[0010] The technical result consists in increasing the tightness of the tap in the closed position by creating an additional radial force pressing the inserts to the plug, the magnitude of which is directly proportional to the operating pressure.

[0011] The technical result is achieved in that the plug valve comprises a housing, a floating sealing unit consisting of a cylindrical plug and two inserts installed on opposite sides of the cylindrical plug between the cylindrical plug and the housing, each of the inserts is made in the form of a cylinder sector containing a central through hole and a curvilinear groove on the outer cylindrical surface for installing an elastic sealing element, characterized in that the outer cylindrical surface of each insert in the zone located between the through hole and the curvilinear groove is made with a local thickening that forms a support surface for contact with the housing and a gap (h) between the main outer cylindrical surface of the insert and the housing, the height of the said increase relative to the main outer cylindrical surface lies in the range of 0.10 - 0.20 mm, wherein the elastic sealing elements,installed in the curved grooves of the liners, are designed with the possibility of providing preliminary pressing of the liners to the cylindrical plug, the presence of locally thickened support surfaces on the liners with the formation of a gap (h) between the main outer cylindrical surface of the liners and the body ensures, when the working medium under pressure is supplied to the closed plug valve, the penetration of the working medium under pressure into the gap (h) and its effect on the sealing elements, creating an additional force pressing the liners to the cylindrical plug, proportional to the working pressure, and providing a self-pressure effect.

[0012] Also, the technical result is achieved in that the plug valve insert is made in the form of a cylinder sector containing a central through hole and a curved groove on the outer cylindrical surface for installing an elastic sealing element, characterized in that the outer cylindrical surface of the insert in the area located between the through hole and the curved groove is made with a local thickening that forms a supporting surface for the possibility of contact with the plug valve body and a gap (h) between the main outer cylindrical surface of the insert and the plug valve body, the height of the said increase relative to the main outer cylindrical surface lies in the range of 0.10 - 0.20 mm, while the elastic sealing element installed in the curved groove of the insert is made with the possibility of providing preliminary compression of the insert to the cylindrical plug,the presence of a locally thickened support surface on the insert with the formation of a gap (h) between the main outer cylindrical surface of the insert and the body of the plug valve ensures, when the working medium under pressure is supplied to the closed plug valve, the penetration of the working medium under pressure into the gap (h) and its impact on the sealing elements, creating an additional force pressing the inserts to the cylindrical plug, proportional to the working pressure, and providing a self-compression effect.

[0013] Brief description of drawings

[0014] The claimed group of inventions is explained by the following figures.

[0015] Figure 1 shows a general view of the plug valve in longitudinal section,

[0016] Figure 2 - type of insert, support surface, groove for sealing ring, bypass,

[0017] Figure 3 - a schematic section of the sealing unit and the contact points of the insert with the body and the cylindrical plug, as well as filling with buffer lubricant, the working environment with an indication of the direction of its impact on the sealing unit,

[0018] Figure 4 - horizontal cross-section. Pressure distribution through buffer lubricant,

[0019] Figure 5 is a schematic diagram explaining the principle of self-compression of the insert to the plug through the transfer of mechanical force from the pressure of the working medium, an image of the microgap h for self-compression.

[0020] Implementation of the invention

[0021] The sealing unit of the plug valve (Fig. 1) consists of sector inserts (2) and a cylindrical plug (3), made of steel and installed in a steel housing (1) and held in the housing by a housing cover (5), pressed by screws (11). Each insert has the shape of a thin-walled sector of a cylinder with an inner diameter equal to the diameter of the plug (3) and an outer diameter along the annular support surface equal to the inner diameter of the housing (1). In the center of the insert (2), symmetrically, there is a through hole with a diameter equal to the nominal bore. On the outer cylindrical surface of the insert (2), coaxially to the through hole, at a certain diameter there is a groove along a curvilinear trajectory for installing a rubber sealing ring (4) of a circular cross section. The internal cavity of the plug valve is filled with buffer grease (9), pumped through the grease fitting (8).The lubricant (9) is prevented from leaking by the sealing and support rings (6) and (7) installed on the plug, as well as the sealing rings (4) and the sealing ring (10) on the cover (5).

[0022] The surface of the insert (12) (Fig. 2), limited by the contour of the through hole and the wall of the groove 13 of the smallest diameter, is made with a local axisymmetric thickening by the value (h) relative to the entire remaining outer cylindrical surface of the insert (2). Thus, in the assembled valve, the inserts (2) contact the inner cylindrical surface of the body (1) only along this narrow raised annular zone (support surface 12) (Fig. 2). Between the main (not thickened) surface of the insert (2) and the body (1) an annular gap of the value (h) is formed (Fig. 5). This gap is filled with buffer grease (9), which is affected by the pressure of the working medium.Since the surface area in the gap zone (h) on the outer side of the insert (2) is by some amount greater than the surface area in contact in the seal between the plug (3) and the insert (2), during operation a certain pressure difference (pressure differential) arises between the sealing and outer surfaces of the insert (2), the pressure in the gap region (h) of the insert (2) is greater than on the sealing surface between the plug (3) and the insert (2), accordingly, the higher the pressure of the working medium, the more tightly the insert (2) fits to the plug (3), the higher the tightness.

[0023] Working principle of high pressure plug valve with floating sealing unit and self-pressure effect.

[0024] In the initial, closed state, without pressure of the working medium (Fig. 4, A1), the plug (3) and liners (2) are located symmetrically inside the body (1) with minimal assembly gaps and balanced elastic forces of two elastic sealing elements (4) in the form of, for example, rubber rings. The internal cavity of the plug valve is filled with buffer grease (9).

[0025] As the working fluid pressure increases (Fig. 4, A2), the floating seal assembly shifts ("floats") axially along the passageway toward the opposite side of the pressure supply, thereby creating the maximum main gap (15) on the pressure side. The working fluid (16) mechanically exerts pressure through the resulting gap on the seal (4), causing it to shift toward the bypass (14) by a certain amount, thereby affecting the buffer lubricant.

[0026] On the side opposite to the working medium (Fig. 5), the assembly gap becomes equal to 0. The insert (2) is tightly pressed by the plug (3) to the housing (1). The pressure of the working medium is transmitted to the buffer lubricant and acts on the insert (2) in the area of ​​the gap (h). Due to the difference in the areas of action, a self-compression effect occurs. In addition, the pressure penetrates into the groove cavity and begins to act on the outer side surface of the rubber sealing ring (4), which generates a significant axial force acting towards the vertical part of the housing surface, pressing the working surface of the insert (2) to the cylindrical surface of the plug (3).

[0027] The magnitude of this additional force is directly proportional to the pressure of the working medium P рабThus, the higher the pressure in the pipeline, the more tightly the liners are pressed against the plug, ensuring a perfect seal between metal and metal. The system becomes self-regulating and pressure-sealing.

Claims

1. A plug valve comprising a body, a floating sealing unit consisting of a cylindrical plug and two inserts installed on opposite sides of the cylindrical plug between the cylindrical plug and the body, each of the inserts is made in the form of a cylinder sector containing a central through hole and a curved groove on the outer cylindrical surface for installing an elastic sealing element, characterized in that the outer cylindrical surface of each insert in the area located between the through hole and the curved groove is made with a local thickening that forms a supporting surface for contact with the body and a gap (h) between the main outer cylindrical surface of the insert and the body, the height of the said increase relative to the main outer cylindrical surface is in the range of 0.10-0.20 mm, wherein the elastic sealing elements installed in the curved grooves of the inserts,are made with the possibility of providing preliminary pressing of the liners to the cylindrical plug, the presence of locally thickened support surfaces on the liners with the formation of a gap (h) between the main outer cylindrical surface of the liners and the body ensures, when the working medium under pressure is supplied to the closed plug valve, the penetration of the working medium under pressure into the gap (h) and its impact on the sealing elements, creating an additional force pressing the liners to the cylindrical plug, proportional to the working pressure, and providing a self-pressure effect.

2. A plug valve insert made in the form of a cylinder sector containing a central through hole and a curved groove on the outer cylindrical surface for installing an elastic sealing element, characterized in that the outer cylindrical surface of the insert in the area located between the through hole and the curved groove is made with a local thickening that forms a supporting surface for the possibility of contact with the plug valve body and a gap (h) between the main outer cylindrical surface of the insert and the plug valve body, the height of the said increase relative to the main outer cylindrical surface is in the range of 0.10-0.20 mm, wherein the elastic sealing element installed in the curved groove of the insert is made with the possibility of providing preliminary compression of the insert to the cylindrical plug,the presence of a locally thickened support surface on the insert with the formation of a gap (h) between the main outer cylindrical surface of the insert and the body of the plug valve ensures, when the working medium under pressure is supplied to the closed plug valve, the penetration of the working medium under pressure into the gap (h) and its impact on the sealing elements, creating an additional force pressing the inserts to the cylindrical plug, proportional to the working pressure, and providing a self-compression effect.

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