CN114484001A - A kind of LNG forced sealing switch ball valve - Google Patents

Abstract

The invention relates to an LNG forced sealing switch ball valve, which comprises a valve body, a valve cover, a valve seat, a valve ball, a valve rod and a packing assembly, wherein the valve ball is arranged in the valve body; the method is characterized in that: the valve ball is characterized by also comprising a sealing ring, a first bushing, a second bushing and a plane bearing, wherein the sealing ring is arranged on one side of the valve ball, the first bushing is arranged between the upper end of the valve ball and the valve cover, and the second bushing is arranged between the lower end of the valve ball and the valve body; the lower end of the valve rod is provided with a step, and a plane bearing is arranged between the step and the valve cover. The valve ball and the sealing ring are of a detachable combined structure, so that only the sealing ring needs to be replaced even if the sealing surface of the valve ball is abraded, and the maintenance cost is saved; the running torque of the valve is effectively reduced, the wear resistance is improved, and the service life is prolonged.

Description

A kind of LNG forced sealing switch ball valve

technical field

The invention belongs to the technical field of instruments and meters, and relates to an LNG forced sealing switch ball valve.

Background technique

Liquefied natural gas, referred to as LNG, is mainly composed of methane. The natural gas is purified and then undergoes a cryogenic process. After cooling to -162 °C, it becomes a liquid, and the volume is reduced by 600 times. At present, low-temperature ball valves used in LNG receiving stations are mainly imported from abroad. Most of the low-temperature ball valves are sealed with inlaid PCTFE sealing rings on their valve seats, and low-temperature flooding rings (modified PTFE) are used to seal the valve seat radially. However, in the actual use process, because the LNG temperature in the valve is -162 °C, the thermal expansion coefficients of the valve ball, valve seat, PCTFE sealing ring and low temperature flooding ring are different, resulting in low temperature leakage on the end face and radial direction of the valve seat; at the same time, Since the PCTFE sealing ring and the valve ball are always in contact during the valve opening and closing process, frequent switching for a long time will also cause the surface of the PCTFE sealing ring to wear and cause leakage; in addition, most of the low-temperature ball valves imported from abroad have a double-seat sealing structure, and the valve body cavity is easily damaged. Part of the LNG medium is intercepted. When the temperature in the cavity unexpectedly rises to normal temperature, the trapped LNG can be heated and converted into gas, the volume expands 600 times, and the pressure in the cavity is abnormally increased, which may lead to leakage of the valve gasket, or even The risk of valve explosion, the unit is forced to stop operation in order to repair or replace the valve, resulting in unnecessary financial loss and wasted time.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art, improve the performance of the LNG cryogenic ball valve such as low temperature resistance, wear resistance, and pressure resistance in the valve cavity; reduce the opening and closing torque of the valve, prolong the service life; ensure the safety and stability of the device , Efficient operation, providing a LNG forced-sealed on-off ball valve.

In order to achieve the above purpose, the following technical solutions are adopted:

An LNG forced-sealing on-off ball valve, comprising a valve body, a valve cover, a valve seat, a valve ball, a valve stem, and a packing assembly, wherein the valve body is provided with a valve ball, the upper end of the valve ball is provided with a valve stem, and the valve cover is sleeved on the valve The outer side of the rod is fixedly connected with the valve body, a stuffing box is arranged on the valve cover, and a packing assembly is arranged in the stuffing box; it is characterized in that it also includes a sealing ring, a first bushing, a second bushing and a plane bearing, so The valve ball is provided with a sealing ring and a first Nord-Lock gasket, the valve seat, the pressure ring and the second Nord-Lock gasket are sequentially fastened in the seat cavity of the valve body, and the valve ball and the second liner are set into the bottom shaft hole of the valve body, the valve stem is sleeved into the falcon groove of the valve ball, and the valve ball is screwed into the valve seat. A first bushing and a second bushing are arranged between the upper end of the valve ball and the valve cover. It is located between the lower end of the valve ball and the valve body; the lower end of the valve stem is provided with a step, a plane bearing is arranged between the step and the valve cover, and the plane bearing is sleeved on the step of the valve stem.

Preferably, the sealing ring is mounted on the valve ball by using hexagon socket head screws and Nord-Lock gaskets, and a wound gasket is arranged between the sealing ring and the valve ball.

Preferably, the valve cover and the valve body are connected and fixed by bolts, and a wound gasket is provided between the valve cover and the valve body.

Preferably, the packing assembly includes a flood plug ring, a retaining ring, a packing, a packing spacer, a packing pressure sleeve and a packing pressure plate which are sequentially installed in the stuffing box. solid.

Preferably, the center of rotation of the valve ball and the geometric center of the sealing ring are eccentrically arranged, and the center of rotation of the valve ball and the center of the flow passage of the valve body are arranged eccentrically.

Preferably, the sealing ring is a spherical crown.

Preferably, the contact surface between the valve seat and the valve body is a conical surface.

Preferably, a drip plate is provided on the valve cover.

Preferably, the valve cover is provided with a pressure relief hole.

Compared with the prior art, the present invention has the following advantages:

1. The valve ball and the sealing ring of the present invention adopt a detachable combined structure. Even if the sealing surface of the valve ball is worn, only the sealing ring needs to be replaced, which saves maintenance costs.

2. The valve ball of the present invention adopts a double eccentric design, and the valve ball performs a "rotation + translation" double vector cam motion around the center of rotation, that is, the valve ball has zero contact with the valve seat during the opening and closing of the valve, which effectively reduces the valve friction. Running torque, improve wear resistance, especially suitable for LNG working conditions that require frequent switching.

3. The valve seat of the present invention is convenient for installation, overhaul and maintenance, and does not require special installation and removal tooling for the valve seat compared to the conventional LNG ball valve.

4. The valve stem of the present invention drives the valve ball and the valve seat to produce a cam wedge-tight mechanical seal, which can achieve two-way tight shutoff without relying on fluid pressure, and is especially suitable for LNG working conditions that require two-way sealing.

5. The ball valve structure of the present invention has a single valve seat and an open valve cavity, and the LNG medium will not be trapped during the opening and closing process, which fundamentally eliminates the risk of holding pressure in the valve cavity of the LNG cryogenic ball valve, and ensures that the valve is intrinsically safe and reliable.

Description of drawings

Figure 1 is a schematic structural diagram of the present invention.

FIG. 2 is a schematic diagram of the structure of the valve cover of the present invention.

FIG. 3 is a schematic diagram of the installation of the valve ball and the sealing ring of the present invention.

In the figure: 1, valve body; 2, valve cover; 3, valve seat; 4, valve ball; 5, valve stem; 6, stuffing box; 7, first bushing; 8, second bushing; 9, plane Bearing; 10, Step; 11, Hexagon socket head cap screw; 12, First Nord-Lock gasket; 13, First spiral wound gasket; 14, Panzer ring; 15, Retaining ring; 16, Packing; 17, Packing spacer ; 18, packing pressure sleeve; 19, packing pressure plate; 20, fastening screw; 21, second Nord-Lock gasket; 22, second spiral wound gasket; 23, sealing ring; 24, drip plate; 25, pressure relief hole; 26, sealing ring; 27, pressure ring; 28, disc spring.

Detailed ways:

In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments of some, but not all, of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in Figures 1 to 3, an LNG forced-sealing on-off ball valve includes a valve body 1, a valve cover 2, a valve seat 3, a valve ball 4, a valve stem 5, and a packing assembly 16. The valve body 1 is provided with There is a valve ball 4, the upper end of the valve ball 4 is provided with a valve stem 5, the valve cover 2 is sleeved on the outside of the valve stem 5 and is fixedly connected with the valve body 1, the valve cover 2 is provided with a stuffing box 6, and the stuffing box 6 is provided with a The packing assembly 16 is characterized in that it also includes a sealing ring 23, a first bushing 7, a second bushing 8 and a plane bearing 9, and the valve ball 4 is provided with a sealing ring 23 and the first Nord-Lock gasket 12 , the valve seat 3, the pressure ring 27 and the second Nord-Lock gasket 21 are sequentially fastened in the seat cavity of the valve body 1, and the pressure ring 27 is used to fasten the valve seat 3, so that the valve seat 3 is not in the seat cavity. will fall, the tightening screw 20 is used to fix the pressure ring 27, the second Nord-Lock washer 21 prevents the tightening screw 20 from loosening; the valve ball 4 and the second bushing 8 are installed in the bottom shaft hole of the valve body 1, The valve stem 5 is sleeved into the falcon groove of the valve ball 4, and the valve ball 4 is screwed into the valve seat;

A first bushing 7 is arranged between the upper end of the valve ball 4 and the valve cover 2 , the second bushing 8 is located between the lower end of the valve ball 4 and the valve body 1 ; the outer sides of the first bushing 7 and the second bushing 8 are both A bushing seat is provided, the bushing seat is sleeved on the valve ball, the lower end of the valve stem 5 is provided with a step 10, a plane bearing 9 is arranged between the step 10 and the valve cover 2, and the plane bearing 9 is sleeved on the step of the valve stem 5 ; The plane bearing 9 reduces the frictional force when the valve stem 5 rotates.

Further, the sealing ring 23 is mounted on the valve ball 4 by using the socket head cap screws 11 and the first Nord-Lock washer 12, and the first Nord-Lock washer 12 is used to prevent the socket head cap screws 11 from loosening, so that the connection is tighter. The second winding gasket 22 is arranged between the sealing ring 23 and the valve ball 4 , and the second winding gasket 13 is used for sealing between the sealing ring 23 and the valve ball 4 . A sealing ring 26 is provided between the valve seat 3 and the sealing ring 23 for sealing.

Further, the valve cover 2 and the valve body 1 are connected and fixed by bolts, and a first wound gasket 13 is provided between the valve cover 2 and the valve body 1, and the first wound gasket 13 is used for the valve cover 2 and the valve body 1. Seal between valve bodies 1.

Further, the packing assembly 16 includes a pan plug ring 14 , a retaining ring 15 , a packing 16 , a packing spacer 17 , a packing pressing sleeve 18 and a packing pressing plate 19 , which are sequentially installed in the stuffing box 6 . The packing pressing plate 19 uses bolts, disc springs 28 is connected and fixed with the valve cover 2 , and the packing assembly 16 is used for sealing between the valve cover 2 and the valve stem 5 .

Further, the center of rotation of the valve ball 4 and the geometric center of the sealing ring 23 are set eccentrically, the center of rotation of the valve ball 4 and the center of the flow channel of the valve body 1 are set eccentrically, and the double eccentric design of the valve ball 4 makes the valve ball 4 There is no contact with the valve seat during the opening and closing process, and the sealing surface has almost zero wear, which improves the service life of the valve.

Further, the sealing ring 23 has a spherical crown.

Further, the contact surface of the valve seat 3 and the valve body 1 is a conical surface.

Further, the valve cover 2 is provided with a drip plate 24, which is used to prevent the moisture in the air from liquefying at low temperature into water droplets falling on the gasket of the valve body flange, so as to prevent the water droplets from freezing and damaging the gasket.

Further, the valve cover 2 is provided with a pressure relief hole 25 .

Working principle: Due to the double eccentric design of the valve ball, when the valve stem is rotated counterclockwise to open the valve ball, the valve ball will make a cam motion, and will be separated from the valve seat immediately after opening. The entire opening process has no contact with the valve seat, effectively reducing the operation of the valve. Torque; when the valve stem is rotated clockwise to close the valve ball, the valve ball similarly acts as a cam, and the entire closing process has no contact with the valve seat, until the closing end point, relying on the torque of the actuator to achieve mechanical forced sealing, so as to ensure the two-way sealing performance of the valve .

Due to the double eccentric design of the valve ball, there is no contact between the valve ball and the valve seat during the valve opening and closing process, the sealing surface has almost zero wear, and the surface of the valve seat and sealing ring is hardened, which is especially suitable for occasions where LNG requires frequent switching, effectively improving valve life.

Since the valve adopts a single valve seat structure and an open valve cavity, the middle cavity of the valve body will not trap low-temperature medium during the valve opening and closing process, ensuring the safe and reliable operation of the LNG plant.

It can be understood that the above embodiments are only exemplary embodiments adopted to illustrate the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, without departing from the spirit and essence of the present invention, various modifications and improvements can be made, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (9)

1. An LNG force-sealed on-off ball valve, comprising a valve body (1), a valve cover (2), a valve seat (3), a valve ball (4), a valve stem (5), and a packing assembly (16), the A valve ball (4) is arranged in the valve body (1), the valve cover (2) is sleeved on the outside of the valve stem (5) and is fixedly connected with the valve body (1), and a stuffing box (2) is arranged in the valve cover (2). 6), a packing assembly (16) is arranged in the stuffing box (6); it is characterized in that: it also includes a sealing ring (23), a first bushing (7), a second bushing (8) and a plane bearing (9) , the valve ball (4) is provided with a sealing ring (23) and the first Nord-Lock gasket (12), the valve seat (3), the pressure ring (27) and the second Nord-Lock gasket ( 21) Fasten them in the seat cavity of the valve body (1) in sequence, the valve ball (4) and the second bushing (8) are inserted into the bottom shaft hole of the valve body (1), and the valve stem (5) is sleeved into the valve screw the valve ball (4) into the valve seat, a first bushing (7) and a second bushing are arranged between the upper end of the valve ball (4) and the valve cover (2). The sleeve (8) is located between the lower end of the valve ball (4) and the valve body (1); the lower end of the valve stem (5) is provided with a step (10), and a plane is provided between the step (10) and the valve cover (2). The bearing (9), the plane bearing (9) is sleeved on the step of the valve stem (5). 2. The LNG force-sealed on-off ball valve according to claim 1, wherein the sealing ring (23) is mounted on the valve ball by using a socket head cap screw (11) and a first Nord-Lock gasket (12). On (4), a second wound gasket (22) is arranged between the sealing ring (23) and the valve ball (4). 3. The LNG forced sealing switch ball valve according to claim 1, characterized in that: the valve cover (2) and the valve body (1) are connected and fixed by bolts, and the valve cover (2) is connected to the valve body (1). A first wound gasket (13) is arranged between the bodies (1). 4. The LNG forced-sealing on-off ball valve according to claim 1, characterized in that: the packing assembly (16) comprises a pan plug ring (14), a retaining ring (15), a plug ring (14), a retaining ring (15), The packing (16), the packing spacer (17), the packing pressing sleeve (18) and the packing pressing plate (19), the packing pressing plate (19) is fixed with the bonnet (2) by means of bolts and disc springs (28). 5. The LNG force-sealed on-off ball valve according to claim 1, characterized in that: the center of rotation of the valve ball (4) and the center of the sealing ring (23) are eccentrically arranged, and the center of rotation of the valve ball (4) is eccentrically arranged. Set eccentrically from the center of the flow channel of the valve body (1). 6 . The LNG forced-sealing on-off ball valve according to claim 1 , wherein the sealing ring ( 23 ) is a spherical crown. 7 . 7 . The LNG forced-sealing on-off ball valve according to claim 1 , wherein the contact surface between the valve seat ( 3 ) and the valve body ( 1 ) is a conical surface. 8 . 8 . The LNG forced-sealing on-off ball valve according to claim 1 , wherein a drip plate ( 24 ) is arranged on the valve cover ( 2 ). 9 . 9 . The LNG forced-sealing on-off ball valve according to claim 1 , wherein a pressure relief hole ( 25 ) is provided on the valve cover ( 2 ). 10 .

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