An overpressure protection device for the middle cavity of an externally discharging gate valve

Abstract

The present invention discloses an overpressure protection device for the middle cavity of an externally discharging gate valve, which includes an inlet side main pipeline connected to the inlet side of a double gate valve. A pre-valve drain pipeline is communicatively arranged on the side of the inlet side main pipeline, and a drain valve is arranged on the pre-valve drain pipeline. A pressure protection system is communicatively arranged between the pre-valve drain pipeline downstream of the drain valve and the middle cavity of the double gate valve. The overpressure protection system is interconnected with a DCS controller for receiving the detection signal of the overpressure protection system and capable of controlling the operation of the overpressure protection system. By effectively ensuring that the double gate valve is not easily damaged through the pre-valve drain pipeline communicatively arranged at the bottom of the inlet side main pipeline, and by arranging an overpressure protection system between the middle cavity of the double gate valve and the pre-valve drain pipeline, the pressure monitoring of the middle cavity of the double gate valve can be realized, the purpose of automatically discharging the overpressure in the middle cavity of the double gate valve is achieved, and the dual sealing function of the double gate valve is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of overpressure protection for double-gate valves, and more particularly to an overpressure protection device for the middle cavity of an externally discharged gate valve. Background Art

[0002] A double-gate valve, in which the double gates fit the two-side valve seats, has the advantages of simple structure, reliable sealing performance, good sealing performance, small opening and closing torque, long service life, etc., and is widely used in pipeline systems such as electric power, petroleum, natural gas, and chemical industry. Due to its excellent sealing structure on both sides, in some cases, the pressure in the middle cavity of the gate valve may abnormally increase. Usually, after the system fluid medium is started up, it changes from a cold state to a hot state. The main pipeline gate valve is closed in the cold state. When the main pipeline is heated to a certain temperature and pressure condition, the main gate valve can be opened; when the fluid (liquid or gas) accumulates in the middle cavity of the valve, if the temperature of the fluid on the inlet side increases, the temperature of the fluid in the middle cavity will increase due to the principle of heat transfer. Due to the inconsistent expansion coefficients of the metal and the fluid, the volume of the middle cavity of the valve expands much less than the expansion speed of the fluid when heated. When the fluid accumulated in the middle cavity changes from a cold state to a hot state, the fluid may expand rapidly, and some liquids may vaporize, resulting in a sharp increase in pressure, and the increased pressure is often in a geometric progression. The consequences of valve overpressure are very serious. When the pressure in the middle cavity of the valve abnormally increases, the working stresses of its pressure-bearing parts and opening and closing parts (such as valve stems, gate support frames, and packing sleeves) will all increase sharply. The valve plate will be wedged on the valve seat under the action of the expanding fluid, and the driving force of the driving mechanism will be overwhelmed and even unable to start. Seriously, the packing will spray out, the gate support frame will break, the valve stem will be pulled off, and the motor will burn out. These phenomena are not uncommon in high-pressure gate valves on many high-temperature fluid pipelines.

[0003] If no measures are taken for the system, the damage to the system caused by the abnormal pressure rise in the middle cavity of the main gate valve is almost inevitable. The harms are mainly as follows: First, it is the damage to the valve body. When the pressure in the middle cavity abnormally increases, the opening pressure of the valve will increase exponentially. When the actual stress of the material exceeds the allowable stress, the valve cannot be opened or the over-stressed part will rupture, and the whole valve will be damaged or scrapped; Second, it is the damage to the production system. The normal opening and closing of the valve are the key to various industrial process controls. Once this switch control cannot be realized smoothly, the system must be shut down for maintenance. If the weak parts such as the valve body, valve cover, and packing of the overpressure valve leak or rupture, causing the medium to leak externally; when the medium is a high-temperature, high-pressure, toxic, or harmful fluid, the consequences will be more serious, and even the equipment and personnel will be injured, resulting in huge direct or indirect losses.

[0004] There are two traditional ways to relieve pressure in the middle cavity, which are divided into internal pressure relief and external pressure relief methods. Internal pressure relief is to open a pressure relief channel on the valve plate to connect the middle cavity with the inlet side pipeline. When the pressure in the middle cavity rises, the pressure can be released into the inlet pipeline through the pressure relief channel; External pressure relief is to add a pressure relief pipeline outside the valve body and install a safety valve on the pipeline. The middle cavity is connected to the upstream outside the valve body through the pipeline, which is used for connecting the pressure relief channels of the middle cavity and the inlet pipeline.

[0005] For the valve with a pressure relief hole installed for internal pressure relief, since the middle cavity is connected to the inlet side through the pressure relief hole, the sealing surface of the inlet gate plate of the double gate plate loses its sealing function, and only the sealing surface on the outlet side plays a sealing role, losing the advantage of double sealing of the double gate plate. Some internal pressure relief channels are provided with slide valves or sealing balls, which have good sealing effects, but the structure is complex. In addition, after long-term operation in a high-temperature and high-pressure environment, the pressure relief components are prone to jamming and losing their due functions. The method of installing a safety valve pipeline for external pressure relief has a relatively simple system, but lacks system monitoring. When it is difficult to open the valve, it is impossible to judge whether it is caused by pressure buildup in the middle cavity, and it is not easy to judge the reason. Therefore, the above pressure relief methods have limitations and need to be further improved. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an overpressure protection device for the middle cavity of an externally discharging gate valve, so as to solve the problem that the traditional internal pressure relief method will cause the sealing surface of the inlet gate plate of the double gate plate to lose its sealing function, and the problem that the external pressure relief method cannot judge the reason why it is difficult to open the valve, so as to achieve the purpose of monitoring the pressure in the middle cavity of the double gate plate gate valve and automatically discharging the overpressure, so as to ensure the double sealing function of the double gate plate.

[0007] To solve the above technical problems, the technical solutions adopted by the present invention are as follows.

[0008] An overpressure protection device for the middle cavity of an externally discharging gate valve includes an inlet side main pipeline connected to the inlet side of the double gate plate gate valve for transporting high-temperature and high-pressure fluids. A pre-valve drain pipeline is connected to the bottom of the inlet side main pipeline for fully draining water during system startup to prevent water accumulation in the inlet side main pipeline. A drain valve is provided on the pre-valve drain pipeline for controlling the on-off of the pre-valve drain pipeline; A pressure protection system is connected between the pre-valve drain pipeline downstream of the drain valve and the middle cavity of the double gate plate gate valve. The pressure protection system can detect the pressure in the middle cavity of the double gate plate gate valve and discharge the fluid in the middle cavity of the double gate plate gate valve into the pre-valve drain pipeline to achieve the purpose of discharging the pressure in the middle cavity of the double gate plate gate valve. The overpressure protection system is interconnected with a DCS controller for receiving the detection signal of the overpressure protection system and controlling the operation of the overpressure protection system.

[0009] Further optimize the technical solution. The overpressure protection system includes an external drain pipeline main pipe connected to the middle cavity of the double gate valve. An automatic external pressure relief overpressure protection system is connected between the external drain pipeline main pipe and the pre-valve drain pipeline, which can detect the pressure in the middle cavity of the double gate valve and automatically drain the fluid in the middle cavity of the double gate valve into the pre-valve drain pipeline.

[0010] Further optimize the technical solution. The automatic external pressure relief overpressure protection system includes an automatic external drain pipeline connected between the external drain pipeline main pipe and the pre-valve drain pipeline. Along the fluid transportation direction on the automatic external drain pipeline, a pressure sensor for detecting the fluid pressure in the middle cavity of the double gate valve and an electromagnetic drain valve for controlling the on / off of the automatic external drain pipeline are arranged in sequence. The signal output end of the pressure sensor is connected to the input end of the DCS controller, and the controlled end of the electromagnetic drain valve is connected to the output end of the DCS controller.

[0011] Further optimize the technical solution. Normally open manual stop valves are respectively arranged on the automatic external drain pipeline on both sides of the electromagnetic drain valve and the pressure sensor.

[0012] Further optimize the technical solution. The inner diameter of the automatic external drain pipeline is not greater than 10 mm.

[0013] Further optimize the technical solution. A manual external pressure relief overpressure protection system for manual operation to drain the fluid in the middle cavity of the double gate valve into the pre-valve drain pipeline in case of failure of the automatic external pressure relief overpressure protection system is also connected between the external drain pipeline main pipe and the pre-valve drain pipeline.

[0014] Further optimize the technical solution. The manual external pressure relief overpressure protection system includes a manual external drain pipeline connected between the external drain pipeline main pipe and the pre-valve drain pipeline and at least one normally closed manual stop valve arranged on the manual external drain pipeline.

[0015] Further optimize the technical solution. The inner diameter of the manual external drain pipeline is not greater than 10 mm.

[0016] Due to the adoption of the above technical solutions, the technical progress achieved by the present invention is as follows.

[0017] By connecting the pre-valve drain pipeline at the bottom of the main pipeline on the inlet side and arranging an overpressure protection system between the middle cavity of the double gate valve and the pre-valve drain pipeline, the present invention can monitor the pressure in the middle cavity of the double gate valve, achieve the purpose of automatically discharging the overpressure in the middle cavity of the double gate valve, and ensure the double-sealing function of the double gate. Compared with the conventional design of pressure relief in the middle cavity of the double gate valve and the external drain pipeline of the safety valve, the real-time monitoring of the pressure in the middle cavity of the double gate valve and the purpose of automatic overpressure discharge can be realized.

[0018] When the pressure sensor and the electromagnetic relief valve in the automatic external relief pipeline of the present invention fail, the third manual stop valve and the fourth manual stop valve can be closed to repair the pressure sensor and the electromagnetic relief valve.

[0019] The manual external pressure relief overpressure protection system can manually open the first manual stop valve and the second manual stop valve when the automatic external pressure relief overpressure protection system fails, so that the fluid in the middle cavity of the double gate valve is discharged into the pre-valve drain pipeline through the manual external relief pipeline, realizing the discharge of the pressure in the middle cavity of the double gate valve. Brief Description of the Drawings

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] Wherein: 1. Inlet side main pipeline, 2. Double gate valve, 3. Drain valve, 4. Second manual stop valve, 5. First manual stop valve, 6. External relief pipeline outlet point, 7. External relief pipeline main pipe, 8. Manual external relief pipeline, 9. Pre-valve drain pipeline, 10. Fourth manual stop valve, 11. Electromagnetic relief valve, 12. Pressure sensor, 13. Third manual stop valve, 14. Automatic external relief pipeline. Detailed Embodiments

[0022] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0023] Embodiment 1

[0024] An overpressure protection device for the middle cavity of an external relief gate valve, in combination with Figure 1 As shown, it includes an inlet side main pipeline 1, a pre-valve drain pipeline 9, a drain valve 3, an overpressure protection system and a DCS controller.

[0025] The inlet side main pipeline 1 is connected to the inlet side of the double gate valve 2 and is used to transport high-temperature and high-pressure fluid.

[0026] The pre-valve drain pipeline 9 is connected and arranged at the bottom of the inlet side main pipeline 1 and is used to play a role in fully draining water during system startup to prevent the accumulation of drain water in the inlet side main pipeline 1.

[0027] The drain valve 3 is arranged on the pre-valve drain pipeline 9 and is used to control the on-off of the pre-valve drain pipeline 9.

[0028] The overpressure protection system is connected and arranged between the pre-valve drain pipeline 9 downstream of the drain valve 3 and the middle cavity of the double gate valve 2, and is used to be able to detect the pressure in the middle cavity of the double gate valve and be able to discharge the fluid in the middle cavity of the double gate valve into the pre-valve drain pipeline 9 to achieve the purpose of discharging the pressure in the middle cavity of the double gate valve. The overpressure protection system is interactively connected with the DCS controller.

[0029] The overpressure protection system includes an external drain pipeline main pipe 7 connected to the middle cavity of the double-gate valve 2. A through-hole is drilled in the middle cavity of the double-gate valve 2, which is the external drain pipeline extraction point 6. The external drain pipeline extraction point 6 is preferably at a position with relatively good valve body strength design and convenient for pipeline welding operation. The external drain pipeline main pipe 7 is connected to the external drain pipeline extraction point 6. An automatic external pressure relief overpressure protection system is connected between the external drain pipeline main pipe 7 and the pre-valve drain pipeline 9. The automatic external pressure relief overpressure protection system is used to detect the pressure in the middle cavity of the double-gate valve and automatically drain the fluid in the middle cavity of the double-gate valve into the pre-valve drain pipeline 9. The drain valve 3 is arranged on the pre-valve drain pipeline 9 between the inlet side main pipeline 1 and the automatic external pressure relief overpressure protection system.

[0030] The automatic external pressure relief overpressure protection system includes an automatic external drain pipeline 14 connected between the external drain pipeline main pipe 7 and the pre-valve drain pipeline 9. The inlet of the automatic external drain pipeline 14 is connected to the external drain pipeline main pipe 7, and the outlet of the automatic external drain pipeline 14 is connected to the pre-valve drain pipeline 9. A pressure sensor 12 and an electromagnetic drain valve 11 are arranged on the automatic external drain pipeline 14 in sequence according to the fluid transportation direction. The pressure sensor 12 is arranged on the automatic external drain pipeline 14. Since the automatic external drain pipeline 14 is connected to the middle cavity of the double-gate valve, the pressure sensor 12 can detect the fluid pressure in the middle cavity of the double-gate valve. The signal output end of the pressure sensor 12 is connected to the input end of the DCS controller. The electromagnetic drain valve 11 is used to control the on-off of the automatic external drain pipeline 14, and the controlled end of the electromagnetic drain valve 11 is connected to the output end of the DCS controller.

[0031] The inner diameter of the automatic external drain pipeline 14 is not greater than 10 mm. The material of the automatic external drain pipeline 14 is selected to be the same as that of the inlet side main pipeline 1, and the wall thickness selection follows the design specifications.

[0032] The automatic external drain pipeline 14 can automatically open when the pressure in the middle cavity of the double-gate valve exceeds the set value, drain the middle cavity pressure, and automatically close after the pressure drops to the set value.

[0033] Normally open manual stop valves are respectively arranged on the automatic external drain pipeline 14 on both sides of the electromagnetic drain valve 11 and the pressure sensor 12. The normally open manual stop valve includes a third manual stop valve 13 arranged upstream of the pressure sensor 12 and a fourth manual stop valve 10 arranged downstream of the electromagnetic drain valve 11. The third manual stop valve 13 and the fourth manual stop valve 10 are in a normally open state to ensure that the right end of the automatic external drain pipeline 14 is connected to the middle cavity of the double-gate valve.

[0034] The DCS controller is used to receive the detection signals of the overpressure protection system and can control the operation of the overpressure protection system. It can realize the real-time monitoring of the pressure in the middle cavity of the double-gate valve and has functions of high-pressure alarm, automatic overpressure relief, and automatic closing after pressure relief. The output end of the DCS controller is connected with an alarm lamp and a main control display screen. The alarm lamp can blink for alarm under the control of the DCS controller, and the main control display screen can display the pressure value detected by the pressure sensor 12.

[0035] The actual operation process of this embodiment is as follows.

[0036] Before the inlet side main pipeline 1 is put into operation, the double-gate valve 2 is closed and the drain valve 3 is opened for the valve front drain pipeline 9. The inlet side main pipeline is slowly heated for warming up and draining the condensate to prevent a large amount of high-temperature and high-pressure fluid from suddenly flowing into the inlet side main pipeline, rapid temperature rise, and thermal shock resulting in fatigue damage of the pipeline and the double-gate valve. After the warming-up of the inlet side main pipeline is completed (parameters such as the pressure, temperature, and cleanliness of the condensate in the main pipeline are qualified), the drain valve 3 is closed and the double-gate valve 2 is opened as required, and the high-temperature and high-pressure fluid flows into the double-gate valve.

[0037] In the operating state, the third manual stop valve 13 and the fourth manual stop valve 10 are in the open state. The pressure sensor 12 monitors the pressure in the middle cavity of the double-gate valve and displays the real-time pressure P value on the main control display screen. When the P value exceeds K1 times the design pressure of the high-temperature and high-pressure fluid pipeline, the alarm lamp blinks for alarm; when the P value exceeds K2 times the design pressure of the high-temperature and high-pressure fluid pipeline, the DCS controller controls the electromagnetic relief valve 11 to open and relieve the pressure in the middle cavity of the double-gate valve.

[0038] In this embodiment, if the pressure sensor 12 and the electromagnetic relief valve 11 in the automatic external relief pipeline fail, the third manual stop valve 13 and the fourth manual stop valve 10 can be closed for maintenance of the pressure sensor 12 and the electromagnetic relief valve 11.

[0039] Embodiment 2

[0040] Based on Embodiment 1, the difference between this embodiment and Embodiment 1 is that a manual external pressure relief overpressure protection system is also connected and arranged between the main pipe 7 of the external relief pipeline and the valve front drain pipeline 9. The manual external pressure relief overpressure protection system is used for manual operation in the case of the failure of the automatic external pressure relief overpressure protection system to drain the fluid in the middle cavity of the double-gate valve into the valve front drain pipeline 9. The manual external pressure relief overpressure protection system, namely the manual pressure relief redundancy system, is arranged in parallel with the automatic external pressure relief overpressure protection system.

[0041] The manual external pressure relief overpressure protection system includes a manual external relief pipeline 8 connected and arranged between the main pipe 7 of the external relief pipeline and the valve front drain pipeline 9 and at least one normally closed manual stop valve arranged on the manual external relief pipeline 8.

[0042] The inner diameter of the manual external drain pipe 8 is not greater than 10 mm. The material of the manual external drain pipe 8 is selected to be the same as that of the main pipe 1 on the inlet side, and the wall thickness selection follows the design specifications.

[0043] In the present invention, there are two normally closed manual stop valves, namely the first manual stop valve 5 and the second manual stop valve 4.

[0044] When the electromagnetic drain valve 11 is opened for N seconds and the pressure P value in the middle cavity of the double gate valve does not decrease and exceeds K3 times the design pressure of the high-temperature and high-pressure fluid pipeline, the DCS controller controls the alarm light to alarm, indicating that there is a fault in the automatic external drain pipe 14. The operator opens the first manual stop valve 5 and the second manual stop valve 4 on the manual external drain pipe 8 to drain the pressure in the middle cavity of the double gate valve. When the pressure in the middle cavity of the double gate valve drops back to the P value, the first manual stop valve 5 and the second manual stop valve 4 are closed.

Claims

1. An overpressure protection device for the middle cavity of an externally discharging gate valve, comprising an inlet side main pipeline (1) connected to the inlet side of a double gate valve (2) for conveying high-temperature and high-pressure fluid, characterized in that: A pre-valve drain pipe (9) for fully draining water when the system starts up to prevent water accumulation in the inlet-side main pipe (1) is connected to the bottom of the inlet-side main pipe (1). A drain valve (3) for controlling the on / off of the pre-valve drain pipe (9) is provided on the pre-valve drain pipe (9). A overpressure protection system is connected between the pre-valve drain pipe (9) downstream of the drain valve (3) and the middle cavity of the double-gate valve (2), which can detect the pressure in the middle cavity of the double-gate valve and discharge the fluid in the middle cavity of the double-gate valve into the pre-valve drain pipe (9) to achieve the purpose of discharging the pressure in the middle cavity of the double-gate valve. The overpressure protection system is interconnected with a DCS controller for receiving the detection signal of the overpressure protection system and controlling the operation of the overpressure protection system. The overpressure protection system includes an external discharge pipe main (7) connected to the middle cavity of the double-gate valve (2). An automatic external overpressure protection system for detecting the pressure in the middle cavity of the double-gate valve and automatically discharging the fluid in the middle cavity of the double-gate valve into the pre-valve drain pipe (9) is connected between the external discharge pipe main (7) and the pre-valve drain pipe (9). The automatic external overpressure protection system includes an automatic external discharge pipe (14) connected between the external discharge pipe main (7) and the pre-valve drain pipe (9). A pressure sensor (12) for detecting the fluid pressure in the middle cavity of the double-gate valve and an electromagnetic discharge valve (11) for controlling the on / off of the automatic external discharge pipe (14) are arranged in sequence on the automatic external discharge pipe (14) along the fluid transmission direction. The signal output end of the pressure sensor (12) is connected to the input end of the DCS controller, and the controlled end of the electromagnetic discharge valve (11) is connected to the output end of the DCS controller. Normally open manual stop valves are respectively arranged on the automatic external discharge pipe (14) on both sides of the electromagnetic discharge valve (11) and the pressure sensor (12). The inner diameter of the automatic external discharge pipe (14) is not greater than 10 mm. A manual external overpressure protection system for manual operation to discharge the fluid in the middle cavity of the double-gate valve into the pre-valve drain pipe (9) in case of failure of the automatic external overpressure protection system is also connected between the external discharge pipe main (7) and the pre-valve drain pipe (9). The manual external overpressure protection system includes a manual external discharge pipe (8) connected between the external discharge pipe main (7) and the pre-valve drain pipe (9) and at least one normally closed manual stop valve arranged on the manual external discharge pipe (8).

2. The overpressure protection device for the middle cavity of the externally discharging gate valve according to claim 1, characterized in that: The inner diameter of the manual external discharge pipe (8) is not greater than 10 mm.

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