CN112032377A - A fast-response pilot-operated safety valve and system overpressure fast protection method - Google Patents

Abstract

The invention discloses a quick-response pilot-type safety valve and a system overpressure rapid protection method. The pilot-type safety valve comprises a valve body, a main valve core, a pilot valve core, a pilot spring, a spring seat, a main spring, a lower spring group, Upper spring group, valve cover, pressure regulating handwheel and pilot outlet channel; the main spool of the valve body can move vertically under the limit of the lower spring group and the upper spring group; there is a stepped through hole inside the main spool, The pilot spool is located above the stepped protrusion of the through hole. The top of the pilot spool is coaxially fixed with a pilot spring, a spring seat, a main spring and a pressure regulating handwheel. It moves up and down under the action of the spring. The invention utilizes the lower spring group, the upper spring group, the main spring and the pilot spring to form the initial pre-tightening force on the main valve core, the pilot valve core and the main valve core can be automatically contacted or separated according to the system pressure, and the response speed is fast. It can adapt to different system pressures and effectively improve the safety of the system.

Description

A fast-response pilot-operated safety valve and system overpressure fast protection method

technical field

The invention belongs to the field of safety valves, in particular to a fast-response pilot safety valve and a system overpressure fast protection method.

Background technique

The pilot-operated safety valve is composed of a main valve and a small-volume pilot valve, and is an overpressure protection device. The working principle is that when the inlet pressure of the valve exceeds the safe value, the fluid pressure acts on the pilot spool, pushing the pilot valve to open, thereby reducing the pressure at the upper end of the main valve, and automatically opening the main valve to relieve the system under the action of the pressure difference. Return system pressure to normal.

Industrial systems are developing towards large-scale and centralized development. Once system problems are not solved in time, accidents will occur, endanger the safety of operators, and affect the supply of social products. The pilot-operated safety valve is a common device for protecting system safety. In order to deal with the problems endangering the system safety in time, the requirements for the opening speed of the pilot-operated safety valve are getting higher and higher. In the existing pilot-operated safety valve, the pilot valve is placed outside the main valve, and is connected to the main valve by a conduit. The liquid must first open the pilot valve to open the main valve, and the leakage flow of the pilot valve cannot ensure that the system pressure can be reduced in time and quickly, and the system often causes explosions, cracks and other accidents due to the slow pressure relief speed. The patents at this stage mainly focus on the structural improvement of the sealing structure of the pilot-operated safety valve and the use of low-pressure working conditions, and there are relatively few patents on improving the opening speed of the pilot-operated safety valve.

Therefore, it is of great significance to study how to improve the opening speed of the pilot-operated safety valve.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the defects of the prior art, and to provide a fast-response pilot safety valve, the pilot valve core and the main valve core can be automatically contacted or separated according to the system pressure, and have a faster response speed , can quickly adapt to different system pressures, can effectively improve the safety performance of the system. Furthermore, the present invention also provides a rapid protection method for system overpressure based on a quick-response pilot-operated safety valve.

The concrete technical scheme adopted in the present invention is as follows:

A quick-response pilot-operated safety valve, comprising a valve body, a main spool, a pilot spool, a pilot spring, a spring seat, a main spring, a lower spring group, an upper spring group, a valve cover, a pressure regulating handwheel and a pilot outlet aisle;

The top of the valve body is detachably fixed with the valve cover, and the main valve core is arranged at the inflow channel inside the valve body. The bottom of the main valve core can completely close the inflow channel where it is located; one end of the lower spring group is connected to the main valve. The bottom of the core is connected and fixed, and the other end is connected and fixed with the inner wall of the valve body; one end of the upper spring group is connected and fixed with the top of the main valve core, and the other end is connected and fixed with the lower end of the valve cover; the positions of the lower spring group and the upper spring group are in the vertical direction. Corresponding to each other, the main spool can move vertically under the limit of the lower spring group and the upper spring group;

The inside of the main spool is axially provided with a stepped through hole that gradually expands from bottom to top, and the through hole communicates with the inflow channel; the pilot spool is located above the stepped protrusion of the through hole, and can pass through the stepped protrusion The through hole is completely closed by the matching relationship; the top of the pilot valve core is coaxially fixed with a pilot spring, a spring seat, a main spring and a pressure regulating handwheel in sequence, and the spring seat is located above the main valve core and can be The matching relationship on the upper surface of the main valve core completely closes the through hole; the pressure regulating handwheel is located outside the valve body, and the initial compression amount of the main spring can be adjusted by the pressure regulating handwheel; both the pilot valve core and the spring seat can be connected between the pilot spring and the It moves up and down under the action of the main spring, and when the pilot valve core moves up, it can drive the spring seat to move up;

The valve body chamber located above the main spool is provided with a pilot outlet channel that communicates with the outlet channel of the main valve. The pilot spring, the main spring, the lower spring group and the upper spring group can be compressed in the vertical direction and are all uniform in the initial state. In the compressed state; in the initial state, the bottom of the main spool is in contact with the inside of the valve body and the joint is closed, the pilot spool cooperates with the stepped protrusion to completely close the through hole, and the bottom of the spring seat is on the main spool. Surface fit and the fit is closed.

Preferably, the number of springs in the lower spring group and the upper spring group is multiple.

Further, the number of springs in the lower spring group and the upper spring group are both four, and the springs in the lower spring group and the upper spring group are evenly distributed at equal angles along the circumferential direction of the main valve core.

Further, the stiffness of the springs in the lower spring group and the upper spring group are the same, and the initial compression amount of the upper spring group is smaller than that of the lower spring group.

Preferably, the top of the valve body and the valve cover are connected and fixed by screws or studs.

Preferably, the valve body at the bottom of the main valve core is provided with a mounting hole, and the mounting hole is used for placing the lower spring group.

Preferably, a sealing packing is used for sealing between the main valve core and the valve body to ensure the sealing effect.

Preferably, a flange is installed and fixed at the bottom of the valve body.

Preferably, the pilot valve core is a valve core structure with a gradually reduced bottom, which can partially extend into the hole formed by the stepped protrusion to cooperate with the stepped protrusion, so as to completely close the internal through hole of the main valve core.

Another object of the present invention is to provide a system overpressure rapid protection method based on any one of the above-mentioned pilot-operated safety valves, the details of which are as follows:

S1: When the system pressure is within the normal range, the pilot spool is in close contact with the main spool under the action of the pilot spring to ensure sealing; the main spool acts on the pre-tightening force of the lower spring group, the upper spring group, the main spring and the pilot spring The lower part is in close contact with the valve body to prevent the inflow of fluid, and the pilot-operated safety valve is in a closed state;

S2: When the system pressure exceeds the safety range and the rise does not exceed the rated threshold, the fluid pushes the pilot spool to move upward, and the upward-moving pilot spool drives the spring seat to disengage from the main spool; the fluid passes through the lower inlet of the pilot safety valve It flows into the inflow channel, enters the through hole inside the main valve core, flows into the pilot outlet channel through the gap between the spring seat and the main valve core, and finally flows out through the main valve outlet channel;

S3: On the basis of S2, when the system pressure continues to rise, the main spool will overcome the preload of the upper spring group under the action of the system pressure, the preload force of the lower spring group and the upward pressure difference caused by the leakage of the pilot spool. The tightening force and the gravity of the main valve core move upward and leave the valve body; the fluid can flow out through the main valve outlet channel through the gap between the main valve core and the valve body;

S4: On the basis of S2 or S3, when the system pressure no longer rises and returns to the normal range, the pilot spool that has been leaked through the pilot outlet channel will move down and return to the initial state position, and the main spool will be close to the valve body Contact, the pilot safety valve returns to the closed state;

S5: When the system pressure exceeds the safety range and the rise exceeds the rated threshold, the fluid directly pushes the main spool to move upward, so that the main spool leaves the valve body under the force of the lower spring group; the fluid can pass through the gap between the main spool and the valve body. The gap between the valves flows out through the outlet channel of the main valve;

S6: On the basis of S5, when the system pressure no longer rises and returns to the normal range, the main spool will move down and return to the initial state position, and the pilot-operated safety valve will return to the closed state.

Compared with the prior art, the present invention has the following beneficial effects:

The sealing surface of the pilot valve core of the pilot-operated safety valve of the present invention is far away from the mainstream liquid, and is less damaged by liquid scouring, so that a good sealing effect can be better maintained; and the sealing structure at the opening of the main valve core adopts the same Packing and sealing between the valve body can avoid the damage caused by the repeated washing of the liquid. At the same time, opening the spring chamber on the valve body can further prevent the leakage of the fluid, and the sealing effect is better;

The pilot-operated safety valve of the present invention can choose different opening modes according to different fluid pressures, which improves the opening speed and ensures that the system has sufficient safety; and the increase range of the fluid pressure can be adjusted by changing the pressure regulating handwheel;

In the present invention, the pilot valve core is placed inside the main valve core, and the lower spring group, the upper spring group, the main spring and the pilot spring are used to form the initial pre-tightening force for the main valve core. The pressure automatically realizes contact or separation, and the response speed is fast, which can quickly adapt to different system pressures and effectively improve the safety of the system.

Description of drawings

1 is a schematic structural diagram of a pilot-operated safety valve of the present invention;

In the figure: 1. Flange; 2. Valve body; 3. Lower spring group; 4. Sealing packing; 5. Main valve core; 6. Pilot valve core; 7. Pilot spring; 8. Spring seat; 9. Upper spring group; 10, stud bolt; 11, valve cover; 12, main spring; 13, pressure regulating handwheel; 14, screw; 15, pilot outlet channel.

Detailed ways

The present invention will be further elaborated and described below with reference to the accompanying drawings and specific embodiments. The technical features of the various embodiments of the present invention can be combined correspondingly on the premise that there is no conflict with each other.

As shown in FIG. 1 , in this embodiment, a quick-response pilot-operated safety valve is provided. The pilot-operated safety valve includes a valve body 2 , a main valve core 5 , a pilot valve core 6 , a pilot spring 7 , and a spring seat. 8. The main spring 12, the lower spring group 3, the upper spring group 9, the valve cover 11, the pressure regulating handwheel 13 and the pilot outlet channel 15. The structure of each component and the connection relationship between the components will be described in detail below.

A valve cover 11 is fixed on the top of the valve body 2, and the valve body 2 and the valve cover 11 are detachably connected. The bottom of the valve body 2 and the outlet end of the main valve outlet channel of the valve body 2 are fixedly installed with a flange 1. . In this embodiment, the top of the valve body 2 and the valve cover 11 are connected and fixed by screws 14 or stud bolts 10 , and the valve body 2 and the flange 1 are fixed by welding. A main valve core 5 is provided at the inflow channel inside the valve body 2 , and the bottom of the main valve core 5 can completely close the inflow channel where it is located. In this embodiment, the bottom of the main valve core 5 can completely cover the cross section of the inflow channel where it is located, and the connection between the main valve core 5 and the inside of the valve body 2 is closed, and fluid cannot pass through. The main valve core 5 and the valve body 2 are sealed by the annular sealing packing 4 to ensure the sealing effect and avoid the direct erosion and damage of the sealing structure by the fluid.

The lower spring group 3 is fixedly arranged at the bottom of the main valve core 5 , one end of the lower spring group 3 is connected and fixed with the bottom of the main valve core 5 , and the other end is connected and fixed with the inner wall of the valve body 2 . In this embodiment, in order to ensure a better sealing effect, a mounting hole can be opened on the valve body 2 at the bottom of the main valve core 5, and the mounting hole is used to place the lower spring group 3, and the lower spring group 3 can be completely compressed. into the installation hole, so that the bottom of the main valve core 5 and the valve body 2 can be in close contact. In addition, the installation hole can increase the pressure when the fluid flows in, generate a negative pressure difference, prevent the fluid from further inflow, and ensure the sealing effect.

The upper spring group 9 is fixedly arranged on the top of the main valve core 5 , one end of the upper spring group 9 is connected and fixed with the top of the main valve core 5 , and the other end is connected and fixed with the lower end of the valve cover 11 . The positions of the lower spring group 3 and the upper spring group 9 correspond to each other in the vertical direction, and the main valve core 5 can move in the vertical direction under the limit of the lower spring group 3 and the upper spring group 9 . The number of springs in the lower spring group 3 and the upper spring group 9 is multiple. In this embodiment, the number of springs in the lower spring group 3 and the springs in the upper spring group 9 are both four, and the lower spring group 3 and the upper spring group 9 have four springs. The springs in the spring group 9 are evenly distributed at equal angles along the circumference of the main valve core 5 . The stiffness of the springs in the lower spring group 3 and the upper spring group 9 are the same, and the initial compression amount of the upper spring group 9 is smaller than that of the lower spring group 3, which ensures that the main spool 5 receives a smaller resultant force after the pilot spool 6 is opened. And the direction is downward, so when the system pressure reaches a certain level, the main spool 5 can move up quickly under the force of the lower spring group 3, which enhances the response speed.

The inside of the main valve core 5 is provided with a stepped through hole which gradually expands from bottom to top along the axial direction, and the through hole communicates with the inflow channel. The pilot valve core 6 is located above the stepped protrusion of the through hole, and can completely close the through hole through the matching relationship with the stepped protrusion. In this embodiment, the pilot valve core 6 is a valve core structure with a gradually reduced bottom. The pilot valve core 6 can partially extend into the hole formed by the stepped protrusion, and cooperate with the stepped protrusion to realize the internal through hole of the main valve core 5. completely closed. A pilot spring 7 , a spring seat 8 , a main spring 12 and a pressure regulating handwheel 13 are coaxially fixed to the top of the pilot spool 6 in sequence, that is to say, the top of the pilot spool 6 is fixedly connected with a pilot capable of vertical compression Spring 7, the bottom of the pilot spring 7 is fixedly connected with the top of the pilot valve core 6, the top of the pilot spring 7 is fixedly connected with a spring seat 8, the bottom of the spring seat 8 is fixedly connected with the top of the pilot spring 7, and the top of the spring seat 8 is fixed A main spring 12 capable of vertical compression is connected, the bottom of the main spring 12 is fixedly connected with the top of the spring seat 8 , and the top of the main spring 12 is fixedly connected with a pressure regulating handwheel 13 . The spring seat 8 is located above the main valve core 5 and can completely close the through hole through the matching relationship with the upper surface of the main valve core 5 . In this embodiment, the outer circumference of the transverse section of the spring seat 8 is larger than the size of the through hole at the position where the bottom surface of the spring seat 8 is located. When the spring seat 8 is in contact with the main valve core 5, the bottom surface of the spring seat 8 can make the The vias are completely covered and the connections are closed. The pressure regulating handwheel 13 is fixedly connected to the top of the main spring 12 through a rod, the rod penetrates the valve cover 11 and is connected to the pressure regulating handwheel 13 located outside the valve body 2 , and a thread is formed between the rod and the valve cover 11 Connected so that the initial compression amount of the main spring 12 can be adjusted at a fixed value by rotating the pressure regulating handwheel 13 . Both the pilot valve core 6 and the spring seat 8 can move up and down under the action of the pilot spring 7 and the main spring 12, and when the pilot valve core 6 moves up, it can drive the spring seat 8 to move up to realize the pressure relief function of the pilot safety valve. When the pilot valve core 6 moves up, the spring seat 8 is driven to separate from the main valve core 5, and the force on the main valve core 5 gradually becomes smaller, so that the main valve core 5 is easy to open. Adjusting the pressure regulating handwheel 13 can adjust the initial compression amount of the spring 12, thereby changing the safe range value of the system fluid pressure.

The chamber of the valve body 2 located above the main valve core 5 is provided with a pilot outlet channel 15 that communicates with the main valve outlet flow channel. The pilot spring 7, the main spring 12, the lower spring group 3 and the upper spring group 9 can all be vertically arranged. It is compressed in the direction and is in a compressed state in the initial state, so as to ensure that the sealing structure at the main valve core 5 has sufficient initial preload. In the initial state, the bottom of the main valve core 5 is in contact with the inside of the valve body 2 and the joint is closed, the pilot valve core 6 cooperates with the stepped protrusion to completely close the through hole, and the bottom of the spring seat 8 is on the main valve core 5. Surface fit and the fit is closed.

The system overpressure rapid protection method based on the above pilot safety valve is as follows:

S1: When the system pressure is within the normal range, the pilot spool 6 will be in close contact with the main spool 5 under the action of the pilot spring 7 to ensure the sealing effect. The main valve core 5 is in close contact with the valve body 2 under the preloading force of the lower spring group 3 , the upper spring group 9 , the main spring 12 and the pilot spring 7 , thereby preventing the inflow of fluid. At this time, the pilot-operated safety valve is closed, and the system can operate normally without the leakage protection of the pilot-operated safety valve.

S2: When the system pressure exceeds the safety range and the rise does not exceed the rated threshold, the rated threshold means that the upward pressure of the system can only overcome the preloading force of the main spring 12 and the pilot spring 7 and the gravitational action of the pilot spool 6 to make the pilot The valve core 6 moves up, but cannot overcome the preload force of the upper spring group 9 and the gravitational force of the main valve core 5, so that the main valve core 5 moves up. In this case, the fluid pushes the pilot spool 6 to move upward, and at the same time, the upwardly moving pilot spool 6 drives the spring seat 8 to disengage from the main spool 5 . At this time, the fluid flows into the inflow channel through the lower inlet of the pilot safety valve, enters the through hole inside the main spool 5, flows into the pilot outlet channel 15 through the gap between the spring seat 8 and the main spool 5, and finally passes through the main spool 5. The valve outlet runner flows out.

S3: On the basis of S2, when the system pressure continues to rise, the main spool 5 overcomes the preload force of the upper spring group 9 and the main valve under the action of the system pressure and the upward pressure difference caused by the leakage of the pilot spool 6. The gravity of the core 5 moves upward, and the main valve core 5 leaves the valve body 2 under the force of the lower spring group 3 . At this time, the fluid can pass through the gap between the main valve core 5 and the valve body 2 and flow out through the main valve outlet channel.

It should be noted that, according to the difference in the preload force of the main spring 12 and the pilot spring 7, when the main spool 5 moves upward, the pilot spool 6 may fit with the main spool 5, and the fluid can only flow from the main spool 5. The gap between the valve core 5 and the valve body 2 flows out through the outlet channel of the main valve. In addition, the pilot spool 6 may not fit with the main spool 5. At this time, part of the fluid flows out from the gap between the main spool 5 and the valve body 2 through the outlet channel of the main valve, and the other part of the fluid flows through the main valve. The gap between the spring seat 8 and the main valve core 5 flows into the pilot outlet channel 15 and finally flows out through the main valve outlet channel.

S4: On the basis of S2 or S3, when the system pressure no longer rises and returns to the normal range, the pilot spool 6 that has been discharged through the pilot outlet channel 15 will move downward and return to the initial state position, and the main spool 5 In close contact with valve body 2, the pilot-operated safety valve returns to the closed state.

S5: When the system pressure exceeds the safe range and the rise exceeds the rated threshold, the fluid directly pushes the main spool 5 to move upward, so that the main spool 5 leaves the valve body 2 under the force of the lower spring group 3. At this time, the fluid can pass through the gap between the main valve core 5 and the valve body 2 and flow out through the main valve outlet channel.

S6: On the basis of S5, when the system pressure no longer rises and returns to the normal range, the main spool 5 will move down and return to the initial state position, and the pilot-operated safety valve will return to the closed state.

When the system pressure rises again and exceeds the safety range, the pilot-operated safety valve will repeat the above process according to the actual state.

The working principle of the present invention is as follows: when the valve is in the closed state, the fluid enters from the lower side inlet and is located at the front end of the main valve core. However, the initial compression of the upper spring group 9 is smaller than that of the lower spring group 3, so the preloading force of the main spool is provided by the pilot spring 7 and the main spring 12, and the magnitude of the preloading force is the same as the pressure when the pilot spool 6 is opened. Related, can be set by rotating the pressure regulating handwheel 13 as required.

In the present invention, the pilot valve core is placed inside the main valve core, and the lower spring group, the upper spring group, the main spring and the pilot spring are used to form the initial pre-tightening force for the main valve core. The pressure automatically realizes contact or separation, and the response speed is fast, which can quickly adapt to different system pressures and effectively improve the safety of the system.

The above-mentioned embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. Various changes and modifications can also be made by those of ordinary skill in the relevant technical field without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims (10)

1. A quick-response pilot-operated safety valve, characterized by comprising a valve body (2), a main valve core (5), a pilot valve core (6), a pilot spring (7), a spring seat (8), a main valve spring (12), lower spring group (3), upper spring group (9), valve cover (11), pressure regulating handwheel (13) and pilot outlet channel (15); A valve cover (11) is detachably fixed on the top of the valve body (2), a main valve core (5) is arranged at the inflow channel inside the valve body (2), and the bottom of the main valve core (5) can The inflow channel of the valve body is completely closed; one end of the lower spring group (3) is connected and fixed with the bottom of the main valve core (5), and the other end is connected and fixed with the inner wall of the valve body (2); one end of the upper spring group (9) is connected with the main valve core (5) The top is connected and fixed, and the other end is connected and fixed with the lower end of the valve cover (11); the positions of the lower spring group (3) and the upper spring group (9) correspond to each other in the vertical direction, and the main valve core (5) can The spring group (3) and the upper spring group (9) move in the vertical direction under the limit; The main valve core (5) is provided with a stepped through hole which gradually expands from bottom to top along the axial direction, and the through hole is communicated with the inflow channel; the pilot valve core (6) is located above the stepped protrusion of the through hole, The through hole can be completely closed through the matching relationship with the stepped protrusion; the top of the pilot valve core (6) is coaxially fixed with the pilot spring (7), the spring seat (8), the main spring (12) and the adjustment. The pressure handwheel (13), the spring seat (8) is located above the main valve core (5), and can completely close the through hole through the matching relationship with the upper surface of the main valve core (5); the pressure regulating handwheel (13) ) is located outside the valve body (2), and the initial compression amount of the main spring (12) can be adjusted by the pressure regulating handwheel (13); It moves up and down under the action of the main spring (12), and when the pilot valve core (6) moves up, it can drive the spring seat (8) to move up; The chamber of the valve body (2) located above the main valve core (5) is provided with a pilot outlet channel (15) which communicates with the outlet flow passage of the main valve, a pilot spring (7), a main spring (12), a lower spring group ( 3) Both the upper spring group (9) and the upper spring group (9) can be compressed in the vertical direction and are in a compressed state in the initial state; in the initial state, the bottom of the main spool (5) and the inside of the valve body (2) fit and fit The pilot valve core (6) cooperates with the stepped protrusion to completely close the through hole, and the bottom of the spring seat (8) is abutted with the upper surface of the main valve core (5) and the abutment is closed. 2 . The pilot-operated safety valve according to claim 1 , wherein the number of springs in the lower spring group ( 3 ) and the upper spring group ( 9 ) is multiple. 3 . 3. The pilot-operated safety valve according to claim 2, wherein the number of springs in the lower spring group (3) and the upper spring group (9) are both four, and the lower spring group (3) and The springs in the upper spring group (9) are evenly distributed at equal angles along the circumference of the main valve core (5). 4. The pilot-operated safety valve according to claim 2, characterized in that the stiffness of the springs in the lower spring group (3) and the upper spring group (9) are the same, and the initial compression of the upper spring group (9) The amount is smaller than that of the lower spring group (3). 5 . The pilot-operated safety valve according to claim 1 , wherein the top of the valve body ( 2 ) and the valve cover ( 11 ) are connected and fixed by screws ( 14 ) or stud bolts ( 10 ). 6 . 6 . The pilot-operated safety valve according to claim 1 , wherein the valve body ( 2 ) at the bottom of the main spool ( 5 ) is provided with a mounting hole, and the mounting hole is used to place the lower spring group ( 3 ). 7 . . 7 . The pilot-operated safety valve according to claim 1 , wherein the main valve core ( 5 ) and the valve body ( 2 ) are sealed by sealing packing ( 4 ) to ensure the sealing effect. 8 . 8 . The pilot-operated safety valve according to claim 1 , wherein a flange ( 1 ) is installed and fixed at the bottom of the valve body ( 2 ). 9 . 9 . The pilot-operated safety valve according to claim 1 , wherein the pilot valve core ( 6 ) is a valve core structure with a gradually reduced bottom, which can partially extend into the holes formed by the stepped protrusions and the stepped protrusions. 10 . In cooperation, the internal through hole of the main spool (5) is completely closed. 10. A system overpressure rapid protection method based on any one of the pilot safety valves of claims 1 to 9, characterized in that the details are as follows: S1: When the system pressure is within the normal range, the pilot spool (6) is in close contact with the main spool (5) under the action of the pilot spring (7) to ensure sealing; the main spool (5) is in the lower spring group (3) , The upper spring group (9), the main spring (12) and the pilot spring (7) are in close contact with the valve body (2) under the action of the pre-tightening force to prevent fluid from flowing in, and the pilot safety valve is in a closed state; S2: When the system pressure exceeds the safety range and the rise does not exceed the rated threshold, the fluid pushes the pilot spool (6) to move upward, and the upwardly moving pilot spool (6) drives the spring seat (8) and the main spool (5) ) is disengaged; the fluid flows into the inflow channel through the lower inlet of the pilot safety valve, enters the through hole inside the main spool (5), and flows into the pilot outlet through the gap between the spring seat (8) and the main spool (5). channel (15), and finally flows out through the outlet flow channel of the main valve; S3: On the basis of S2, when the system pressure continues to rise, the upward pressure difference of the main spool (5) caused by the system pressure, the preload force of the lower spring group (3) and the leakage of the pilot spool (6) Under the action, it overcomes the pre-tightening force of the upper spring group (9) and the gravity of the main spool (5) to move upward and leave the valve body (2); the fluid can pass between the main spool (5) and the valve body (2) the gap, and flows out through the outlet channel of the main valve; S4: On the basis of S2 or S3, when the system pressure no longer rises and returns to the normal range, the pilot spool (6) that has been discharged through the pilot outlet channel (15) will move down and return to the initial state position, and the main The valve core (5) is in close contact with the valve body (2), and the pilot-operated safety valve returns to the closed state; S5: When the system pressure exceeds the safe range and the rise exceeds the rated threshold, the fluid directly pushes the main spool (5) to move upward, so that the main spool (5) leaves the valve body (2) under the force of the lower spring group (3). ); the fluid can flow out through the main valve outlet channel through the gap between the main valve core (5) and the valve body (2); S6: On the basis of S5, when the system pressure no longer rises and returns to the normal range, the main spool (5) will move down and return to the initial position, and the pilot-operated safety valve will return to the closed state.

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