An overpressure protection device

Abstract

The present invention relates to the technical field of mechanical seal protection structures, and in particular to an overpressure protection device, comprising a shaft sleeve, a dynamic ring, a floating static ring assembly, a sealing chamber, a middle cover and an overpressure protection valve, wherein the sealing chamber, the dynamic ring, the floating static ring assembly and the middle cover enclose a sealing area, and an overpressure protection valve is provided between the sealing area and the atmospheric side of the middle cover; the overpressure protection valve comprises a valve body, a steel ball and a preload spring, a tapered hole is provided in the valve body, the inner diameter of the tapered hole gradually increases from the sealing area to the outside, the steel ball is installed in the tapered hole, and a preload spring is installed in the valve body, the preload spring abuts against the steel ball and can provide a force to push the steel ball toward the tapered hole. The advantage of the present invention is that when the pressure in the sealing area exceeds the maximum allowable pressure of the seal, the leak is discharged through the overpressure protection valve, and then collected and discharged by the next level of seal, so that the sealing area is timely depressurized under the overpressure state, thereby protecting the seal from damage.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical sealing protection structures, in particular to an overpressure protection device. Background Art

[0002] In nuclear power plant equipment, the sealing performance of the main pump is particularly critical. The internal pressure of the main pump can reach 158 bar. The existing sealing structure uses multiple stages of sealing to achieve gradual pressure reduction, ultimately preventing the medium within the main pump from leaking into the atmosphere. In the event of an emergency power outage, if seals I and II fail, the medium within the pump body will gradually leak toward seal III. However, seal III cannot withstand the high pressure, which will damage the dynamic and static rings of seal III, causing the medium to leak. Ensuring that seal III remains intact during a power outage is a pressing issue. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an overpressure protection device. When the pressure in the sealing area exceeds the maximum allowable pressure of the seal, it leaks and is discharged through the overpressure protection valve, and then collected and discharged by the next level of seal, so that the sealing area can be depressurized in time under overpressure conditions, thereby protecting the seal from damage.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] An overpressure protection device comprises a shaft sleeve, a dynamic ring, a floating static ring assembly, a sealing chamber, a middle cover, and an overpressure protection valve, wherein the shaft sleeve is mounted on the main shaft, the dynamic ring is fixedly mounted on the shaft sleeve, the sealing chamber is fixed on the pump body, the middle cover is fixed on the sealing chamber, the floating static ring assembly is mounted on the inner side of the middle cover, and the sealing surface of the floating static ring assembly abuts against the dynamic ring;

[0006] The sealing cavity, the dynamic ring, the floating static ring assembly and the middle cover enclose a sealing area, and an overpressure protection valve is provided between the sealing area and the atmosphere side of the middle cover;

[0007] The overpressure protection valve includes a valve body, a steel ball, and a pre-tightening spring. A conical hole is provided in the valve body, and the inner diameter of the conical hole gradually increases from the sealing area to the outside. The steel ball is installed in the conical hole. A pre-tightening spring is installed in the valve body. The pre-tightening spring abuts against the steel ball and can provide a force to push the steel ball toward the conical hole.

[0008] Furthermore, the overpressure protection valve also includes an adjusting screw ring, which is a hollow structure. The adjusting screw ring is connected to the end of the valve body through threaded fitting, and the end of the preload spring away from the steel ball abuts against the adjusting screw ring.

[0009] Furthermore, the overpressure protection valve is installed on the static ring seat, and the static ring seat is provided with a cavity A for installing the overpressure protection valve and a through hole A that can connect the cavity A with the atmospheric side of the middle cover, and the overpressure protection valve is installed in the cavity A.

[0010] Furthermore, the valve body is fixed in the cavity A by a clamping ring, and a valve body sealing ring is provided between the outer wall of the valve body and the inner wall of the cavity A.

[0011] Furthermore, the inlet of the overpressure protection valve faces one side of the middle cover.

[0012] Furthermore, the inlet of the overpressure protection valve faces the dynamic ring.

[0013] Furthermore, the overpressure protection valve is installed on the middle cover, and the middle cover is provided with a cavity B for installing the overpressure protection valve and a through hole B that can connect the cavity B with the atmospheric side of the middle cover, and the overpressure protection valve is installed in the cavity B.

[0014] Furthermore, the valve body is fixed in the cavity B by a clamping ring, and a valve body sealing ring is provided between the outer wall of the valve body and the inner wall of the cavity B.

[0015] Furthermore, a No. III sealed injection hole and a No. III sealed leakage hole are respectively opened radially on the atmosphere side of the middle cover.

[0016] Furthermore, the floating stationary ring assembly includes a stationary ring support, a stationary ring seat, a stationary ring, a compensation spring and an anti-rotation pin A. The stationary ring support is fixedly installed on the inner side of the middle cover, and the stationary ring seat is slidably mounted on the stationary ring support. A compensation spring extending axially along the main shaft is installed between the stationary ring seat and the stationary ring support. The stationary ring is fixedly installed on the stationary ring seat, and the sealing surface of the stationary ring abuts against the dynamic ring.

[0017] Furthermore, a stationary ring seat sealing ring is provided between the stationary ring seat and the stationary ring support member, and a dynamic ring sealing ring is provided between the dynamic ring and the shaft sleeve.

[0018] The present invention has the following advantages:

[0019] 1. The present invention installs an overpressure protection valve in the sealing area of ​​seal III. When the pressure in the sealing area exceeds the maximum allowable pressure of the seal, the pressure is leaked and discharged through the overpressure protection valve, and then collected and discharged by the next level seal, so that the sealing area can be depressurized in time under overpressure state, thereby protecting the dynamic seal from damage.

[0020] 2. The overpressure protection valve pushes the steel ball into the tapered hole through the pre-tightened spring. When the pressure in the sealing area is lower than the opening pressure of the overpressure protection valve, the steel ball seals the tapered hole to ensure its sealing performance. A small amount of leakage medium in the sealing area can be collected through the No. II sealing leakage hole.

[0021] 3. The overpressure protection valve of the present invention can be installed on the stationary ring seat or on the middle cover, and the installation method is flexible and changeable. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a cross-sectional view of the present invention;

[0023] Figure 2 is a cross-sectional view of embodiment 1 of the present invention;

[0024] Figure 3 is a cross-sectional view of embodiment 2 of the present invention;

[0025] Figure 4 is a cross-sectional view of embodiment 3 of the present invention;

[0026] Figure 5 is a cross-sectional view of the overpressure protection valve of the present invention;

[0027] Figure 6 A cross-sectional view of a parking seal according to the present invention;

[0028] In the figure: 1-main shaft, 2-sleeve, 3-sealing chamber, 4-dynamic ring, 5-dynamic ring sealing ring, 6-middle cover, 7-stationary ring support, 8-stationary ring seat, 9-stationary ring, 10-stationary ring seat sealing ring, 11-compensation spring, 12-anti-rotation pin A, 13-sealing area, 14-overpressure protection valve, 15-No. II sealing leakage hole, 16-No. III sealing injection hole, 17-No. III sealing leakage hole, 18-valve body, 19-clamping ring, 20-valve body sealing ring, 21-conical hole, 22-steel ball, 23-preload spring, 24-adjusting screw ring, 25-end cover, 26-parking sealing ring, 27-parking sealing seat, 28-parking sealing air inlet, 29-pushing surface, 30-parking sealing surface, 31-parking sealing spring, 32-anti-rotation pin B. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0030] like Figure 1As shown, seals No. I, II, III, and IV (the shutdown seal) are positioned on main shaft 1 in the direction of medium leakage. During normal operation, seal I can withstand pressures exceeding 158 bar. Any minor leakage is collected through the leak collection port on seal II. However, during a full power outage (SBO operation), when main shaft 1 stops, seals I and II become ineffective, and the pressure at seal III gradually rises. Since seal III can only withstand a maximum pressure of 2 bar under normal conditions, this rising pressure could damage the dynamic and static rings of seal III. Therefore, the present invention incorporates an overpressure protection device on seal III to prevent damage during SBO operation.

[0031] like Figures 1 to 5 As shown, an overpressure protection device includes a sleeve 2, a dynamic ring 4, a floating static ring assembly, a sealing chamber 3, a middle cover 6, and an overpressure protection valve 14. The sleeve 2 is mounted on the main shaft 1, the dynamic ring 4 is fixedly mounted on the sleeve 2, the sealing chamber 3 is fixed to the pump body, the middle cover 6 is fixed to the sealing chamber 3, the floating static ring assembly is mounted on the inner side of the middle cover 6, and the sealing surface of the floating static ring assembly abuts against the dynamic ring 4 to form a seal.

[0032] The sealing chamber 3, the dynamic ring 4, the floating static ring assembly, and the middle cover 6 enclose a sealing area 13. Leakage from seal No. II enters the sealing area 13. An overpressure protection valve 14 is provided between the sealing area 13 and the atmosphere side of the middle cover 6. When the pressure of the medium in the sealing area 13 exceeds the opening pressure of the overpressure protection valve 14, the medium leaks from the overpressure protection valve 14 to the atmosphere side of the middle cover 6 (i.e., seal No. IV).

[0033] The overpressure protection valve 14 includes a valve body 18, a steel ball 22, and a preload spring 23. A tapered hole 21 is provided within the valve body 18, the inner diameter of which gradually increases from the sealing area 13 outward. The steel ball 22 is mounted within the tapered hole 21, and a preload spring 23 is installed within the valve body 18. The preload spring 23 abuts against the steel ball 22 and provides a force that pushes the steel ball 22 toward the tapered hole 21. Medium enters the valve body 18 through the inlet and acts on the surface of the steel ball 22. When the medium pressure exceeds the preload force of the preload spring 23, the medium pushes the steel ball 22, overcoming the work done by the preload spring 23. When a gap forms between the steel ball 22 and the tapered hole 21, the medium can leak outward.

[0034] Furthermore, the overpressure protection valve 14 includes an adjusting screw 24, which is a hollow structure and is threadedly connected to the end of the valve body 18. The end of the preload spring 23, away from the steel ball 22, abuts against the adjusting screw 24. Before the overpressure protection valve 14 leaves the factory, the manufacturer can adjust the preload force of the preload spring 23 to adjust the opening pressure of the overpressure protection valve 14. To ensure that the flow of the medium is not affected, the adjusting screw 24 is designed as a hollow structure, allowing the medium to leak out of the overpressure protection valve 14 smoothly when overpressure occurs.

[0035] In order to facilitate the disassembly of the overpressure protection valve 14, an internal thread is provided in the inner cavity of the outlet of the valve body 18. When disassembly is required, the overpressure protection valve 14 is pulled out by screwing a threaded pull rod into the inner thread of the inner cavity of the outlet of the valve body 18. In order to protect the threads of the internal thread, after the overpressure protection valve 14 is installed in place, a guide screw sleeve 33 is screwed into the inner cavity of the outlet of the valve body 18. The guide screw sleeve 33 has an external thread that can be screwed together with the internal thread of the inner cavity of the outlet of the valve body 18. The guide screw sleeve 33 also has an inner hole for the leakage medium to pass through. In order to facilitate the removal of the guide screw sleeve 33, a cutting edge is provided at the upper end of the guide screw sleeve 33, and the guide screw sleeve 33 can be turned with a flat-blade screwdriver. In order to prevent the guide screw sleeve 33 from automatically falling out when the equipment is running, a pressure ring 34 is provided below the retaining ring 19. The pressure ring 34 can limit the axial movement of the guide screw sleeve 33.

[0036] There are various structures for the installation position of the overpressure protection valve 14, and the present invention lists three installation methods.

[0037] Example 1:

[0038] like Figure 2 As shown, the overpressure protection valve 14 is installed on the stationary ring seat 8. The stationary ring seat 8 is provided with a cavity A for installing the overpressure protection valve 14 and a through hole A that can connect the cavity A with the atmospheric side of the middle cover 6. The overpressure protection valve 14 is installed in the cavity A.

[0039] The valve body 18 is fixed in the cavity A by a clamping ring 19 . The valve body 18 and the stationary ring seat 8 form a whole. A valve body sealing ring 20 is provided between the outer wall of the valve body 18 and the inner wall of the cavity A.

[0040] The inlet of the overpressure protection valve 14 faces one side of the middle cover 6 .

[0041] Example 2:

[0042] like Figure 3 As shown, the difference from embodiment 1 is that the inlet of the overpressure protection valve 14 faces the side of the dynamic ring 4.

[0043] Example 3:

[0044] like Figure 4As shown, the overpressure protection valve 14 is installed on the middle cover 6. The middle cover 6 is provided with a cavity B for installing the overpressure protection valve 14 and a through hole B that can connect the cavity B with the atmospheric side of the middle cover 6. The overpressure protection valve 14 is installed in the cavity B. The advantage of installing the overpressure protection valve 14 on the middle cover 6 is that it protects the structural integrity of the static ring seat 8, does not require drilling holes on the static ring seat 8, and makes the structural stability of the static ring seat 8 better. The middle cover 6 is larger in size and has a larger opening space to facilitate the installation of the overpressure protection valve 14. In addition, the overpressure protection valve 14 is installed on the middle cover 6, which makes it more convenient to disassemble and assemble the overpressure protection valve 14.

[0045] In the above three embodiments, the valve body 18 is fixed in the cavity B by a clamping ring 19 , and a valve body sealing ring 20 is provided between the outer wall of the valve body 18 and the inner wall of the cavity B.

[0046] Furthermore, a No. III seal injection hole 16 and a No. III seal leakage hole 17 are radially formed on the atmospheric side of the middle cover 6. When the entire plant is powered off, the No. III seal injection hole 16 injects sealing water at a pressure slightly higher than that of the No. III seal, and the water is discharged from the No. III seal leakage hole 17, forming a boundary pressure on the atmospheric side of the No. III seal to prevent the leaking medium from the No. III seal from entering the parking seal. The leaked medium is then guided to the No. III seal leakage hole 17, discharged along with the sealing water, and collected.

[0047] Furthermore, the floating stationary ring assembly includes a stationary ring support 7, a stationary ring seat 8, a stationary ring 9, a compensation spring 11 and an anti-rotation pin A12. The stationary ring support 7 is fixedly installed on the inner side of the middle cover 6, and the stationary ring seat 8 is slidably mounted on the stationary ring support 7. A compensation spring 11 extending axially along the main shaft 1 is installed between the stationary ring seat 8 and the stationary ring support 7. The stationary ring 9 is fixedly installed on the stationary ring seat 8, and the sealing surface of the stationary ring 9 abuts against the dynamic ring 4.

[0048] Furthermore, a stationary ring seat sealing ring 10 is provided between the stationary ring seat 8 and the stationary ring support 7 , and a dynamic ring sealing ring 5 is provided between the dynamic ring 4 and the shaft sleeve 2 .

[0049] It should be noted that a No. II sealing leakage hole 15 is radially opened on the sealing chamber 3, and the No. II sealing leakage hole 15 is connected to the sealing area 13. When the medium leaking from the No. II seal enters the sealing area 13, it can be discharged and collected through the No. II sealing leakage hole 15.

[0050] like Figure 6As shown, the final seal on main shaft 1 is the shutdown seal, located inside end cap 25. It comprises a shutdown seal ring 26 and a shutdown seal seat 27. The shutdown seal ring 26 and end cap 25 are capable of sliding relative to each other. The shutdown seal seat 27 is fixed to the shaft sleeve 2. A shutdown seal gas inlet 28 is radially defined in end cap 25. The end face of shutdown seal ring 26 facing away from end cap 25 serves as a push surface 29. When shutdown is required, shutdown seal gas (N2) enters through inlet 28 and acts on push surface 29, pushing shutdown seal ring 26 toward shutdown seal seat 27. When the upper end face of shutdown seal ring 26 abuts the lower end face of shutdown seal seat 27, the shutdown seal is established. After a power outage, seals I and II fail. Seal III cannot withstand the high pressure. Even when medium enters the shutdown seal through overpressure protection valve 14, shutdown seal gas can be introduced, closing the shutdown seal and preventing medium from leaking directly to the atmosphere on the end cap 25.

[0051] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. An overpressure protection device, characterized in that: It includes a shaft sleeve, a dynamic ring, a floating static ring assembly, a sealing chamber, a middle cover and an overpressure protection valve. The shaft sleeve is installed on the main shaft, the dynamic ring is fixedly installed on the shaft sleeve, the sealing chamber is fixed on the pump body, the middle cover is fixed on the sealing chamber, the floating static ring assembly is installed on the inner side of the middle cover, and the sealing surface of the floating static ring assembly abuts against the dynamic ring. The sealing cavity, the dynamic ring, the floating static ring assembly and the middle cover enclose a sealing area, and an overpressure protection valve is provided between the sealing area and the atmosphere side of the middle cover; The overpressure protection valve includes a valve body, a steel ball, and a preload spring. A tapered hole is provided in the valve body, and the inner diameter of the tapered hole gradually increases from the sealing area to the outside. The steel ball is installed in the tapered hole. The valve body is equipped with a preload spring, which abuts against the steel ball and can provide a force to push the steel ball toward the tapered hole. The overpressure protection valve is installed on the stationary ring seat. The stationary ring seat is provided with a cavity A for installing the overpressure protection valve and a through hole A that can connect the cavity A with the atmospheric side of the middle cover. The overpressure protection valve is installed in the cavity A. The valve body is fixed in the cavity A by a clamping ring, and a valve body sealing ring is provided between the outer wall of the valve body and the inner wall of the cavity A; The inlet of the overpressure protection valve faces one side of the middle cover; The atmosphere side of the middle cover is provided with a sealed injection hole No. III and a sealed leakage hole No. III in the radial direction; The floating stationary ring assembly includes a stationary ring support, a stationary ring seat, a stationary ring, a compensation spring and an anti-rotation pin A. The stationary ring support is fixedly mounted on the inner side of the middle cover, the stationary ring seat is slidably sleeved on the stationary ring support, a compensation spring extending along the axial direction of the main shaft is installed between the stationary ring seat and the stationary ring support, the stationary ring is fixedly mounted on the stationary ring seat, and the sealing surface of the stationary ring abuts against the dynamic ring; A stationary ring seat sealing ring is provided between the stationary ring seat and the stationary ring support member, and a dynamic ring sealing ring is provided between the dynamic ring and the shaft sleeve; Seal No. I, seal No. II, seal No. III and seal No. IV are arranged in sequence on the main shaft along the leakage direction of the medium. When the equipment is operating normally, seal No. I can withstand a pressure of more than 158 bar. If there is a small amount of leakage, it can be collected through the leakage collection port at seal No. II. When the power is off in the entire plant, the main shaft stops, seals No. I and No. II fail, and the pressure at seal No. III gradually rises. Under normal circumstances, the maximum pressure that seal No. III can withstand is only 2 bar. In order to prevent the rising pressure from damaging the dynamic and static rings of seal No. III, the overpressure protection device is set at seal No. III to prevent seal No. III from being damaged when the power is off in the entire plant.

2. An overpressure protection device, characterized in that: It includes a shaft sleeve, a dynamic ring, a floating static ring assembly, a sealing chamber, a middle cover and an overpressure protection valve. The shaft sleeve is installed on the main shaft, the dynamic ring is fixedly installed on the shaft sleeve, the sealing chamber is fixed on the pump body, the middle cover is fixed on the sealing chamber, the floating static ring assembly is installed on the inner side of the middle cover, and the sealing surface of the floating static ring assembly abuts against the dynamic ring. The sealing cavity, the dynamic ring, the floating static ring assembly and the middle cover enclose a sealing area, and an overpressure protection valve is provided between the sealing area and the atmosphere side of the middle cover; The overpressure protection valve includes a valve body, a steel ball, and a preload spring. A tapered hole is provided in the valve body, and the inner diameter of the tapered hole gradually increases from the sealing area to the outside. The steel ball is installed in the tapered hole. The valve body is equipped with a preload spring, which abuts against the steel ball and can provide a force to push the steel ball toward the tapered hole. The overpressure protection valve is installed on the stationary ring seat. The stationary ring seat is provided with a cavity A for installing the overpressure protection valve and a through hole A that can connect the cavity A with the atmospheric side of the middle cover. The overpressure protection valve is installed in the cavity A. The valve body is fixed in the cavity A by a clamping ring, and a valve body sealing ring is provided between the outer wall of the valve body and the inner wall of the cavity A; The inlet of the overpressure protection valve faces the side of the dynamic ring; the atmosphere side of the middle cover is radially provided with a No. III sealing injection hole and a No. III sealing leakage hole; The floating stationary ring assembly includes a stationary ring support, a stationary ring seat, a stationary ring, a compensation spring and an anti-rotation pin A. The stationary ring support is fixedly mounted on the inner side of the middle cover, the stationary ring seat is slidably sleeved on the stationary ring support, a compensation spring extending along the axial direction of the main shaft is installed between the stationary ring seat and the stationary ring support, the stationary ring is fixedly mounted on the stationary ring seat, and the sealing surface of the stationary ring abuts against the dynamic ring; A stationary ring seat sealing ring is provided between the stationary ring seat and the stationary ring support member, and a dynamic ring sealing ring is provided between the dynamic ring and the shaft sleeve; Seal No. I, seal No. II, seal No. III and seal No. IV are arranged in sequence on the main shaft along the leakage direction of the medium. When the equipment is operating normally, seal No. I can withstand a pressure of more than 158 bar. If there is a small amount of leakage, it can be collected through the leakage collection port at seal No. II. When the power is off in the entire plant, the main shaft stops, seals No. I and No. II fail, and the pressure at seal No. III gradually rises. Under normal circumstances, the maximum pressure that seal No. III can withstand is only 2 bar. In order to prevent the rising pressure from damaging the dynamic and static rings of seal No. III, the overpressure protection device is set at seal No. III to prevent seal No. III from being damaged when the power is off in the entire plant.

3. An overpressure protection device, characterized in that: It includes a shaft sleeve, a dynamic ring, a floating static ring assembly, a sealing chamber, a middle cover and an overpressure protection valve. The shaft sleeve is installed on the main shaft, the dynamic ring is fixedly installed on the shaft sleeve, the sealing chamber is fixed on the pump body, the middle cover is fixed on the sealing chamber, the floating static ring assembly is installed on the inner side of the middle cover, and the sealing surface of the floating static ring assembly abuts against the dynamic ring. The sealing cavity, the dynamic ring, the floating static ring assembly and the middle cover enclose a sealing area, and an overpressure protection valve is provided between the sealing area and the atmosphere side of the middle cover; The overpressure protection valve includes a valve body, a steel ball, and a preload spring. A tapered hole is provided in the valve body, and the inner diameter of the tapered hole gradually increases from the sealing area to the outside. The steel ball is installed in the tapered hole. The valve body is equipped with a preload spring, which abuts against the steel ball and can provide a force to push the steel ball toward the tapered hole. The overpressure protection valve is installed on the middle cover. The middle cover is provided with a cavity B for installing the overpressure protection valve and a through hole B that can connect the cavity B with the atmospheric side of the middle cover. The overpressure protection valve is installed in the cavity B. The valve body is fixed in the cavity B by a clamping ring, and a valve body sealing ring is provided between the outer wall of the valve body and the inner wall of the cavity B; The atmosphere side of the middle cover is provided with a sealed injection hole No. III and a sealed leakage hole No. III in the radial direction; The floating stationary ring assembly includes a stationary ring support, a stationary ring seat, a stationary ring, a compensation spring and an anti-rotation pin A. The stationary ring support is fixedly mounted on the inner side of the middle cover, the stationary ring seat is slidably sleeved on the stationary ring support, a compensation spring extending along the axial direction of the main shaft is installed between the stationary ring seat and the stationary ring support, the stationary ring is fixedly mounted on the stationary ring seat, and the sealing surface of the stationary ring abuts against the dynamic ring; a stationary ring seat sealing ring is provided between the stationary ring seat and the stationary ring support, and a dynamic ring sealing ring is provided between the dynamic ring and the shaft sleeve; Seal No. I, seal No. II, seal No. III and seal No. IV are arranged in sequence on the main shaft along the leakage direction of the medium. When the equipment is operating normally, seal No. I can withstand a pressure of more than 158 bar. If there is a small amount of leakage, it can be collected through the leakage collection port at seal No. II. When the power is off in the entire plant, the main shaft stops, seals No. I and No. II fail, and the pressure at seal No. III gradually rises. Under normal circumstances, the maximum pressure that seal No. III can withstand is only 2 bar. In order to prevent the rising pressure from damaging the dynamic and static rings of seal No. III, the overpressure protection device is set at seal No. III to prevent seal No. III from being damaged when the power is off in the entire plant.

4. An overpressure protection device according to claim 1, 2 or 3, characterized in that: The overpressure protection valve also includes an adjusting screw ring, which is a hollow structure. The adjusting screw ring is connected to the end of the valve body through threaded fitting, and the end of the preload spring away from the steel ball abuts against the adjusting screw ring.

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