Backpressure backflow prevention pilot operated safety valve

Abstract

The utility model relates to a backpressure backflow prevention pilot operated safety valve which comprises a main valve and a pilot valve, an inlet of the pilot valve is communicated with an inlet of the main valve, and the main valve comprises a valve body, a valve seat, a valve clack, a valve cover and a guide sleeve. The anti-backflow valve is characterized in that an anti-backflow device composed of a three-way valve body and a piston is arranged at an outlet of a piston cavity of the main valve, when back pressure of a discharge outlet of the main valve is larger than working pressure of an inlet, the back pressure pushes the piston to move leftwards, medium pressure of the discharge outlet enters the piston cavity, a valve clack is prevented from being opened, and vibration caused by mistaken opening of the valve clack due to back pressure backflow is prevented; the valve has the advantages of reliable sealing performance, long service life and the like.

Description

Technical Field

[0001] The utility model relates to a safety valve, in particular to a pilot-operated safety valve. The utility model is suitable for a medium pipeline system with a discharge port having back pressure. Background Art

[0002] The pilot-operated safety valve uses a small-diameter pilot valve to control a large-diameter main valve, so as to reduce the product volume and improve the accuracy of the set pressure. For example, the pilot-operated safety valve with patent number CN202321419558.4 includes a pilot valve and a main valve. The pilot valve is connected to the main valve inlet cavity and piston cavity through the lower conduit and the upper conduit respectively. When the main valve inlet pressure exceeds the pilot valve set pressure, the pilot valve opens to release the piston cavity pressure, and the medium pressure pushes the main valve disc to open and discharge the medium pressure, thereby protecting the safety of the equipment on the main valve inlet side. However, in the working condition where the main valve discharge port is connected to the pressure pipeline, when the back pressure of the discharge port is greater than the working pressure on the main valve inlet side, the main valve disc is easily opened by mistake, causing the main valve disc to vibrate and collide frequently with the valve seat, affecting the sealing performance and product service life. Summary of the invention

[0003] The utility model aims at the shortcomings of the prior art and provides a back pressure backflow prevention pilot safety valve which can prevent the valve disc from being opened by mistake and causing vibration due to back pressure backflow, has good sealing performance and long service life.

[0004] The technical scheme of the utility model is: a back pressure backflow prevention pilot safety valve, including a main valve and a pilot valve, the pilot valve inlet is connected with the main valve inlet through a pressure guide pipe, the main valve includes a valve body, a valve seat, a valve disc, a valve cover, and a guide sleeve, the upper end of the guide sleeve is fixedly sealed and pressed between the upper end face of the valve body and the lower end face of the valve cover, the outer cylindrical surface of the valve disc is dynamically sealed and installed in the inner hole of the guide sleeve, the lower end face of the valve disc is provided with a sealing surface that cooperates with the valve seat, a spring is installed in the piston cavity formed between the back of the valve disc and the valve cover, and the pilot valve control port is connected with the piston cavity through a pressure relief pipe; its characteristics are: : A backflow prevention device is arranged between the pressure relief pipe and the piston cavity, and the backflow prevention device consists of a three-way valve body and a piston. The first port of the three-way valve body is coaxial with the second port, and the center line of the third port is perpendicular to the center line of the first port. The first port is connected with the pilot valve control port, the second port is connected with the main valve discharge port, and the third port is connected with the piston cavity. The piston adopts a cylindrical structure and is movably installed in the circular hole valve cavity between the first port and the second port. Sealing surfaces that cooperate with the sealing seats in the first port and the second port are respectively provided at both ends of the piston.

[0005] Preferably, the sealing seats in the first port and the second port adopt inner conical sealing surfaces, and the sealing surfaces at both ends of the piston are composed of sealing rings embedded in small-diameter outer cylindrical surfaces.

[0006] Preferably, the sealing seats in the first port and the second port adopt inner conical sealing surfaces, and the sealing surfaces at both ends of the piston adopt outer conical sealing surfaces with the same taper as the inner conical sealing surface of the sealing seat.

[0007] The beneficial effects of the utility model compared with the prior art are as follows: a backflow prevention device consisting of a three-way valve body and a piston is arranged between the pressure relief pipe and the piston chamber. When the back pressure at the discharge port of the main valve is greater than the inlet working pressure, the back pressure pushes the piston to move left, and the medium pressure at the discharge port enters the piston chamber to prevent the valve disc from opening, thereby preventing the back pressure from flowing back and causing the valve disc to open by mistake and produce vibration. The utility model has the advantages of reliable sealing performance and long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a structural schematic diagram of the utility model.

[0009] Figure 2 This utility model Figure 1 Schematic diagram of the structure of the backflow prevention device when the medium back pressure is less than the working pressure.

[0010] Figure 3 This utility model Figure 1 Schematic diagram of the structure of the backflow prevention device when the back pressure is greater than the working pressure.

[0011] In the figure: 1 valve body, 2 valve seat, 3 discharge port, 4 valve disc, 5 guide sleeve, 6 spring, 7 valve cover, 8 backflow prevention device, 9 pilot valve, 10 pressure guide pipe, 11 three-way valve body, 12 piston, 13 sealing ring, 14 first port, 15 second port, 16 third port. DETAILED DESCRIPTION

[0012] like Figure 1The anti-back pressure backflow pilot safety valve shown in the figure comprises a main valve and a pilot valve 9. The inlet of the pilot valve 9 is connected with the inlet of the main valve through a pressure-leading pipe 10. The main valve comprises a valve body 1, a valve seat 2, a valve disc 4, a valve cover 7, and a guide sleeve 5. The upper end of the guide sleeve 5 is fixedly sealed and pressed between the upper end face of the valve body 1 and the lower end face of the valve cover 7. The outer cylindrical surface of the valve disc 4 is dynamically sealed and installed in the inner hole of the guide sleeve 5. The lower end face of the valve disc 4 is provided with a sealing surface that cooperates with the valve seat 2. A spring 6 is installed in the piston cavity formed between the back side of the valve disc 4 and the valve cover 7. The control port of the pilot valve 9 is connected with the piston cavity through a pressure relief pipe. When the inlet pressure of the main valve exceeds the set pressure of the pilot valve 9, the pilot valve 9 opens, the piston cavity pressure is discharged through the pilot valve 9, and the inlet pressure of the main valve pushes the valve disc 4 to open and discharge the pressure. When the inlet pressure of the main valve is discharged to be lower than the set pressure of the pilot valve 9, the pilot valve 9 is closed, and the inlet pressure of the main valve The force enters the piston cavity through the pressure-leading pipe 10 and the control port of the pilot valve 9 and pushes the valve disc 4 to close together with the spring 6; its characteristic is that: an anti-backflow device 8 is arranged between the pressure relief pipe and the piston cavity, and the anti-backflow device 8 is composed of a three-way valve body 11 and a piston 12. The first port 14 of the three-way valve body 11 is coaxial with the second port 15, that is, the center lines of the two coincide, and the center line of the third port 16 is perpendicular to the center line of the first port 14. The first port 14 is connected with the control port of the pilot valve 9, the second port 15 is connected with the discharge port 3 of the main valve, and the third port 16 is connected with the piston cavity. The piston 12 adopts a cylindrical structure and is movably installed in the circular hole valve cavity between the first port 14 and the second port 15, and can move in the circular hole valve cavity. Sealing surfaces that cooperate with the sealing seats in the first port 14 and the second port 15 are respectively provided at both ends of the piston 12. The discharge port 3 is connected to the pressure pipeline, and the medium pressure of the discharge port 3 becomes the back pressure of the valve disc 4. When the back pressure is less than the inlet working pressure of the valve body 1, the piston 12 moves rightward and seals with the sealing seat in the second port 15. Figure 2 As shown, the medium pressure at the inlet of the valve body 1 enters the piston chamber through the pressure-inducing pipe 10, the control port of the pilot valve 9, the first port 14, and the third port 16, and pushes the valve disc 4 and the valve seat 2 together with the spring 6 to seal; when the back pressure is greater than the inlet working pressure of the valve body 1, the piston 12 moves left and seals with the sealing seat in the first port 14, as shown in FIG. Figure 2 As shown, the medium pressure in the discharge port 3 enters the piston chamber through the second port 15 and the third port 16, and together with the spring 6 pushes the valve disc 4 to seal with the valve seat 2, preventing the back pressure from pushing the valve disc 4 to open by mistake, avoiding the backflow of the medium at the discharge port 3 and the vibration of the valve disc 4 and the collision with the valve seat 2 to cause damage to the sealing surface, thereby affecting the sealing performance and the service life of the product.

[0013] The sealing seats in the first port 14 and the second port 15 adopt inner conical sealing surfaces, and the sealing surfaces at both ends of the piston 12 are composed of sealing rings 13 embedded in the small diameter outer surface. The sealing rings 13 and the inner conical sealing surfaces are pressed and sealed to improve the sealing wedge tightening force, so that the piston 12 can be reliably separated from the sealing seat. The piston 12 is made of plastic material, such as Figure 2 , Figure 3 The small diameter outer cylindrical surface is an annular step with a diameter smaller than the diameter of the piston 12 cylinder provided at both ends of the piston 12 cylinder.

[0014] The sealing seats in the first port 14 and the second port 15 adopt inner conical sealing surfaces, and the sealing surfaces at both ends of the piston 12 adopt outer conical sealing surfaces with the same taper as the inner conical sealing surface of the sealing seat. The piston 12 is made of metal material and is suitable for high temperature working conditions.

Claims

1. A back pressure backflow prevention pilot safety valve, comprising a main valve and a pilot valve (9), wherein the inlet of the pilot valve (9) is communicated with the inlet of the main valve through a pressure guide pipe (10), the main valve comprises a valve body (1), a valve seat (2), a valve disc (4), a valve cover (7), and a guide sleeve (5), wherein the upper end of the guide sleeve (5) is fixedly sealed and press-fitted between the upper end surface of the valve body (1) and the lower end surface of the valve cover (7), the outer cylindrical surface of the valve disc (4) is dynamically sealed and installed in the inner hole of the guide sleeve (5), the lower end surface of the valve disc (4) is provided with a sealing surface that cooperates with the valve seat (2), a spring (6) is installed in a piston cavity formed between the back surface of the valve disc (4) and the valve cover (7), and the control port of the pilot valve (9) is communicated with the piston cavity through a pressure relief pipe; wherein: A backflow prevention device (8) is provided between the pressure relief pipe and the piston cavity. The backflow prevention device (8) is composed of a three-way valve body (11) and a piston (12). The first port (14) and the second port (15) of the three-way valve body (11) are coaxial, and the center line of the third port (16) is perpendicular to the center line of the first port (14). The first port (14) is connected to the control port of the pilot valve (9), the second port (15) is connected to the discharge port (3) of the main valve, and the third port (16) is connected to the piston cavity. The piston (12) adopts a cylindrical structure and is movably installed in the circular hole valve cavity between the first port (14) and the second port (15). Sealing surfaces that cooperate with sealing seats in the first port (14) and the second port (15) are respectively provided at both ends of the piston (12).

2. The anti-back pressure backflow pilot safety valve according to claim 1 is characterized in that: The sealing seats in the first port (14) and the second port (15) adopt inner conical sealing surfaces, and the sealing surfaces at both ends of the piston (12) are composed of sealing rings (13) embedded in small-diameter outer cylindrical surfaces.

3. The anti-back pressure backflow pilot safety valve according to claim 1 is characterized in that: The sealing seats in the first port (14) and the second port (15) adopt inner conical sealing surfaces, and the sealing surfaces at both ends of the piston (12) adopt outer conical sealing surfaces with the same taper as the inner conical sealing surfaces of the sealing seats.

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