CN201810837U - Piston sealing type safety valve - Google Patents

Abstract

The utility model relates to a piston sealing type safety valve which comprises a valve body, a valve cover and a pressure adjusting device, wherein the pressure adjusting device is arranged in the valve cover; the valve body is arranged under the pressure adjusting device; one side of the middle part or the middle upper part of the valve body is designed with a pressure release hole and is fastened and connected with the valve cover by a connecting bolt nut; and the piston sealing type safety valve is characterized in that the valve body is internally provided with a sealing piston, the top of which is connected with the pressure adjusting device. The utility model improves the structure of the safety valve which is commonly used at present, namely, leads a valve body and a sealing cylinder of the existing safety valve to be manufactured into a whole, thus not only simplifying the structure, but also realizing the dynamic seal matching of the sealing piston and a sealing seat. The pressure bearing area of a piston of the piston sealing type safety valve is unchangeable all the time and is not influenced by back pressure, and the blowdown of the safety valve is zero, so that the actions such as opening, discharging and returning of the safety valve are very stable, and the phenomena of chatter and flutter are not generated.

Description

A piston-sealed safety valve

technical field

The invention relates to an overpressure safety protection device for pressure-bearing special equipment, in particular to a piston-sealed safety valve applied to pressure-bearing special equipment. the

Background technique

The safety valve is automatically opened and closed according to the working pressure of the pressure system. It is generally installed on the equipment or pipelines of the closed system to protect the safety of the system. It is the main safety accessory on the pressure-bearing special equipment such as boilers, pressure vessels, and pressure pipelines. one. When the pressure in the protected equipment exceeds the design pressure, the safety valve will automatically open to discharge the medium with excessive pressure in the equipment, reducing the pressure in the equipment, thereby preventing the equipment from being damaged by overpressure and effectively preventing accidents; When the pressure in the equipment drops to the set pressure, the safety valve will automatically close to protect the normal operation of the pressure-bearing equipment. the

At present, the types of safety valves widely used mainly include spring safety valves, lever (weight hammer) safety valves and pulse safety valves. The sealing methods of these three safety valves mostly adopt the disc (spool) sealing type, which are classified as disc sealing safety valves. The main disadvantages of the disc (spool) sealed safety valve are: 1. Since the diameter of the disc (spool) is larger than the diameter of the flow channel (throat diameter), and is affected by the back pressure, the disc is under pressure before and after opening 2. The opening and closing pressure difference (difference between opening pressure and reseating pressure) is relatively large, generally 4% to 10% of the opening pressure , if the opening and closing pressure difference is too small, the valve disc will produce frequency jump and chatter, thereby shortening the service life of the safety valve, if the opening and closing pressure difference is too large, the reseating pressure will be too low, resulting in unnecessary waste And pollution even affects normal production. the

In terms of safety valves used in pressure-bearing special equipment, we retrieved public documents: Chinese patent application number: 02158116.9, application date: 2002.12.25, name: adjustable pressure safety valve device with pointer, publication (announcement) number: CN1510322A , Applicant (patent) person: Tianjin Bohai Chemical Co., Ltd. Tianjin Chemical Plant, the literature discloses a pointer adjustable pressure safety valve device composed of housing 13, screw mandrel rotary compression spring device, pressure spring and piston sealing device. However, since the device follows the principle of the traditional disc-sealed safety valve, the diameter of the piston is larger than the diameter of the flow channel, and there are also unsteady opening, discharge, and seat return actions of the safety valve, as well as large opening and closing pressure differences or Technical defects such as safety valve frequency jump and chatter. the

Contents of the invention

The object of the present invention is to propose a piston-sealed safety valve with zero opening and closing pressure difference and no frequency jump and chattering phenomenon, aiming at the inability of the existing background technology to solve the above technical problems. the

The present invention is achieved like this:

The piston-sealed safety valve includes a valve body, a valve cover and a pressure regulating device, the pressure regulating device is arranged in the valve cover, the valve body is installed below the pressure regulating device, and the middle or upper side of the valve body is designed with a drain The pressure hole is tightly connected to the valve cover through connecting bolts and nuts. It is characterized in that: a sealing piston is arranged inside the valve body, and the top of the sealing piston is connected with the pressure regulating device. the

The above-mentioned piston-sealed safety valve has a pressure relief hole designed on one side of the middle or upper middle of the valve body, and the cross-sectional area of the pressure relief hole is not smaller than the cross-sectional area of the inner cavity of the valve body. the

In the above-mentioned piston-sealed safety valve, a groove is designed in the inner cavity of the valve above the top edge of the pressure relief hole, and an O-ring is installed on the groove to seal the pressure-relieving medium in the cavity of the valve body. inside, forcing it out of the relief passage. the

The above-mentioned piston-sealed safety valve, the sealing piston is designed to be solid or hollow, and there is a groove on the outside 2-5mm away from the bottom of the piston, and an O-ring is installed on the groove to seal the medium in the inside the device. the

When the safety valve is in a low-load or zero-load state, the bottom of the sealing piston is below the bottom edge of the pressure relief hole. Both the spring and the spring must withstand a pressure equal to the set pressure; when the safety valve is ready to take off (that is, the set pressure), the bottom of the sealing piston is at the bottom edge of the pressure relief hole; when the safety valve is at the opening pressure, the sealing piston The bottom is above the top edge of the relief hole. the

The above-mentioned piston-sealed safety valve has a pressure regulating device including a spring, an upper spring seat, a pressure regulating screw, and a lock nut. Connected with the pressure regulating screw, the pressure regulating screw is fixed on the valve cover through the thread and the lock nut, and the opening pressure of the safety method can be adjusted. the

Advantages of the present invention:

1. The piston-sealed safety valve of the present invention, because the pressure-bearing area of the piston is always constant, and is not affected by back pressure, so that the opening, discharge, and reseating processes of the safety valve are very stable, and the safety valve The action of opening the discharge is to gradually increase with the increase of the medium pressure until it reaches the maximum discharge, and then gradually decrease with the decrease of the medium pressure until it returns to the seat. the

2. The piston-sealed safety valve of the present invention, because the piston and the sealing seat are in a dynamic sealing fit, the piston-sealed safety valve not only has zero pressure difference between opening and closing, but also does not produce frequency jump and flutter. the

Description of drawings

Fig. 1 is a front sectional view of a piston-sealed safety valve of the present invention. the

Fig. 2 is a solid design drawing of the piston of the piston-sealed safety valve of the present invention. the

Fig. 3 is a hollow design drawing of the piston of the piston-sealed safety valve of the present invention. the

Fig. 4 is a graph of the pressure and opening height of the disc sealing safety valve. the

Fig. 5 is a graph of pressure and opening height of a piston-sealed safety valve. the

In the figure, 1 is the valve body, 2 is the O-ring, 3 is the piston, 4 is the O-ring, 5 is the connecting bolt and nut, 6 is the valve cover, 7 is the spring, 8 is the upper spring seat, and 9 is the adjustment Pressure screw, 10 is the lock nut, 11 is the valve cap; Ps is the set pressure, Pb is the opening pressure, Pr is the reseating pressure, h is the opening height of the valve disc. the

Detailed ways

Example 1

As shown in Figure 1, a piston-sealed safety valve has a pressure regulating device inside the bonnet (6), and the bonnet (6) is fastened to the valve body (1) through connecting bolts and nuts (5), and the valve body (1) A pressure relief hole (12) is designed on one side of the middle or upper middle part, and a sealing piston (3) is arranged inside the valve body (1), and the top of the sealing piston (3) is connected with the pressure regulating device; the lower spring seat is connected with the sealing The piston (3) is connected as a whole and connected with the upper spring seat (8) through the spring (7), and the upper spring seat (8) is connected with the pressure regulating screw (9), and the pressure regulating screw (9) is threaded and locked nut (10) is fixed on the valve cover (6); one side of the middle part of the valve body (1) is designed with a pressure relief hole (12), and the cross-sectional area of the pressure relief hole is not less than the internal cavity cross-sectional area of the valve body (1); There is a groove in the inner cavity of the body (1) about 3-10mm away from the upper outlet, and an O-ring (4) is installed on the groove; the sealing piston (3) is designed to be solid or hollow, and is 2 A groove is arranged on the outer side at ~5mm, and an O-shaped sealing ring (2) is installed on the groove. the

Comparison of the curves of pressure and opening height of disc seal safety valve and piston seal safety valve

According to the definition of safety valve setting (opening) pressure, opening (discharging) pressure and reseating pressure, and according to the experimental situation, draw the curves of pressure and opening height of disc-sealed safety valve and piston-sealed safety valve respectively, horizontal The coordinates are the opening height of the valve disc or piston, and the ordinate is the medium pressure in the equipment, where Ps is the set pressure, Pb is the opening pressure, Pr is the reseating pressure, and h is the opening height of the valve disc. the

For disc sealing type safety valve, it can be known from Figure 4 that point 1 (0, Ps) is the position of the disc at the set pressure, point 2 (h, Pb) is the position of the disc at the cracking pressure, and point 3 ( 0, Pr) is the position of the disc back to the seat pressure, due to the defects of the design, resulting in Ps (setting pressure) greater than Pr (back to the seat pressure), which makes the opening, discharge, back to the action of this type of safety valve The cause of instability and generation of frequency jump and flutter phenomenon is the defective place of the prior art. the

For the piston-sealed safety valve, it can be seen from Figure 5 that since the diameter of the sealing piston is equal to the diameter of the flow channel, the opening and closing pressure difference is zero, so there is Ps (set pressure) = Pr (reseating pressure), that is, point 1 and point 3 are in the same position in the figure, thereby overcoming the defects of the prior art, so that the opening, discharge and reseating of the safety valve are all very stable, and no frequency jump and flutter phenomenon will occur. the

Claims (5)

1. piston sealed safety valve, comprise valve body (1), valve gap (6) and pressure regulator, pressure regulator is located in the valve gap (6), valve body (1) is installed in the below of pressure regulator, the one side design of valve body (1) middle part or middle and upper part has relief hole (12), and be fastenedly connected by connecting bolt nut (5) and valve gap (6), it is characterized in that: valve body (1) inside is provided with packed-piston (3), and packed-piston (3) top is connected with pressure regulator.

2. piston sealed safety valve according to claim 1 is characterized in that: the section area of relief hole (12) is not less than the intracavity section area of valve body (1).

3. piston sealed safety valve according to claim 1 is characterized in that: along the design of above valve body (1) inner chamber a groove is arranged in relief hole (12) top sides, O-ring seals (4) is installed on the groove.

4. piston sealed safety valve according to claim 1 is characterized in that: packed-piston (3) is designed to solid or hollow, and is provided with a groove in the outside at distance piston base 2～5mm place, and O-ring seals (2) is installed on the groove.

5. piston sealed safety valve according to claim 1, it is characterized in that: pressure regulator comprises spring (7), upper spring seat (8), screw press (9), locking nut (10), lower spring cup is connected as a single entity with packed-piston (3) and is connected with upper spring seat (8) by spring (7), upper spring seat (8) is connected with screw press (9), and screw press (9) is fixed on the valve gap (6) by screw thread and locking nut (10).

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