Found in 2008, We are professional industrial valves manufacturers on wellhead control.

24 hours at your service: admin@sgvalves.com

Working principle of safety valve

by:Sino Valves     2021-11-15

Safety valve opening and closing parts are normally closed under the action of external force. When the medium pressure in the equipment or pipeline rises above the specified value, the medium pressure in the pipeline or equipment is prevented by discharging the medium to the outside of the system Special valves that exceed the specified value. Safety valves belong to the category of automatic valves, which are mainly used to protect boilers, pressure vessels and pipelines.

The working principle of the safety valve (picture)

The working principle of the spring-loaded safety valve is pressure u003d pressure x area. The pressure is the pressure of the spring, and the area is the area of u200bu200bthe sealing surface. When the pressure acting on the sealing surface is multiplied by the area of u200bu200bthe sealing surface, the upward thrust formed is greater than the pressure of the spring, the spring is compressed, the sealing surface opens, and the pressure is discharged through the pressure relief hole.

1. When the pressure in the equipment exceeds the specified working pressure and reaches the opening pressure of the safety valve, the force of the internal medium acting on the alarm flap is greater than the force exerted on it by the loading mechanism, so the valve flap Leaving the valve seat, the safety valve opens, and the medium in the equipment is discharged through the valve seat. At this time, the force exerted by the internal pressure on the valve flap is less than the force exerted on it by the loading mechanism, the valve flap is tightly pressed against the valve seat, the medium stops discharging, and the equipment continues to operate under normal working pressure. Therefore, the safety valve closes or opens by itself through the growth and decline of the medium force on the disc and the force of the loading mechanism to achieve the purpose of preventing equipment overpressure.

2. When the set pressure of the safety valve is greater than the working pressure of the protected system, the valve is in the closed state. At this time, the force acting on the valve clack has the spring preload F, the direction is downward, and the medium The force is upward, and then the supporting force of the valve seat on the disc (sealing force). The specific pressure generated by this sealing force on the sealing surface ensures the necessary sealing between the closing parts of the safety valve.

3. When the pressure in the system rises and exceeds the normal working pressure, because the spring preload and sealing force have not changed at this time, the system pressure rises, causing the sealing surface of the closure The sealing force decreases: With the further increase of the medium pressure, when the inlet pressure is equal to the set pressure of the safety valve, the force between the disc and the valve seat is equal to zero (the sealing force is equal to zero); when the inlet pressure continues to rise When the pressure is slightly higher than the set pressure, the valve flap moves upward and opens suddenly. At this time, the safety valve is in an open state.

4. Once the valve is opened, with the rapid flow of the medium, the annular flow channel enclosed by the inner edge of the recoil disc skirt and the outer diameter of the adjusting ring will throttle the medium, and use With the static pressure of the fluid on the recoil disc, the safety valve disc continues to move up quickly. At this time, the flow is always limited by the opening between the disc and the valve seat until the height of the disc leaving the valve seat reaches a quarter of the flow. After that, the flow rate is controlled by the diameter of the flow channel of the throat, and then the full amount is discharged, so that the pressure of the medium drops rapidly. At this time, the safety valve is in the discharge state.

Structural principle of safety valve

There are two main types of safety valve structures: spring type and lever type. The spring type means that the seal between the valve clack and the valve seat relies on the force of the spring. The lever type relies on the force of the lever and the heavy hammer. With the need for large capacity, there is another impulse safety valve, also called pilot safety valve, which consists of a main safety valve and an auxiliary valve. When the medium pressure in the pipeline exceeds the specified pressure value, the auxiliary valve opens first, the medium enters the main safety valve along the conduit, and the main safety valve is opened to reduce the increased medium pressure.

1. Heavy-hammer lever-type safety valve

The heavy-hammer lever-type safety valve uses a heavy hammer and a lever to balance the force acting on the disc. According to the principle of leverage, it can use a heavy hammer with a smaller mass to obtain a greater force through the increase of the lever, and adjust the opening pressure of the safety valve by moving the position of the heavy hammer (or changing the mass of the heavy hammer).

The heavy hammer lever safety valve has a simple structure, easy to adjust and more accurate, and the added load will not increase greatly due to the rise of the valve disc. It is suitable for high temperature occasions. It used to be more common in the past, especially in boilers and pressure vessels with higher temperatures. However, the heavy-hammer lever-type safety valve has a relatively heavy structure, and the loading mechanism is prone to vibration, and often leaks due to vibration; its return pressure is low, and it is not easy to close and maintain tightness after opening.

2. Spring micro-open safety valve

The spring micro-open safety valve uses the force of a compressed spring to balance the force acting on the disc. The compression amount of the coil spring can be adjusted by turning the adjusting nut on it. With this structure, the opening (setting) pressure of the safety valve can be corrected as required. The spring micro-lift safety valve has a light and compact structure, high sensitivity, unlimited installation location, and low sensitivity to vibration, so it can be used on mobile pressure vessels. The disadvantage of this safety valve is that the applied load will change with the opening of the valve, that is, as the valve flap rises, the compression of the spring increases, and the force acting on the valve flap also increases. This is detrimental to the rapid opening of the safety valve. In addition, the spring on the valve will reduce its elasticity due to the long-term impact of high temperature. When used on a container with a higher temperature, it is often necessary to consider the heat insulation or heat dissipation of the spring, which makes the structure more complicated.

3. Spring full lift safety valve


Contact Us are all following the most compatible manufacturing regulations.
Sino Global Pipeline Construction Equipment Limited also values the time, skills, and expert opinions of our staff. We are committed to providing fair and living wages, reasonable, structured work schedules, and clear duties and spheres of rights and responsibilities for each team member.
Sino Global Pipeline Construction Equipment Limited are trained to think about problems and coming up with solutions, as well as presenting the whole idea in a logical and coherent manner.

Custom message
Chat Online
Chat Online
Chat Online inputting...