Common Points And Differences Of Different Solenoid Valves
Common points and differences of pressure reducing valve, safety valve, pressure relief valve, and voltage-stabilizing valve.
Pressure reducing valve, safety valve, voltage-stabilizing valve, and pressure relief valve are all pressure valves, which are mainly functional differences.
A pressure reducing valve is a device that reduces a high-pressure medium to a low-pressure medium. The characteristic of this valve is to keep the outlet pressure and temperature within a certain range when the inlet pressure is constantly changing.
Safety valve is used to prevent boilers, pressure vessels and other equipment or pipelines from being damaged due to overpressure. When the pressure is slightly higher than the normal working pressure, the safety valve automatically opens to reduce the pressure. When the pressure is slightly lower than the normal working pressure, the safety valve is automatically closed, stopping the discharge of fluid and maintaining the seal.
The pressure relief valve is mainly used in the occasion of excessive pressure. When the pressure is greater than the set value, the inner piece of the valve is opened to release the pressure in time. After the pressure is reduced, it returns to the original position. It is not much different from the safety valve. Mostly used for liquids, and safety valves mostly used for gas and steam.
A voltage-stabilizing valve is a device that keeps the medium in an area within a certain pressure range.
The difference between voltage-stabilizing valve and pressure reducing valve
Pressure reducing valve: Regardless of how the inlet pressure changes, the outlet pressure is reduced to the rated value to reduce pressure. (One is to stabilize the pressure in the proper state)
Voltage-stabilizing valve: No matter how downstream pressure and demand change, maintain a constant upstream pressure. (One is to reduce the pressure from a high place to the proper state)
Safety valve and pressure reducing valve are two types of valves, which are dedicated valves. Among them, the safety valve is a safety relief device, a special valve that only acts when the working pressure exceeds the allowable range to protect the system. The pressure reducing valve belongs to the process valve, which can reduce the pressure of the high-pressure stream to meet the pressure requirements of the subsequent system, and its working process is continuous.
Working principle of pressure reducing valve
1. Direct acting membrane pressure reducing valve
When the pressure on the outlet side increases, the membrane moves upward, the valve opening decreases, the flow rate increases, and the pressure drop should be increased. The pressure behind the valve decreases and the outlet side pressure decreases. When the membrane moves downwards, the valve opening increases, the flow rate decreases, the pressure drop decreases, and the pressure behind the valve increases. The outlet pressure behind the valve always maintains the constant pressure set by the setting adjustment screw.
2. Direct acting bellows type pressure reducing valve
When the pressure on the outlet side increases, the bellows moves upward, the valve opening decreases, the flow rate increases, and the pressure drop should be increased. The pressure behind the valve decreases and the outlet side pressure decreases. When the bellows moves downwards, the valve opening increases, the flow rate decreases, the pressure drop decreases, and the pressure behind the valve increases. The outlet pressure behind the valve always maintains the constant pressure set by the setting adjustment screw.
3. Pilot piston type pressure reducing valve
Twist the adjusting screw to open the valve disc of the pilot valve. The medium enters above the piston from the inlet side. Since the area of the piston is larger than the area of the main valve disc, the piston is pushed down to open the main valve. The opening of the valve changes the pressure above the piston and controls the opening of the main valve flap to keep the pressure behind the valve constant.
4. Pilot diaphragm pressure reducing valve
The working principle is the same as above. The pressure of the upper cavity of the membrane is controlled by the bypass regulating valve.
5. Pilot diaphragm pressure reducing valve
When the adjusting spring is in a free state, both the main valve and the pilot valve are closed. When turning the handwheel clockwise, the pilot valve diaphragm pushes the pilot valve downwards, and the medium flows through the pilot valve to the top of the main diaphragm, thereby pushing the main valve to open the main valve, and the medium flows to the outlet and enters below the pilot valve diaphragm at the same time , The outlet pressure rises to balance with the adjusted spring force. If the outlet pressure increases, the pilot valve diaphragm will move upwards and the pilot valve opening will decrease. At the same time, the flow of the medium entering below the main diaphragm decreases, the pressure drops, and the outlet pressure decreases to reach a new balance, and vice versa.
6. Combined pressure reducing valve
The pressure reducing valve is composed of a main valve, a pilot valve and a stop valve. When the adjusting spring is in a free state, the main valve and pilot valve are closed. Twisting the adjusting screw, the medium pushes the pilot valve open, and at the same time enters the main valve rubber diaphragm chamber and the pressure of the adjustment spring is balanced, enters the main valve rubber diaphragm chamber, makes the rubber diaphragm upward, the main valve opens, and the medium flows to the outlet ( At this time, the shut-off valve is opened to maintain a certain pressure in the chamber), and the outlet medium is fed back to the chamber above the rubber membrane and the chamber below the pilot valve. When the outlet pressure increases, the diaphragm of the pilot valve moves up, the opening of the pilot valve decreases, so that the medium pressure in the chamber decreases. At the same time, the pressure of the chamber decreases, the rubber film of the main valve moves down, and the opening of the main valve decreases. The pressure drops and a new balance is reached; vice versa.
7. Lever type pressure reducing valve
At this time, the pressure reducing valve is balanced by the weight on the lever. The principle of action: When the lever is in a free state, the disc and the valve seat of the double valve seat are in the closed state. Under the action of the inlet pressure, the valve flap is pushed upwards, and pressure is formed at the outlet end. Through the balance weight on the lever, the adjustment is important to the required outlet pressure. When the outlet pressure exceeds a given pressure, the force acting on the upper valve seat due to the medium pressure is greater than the force acting on the lower valve seat, resulting in a certain pressure difference, which causes the valve disc to move downwards and reduces the throttle area. The pressure also drops and a new balance is reached; vice versa.
8. Pilot bellows pressure reducing valve
The structure principle is the same as the pilot piston type pressure reducing valve.