Pressure reducing valves, safety valves, pressure stabilizing valves, and pressure relief valves are all pressure valves, and the main difference is in function.
Pressure reducing valves are devices that reduce high-pressure media to low-pressure media. The characteristic of this valve is that it keeps the outlet pressure and temperature values within a certain range when the inlet pressure is constantly changing.
Safety valves are valves 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 automatically closes, stops discharging fluids, and keeps the seal.
Pressure relief valves are mainly used in situations where the pressure is too high. When the pressure is greater than the set value, the inner plate of the valve is pushed open to release the pressure in time, and returns to its original position after the pressure is reduced. It is not much different from the safety valve. Pressure relief valves are mostly used for liquids, and safety valves are mostly used for gas and steam.

Pressure stabilizing valves are devices that keep the medium in an area within a certain pressure range. Difference from pressure reducing valves:

Pressure reducing valves: Regardless of how the inlet pressure changes, the outlet pressure is reduced to the rated value to reduce the pressure.

Pressure stabilizing valve: maintains a constant upstream pressure regardless of changes in downstream pressure and demand.

Safety valve and pressure reducing valve are two types of valves, which are special valves. Among them, the safety valve is a safety relief device, which is a special valve that only operates when the working pressure exceeds the allowable range to protect the system. The pressure reducing valve is a process valve that can reduce the pressure of high-pressure logistics to meet the pressure requirements of the subsequent system. Its working process is continuous.

Working principle of pressure reducing valve
1. Direct acting diaphragm pressure reducing valve: When the pressure on the outlet side increases, the diaphragm moves upward, the valve opening decreases, the flow rate increases, the pressure drop should be increased, the pressure after the valve decreases, and the pressure on the outlet side decreases. The diaphragm moves downward, the valve opening increases, the flow rate decreases, the pressure drop decreases, and the pressure after the valve increases. The outlet pressure after the valve always maintains a constant pressure set by the setting adjustment screw.
2. Direct acting bellows pressure reducing valve: When the pressure on the outlet side increases, the bellows moves upward, the valve opening decreases, the flow rate increases, the pressure drop should be increased, the pressure after the valve decreases, and the pressure on the outlet side decreases. The bellows moves downward, the valve opening increases, the flow rate decreases, the pressure drop decreases, and the pressure after the valve increases. The outlet pressure after the valve always maintains a constant pressure set by the setting adjustment screw.
3. Pilot piston pressure reducing valve: Turn the adjusting screw to push open the pilot valve disc, and the medium enters the piston from the inlet side. Since the piston area is larger than the main valve disc area, the piston is pushed downward to open the main valve. The pressure of the pressure balance spring after the valve changes the opening of the pilot valve, thereby changing the pressure above the piston, controlling the opening of the main valve disc, and keeping the pressure after the valve constant.
4. Pilot diaphragm pressure reducing valve: The working principle is the same as above. The pressure in the upper chamber of the diaphragm is controlled by the bypass regulating valve.
5. Pilot diaphragm pressure reducing valve: When the regulating spring is in a free state, the main valve and the pilot valve are both closed. When the handwheel is turned clockwise, the pilot valve diaphragm pushes the pilot valve downward, 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 the bottom of the pilot valve diaphragm at the same time. The outlet pressure rises to keep balance with the adjusted spring force. If the outlet pressure increases, the pilot valve diaphragm moves upward and the pilot valve opening decreases. At the same time, the flow rate of the medium entering the lower part of 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 Pressure reducing valve: It consists of a main valve, a pilot valve, and a stop valve. When the adjusting spring is in a free state, the main valve and the pilot valve are in a closed state. Turn the adjusting screw, the medium pushes the pilot valve open, and at the same time enters the rubber film chamber of the main valve to maintain a balance with the pressure of the adjusting spring, enters the rubber film chamber of the main valve, makes the rubber diaphragm upward, the main valve opens, and the medium flows to the outlet (at this time, the stop valve is opened to maintain a certain pressure in the chamber), and the outlet medium is then fed back to the chamber above the rubber film 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, the medium pressure in the chamber decreases, and at the same time the chamber pressure decreases, the rubber film of the main valve moves down, the opening of the main valve decreases, and the outlet pressure decreases to reach a new balance; vice versa.
7. Lever pressure reducing valve: At this time, the pressure reducing valve is balanced by the weight on the lever. Its operating principle: when the lever is in a free state, the valve disc and valve seat of the double valve seat are in a closed state. Under the action of the inlet pressure, the valve disc is pushed upward, and pressure is formed at the outlet end. Through the balance weight on the lever, the important adjustment is transmitted to the required outlet pressure. When the outlet pressure exceeds the given pressure, the force of the medium pressure on the upper valve seat is greater than the force on the lower valve seat, forming a certain pressure difference, causing the valve disc to move downward, reducing the throttling area, and the outlet pressure also decreases to reach a new balance; vice versa.
8. Pilot bellows pressure reducing valve: The structural principle is the same as the pilot piston pressure reducing valve.