First, the function is different 1. The pressure reduci […]
First, the function is different
1. The pressure reducing valve is a kind of valve that reduces the medium with high pressure in the system to a medium with low pressure and maintains the pressure stability. The characteristic of the pressure reducing valve is to maintain the outlet pressure or temperature value under the condition that the inlet pressure is constantly changing. Within a certain range.
2. The pressure relief valve is also a kind of safety valve. It is mainly used in the case of excessive pressure. When the pressure is greater than the set value, the valve inner piece is opened and released in time, and the pressure is reduced to return to the original position. Safety valves are not much different. Pressure relief valves are mostly used for liquids. Safety valves are mostly used for gas and steam.
Second, the principle is different
1. The pressure relief valve is composed of a needle valve I, a pressure gauge 2, a main valve 3, a pilot valve 4, and a connecting pipe.
It is a type of hydraulic control valve. The main valve is divided into upper and lower parts by the diaphragm. The lower chamber of the diaphragm is a water flow passage, and the upper chamber is a control chamber, which controls the opening and closing of the main valve flap. The pilot valve itself is a pressure relief valve. It also has a control chamber and a water flow passage. The flap opening and closing is controlled by the control chamber. The needle valve is a throttle valve that controls the flow of water in the connecting tube.
2. The pressure reducing valve adopts the opening degree of the opening and closing member in the control valve body to adjust the flow rate of the medium, reduce the pressure of the medium, and adjust the opening degree of the opening and closing member by the action of the pressure behind the valve, so that the pressure behind the valve is maintained at Within a certain range, cooling water is sprayed into the valve body or behind the valve to lower the temperature of the medium. This type of valve is called a decompression and desuperheating valve.
Pressure relief valve quick and easy automatic selection is included. The valve is characterized by keeping the outlet pressure and temperature within a certain range in the case of constant changes in inlet pressure.
Third, the classification is different
1. There are two main types of pressure relief valve structures: spring type and lever type.
The spring type refers to the force of the seal of the valve disc and the valve seat against the spring.
The lever type is the force of the lever and the weight.
With the need of large capacity, there is a pulse type pressure relief valve, also known as a pilot pressure relief valve, consisting of a main relief valve and an auxiliary valve. When the medium pressure in the pipeline exceeds the specified pressure value, the auxiliary valve is opened first, the medium enters the main relief valve along the conduit, and the main relief valve is opened to reduce the increased medium pressure.
2. The pressure reducing valve can be divided into membrane type, spring membrane type, piston type, lever type and bellows type according to the structure; the number of valve seats can be artificial single seat type and double seat type; according to the position of the valve flap, it can be divided It is a positive acting and a reactionary.
Pilot-operated pressure reducing valve When the output pressure of the pressure reducing valve is high or the diameter is large, the pressure is directly adjusted by the pressure-regulating spring, the spring stiffness is inevitably too large, and the output pressure fluctuates greatly when the flow rate changes, and the structural size of the valve It will also increase. In order to overcome these disadvantages, a pilot type pressure reducing valve can be employed. The working principle of the pilot type pressure reducing valve is basically the same as that of the direct acting type.
The pressure regulating gas used in the pilot type pressure reducing valve is supplied by a small direct acting pressure reducing valve. If the small direct acting pressure reducing valve is installed inside the valve body, it is called the internal pilot type pressure reducing valve; if the small direct acting pressure reducing valve is installed outside the main valve body, it is called the external pilot type pressure reducing valve. .