What is the composition and classification of self-operated control valves?

The self-operated regulating valve is a control device that does not require external energy sources and relies on the change of the pressure or temperature or flow of the measured medium to automatically adjust according to the preset value. It is an energy-saving instrument. It integrates control and execution of many functions in one. It is a self-contained instrument control system. It integrates the functions of transmitter, controller and actuator. It is different from the control valve in the general sense.

Self-operated control valves include self-operated pressure (micro-pressure) control valves, self-operated (differential pressure) flow control valves, and self-operated temperature control valves. The self-operated pressure regulating valve is one of its family members. Because it does not require external energy, the product structure is simple, easy to use, and has a small maintenance workload. It is especially suitable for urban heating, heating, and no power supply, gas supply and need to be controlled. Occasions.

Composition of self-operated pressure regulating valve
Self-operated pressure regulating valve is a self-contained pressure controller valve. Generally speaking, the medium pressure changes with the change of the medium flow rate. When the medium flow changes, in order to ensure a constant pressure, a self-operated regulating valve is required to control it.

The self-operated pressure regulating valve is composed of three major components, namely:
1. Current limiting elements: valves, etc.;
2. Measuring elements: pressure gauge, valve diaphragm, piston, etc.;
3. Load elements: springs, heavy objects, manpower, etc.

Classification of self-operated pressure regulating valves
1. According to the control after the valve and before the valve, it is divided into: self-operated valve rear (reducing) control valve, self-operated valve front (pressure relief) control valve.
2. According to whether it has a pilot or not, it is divided into: direct acting type and pilot operated self-operated regulating valve
a. Direct acting self-operated control valve
Direct-acting pressure regulating valve is to directly control the valve through the medium itself to achieve the role of pressure regulation. The direct acting pressure regulating valve has the pressure taking form behind the valve and the pressure taking form before the valve. Take the pressure behind the valve, keep the pressure behind the valve within the set range, and achieve the effect of pressure reduction behind the valve. Take pressure in front of the valve, keep the pressure in front of the valve within the set range, and achieve the effect of pressure relief in front of the valve.
b. Pilot operated self-operated control valve
The pilot-operated control valve achieves automatic pressure regulation through mutual control between two valves.

The difference between self-operated pressure regulating valve and control valve
The difference between these two types of products is that the control valve requires both external energy sources (such as power or air source) for driving energy, and external control instrument signals to change the relative position of the shut-off parts in the valve, so as to change the fluid flow rate. The self-operated pressure regulating valve does not require external energy, nor does it need to receive external control instrument signals, and can achieve pressure regulation by relying on the pressure signal of the medium to be adjusted.
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