Self operated regulating valve (self operated control valve) relies on the pressure and temperature of the medium flowing through the valve as energy to drive the valve disc to change the valve opening, achieving automatic operation of regulating pressure, flow rate, and temperature, without the need for external power supply and secondary instruments. Self operated regulating valves are often used to control the pressure behind the valve. Refrigeration solenoid valves
The difference between pneumatic control valve and self operated control valve:
Self regulating valves can not only control the pressure behind the valve, but also control the pressure in front of the valve in many situations. The self regulating valve is actually a pure proportional control system, which may result in residual errors. The regulating valve controls pressure regardless of the flow rate. But for any type of regulating valve, the direct control is the flow rate. The biggest difference between these two types of valves is that the control valve requires both external energy sources (such as power or gas) as driving energy and external control instrument signals to change the relative position of the valve's shut-off component, thereby achieving a change in fluid flow rate. Self regulating valves, on the other hand, do not require external energy sources or signals from external control instruments. They can achieve pressure regulation solely based on the pressure signal of the regulated medium. The characteristic of self operated pressure regulating valve is that it does not have external driving energy, so the operating force of this product is relatively small.
Refrigeration solenoid valve
1. In terms of regulation: Regulating valves have higher regulation accuracy than self operated valves. The regulation accuracy of self operated regulating valves mainly depends on the accuracy of the spring and diaphragm of the self operated valve. Generally, the final regulation accuracy will not be better than 5%, with a guarantee of 10%. However, the final adjustment accuracy of ordinary regulating valves depends on the accuracy of the meter transmitter and the accuracy of the regulator, and the accuracy of the regulator is very high, and its impact is generally ignored. So the regulation accuracy of self operated valves is definitely much worse than that of ordinary regulation circuits. When the regulation accuracy requirements are high, it is not recommended to use self operated valves.
2. Application: One on-site, one remote transmission, one using medium pressure regulation, and one using instrument air. If the regulating valve is led to DCS control, it can be easily changed to the given value, and can be manually quickly closed or opened, with various related trend records. The self regulating valve cannot be adjusted and can only be operated on site. The degree of intelligence will be greatly reduced. Self operated regulating valves are difficult to adjust the set value, so they are used in situations where the setting does not need to be changed frequently, such as supplying lubricating oil to equipment. Self operated regulating valves require pressure from the process medium, so they are not suitable for use in relatively clean environments where the medium has corrosion, particles, etc.
3. Installation and design: Self operated regulating valves have pre valve pressure control and post valve pressure control. During design, proper spacing should be left for the installation of pressure points. During installation, the self regulating valve actuator on the steam pipeline should be installed downwards, and the pressure point should be connected to the condenser from the bottom of the main pipe. The condenser should be higher than the actuator and lower than the steam main pipe to avoid steam overheating and damage to the valve body. In addition, the actuator should be installed upwards. As self regulating valves are commonly used in gas pipes, the pressure point should be opened from the top of the main pipe at this time.
