Gas regulator valve is an important part of the automation control process instrumentation, the correct selection of the normal operation of the system is critical, gas regulator valve selection in addition to pressure, temperature, caliber, material and control valve structure form and other common parameters need to be implemented, but also pay attention to the relevant accessories, the main accessories of gas regulator valve positioner, solenoid valve, valve position feedback, air filtration pressure reducing valve, position-keeping valve, pneumatic relay, etc., the following description of the main accessories selection principles. Pneumatic relays, etc., the following description of the main accessories selection principles.
1. Gas regulator valve positioner
Valve positioner is the main accessory of the pneumatic actuator, which is used with the pneumatic actuator to improve the position accuracy of the valve, to overcome the impact of stem friction and media imbalance force, so as to ensure that the valve is correctly positioned according to the signal from the regulator. The valve positioner is used to convert the control signal into pneumatic signal to the pneumatic actuator, which drives the regulating valve to carry out the adjustment function. Valve positioner is divided into mechanical positioner and intelligent positioner, intelligent positioner than mechanical control accuracy is higher, gas consumption is also low.
2. Solenoid valve of gas regulator valve
When the system needs to achieve program control or two control, you need to use solenoid valve. When selecting the solenoid valve, in addition to AC and DC power supply and voltage, frequency, must pay attention to the relationship between the solenoid valve and regulating valve role type, can be equipped with "normally open" or "normally closed". If the requirement to increase the capacity of the solenoid valve to shorten the action time, you can use two solenoid valves or the solenoid valve as a pilot valve and large-capacity pneumatic relay combination.
3. Gas regulator valve relay
Pneumatic relay is a power amplifier, it can send the air pressure signal to a farther distance, eliminating the lag caused by the lengthening of the signal line, mainly used between the field transmitter and the central control room regulation instrument, or between the regulator and the field regulating valve, there is another role is to amplify or reduce the signal.
4. Converter of gas regulator valve
The converter is divided into gas-electric converter and electric, gas converter, whose function is to achieve a certain relationship between gas and electric signals to convert each other, mainly used to manipulate the pneumatic actuator with electric signals when the 0 ~ 10mA or 4 ~ 20m4 electric signal conversion or 0 ~ 100KPa gas signal into 0 ~ 10mA or 4 ~ 20mA electric signal.
5. The valve position transmitter of pneumatic control valve
When the pneumatic control valve is far away from the control room, in order to be able to accurately understand the switch position of the valve without going to the scene, it should be equipped with a valve position transmitter, that is, the institutional displacement of the valve opening, according to certain laws converted into an electrical signal to the control room, this signal can be a continuous signal reflecting any opening of the valve, can also be considered as the valve positioner reverse action.
6. Stroke switch of pneumatic control valve
Travel switch reflects the valve switch two positions, and at the same time send an indication signal device, the control room can be based on this signal, to determine the state of the pneumatic control valve switch in order to take appropriate measures.