Level control valve accessories introduction complete works

Level control valve accessories introduction complete works

April 23, 2019

The level control valve positioner is the main accessory of the pneumatic actuator. It is used with the pneumatic actuator to improve the position accuracy of the valve and overcome the influence of the valve stem friction and the medium imbalance force, thus ensuring the valve's signal according to the regulator. Achieve correct positioning.

In the following cases, the locator should be equipped:

  • When the medium pressure is high and the pressure difference is large;
  • When the diameter of the regulating valve is large (DN>100);
  • High temperature or low temperature regulating valve;
  • When it is necessary to increase the operating speed of the regulating valve;
  • When using a standard signal to operate a non-standard spring actuator (spring range other than 20 to 100 KPa);
  • When used for split control;
  • When the valve is reversed (air-closed and air-opened);
  • When it is necessary to change the flow characteristics of the valve (the positioner cam can be changed);
  • No spring actuator or piston actuator, to achieve proportional action;
  • When using an electrical signal to operate a pneumatic actuator, a distribution-gas valve positioner is required.

Solenoid valve: When the system needs to implement program control or two-position control, it needs to be equipped with a solenoid valve. When using the solenoid valve, in addition to the AC and DC power supply, voltage and frequency, it is necessary to pay attention to the relationship between the solenoid valve and the regulating valve. It can be used with "normally open" or "normally closed". If you want to increase the capacity of the solenoid valve to shorten the operating time, you can use two solenoid valves in parallel or use the solenoid valve as a pilot valve in combination with a large-capacity pneumatic relay.

Pneumatic relay:

Pneumatic relay is a power amplifier that can send the air pressure signal to a remote location to eliminate the hysteresis caused by the lengthening of the signal pipeline. It is mainly used between the field transmitter and the central control room, or Another function between the regulator and the field regulator is to amplify or reduce the signal.


The converter is divided into a gas-to-electric converter and an electric-to-gas converter, and its function is to realize a mutual conversion between gas and electric signals, and is mainly used for 0 to 10 mA or 4 to when the pneumatic actuator is operated by the electric signal. 20mA electrical signal conversion or 0~100KPa air signal is converted into 0~10mA or 4~20mA electrical signal.

Air filter pressure reducing valve:

The air filter pressure reducing valve is an accessory in the industrial automation instrument. Its main function is to filter and purify the compressed air from the air compressor and stabilize the pressure at the required value. It can be used in all kinds of pneumatic instruments and solenoid valves. Air supply and voltage regulator for cylinders, spray equipment and small pneumatic tools.

Self-locking valve (positional valve):

A self-locking valve is a device that holds the valve position. Pneumatic control valve When the gas source fails, the device can cut off the air supply signal, so that the pressure signal of the membrane chamber or cylinder is maintained at the moment before the fault, so that the valve position is also maintained at the position before the fault. To the role of retention.

Valve position transmitter

When the regulating valve is far away from the control room, in order to accurately understand the switch position of the valve, it is necessary to equip the valve position transmitter, that is, the mechanism displacement of the valve opening degree is converted into an electric signal to the control room according to a certain rule. The signal can be a continuous signal reflecting any opening of the valve, or it can be considered as the reverse action of the valve positioner.

Travel switch (return)

The travel switch reflects the two extreme positions of the valve switch and simultaneously sends out a signal indicating device. According to this signal, the control room can infer the switch state of the valve to take corresponding measures.