How to choose and install pneumatic accessories (pneumatic accelerators) of pneumatic control valves?

This thing you are talking about is called "pneumatic relay", and Baidu can find the relevant information at once.

It does not take the flow coefficient as the selection index.

There are two common selection methods: one is to directly select the type according to the stroke of the control valve, and the other is to select the type according to the output gas volume of the relay per minute as needed.

In fact, there is almost no need to add relay to the regulating valve with positioner. First, the displacement of the positioner is optional, so it is more convenient and labor-saving to choose an atmospheric potentiometer than to add a relay. Second, the excessive acceleration of the regulating valve will form self-excited oscillation with the positioner, which is unsightly. In the early years, the pneumatic regulator in the control room would not use this thing directly and remotely.

The inlet and outlet of "pneumatic relay" are connected in series in the pipeline from the positioner to the membrane head, and the air source is connected.