Volume Booster is a high volume amplifier used to increase the operating speed of the actuator, preventing the time lags, in the systems where controller and the control valve are separated by extremely long piping runs…
Volume Booster receives the low volume signal from the controller and transmits from an auxiliary supply a high volume signal to the control valve actuator.
Volume Booster is specially recommended for the use with large capacity diaphragm actuator.
Input pressure acting upon the effective area of the upper diaphragm produces a force, which is opposed by the output pressure exerted upon the effective area of the lower diaphragm.
The opposing forces are in direct 1:1 ratio.
Hence any increase in the input pressure will cause the diaphragm assembly opening the pilot valve to admit a sufficient supply of air to the output to rebalance the input pressure.
A decrease in input pressure will cause the diaphragm assembly to lift off the exhaust port reducing the output and again rebalancing the input.
Equalising valve, by-passes slow small signal variations.
Reference - Valve Solutions