You could find pressure-control valves on most CNC brush machines, here are some tips you might be interested to read.
Pressure-control valves are used in hydraulic circuits to maintain desired pressure levels in various parts of the circuits.
A pressure-control valve maitains the desired pressure level by (1) diverting higher-pressure fluid to a lower-pressure area, thereby limiting the pressure in the higher pressure area, or (2) restricting flow into another area.
Valve that diverts fluid can be safety, relief, counter-balance, sequence, and unloading types. Valves that restricts flow into anotehr area can be of the reducing type.
A pressure-control valv may also be defined as either a normally closed or normally open two-way valve. Relief, sequence, unloading and counterbalance valves are normally closed, two-way valves are partially or fully opened while performing their design functioin. A reducing valve is a normally opened valve that restricts and finally blocks fluid flow into a secondary area.
With either type of operation, the valve can be said to automatically create an orifice to provide the desired pressure control. An orifice is not always created when the valve is piloted from an external source. One valve of this type is the unloading valve -- it is not self-operating; it depends on a signal from an external source. Relief, reducing counter-balance, and sequence valves can be fully automatic in operation, with the operating signal taken from within the envelop.