Orifices are often used in conjunction with spool valves to restrict fluid flow for timing purposes or to prevent valve fluctuations.
The orifice is designed to prevent sudden or undue movement of a valve.
In this basic primary regulator valve the orifice is in the circuit leading to the large differential spool area.
The build up of line pressure from the pump acts via the orifice to move the valve against the spring force.
This uncovers the exhaust port to release excess fluid and allows fluid at a controlled line pressure to pass to the rest of the hydraulic system.
The pressure is determined by the tension of the spring but pressure fluctuations are reduced since the orifice prevents the valve from reacting quickly and this stabilizes the regulated pressure.
