A direct acting relief valve is the most basic of the pressure controls, consisting of only one poppet and one spring. It is used to limit maximum system pressure.
The advantages of a direct acting style of relief valve are that it is:
This valve is good for controlling sudden, momentary pressure spikes. It can also be used as a pilot control for other valves.
Below are some variations of the schematic symbol for a direct acting relief valve. The P label is the inlet port from the pump and the T label is the port that leads back to tank.
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