Outlet Size of Relief Valve

Careful with "Always"...

Not always true in Industrial Hydraulics.

Hi,

You do not say that the system is an oil hydraulic one. However assuming that it is then the return from the valve (any valve) back to the reservoir is a loss of power which is to be avoided. As the flow over a relief valve will vary as the system works then the size of the line has to be such as to minimize the losses. Many propriety relief valves do however have the same outlet port as inlet port. Often relief valves are teed off the line rather than being in the line. Any back pressure in the tank line will be additive to the relief valve setting thus causing the setting to vary with a change in flow. Not a desirable feature in a well designed circuit.

The rule of thumb for oil velocity in pipes is 5/7 m/sec for pressure lines 3 m/sec for return lines and 1m/s for suction lines. The 7 m/sec is often considered only suitable for closed loop transmission circuits.

I hope this answers your question.

Oliver Dunthorne

Hydraulic Engineer

This is possibly because you easily confuse personal experience with the mystical laws of the universe.