Balanced, Pilot Operated Relief Valves

Objective

Demonstrate how a pilot operated relief valve functions, and why it's often chosen for high-pressure, high-flow applications.

What is a Balanced, Pilot Operated Relief Valve?

A balanced relief valve is made up of a main poppet and a pilot poppet. The main poppet receives the same pressure on the top and bottom of it, so the minimal extra pressure from the spring is all that’s required to keep it closed.

The advantages of a balanced, pilot operated valve are that it:

  • has a very small pressure override
  • maintains the system at a more constant pressure
  • creates less heat

A balanced, pilot operated relief valve is a good choice for high pressure, high flow applications.
While the correct name for this valve is balanced, pilot operated relief valve, it’s a little redundant, since all balanced relief valves must be pilot operated.

Schematic Symbols

While many schematic drawings would still show a simple relief valve symbol for a balanced, pilot operated relief valve, a more complete and accurate symbol might look like one of these drawings below.

X
P
T
Balance Orifice
Weak
Spring
Strong Spring
Main
Poppet
Pilot Poppet

X
P
T
Balance
Orifice
Weak Spring
Strong Spring
Main Poppet
Pilot
Poppet
P
T
Balance Orifice
Weak
Spring
Strong
Spring
Main
Poppet
Pilot Poppet

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