Symbols for Pilot-Operated Reliefs

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Because of the complexity of the pilot circuit and its many optional uses, the symbol representation of a pilot operated relief can become quite complicated. The following symbol for a pilot operated relief with a normally open solenoid venting feature is a typical example.

This symbol is complete in showing the main poppet (low pressure, high volume relief), the pilot relief (high pressure, low volume), the orifices which establish pressure decay in the pilot circuit, and the solenoid valve for venting. In common practice, the industry does not use symbols of this complexity. Over the years, it has become standard practice to represent both pilot operated and direct operated reliefs with the simpler direct operated relief valve symbol. This, however, often leads to confusion, since the total function cannot be represented in this manner. Rexroth has developed and will be promoting the use of a new simplified symbol for representing pilot operated reliefs.

The following are variations showing this simplified symbol with various uses of the pilot circuit:

Above: Various schematics for remote pilots.

Hydraulic line color-coded legend. Used in schemaics.

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Tuesday, April 30, 2013 12:28

Make-Up Check Port Relief Valve Directional Control From Pump From Pump Directional Control Fly wheel Hydraulic Motor Crossport Reliefs X port Y drain P1 P2 Tank 1. This closed-in arrow represents the pilot circuit’s interfaced between... 3. and the pilot spring. 2. the main poppet... Simple Pilot Operated Relief Pilot Operated Relief with External Drain Remote Pilot Remote Pilot Control Multiple Pressure Control and Vent