Parker’s pilot operated ventable relief valves provide high accurate and reliable performance for hydraulic circuits that require multiple pressure relief settings or require a remotely pilot controlled relief. These valves can work with hydraulic systems that reach pressures up to 420 bar (6000 psi) and flows up to 400 lpm (106 gpm) and aren’t necessarily sensitive to leakage due to the spool design. Parker’s pilot operated ventable relief valves are designed unloading or remotely controlled applications and can be use anywhere within mobile hydraulic and industrial markets, such as presses, clamps, or lift circuits.

Markets:
• Miscellaneous Industrial
• Miscellaneous Manufacturing
• Miscellaneous Mobile

Features/Benefits:
• High flow capacity
• Integral 250 micron pilot flow filter
• All external parts zinc plated
• High accuracy - pilot operated design
• Hardened, precision ground parts for durability
• Compact size for reduced space requirements

Applications:
• Pump relief
• Press or clamp circuits
• Remote control applications
• Vented Unloading

Additional Technical Insight:
Ventable relief valves are pilot operated, spool type pressure controls.  Like other pilot operated relief valves, the ventable relief has a main pilot spring chamber, and a bias spring chamber separated by a pilot orifice.  The internal adjustment controls the main pilot spring setting.  When pressure in the system builds above the setting of the main pilot setting, the pilot seat will lift allowing the spool to travel to the open position passing flow.  What makes ventable relief valves unique is the valve offers an isolated vent chamber that is connected to the bias spring chamber.  This allows for the valve to open at a lower pressure than the setting of the main spring.

The circuit designer has the ability to apply an external control valve or valves to set the operating pressure of the bias spring that must be overcome to allow the valve to open.  This is an ideal solution in applications that may require variable pressure settings in normal operation.

One must consider the leakage component when applying any pilot operated spool type relief valve, as by design, the spool will pass a small leakage flow.