Pilot operated hydraulic pressure relief valve simulation

Learn how a pilot operated pressure relief valve works

 

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Last Updated
2010-06-17

 


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This section allows you to test a typical pilot operated relief valve. Flow and pressure settings can be adjusted and it also demonstrates the effect of back pressure in the tank line.

Experiment with this pilot operated pressure relief valve

Try the following experiments

This simulates a pilot operated relief valve on a typical hydraulic test stand.


This relief valve is designed to limit the pressure in line 1 relative to the pressure in line 2


The relief valve setting can be adjusted by clicking on and dragging the "% set" slide bar.


The inlet pressure on port 1 can be adjusted by clicking on and dragging the "pressure 1" slide bar.

Back pressure on port 2 can be adjusted by clicking on and dragging "pressure 2" slide bar and the flow rate by clicking on and dragging the " L/ min" slide bar.


When the inlet pressure on port 1 reaches the setting of the relief valve, the pilot section will open.


Flow across the orifice in the main spool will induce a pressure drop and cause it to open and connect port 1 to port 2.


Adding back pressure onto port 2 will add to the pressure setting of the valve.


This valve is a spool type design so it will have a continuous low leakage from port 1 to 2.


This valve cannot open from port 2 to 1 and can be demonstrated by setting a higher pressure on port 2 relative to setting on port 1.

DESIGN FEATURES - for pilot operated relief valves

A significant benefit of the Sun Hydraulics, cartridge system is the ability of the honed spool section to float relative to the cartridge's thread.

It is not possible to maintain good concentricity tolerances in threaded bore. This means that often the misalignment between the thread and the cavity can result in side loads being applied to the cartridge body. Any side load that is present will tend to distort the cartridge body and can have a significant effect on the machined clearances inside. These variations will effect the valve's internal leakage and therefore its contamination resistance. In some cases the spools' may make contact with the bores and provide intermittent or unacceptable performance.

Sun's floating design will compensate for misalignments in the cavity. This security allows tighter machining tolerances to be maintained and therefore more reliable and better performing valves.

Description of pilot operated relief valve components

ADJUSTING SCREW - Compresses the pilot spring to change the relief valve setting. C/W 'O' ring and backup seals.


LOCKING NUT - Locks the adjusting screw in position to maintain the pressure relief setting.


STOP RING - Security clip to ensure that the spring is not fully compressed and the pressure level set too high.


PILOT SPRING END - Retains and aligns the pilot pressure spring as well as removing the torque effect during adjustment.


PILOT SPRING - Sets the valve's cracking pressure. Different springs are available for the each pressure setting.


PILOT POPPET ASSEMBLY - The ball bearing is located firmly in the retainer and forms a positive seal for the pilot flow.


POPPET SEAT - As well as providing the seat for the pilot poppet this component also retains the main spool spring. C/W 'O' ring.


HONED ASSEMBLY- The honed bore holds the main spool and is floating to avoid cavity side load distortions. C/W 'O' ring and backup seals.


MAIN SPOOL - Pilot flow across the orifice forces the spool back, to open the main relief flow path.


MAIN SPOOL SPRING - this spring balances the pilot flow force across the orifice and regulates the valve's relief pressure.


RETAINING WIRE - Locates the main spool assembly onto the cartridge body while allowing radial movement to stop side loads.


CARTRIDGE BODY - The cartridge body supports internal components and allows the complete valve to be screwed into the cavity.


MANIFOLD - The cartridge is mounted into a cavity that can be machined into any manifold or machine body.


ORIFICE - The orifice locates in the pilot seat and controls the pilot poppet response and flow.


PRESSURE 1 - Click and drag the slide button to change the pressure on line one (up stream) of the relief valve. Release mouse to stop slider.


PRESSURE 2 - Click and drag the slide button to change the pressure on line two (downstream) of the relief valve. Release mouse to stop slider.


FLOW LEVEL - Click and drag the slide button to change the maximum flow available to the relief valve. Release mouse to stop slider.


VALVE SETTING - Click and drag the slide button to change the relief valve's pressure setting. Release mouse to stop slider.

 


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