Pressure Relief Valve Test

Experiment with this pressure relief valve

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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

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Suggested exercises and observations

1. Change the system pressure 1 slider to observe how the pilot valve and then main spool open.

2. Change the valve setting slider to observe how it changes the relief valve set pressure.

3. Change the flow slider to see how the actual relief pressure value changes as the flow changes.

4. Change the return pressure 2 slider to observe how this affect the valve set pressure.

Experiment 1: In the pilot operated relief valve simulation. Adjust the supply line pressure 1.

Question 1: Which valve section opens first or do the pilot and main stage valves open at the same time?

The pilot stage opens first.

Experiment 2: Adjust the flow rate while the relief valve is operating.

Question 2: Does the supply line pressure stay stay the same, increase or decrease?

It increases as the pressure drop across the valve increases.

Experiment 3: Adjust the return line pressure at 2

Question 3: Does the supply line pressure stay stay the same, increase or decrease?

It increases because the pressure at inlet is equal to the back pressure plus the drop across the valve.

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 (upstream) 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.

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 a 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 affect 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.