Pressure control valve simulation

Experiment with pressure control valves

Pressure control valve simulations

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Direct Operated Relief Valve Exercises and observations

1. Select Pressure>1_Direct Operated Relief Valve, from the drop-down list.

♦ Drag the pressure guage onto the relief valve to display the pressure upstream of the valve.

♦ Click on the pressure relief valve symbol to open the setup box.

♦ Adjust the relief valve setting pressure and observe how the line pressure changes.

♦ Click on and adjust the maximum pump pressure and flow settings.

♦ Experiment with different pump and valve settings until you understand what pressures to expect.

Experiment: Open circuit Pressure/1_Direct Operated Relief Valve. Move the test gauge over the relief valve. Click on the relief valve symbol. Change the pressure setting and observe how the upstream pressure changes.

Question: What happens when the relief valve's pressure setting is changed?

Upstream pressure is controlled by the relief valve setting

Experiment: Set the relief valve to 100 bar. Click on the tank symbol and change the pressure to 5 bar. Observe how the pressure upstream of the relief valve changes. Try other pressures then return to 0.5 bar.

Question: What happens when the return line pressure increase to 5 bar?

The pressure increases to the relief valve setting PLUS the tank pressure

Experiment: Drag the printer icon over the relief valve. Increase the flow from 5 to 100 L/min by clicking the right arrow on the scroll bar. At each step press the large printer icon. Copy the results and plot the graph in a spreadsheet.

Question: Is the actual pressure dependent on the pump flow rate?

Upstream pressure increases as flow increases

Experiment: Click on the relief valve and set the bar/100 L/min to 2 and then 4 bar, plotting a new curve each time. Compare these curves with those from commercial relief valves, either published data or test data.

Question: What is an appropriate pressure rise rate with flow rate?

Each valve type has a different flow vs pressure curve

Experiment: Hysteresis is sometimes known as reseat pressure. Increase the flow in steps from 5 to 100 L/min by clicking the right arrow on the scroll bar then decrease back with the left arrow, pressing the large printer icon at each step. Copy the results and plot the graph in a spreadsheet. Click on the relief valve and set the hysteresis to 4 bar, then re-plot the curve.

Question: How does hysteresis affect the pressure setting?

Hysteresis causes a different pressure level as flow reduces compared to when it opens.

Experiment: Click on the relief valve symbol and select the pilot-operated option from the drop-down box. Compare the performance with the direct-acting version to identify the main difference.

Question: What is the main difference between direct action and pilot-operated valves?

The pilot operated version has a small leakage flow. Performance characteristics are likely to be different in the manufacturer datasheets.

Experiment: Click on the relief valve symbol and select the pilot-operated version from the drop down-menu. Observe if the pressure upstream of the relief valve changes.

Question: Is the pilot-operated valve sensitive to return line pressure changes?

The external drain line on this valve makes the pressure independent of return line pressure.

Pilot Operated Relief Valve Exercises and observations

♦ Select Pressure>2_Remote Piloted Relief Valve, from the drop-down list.

Experiment: Open Pressure/2_Remote Piloted Relief Valve. Move the test gauge around the circuit to understand the flows and pressure drops.

Question: Why is the relief valve open?

Open Pressure/2_Remote Piloted Relief Valve. Move the test gauge around the circuit to understand the flows and pressure drops.

Experiment: Click on the pressure reducing valve symbol. Adjust the pressure setting and observe when the relief valve changes state. Click on the pressure relief valve symbol. Adjust its setting and until you fully understand how it is being controlled by the pilot pressure.

Question: What controls the opening and closing of the pressure relief valve?

The pressure valve outlet pressure controls the relief valve opening.

Experiment: Set the reducing valve pressure below the relief valve opening pressure. Click on each variable orifice symbol to adjust their size. Find the combination where the relief valve opens to limit the pressure.

Question: Which orifice adjustment will open the relief valve.

A large top orifice and small lower orifice will result in the relief valve opening

Experiment: Use the two orifice sizes to open and shut the relief valve with its supply pressure level.

Question: Does the normal relief valve function still work?

Yes

Experiment: Set the relief valve to 100 bar. Click on the tank symbol and change the pressure to 5 bar. Observe how the pressure upstream of the relief valve changes. Try other pressures then return to 0.5 bar.

Question: What happens when the return line pressure increase to 5 bar?

The external drain line on this valve makes the pressure independent of return line pressure.

Pressure Reducing Valve Exercises and observations

♦ Select Pressure> 3_Reduced Supply Pressure, from the drop-down list.

Experiment: Open circuit Pressure/3_Reduced Supply Pressure. Move the test gauge over the reducing valve. Click on the reducing valve symbol. Change the pressure setting and observe how the downstream pressure changes.

Question: What happens when the reducing valve's pressure setting is changed?

Downstream pressure is controlled by the reducing valve setting

Experiment: Open Pressure/4_Reducer Valve Motor Shock. Click on the motor symbol and increase the motor torque until the motor stops turning. Experiment with the reducing valve setting and motor torque until you fully understand the relationship. Check the maximum torque with theoretical calculations.

Question: At what torque does the motor stop rotating?

Between 7-8 Nm

Experiment: Set the reducing valve to 100 bar. Click on the tank symbol and change the pressure to 5 bar. Observe how the pressure downstream of the reducing valve changes. Try other pressures then return to 0.5 bar.

Question: What happens when the return line pressure increases to 5 bar?

The reduced pressure remains the same but the load pressure increase. All reducing valves have external vent reference pressures.

Experiment: Drag the printer icon over the reducing valve. Increase the pump flow from 5 to 100 L/min by clicking the right arrow on the scroll bar. At each step press the large printer icon but you'll also need to change the load to find the pressure it's reducing to at the set flow. Copy the results and plot the graph in a spreadsheet.

Question: Is the controlled pressure dependent on the pump flow rate?

Yes but it's difficult to test

Sequence Valve Exercises and observations

♦ Select Pressure> 5_Sequence Valve

Experiment: Open circuit Pressure/5_Sequence Valve. Operate the sequence valve and click on the valve to change its pressure setting. Adjust the relief valve setting after the sequence valve and observe how the two valves interact.

Question: How does a sequence valve work?

The sequence valve opens when the supply pressure is above the set pressure and closes when it's below the set pressure

Experiment: Move the test gauge to the sequence valve. Click on the relief valve and change its pressure setting. Observe how the relief valve pressure setting affects the sequence valve input and output pressures.

Question: What effect does the downstream pressure have on the sequence valve setting?

Downstream pressure has little effect on the setting level. This is because the sequence valve has a pilot drain that references the tank pressure.

Experiment: Move the test gauge to the sequence valve. Click on the pump and change its pressure setting. Observe how the pump pressure setting affects the sequence valve input and output pressures.

Question: What effect does the upstream pressure have on the sequence valve setting?

Upstream pressure has little effect on the sequence valve setting level

Experiment: Open circuit Pressure/6_Compare Sequence and Relief. Move the test gauge to the first relief valve in the top line. Repeat the above experiments with the relief valve in the top line. Observe the differences between how the sequence valve operated.

Question: Compare the sequence valve with that of a relief valve.

Relief valve control pressures depend on other valves in the line.

Experiment: Open Circuits/Clamp then Drive Circuit. Operate the solenoid valve and observe how the sequence valve operates within the circuit.

Question: What does the sequence valve do in this application?

The sequence valve switches as the cylinder stops and pressure rises.

Diagnose these technical issues

♦ Select Pressure> Diagnose 1 Relief Valve

Experiment: Open Pressure/Diagnose 1 Relief Valve. Click on each component to check its size and setup. Three areas that are poorly designed in this circuit

Question: Diagnose the 3 issues with this relief valve circuit?

Compare the flow to valve sizes, system line pressures and closeness of settings.

Experiment: Open Pressure/Diagnose 2 Reducing Valve. Operate the solenoid valves. Consider what type of reducing valve has been used and potential issues in this application.

Question: Diagnose the issues with this reducing valve circuit?

A reducing/relieving version is required but application is poor as full flow may go through the drain line.

Experimental Valve Testing

♦ Select Pressure> Test 1 Reducing Valve

Experiment: Open Pressure/Test 1 Reducing Valve. Experiment with different load pressures, flows, and valve configurations. Use the printer icon and button to take measurements and print out results via a spreadsheet.