Flow control valve simulation

Flow control valve virtual test rig

Flow control valve exercises and observations

♦ Select Flow>1_Variable Orifice Flow Control, from the drop-down list.

Experiment: Open circuit Flow/1_Variable Orifice Flow Control Valve. Move the test gauge over the orifice. Click on the variable orifice symbol. Change the restriction diameter from 10 to 6mm.

Question: What happens when the orifice size is changed from 10 to 6mm?

Flow stays the same but pressure drop increases.

Experiment: Click on the variable orifice symbol and change the restriction diameter to 3mm.

Question: What happens when the orifice size is changed from 6 to 4mm?

The pressure drop increases and the pump flow drops.

Experiment: Drag the printer icon over the flow control valve. Reduce the orifice size in 1mm steps from 10 to 2mm pressing the large printer icon each time. Copy the results and plot the graph in a spreadsheet.

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

Below pump pressure setting the flow does not change. Above the pressure setting the pump flow reduces.

Experiment: Reload circuit Flow/1_Variable Orifice Flow Control Valve. Click on the motor symbol. Change the load torque and observe the effect on the motor speed e.g. flow rate. Repeat with 6 and 4mm orifice.

Question: Is the flow rate sensitive to the load on the system?

Load pressure affects the pressure drop across the orifice and therefore the circuit flow rate.

Experiment: Click on the FCV symbol and select the meter-in option from the drop down box. Repeat the above test to identify any differences.

Question: What difference does a meter-in flow control valve make?

There are not differences as the check valve is shut.

Experiment: Click on the FCV symbol and select the meter-out option from the drop-down box. Repeat the above test but also change the nominal size of the valve to the same size as the restrictor.

Question: What difference does a meter-out flow control valve make?

The check valve bypasses the flow control. Unless the valve size is so small it restricts the flow in the same way the restrictor did.

Pressure compensated flow control exercises

♦ Select Flow> 2_Pressure Compensated Flow Control, from the drop-down list.

Experiment: Open circuit Flow/2_Pressure Compensated Flow Control. Move the test gauge over the FCV. Click on the variable orifice symbol. Compare the settings to the variable orifice.

Question: What is the difference between setting a pressure compensated valve compared to a variable orifice?

We now set flow not orifice size

Experiment: Open circuit Flow/2_Pressure Compensated Flow Control. Move the test gauge over the FCV. Click on the variable orifice symbol. Change the flow rate from 100 to 60L/min.

Question: What happens when the flow rate is changed from 100 to 60L/min?

The flow changes but the pressure drops stay the same

Experiment: Compare input power required for the PC and orifice FCVs under the same operating conditions

Question: Is the pressure compensated FCV more energy efficient than the variable orifice FCV

The pressure compensated valve increase the supply pressure to the max pump setting and therefore uses more energy

Experiment: Drag the printer icon over the flow control valve. Reduce the flow rate from 100 to 10L/min, pressing the large printer icon at each step. Copy the results and plot the graph in a spreadsheet.

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

Flow rates and pressures are independent of pump displacement.

Experiment: Click on the motor symbol. Change the load torque and observe the effect on the motor speed e.g. flow rate. Repeat with different FCV flow settings.

Question: Is the flow rate sensitive to the load on the system?

Load pressure affects the downstream pressure but not the flow rate.

Meter-in flow control exercises and observations

♦ Select Flow> 3_Meter-In Flow Control, from the drop-down list.

Experiment: Open circuit Flow/3_Meter-In Flow Control. Click on the cylinder rod. Look at the loads on the cylinder and complete manual calculations to check what the pressures should be.

Question: What type of load does this circuit have?

The cylinder is held under higher pressures while extending and retracting.

Experiment: extend the cylinder and move the test gauge around the circuit to understand where pressure drop is that controls the flow.

Question: Where is the flow rate controlled while extending the cylinder?

The orifice before the cylinder controls the flow. meter-in.

Experiment: retract the cylinder and measure the pressures around the circuit. Knowing that hydraulics is a braking technology and we use pressure drops to control movement. Consider how this is achieved while retracting with meter-in controls.

Question: How is the flow rate controlled while retracting the cylinder?

It's not. meter-in allows the load to fall out of control. Or worse, create negative pressures.

Experiment: Click on the FCV valves to see the restrictor size. Observe the flow rates through the flow control valves.

Question: Will the same extend and retract speeds require the same size orifice.

The cylinder bore side has twice the flow so would need a larger orifice than the annulus side

Flow control valve exercises and observations

♦ Select Flow> 4_Meter-Out Flow Control, from the drop-down list.

Experiment: Open circuit Flow/4_Meter-Out Flow Control. Operate the directional valve and compare circuit pressures with those seen using the meter-in circuit.

Question: Compare meter-out with meter-in control?

The cylinder is held under higher pressures while extending and retracting.

Experiment: Extend the cylinder and move the test gauge around the circuit to understand the location of the pressure drop that controls the flow.

Question: Where is the flow rate controlled while extending the cylinder?

The orifice after the cylinder controls the flow. meter-out.

Experiment: Retract the cylinder and measure the pressures around the circuit. Knowing that hydraulics is a braking technology and we use pressure drops to control movement. Consider how this is achieved while retracting with meter-out controls.

Question: How is the flow rate controlled while retracting the cylinder?

meter-out restricts the flow as it exits the bore to stop the load falling out of control. There are no negative pressures.

Experiment: Move the test gauge to the cylinder body. Operate the raise solenoid then double click on the cylinder to freeze its movement (but not performance). Restrict the extend side FCV size until the pump flow rate starts to fall. Observe what happens to the pressures as the flow is restricted.

Question: Approximately what size restrictor is required start slowing the extend speed?

Below 1mm the annulus pressure increase to higher than the bore pressure.

Experiment: Modify the physical parameter of the component in the circuit until you isolate what causes the pressure increase.

Question: What parameter causes the annulus pressure to exceed the maximum pump supply presssure?

The cylinder area ratio (bore to annulus area) causes the pressure to exceed the pump input pressure.

Experiment: Modify the loads acting on the cylinder and observe how the pressures change. Reduce the loads to zero to note the worse case pressure intensification. Compare this figure with the figure you calculate using the cylinder areas.

Question: What other parameters affect the level of annulus intensification pressure and what is the worse case?

The cylinder loads affect the intensification pressure. Zero or negative loads give the highest pressure.

Diagnose the cylinder retraction instability

♦ Select Pressure> Diagnose 1 FCV POCheck

Experiment: Open Flow/Diagnose 1 FCV POCheck. extend and retract the cylinder. Change different parameters until you remove the judder and understand what causes it.

Question: Diagnose the cylinder retract instability?

Submit your answer with your coursework

Experimental Valve Testing

♦ Select Pressure> Test 1 Motor FCV

Experiment: Open Flow/Test 1 Motor FCV. Experiment with different loads, flows, pressure and valve configurations. Use the printer icon and button to take measurements and print out results via a spreadsheet.

Question: Experiment with a speed contol motor circuit?

Printout and discuss results

Experiment: Click on the FCV valves to see the restrictor size. Observe the flow rates through the flow control valves.

Question: Record the bore and annulus pressures while extending and retracting the cylinder with different loads?

Printout and discuss results

Flow control valve simulation

Experiment with flow control valves

Flow control valve virtual test rig

Flow control valve exercises and observations

Pressure compensated flow control exercises

Meter-in flow control exercises and observations

Flow control valve exercises and observations

Diagnose the cylinder retraction instability

Experimental Valve Testing