Circuit simulation experiment

Follow the exercises listed below.

1. Select Supply>1 Fixed pump experiment, from the drop-down lists

♦ Click on and drag the green pressure gauge and place it over each pipe.

♦ Observe how the pressure changes around the circuit and think about what is causing this.

♦ Leave the gauge over the line before the directional valve and right-click on the directional valve to open the setup menu.

♦ Change the nominal size from 6 to 16mm. Observe what happens to the local pressure.

♦ Operate the cylinder extend solenoid.

♦ Observe what happens to the line pressure as the cylinder is moving and when it reaches the end of its stroke.

♦ Right-click on the cylinder rod to change the loads then operate the solenoid valve to see how the line pressures have changed.

♦ Check the pressure you see against hand calculations.

Experiment 1: It's normal for flow through the pipes to create small, local pressures.

Question 1: Why might the reservoir pressure be set above zero bar?

Answer

Experiment 2: Flow through an orifice will create a pressure drop across the orifice.

Question 2: If you increase the nominal size of the valve will the pressure drop increase or fall?

Answer

Experiment 3: Open center circuits stay at low pressure when not being used.

Question 3: What are the benefits of open center circuits?

Answer

1. Select Supply>2 Fixed pump open center valves, from the drop-down lists.

♦ Click on the solenoids to operate the valves independently to observe how the cylinders move.

♦ Operate the two valves at the same time to explore how the movement of one cylinder affects the speed of movement of the other.

♦ Connect the supply node directly to the P port of each valve and observe what happens when each solenoid is operated. Or select the closed center circuit 3 and change the valves to open center.

Experiment 4: With two open center valves the return from one valve is fed into the supply of the second valve.

Question 4: What happens if both cylinders are operated together and one cylinder has reached the end of its stroke?

Answer

1. Select Supply>3 Fixed pump closed center valves, from the drop-down lists.

♦ Click on and drag the green pressure gauge and place it over each pipe.

♦ Observe how the pressure changes around the circuit and think about what is causing this.

♦ Operate the two valves independently to observe how the cylinders move.

♦ Operate the two valves at the same time to observe how the cylinders move.

♦ Observe what happens to the line pressure as one cylinder is moving and when it reaches the end of its stroke.

♦ Click on a cylinder rod and increase the friction force. Then operate the valves together to observe how the cylinders move.

Experiment 5: With two closed center valves the supply and return flows work independently of each other.

Question 5: What happens if both cylinders are operated together and one cylinder has reached the end of its stroke?

Answer

Experiment 6: With two closed center valves the cylinder speed will depend on the amount of flow they each take from the pump.

Question 6: What dictates how much flow each cylinder takes from the pump?

Answer

1. Select Supply>4 Fixed pump with accumulator, from the drop-down lists.

♦ Click on and drag the green pressure gauge and place it over each pipe until the accumulator is fully charged and the pump is switched to minimum pressure.

♦ Observe how the pressure changes around the circuit and think about what is causing this.

♦ Place the green pressure gauge over the accumulator to observe it's condition.

♦ Operate the valve to observe how the flow from the accumulator to the cylinder exceeds the maximum flow supplied by the pump.

♦ Experiment by changing the accumulator pre-charge pressure and relief valve setting to observe how this affects the stored volume of fluid in the accumulator.

Experiment 7: Accumulators store fluid under pressure so that it can be released into the system when required.

Question 7: What would happen if the pre-charge pressure was much lower than the working pressure?

Answer

Experiment 8: Accumulators are pre-charged with nitrogen to a given pressure, generally 90% of the system pressure.

Question 8: What would happen if the pre-charge pressure was above the maximum system pressure?

Answer

1. Select Supply>5 Variable pump closed center valves, from the drop-down lists.

♦ Click on and drag the green pressure gauge and place it over each of the two directional valves.

♦ Observe how the A and B line pressures are different in both valves and think about what is causing this.

♦ Operate the two valves independently to observe how the cylinders move.

♦ Operate the two valves at the same time to observe how the cylinders move.

♦ Compare the operation and performance of this circuit with that from the fixed displacement pump.

Experiment 9: A variable displacement pump only supplies the flow required by the circuit

Question 9: What happens if both cylinders are operated together and one cylinder has reached the end of its stroke?

Answer

Experiment 10: With two closed center valves the cylinder speed will depend on the amount of flow they each take from the pump.

Question 10: What dictates how much flow each cylinder takes from the pump?

Answer

Experiment 11: Directional spools are supplied with a range of different center conditions.

Question 11: What is the main difference between the closed center and A+B to tank, versions shown?

Answer

1. Select Supply>Diagnose 1 fixed pump, from the drop-down lists.

♦ Operate the directional valve. Click on the components to see their loads and settings.

♦ Diagnose what the issues with this system might be.

1. Select Supply>Test pump performance, from the drop-down lists.

♦ The orifice represents pump leakage, this increases if the pump is failing.

♦ Click and drag the small printer icon over the relief valve. Then press the large printer icon in the top menu bar

♦.Continue to change the pressure and click the large printer icon until you have sufficient test results to copy and plot in a spreadsheet graph.

♦ Right-click on the orifice to change its size. Then repeat the graph plot to compare the pump performance.