Pump supply sections
Topics and outcomes
Expected outcomes: Understand the impact of open center vs closed center valves used with fixed and variable displacement pumps including their operating efficiencies.
Level: 2-4 Novice to improver
Topic covered: Fixed displacement pump power supplies
- Power unit design energy efficiency
- Comparing open center with closed center design
- Comparing circuit operation with series and parallel valves
Fixed displacement pump with open centre valve
Question: What is the pressure at the pump
Experiment: Open circuit Supply/1 Fixed Pump Experiment. Place test gauge on pump. The flow passes straight through the valve to tank. The relief valve is shut.
Question: Why is the pump pressure so high when no useful work is being done
Experiment: Place test gauge on each pipe to see how pressure changes around the circuit. Click on the pump and adjust the flow rate to see how this affects the pressure.
Question: What pressure is seen at the pump with the cylinder moving
Experiment: Click on each solenoid valve and measure the circuit pressure with the test gauge. Double click the cylinder to stop/start it moving. Drag the small print icon to the pump then click the larger top print button to save the results.
Question: What causes the pump pressure when the cylinder is moving
Experiment: Click on the cylinder rod to open the load setup window. Change the frictional load and observe how the pressure changes. Drag the small print icon to the pump then click the larger top print button to save the results.
Question: What pressure is seen at the pump with the cylinder at its end stops
Experiment: Extend and retract the cylinder to its end stops and record the pump pressures. Click the larger top print button to save the results.
Question: What controls the pressure at maximum cylinder extension
Experiment: Move the test gauge over the pipes to see the flow paths. Place the gauge on the relief valve. Observe how the relief valve symbol changes.
Fixed pump open centre series circuit
Question: What is the pressure at the pump
Experiment: Open circuit Supply/2 Fixed Pump Open Center Valves.
Question: Will both cylinders operate on their own
Experiment: Click one solenoid at a time to operate each valve individually.
Question: Will both cylinders move at the same time
Experiment: Operate both cylinders at the same time so that the fluid coming out of one cylinder goes into the next.
Question: Will both cylinders always move at the same time
Experiment: Operate cylinder one then operate cylinder 2 afterwards.
Compare open center ws closed center circuit performance
Question: What is the pressure at the pump
Experiment: Open circuit Supply/3 Fixed Pump Closed Center Valves.
Question: Will both cylinders operate on their own
Experiment: Click one solenoid at a time to operate each valve individually.
Question: Will both cylinders move at the same time
Experiment: Operate both cylinders at the same time. Click the rods to change the loads on each cylinder.
Fixed pump with accumulator
Question: What is the pressure at the pump
Experiment: Open circuit Supply/4 Fixed Pump with Accumulator. Move test gauge over pump
Question: How long does the accumulator take to charge
Experiment: Change the pump flow and spool leakage to record their effect on charging time
Question: Does an accumulator reduce the energy used in a closed center system
Experiment: Move the test gauge over the pipes to see the flow rate and pressure changes.
Question: What volume of fluid does the accumulator store
Experiment: Change the relief valve setting and accumulator pre-charge pressure to observe the effects
Question: How much power is used in standby condition
Experiment: Read the power consumption from the top left meter or calculate the flow * pressure value
Variable displacement pump with closed center valves
Question: What is the pressure at the pump
Experiment: Open circuit Supply/5 Variable Pump Closed Center Valves. Move test gauge over pump
Question: What is the relief valve pressure setting
Experiment: Click on the relief valve to open its setting window to see the opening set value.
Question: How much power is consumed at standby with pump and then relief valve control
Experiment: Read the power in with the variable pump backing off then lower the relief valve setting until this controls the pressure
Question: Why is the relief valve required
Experiment: Increase the pump pressure setting as might happen if the pump controller failed
Diagnose issues with this circuit
Question: What's wrong with this circuit
Experiment: Open circuit Supply/Diagnose 1 Fixed Pump. What would you do to improve the efficiency and safety of this circuit
Hydraulic pump performance testing
Question: Measure the PQ curve for this pump
Experiment: Open circuit Supply/Test Pump Perfomance. The orifice represents the pump leakage (volumetric efficiency). Place small printer over R/V, change pressure setting and press top printer icon.