Theory Experiments

Experiment with some basic theory simulations

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Industrial power unit calculation

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Suggested exercises and observations

1. Select menu button 1 (Operate Power Unit)

♦ Adjust the top slide bar that controls the spool valve orifice diameter.

♦ Observe how the supply pressure remains the same at all points in the pipework between the pump and control valve.

♦ Observe how all of the energy generated at the pump is available at the gear motor.

♦ With the control valve open, adjust the second slide bar that controls the load pressure on the gear motor.

♦ Observe how when the load pressure changes, the pressure drop across the control valve and therefore the flow rate through the valve also changes.

2. Return to the home screen then select menu button 2 (Pump minimum inlet pressure head calculation)

♦ Adjust the top slide bar that changes the height above sea level.

♦ Observe how the absolute pressure reduces the higher up the mountain the power unit is located.

♦ Adjust the third slide bar and change the fluid head pressure to zero.

♦ The gauge pressure would now be zero on the pump but note how the absolute pressure, which would push fluid into the pump, is still greater than zero.

3. Depending on your facilities, fill a container (plastic bottle) with hot/warm fluid.

♦ Seal the lid tight and poor cold fluid over the bottle. Observe what happens to the bottle as it cools.

♦ Calculate the volume change based on the temperature change.

Experiment 1: Consider how pressure is transmitted around a circuit.

Question 1: With no flow, what will the pressure be 100 meters further down the pipeline if it is 50bar at the pump?

The pressure will still be 50 bar at 100 meters or 1000 meters away

Experiment 2: Consider the difference between gauge and absolute pressure.

Question 2: If a pressure gauge says 10 bar, what is the approximate absolute pressure at sea level?

11 bar absolute because absolute pressure is approximately 1 bar at sea level. Pressure gauges cannot read atmospheric pressure.

Experiment 3: Air and hydraulic oil are both fluids. Air can be compressed.

Question 3: Is hydraulic fluid compressible? And should we consider compressibility in our calculations?

No, Yes, No, and Yes. We consider that fluid is incompressible although it is slightly. Most calculations ignore the compressibility because it is not significant although it does become important in very dynamic applications.