1. Sizing of Hydraulic of Hydraulic Pump and Motor
Calculate the load torque on the hydraulic motor.
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· 1000 9.81 0.1 · Calculate the displacement of the hydraulic motor. Assume that the system design
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pressure is 3000 psi (20.7 X 10 Pa) and the relief valve relief valve is set somewhat higher (say 23 X 6
10 Pa). Note that under normal operating conditions, the relief valve should never open. It is only included in the circuit as a safety backup should the winch jam or be overloaded.
Calculate the volumetric flow rate into the hydraulic winch motor. Start by calculating the angular velocity of the winch motor. The angular velocity is equal to the translational velocity of the of the mass divided by the circumference of the of the winch drum.
Calculate the displacement of the of the hydraulic pump. The pump must deliver the required volumetric flow rate to the hydraulic winch motor. Assume that the electric motor driving the pump is a 3‐phase induction motor rotating at 1750 RPM.
Note that it may be safer to size the electric motor based on the relief valve setting of 6
23 X 10 Pa. In this way if the winch is overloaded or jammed, the electric motor will have the power to deliver the full flow rate of the pump through the relief valve. In this case the pump torque becomes:
Note that a standard motor that can deliver at least 12.6 Hp must be selected; say 15 Hp.
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To verify the results, calculate the power of the motor by taking the product of force times velocity of the load adjusted for the pump and motor efficiencies.
Calculate the increase in temperature of the oil for one cycle of raising and lowering the mass. Assume that the volume of oil in the reservoir is 40 liters. •
The increase in oil temperature is due to the flow through the load holding valve as the load is lowered. A load holding valve has an integrated check valve that allows free flow in one direction to raise the load. In the other direction the load holding valve maintains a preset pressure to support the load regardless of the system pressure. In this problem, the hydraulic winch motor was sized to raise the load at a system design pressure of 6
20.7 X 10 Pa. As with the relief valve, the load holding valve must be set somewhat 6
higher than the design pressure (say 23 X 10 Pa). This implies that in order to lower the 6
load, the pump must generate the difference (2.3 X 10 Pa or approximately 330 psi). The quantity of energy that contributes to an increase in the oil temperature for one cycle of lowering the load can be calculated as follows:
