Question: Design a circuit with correct contamination control for the machine in Problem.
Pump A Circuit Variable displacement axial piston pump Axial piston motor Operating pressure (average) 1600 psi Circuit is used to propel the machine in the forward and reverse directions.
Pump B Circuit Fixed displacement axial piston pump Axial piston motor Operating pressure (average) 3600 psi
The Pump B circuit is used to power a rotary mechanism that turns in one direction. Petroleum oil is the fluid for the system, and both pumps pull fluid from the same reservoir. The temperature control ensures that the fluid temperature does not exceed 140°F. The machine will not be operated where cold starts are required, and it will not be subjected to dynamic maneuvers where high shocks are required. 1. Select the cleanliness code required for both circuits.
2. Draw circuit diagrams for both circuits showing the completed circuit with filters in place.
Problem: A mobile machine has two hydrostatic transmissions. One hydrostatic transmission propels the machine, and the other transmission powers a rotary mechanism on the machine. A diesel engine drives a twin pump mount at 2000 rpm. Pump A (propel transmission) is mounted on the right side of the pump mount, and Pump B (rotary mechanism transmission) is mounted on the left side. These transmissions are specified as follows:
Pump A: Variable displacement pump 4.57 in3/rev maximum displacement Fixed displacement motor 4.57 in3/rev displacement Charge pump displacement 1.03 in3/rev Charge pump relief 350 psi Case pressure 40 psi
Pump B: Fixed displacement pump 2.56 in3/rev displacement Fixed displacement motor 2.56 in3/rev displacement Charge pump displacement 0.86 in3/rev Charge pump relief 290 psi Case pressure 40 psi
Average operating pressure for the Pump A circuit is estimated to be 1600 psi. Pump and motor overall efficiencies are estimated to be 93.5%, and volumetric efficiencies are estimated to be 97.5%. The pump will operate most of the time at 75% of maximum displacement. Average operating pressure for the Pump B circuit is estimated to be 3600 psi. Pump and motor overall efficiencies are estimated to be 92% and volumetric efficiencies are estimated to be 95.5%. Maximum ambient temperature is 95°F, and we must design for a maximum fluid temperature of 140°F. You may use the following assumptions:
1. The overall heat transfer coefficient for all heat transfer surfaces is U = 30 Btu/h⋅ft2⋅F.
2. 25% of the total heat generated is dissipated from the surface of the lines and components:
a. Calculate total heat generated by the two hydrostatic transmissions.
b. Design the reservoir with a capacity equal to four times the total reservoir flow (both circuits). You may use any shape you like. Calculate the total heat dissipated by the system (qsys) and reservoir (qres). If additional heat exchange is needed, write the specifications for a finned-tube oil cooler for the machine.