Hydraulic Pump Service Flashcards
Hydraulic pumps that are able to change the capacity of their pumping chambers are called:
Variable displacement pumps.
As pump outlet pressure increases, the pump’s internal leakage decreases.
False
State the function of the trap in a gear pump pressure plate.
The trap provides an escape path for oil trapped between the gear teeth as they come into mesh.
List two reasons why oil pressure from the pumping chambers of an axial piston pump is connected to the piston shoes.
A. To lubricate the ball and socket joint between the piston and the shoe as well as the contact area between the shoe and the swash plate.
B. Balance the piston by offsetting the forces generated by the pressure in the pumping chamber.
List three general guidelines that should be observed when disassembling a hydraulic pump.
A. Mark pump housings so that they can be returned to their proper location during assembly.
B. Determine the correct direction of driveshaft rotation for unidirectional pumps so that the pump can be returned to the proper rotation on assembly.
C. Be sure to keep mated components (such as gear sets, pistons and barrels) together so that they can be returned to their original positions.
List three reasons that could cause a hydraulic pump to lack lubrication.
A. Using improper hydraulic oil for the application and climatic conditions.
B. Low reservoir oil level which causes the pump inlet to become uncovered.
C. Severe aeration.
Why should the adjustment of system pressure controls be backed off prior to starting a machine in which the hydraulic pump has been replaced?
Pressure controls are backed off to prevent overloading the pump if the pressure controls have been misadjusted prior to pump replacement.
A pump termed reversible is able to:
Reverse the direction of oil flow through the pump.
Why do manufacturers of gear pumps with aluminum housings allow the gears to cut a gear path into the pump housings during break in?
To provide good volumetric efficiency by keeping gear tip clearance to a minimum.
Why is some internal leakage necessary within all hydraulic pumps?
Internal leakage lubricates moving pump parts.
The oil that gathers in the case of an axial piston pump comes from:
Internal leakage.
The most common cause of pitted erosion on the internal surfaces of the pump is:
Cavitation.
List four tasks that should be performed when a hydraulic pump is installed to ensure that the system is clean enough to ensure good pump service life.
A. The hydraulic oil may need to be changed or filled.
B. Hydraulic filters must be service.
C. The hydraulic reservoir must be thoroughly cleaned.
D. The complete system may have to be flushed.
