1.3 Hydraulic Pumps 565g1

Operation of Hydraulic Pumps Section 1.3

Element 1.3

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Pump Identification Gear Pump Identification.

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Pump Identification

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Pump Drives

Direct Coupling. Damper disc with spring type cushions. The hydraulic pump is coupled direct to the engine flywheel. The damper will absorb the engine vibrations and torque fluctuations

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Pump Drives

PTO Drive. Allows multiple pumps to be driven from the one drive. Specific drive gear ratio’s are calculated to ensure optimum pump speed is achieved

Pump couples into drive gear

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Cavitations Oil vapor bubble are created in the hydraulic pump due to a vacuum in the pump inlet. The bubbles are carried through the pump, as pressure increases they implode (collapse rapidly) when exposed to the high pressure.

Cavitation causes:

Restriction at the pump inlet. Intake hose too small. Reservoir too low.

High pressure will compress the bubbles creating extreme pressure causing the buzzing noise

A vacuum in pressure as oil is drawn into pump form the vapor or air bubbles.

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Aeration Aeration is air entering the hydraulic system on the inlet side of the hydraulic pump. The air when compressed at the pump causes air cushions through out the system. This results in loss of actuator control and over heating Cause of Aeration: Stable

Normal

1. Loss clamps around pump inlet pipe. 2. Loss hose fittings (return lines)

3. Fluid level low. Unstable movement

Aeration

1.3 Hydraulic Pumps

4. Return oil line to tank is below oil level. 5. Faulty pump shaft seal

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Gear Pump

Basic Operation. The manufacturing clearances between the gears to the wear plates and centre housing is small enough to provide reasonable sealing. As the gears are rotated they picking up the oil from the reservoir, send it around the out-side of the pump, between the gears and housing. Pushing the oil out the other side creating a flow.

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Gear Pump Components

1

3

2

4

1. Drive gear: has an extended shaft to couple into the drive 2. Driven gear: meshes into the drive gear 3. Wear plate seals: stop oil bying from the high pressure to the low pressure 4. Wear plates: are pushed against the gears by out-put pressure reducing clearance between gears and wear-plates.

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Gear Pump Components

5

7 6

Gear Pump Components. 5. Housing: two end housings and centre housing. 6. Front Seal:

To stop air and dirt from being drawn into the hydraulic system. Stop hydraulic oil from transferring into the drive housing.

7. Housing clamp bolts. 1.3 Hydraulic Pumps

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Gear Pump

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Variable Displacement Piston Pump

The Variable Displacement Pump length of stroke can be altered by changing the angle of the swash plate.

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Variable Displacement Piston Pump Components

Servo-piston Input shaft and cradle

Pistons

Impeller

Barrel 1.3 Hydraulic Pumps

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Variable Displacement Piston Pump

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Pump Identification

END of Hydraulic Pumps

1.3 Hydraulic Pumps

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