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HET Period 3 Hydraulics > 301 B - Hydraulic Pump Fundamentals > Flashcards

301 B - Hydraulic Pump Fundamentals Flashcards

1
Q

What number of pistons does a piston pump have? Why?

A

They use an odd number to control pulsations from the pump.

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2
Q

What are some characteristics of a Gear Pump?

A

Cheaper Simple More Rugged Fixed Displacement Bi-Directional

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3
Q

What sort of efficiency does a piston pump have?

A

94-98%

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4
Q

What are the two pistons called that control pressure compensation in a piston pump?

A

A Bias piston constantly achieves max angle Stroking piston changes angle to minimum angle when outlet pressure rises enough.

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5
Q

What are some characteristics of Vane Pumps?

A

Variable displacement More expensive More efficient More susceptible to contamination Square Case

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6
Q

What is the Volumetric Efficiency of a pump?

A

Expresses how well it generates flow.

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7
Q

What is the most commonly used pump in the mobile hydraulics area?

A

An axial piston pump.

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8
Q

Why is a gear pump a fixed displacement?

A

The pockets created by the moving gear teeth never change.

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9
Q

What is the purpose of a hydraulic pump?

A

To change rotary mechanical motion into Hydraulic power.

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10
Q

What two designs of vane tips can be used within a Vane Pump?

A

Bevelled Tip Rounded Tips (Bi-Directional)

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11
Q

How is the displacement of an fixed displacement axial piston pump determined?

A

The displacement is the volume displaced by the largest stroke, times the number of pistons.

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12
Q

What would a PSI Atmosphere Gauge read at sea level?

A

14.7 PSI A

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13
Q

What is pump slip? What does it cause?

A

Oil leaking from the outlet side to the inlet side. Causes a reduction in volumetric efficiency.

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14
Q

When does maximum displacement within a vane pump occur?

A

When the cam ring is pushed its maximum distance off centre of the rotor.

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15
Q

What causes a pump to be unbalanced?

A

As long as the inlet pressure and outlet pressure are different the pump is considered unbalanced.

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16
Q

What pressures do Vane Pumps run at?

A

3500-4000 PSI

17
Q

What are pressure plates within pumps used for?

A

To control the leakage rate and maintain better volumetric efficiency.

18
Q

What best describes a Fixed displacement pump?

A

Delivers a constant volume as long as there is constant input.

19
Q

How efficient are Vane Pumps?

A

92-95%

20
Q

What pressure does a Gear pump run at?

A

2500 PSI or less

21
Q

What is the typical volumetric efficiency of a Gear Pump?

A

85-87%

22
Q

How can a pump be described as balanced?

A

If the pump has 2 or more inputs and equal amounts of outputs, then the pump becomes balanced.

23
Q

What is the mechanical efficiency of a pump?

A

The power required to overcome internal friction.

24
Q

On a variable swash plate piston pump, what is the condition of the swash plate at maximum flow?

A

Maximum angle of the pump.

25
Q

What would a PSI G gauge read at sea level?

A

0 PSI

26
Q

What is the specific gravity of oil?

A

0.40 Pounds / Vertical Foot

27
Q

How does a variable vane pump change its displacement?

A

The cam ring is shifted to create larger or smaller pockets for the vanes to shuttle oil.

28
Q

What speed is required to enable a Vane Pump’s vanes to be thrown against the cam ring?

A

600 RPM

29
Q

How does a piston pump achieve pressure compensation?

A

A set of pistons act upon the swash plate to change the angle in relation to outlet pressure.

30
Q

What sort of pressures does a Piston Pump operate at?

A

3500-5000 PSI

31
Q

What is a rotating group in a piston pump?

A

The cylinder barrel, and pistons are called a rotating group.

32
Q

What are the three types of efficiency regarding Hydraulic Pumps?

A

Mechanical Volumetric Overall

33
Q

Why is a minimum and maximum operating speed of a pump given?

A

To provide adequate lubrication but prevent cavitation.

HET Period 3 Hydraulics (9 decks)

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