Pump Fundementals

Question 1

A hydraulic pump converts what forms of energy

Answer 1

Mechanical to Hydraulic

Question 2

What is basic pumping principle

Answer 2

As internal volume increases a low pressure area is created, vice versus on high side

Question 3

What happens if a pump is oversped

Answer 3

Cavitation, the inlet does not have time to fill before the pocket is closed off

Question 4

Volumetric effieciency

Answer 4

Expresses how effectively a hydraulic pump generates flow. calculated by comparing theoretical flow rate and actual flow

Question 5

Advantages of external gear pump

Answer 5

Cheap
More tolerant of contamination
Least complex

Question 6

Unbalanced pumps

Answer 6

When the inlet and the outlet are opposite each other causing the high pressure to push the internal components toward the inlet

Question 7

Uni-directional pump

Answer 7

The pump can only be rotated in one direction

Question 8

On a bi-directional pump what happens if the high pressure check valve leaks

Answer 8

Pump flow will go down as oil is returning to the inlet

Question 9

Intra vane

Answer 9

High pressure oil is pumped into the intra vane pocket at all times
Underside of vane has pocket pressure behind it

Question 10

Vane cam ring

Answer 10

Round will be a un-balanced design
Elliptical will be a balanced design
Vertical holes in ring are connected to the inlet to ensure pump receives sufficient oil

Question 11

To change the direction of a vane pump the cam ring will appear to have rotated ______ degrees

Answer 11

90

Question 12

Vane pump compensator

Answer 12

Compensator spring pushes cam ring to max flow, as outlet pressure increases it pushes the cam ring back towards the compensator spring, deceasing the change in pocket size

Question 13

Vane pump vane tips

Answer 13

Angled are uni-directional

Round, double angle and square are bi-directional

Question 14

The wear in a unbalanced vane pump will show where

Answer 14

The shaft bushings

Question 15

Where should case drain be located on a axial piston pump?

Answer 15

Between 10 and 2

Housing will be over half full to maintain lube (bath lube)

Question 16

The drive shaft of a bent axis piston pump is supported by?

Answer 16

Double taper roller bearing

Question 17

A pump termed reversible is able to

Answer 17

Reverse the direction of oil flow through the pump

Question 18

What are pressure plates used to do in a vane pump

Answer 18

Control the rotor side clearance

Question 19

What is utilized to keep vanes forced against the cam ring

Answer 19

Centrifugal force
High side pressure inside intra vane pocket
pocket pressure acting on backside of vane

Question 20

Radial cam piston pump

Answer 20

Pistons have a dual check system one allows oil to be drawn in from inlet manifold on down stroke, on up stroke intake ball closes and the outlet ball opens and oil goes out to high pressure manifold

Question 21

Variable displacement radial cam piston pump

Answer 21

High pressure oil is pumped into housing and holds pistons up reducing the effective stroke of the piston

Question 22

The 2 factor that determine the amount of internal leakage in a pump are?

Answer 22

Pressure difference between inlet and outlet

Amount of internal clearance

Question 23

What 2 forces act on the vanes of a typical vane pump

Answer 23

Outlet pressure oil

Centrifugal

Question 24

Pressure plates in vane pumps are used to control what

Answer 24

Rotor side clearance

Question 25

Comparing input power to output power of a pump is what eff.

Answer 25

Overall

Question 26

As a pumps outlet pressure increases what happens to leakage

Answer 26

Increase

Question 27

A hydraulic control system that copies the movement of the control lever is called a

Answer 27

Servo system