19301b

Question 1

3 major types of pumps?

Answer 1

Gear, Vane, piston

Question 2

Hydraulic pumps convert what types of energy?

Answer 2

Mechanical to hydraulic

Question 3

The volume of hydraulic oil delivered in one revolution of the pumps drive shaft is called?

Answer 3

Pumps displacement

Question 4

Define a fixed displacement pump.

Answer 4

Constant pumping chamber volume delivering the same amount of fluid every revolution. (with constant input rpm)

Question 5

Define a variable displacement pump.

Answer 5

Pump that is able to change the volume of its pumping chamber by movement of a cam ring or swash plate

Question 6

How do reversible variable displacement pumps work?

Answer 6

The swash plate is able to move in either direction from zero location. Most commonly seen as a hydrostatic transmission

Question 7

A pumps max flow rate is directly proportional to?

Answer 7

The speed at which it is driven

Question 8

Pump efficiency is categorized into three sections, what are they?

Answer 8

Mechanical efficiency
Volumetric efficiency
Overall efficiency

Question 9

Define mechanical efficiency.

Answer 9

The amount of power required to overcome the internal friction of the pump

Question 10

Define volumetric efficiency

Answer 10

How effectively a hydraulic pump generates flow by comparing a pumps theoretical and actual flow rate.

Question 11

What is slip?

Answer 11

Oil leaking from the outlet/pressure side of a hydraulic pump to the inlet/low pressure side of the pump.

Question 12

Define overall efficiency

Answer 12

Overall efficiency accounts for both mechanical and flow losses within the pump

Question 13

What are some advantages of an external gear pump?

Answer 13

Least complex
Less expensive
More rugged

Question 14

Disadvantages of an external gear pump

Answer 14

Lowest max operating pressure

No variable displacement designs

Question 15

Advantages of a vane pump?

Answer 15

Increased precision makes it more efficient and able to operate at higher pressures

Can be built variable

Question 16

Disadvantages of vane pumps?

Answer 16

More expensive

More susceptible to contamination damage

Question 17

What is the purpose of a pressure plate?

Answer 17

Keeps internal clearances to a minimum in order to maintain good pump efficiency

Limits internal leakage

Question 18

Purpose of rotor in a vane pump?

Answer 18

Splined to the drive shaft and slotted to hold vanes

Question 19

Excessive leakage of the vanes will do what?

Answer 19

Lower pump efficiency

Question 20

What two forces are acting on the vane during pump operation?

Answer 20

Centrifugal force

Outlet oil pressure

Question 21

Are elliptical cam vane pumps balanced or unbalanced?

Answer 21

Balanced pump and fixed displacement

Question 22

What is the difference between balanced and unbalanced vane pumps?

Answer 22

Balanced vain pumps have a fixed displacement and pressure is equal on both sides of the rotor.

Unbalanced vane pumps can be variable displacement and have higher pressure acting on one side of the rotor

Question 23

Intervane have what pressure acting on the vane at all times?

Answer 23

Outlet pressure

Question 24

Can vane pumps flow direction be changed without driveshaft rotational change?

Answer 24

Yes, if the cam ring can be flipped over

Question 25

What are the 3 common types of piston pumps?

Answer 25

Radial

Axial

Bent axis

Question 26

What are the two designs of radial piston pumps?

Answer 26

Rotating cam

Rotating piston pump

Question 27

Are radial piston pumps fixed or variable displacement?

Answer 27

Both

Question 28

The cylinder barrel and pistons in an axial piston pump is often referred to as?

Answer 28

Rotating group

Question 29

How are the pistons balanced in an axial piston pump design?

Answer 29

Oil in the chamber acts against oil sitting under the shoe and ball creating a cancelling force