Hydraulic Pump Fundamentals 190301b

Question 1

The hydraulic pump converts___________ into ___________

Answer 1

Mechanical energy into hydraulic energy.

Question 2

Three types of piston pumps are:

Answer 2

1. Axial
2. Bent Axial
3. Radial

Question 3

Explain fixed displacement pumps:

Answer 3

The volume of oil delivered in one revolution will be the sum of the capacities of all gears, vanes or pistons.

Capacity of each, gear, bane or piston cannot be changed therefore it is “fixed”

Question 4

Explain variable displacement pumps:

Answer 4

Gear pumps cannot be variable.

Vane pumps change their displacement using a bias spring/piston to move the cam ring.

Piston pumps use a bias spring/piston or a servo to change the angle of the swash plate.

Question 5

Two types of radial piston pumps are:

Answer 5

1. Rotating cam

2. Rotating piston

Question 6

Mechanical efficiency is ?

Answer 6

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

Question 7

Volumetric efficiency is ?

Answer 7

How effectively a hydraulic pump generates flow.

Question 8

Overall efficiency is ?

Answer 8

Comparing input power with power delivered by the pump.

Question 9

Pumps that operate in one direction only are called ?

Answer 9

Unidirectional.

Question 10

Which is port is bigger inlet or outlet ?

Answer 10

Inlet port

low pressure

Question 11

Which port is smaller, outlet or inlet ?

Answer 11

Outlet port

(High pressure)

Question 12

What purpose does the pressure plates serve ?

Answer 12

To maintain good volumetric efficiency as the outlet pressure builds.

Question 13

What are two common and 2 other types of vane blades ?

Answer 13

1. Angled tip (common)
2. Rounded tip ((common) also bi directional)
3. Spring loaded
4. Intra vane

Question 14

Two forces acting on the vanes while the pump is running are ?

Answer 14

1. Centrifugal force.

2. Outlet oil pressure ported to the underside of the vane.

Question 15

When the internal volume of a hydraulic pump increases, the pressure:

Answer 15

Decreases.

Question 16

Oil is forced out of the pump when the volume of the pumping chamber is:

Answer 16

Decreased.

Question 17

Pumps that have a constant pumping chamber volume are?

Answer 17

Fixed displacement.

Question 18

Pumps that can change their pumping capacities are ?

Answer 18

Variable displacement.

Question 19

A reversible pump is able to do what ?

Answer 19

Reverse the direction of oil flow through the pump.

Question 20

Three things that makeup pump efficiency are:

Answer 20

1. Mechanical efficiency.
2. Volumetric efficiency
3. Overall efficiency.

Question 21

As pump outlet pressure increases, the pump’s__________ increases as well.

Answer 21

Internal leakage.

Question 22

Internal leakage in a pump does what ?

Answer 22

Lubricates moving parts in the pump.

Question 23

Two things that determine the amount of internal leakage in a pump are:

Answer 23

1. The pressure difference between the pump inlet and outlet ports.
2. The amount of internal clearances within the pump.

Question 24

A unidirectional pump driven opposite to its intended direction will:

Answer 24

Have the flow through the pump reversed.

Question 25

What shape cam rings are used in balanced and unbalanced vane pumps ?

Answer 25

Unbalanced: cam ring is circular.

Balanced: cam ring is elliptical.

Question 26

How does a variable displacement vane pump change its displacement ?

Answer 26

By changing the eccentricity between the rotor and cam ring centres.

Question 27

Two forces that act on the vanes is a typical vane pump?

Answer 27

1. Centrifugal force.

2. Outlet pressure acting on the bottom of the vane.