Alberta Individual Learning Modules - 190103i

Question 1

A hydraulic pump with a displacement of 135cm³/rev is driven at 2000 rpm. A flowmeter installed in the pump outlet indicates that the pump delivers 254 L/min. What is the pump’s volumetric efficiency?

Answer 1

94%

135 cm³ x 2000 rpm
_____________________ = 270

1000 (metric constant)

1000 cm³ = 1 Litre

254/270 = 0.94 = 94%

Question 2

As pump outlet pressure increases, the pump’s internal leakage decreases. (True or False)

Answer 2

False.

As pump outlet increases, the pump’s internal leakage also increases.

Question 3

Why is some internal leakage necessary within all hydraulic pumps?

Answer 3

Internal leakage lubricates moving pump parts.

Question 4

The two (2) factors that determine the amount of internal leakage in a pump are:

Answer 4

1) the pressure between the pump inlet and outlet ports.

2) the amount of internal clearances within the pump.

Question 5

The most common cause of pitted erosion on the internal surfaces of the pump is:
a) overloading
b) contamination
c) lack of lubrication
d) cavitation

Answer 5

d) cavitation

Question 5

The hydraulic pump converts __________ energy to __________ energy.

Answer 5

mechanical

hydraulic

Question 6

A hydraulic pump creates pressure. (True or False)

Answer 6

False.

The hydraulic pump does not create pressure; it creates FLOW. The resistance to pump flow creates pressure.

Question 7

The most important characteristic of a non-positive displacement pump is that ____________.

Answer 7

inlet and outlet pressure ports are hydraulically connected.

Question 8

Which of the following is a non-positive displacement pump?

a) gear pump
b) vane pump
c) piston pump
d) engine water pump

Answer 8

d) engine water pump

Question 9

The main advantage of a positive displacement pump over a non-positive displacement pump is that ____________.

Answer 9

flow does not decrease significantly as pressure increases.

Question 10

The two (2) factors that affect pump flow rate are ______ ______ and ______ ______ ______.

Answer 10

pump displacement

input shaft speed

Question 11

Pump displacement refers to ______________.

Answer 11

the volume of liquid that a pump delivers in one revolution.

Question 12

A 100 cm³/rev pump that is driven at 1500 rpm produces a flow rate of:

a) 15 L/min
b) 100 L/min
c) 150 L/min
d) 1000 L/ min

Answer 12

c) 150 L/min

100 cm ³ x 1500 rpm
_____________________ = 150

1000 (metric constant)

1000 cm³ = 1 Litre

Question 13

The term used to express the amount of power required to overcome a pump’s internal friction is _______ _______ .

Answer 13

mechanical efficiency

Question 14

The theoretical flow rate of a pump is 285 L/min. What is the pump’s actual flow rate if the pump has a volumetric efficiency of 92%?

a) 22.8 L/min
b)228 L/min
c) 262.2 L/min
d) 547.2 L/min

Answer 14

c) 262.2 L/min

285 x 0.92 = 262.2

Question 15

Cavitation occurs in a hydraulic pump when:

a) inlet pressure falls too low.
b) inlet pressure is too high.
c) outlet pressure is too low.
d) outlet pressure is too high.

Answer 15

a) inlet pressure fall too low.

Question 16

Pump inlet pressure is affected by ____ ____ ____ and ____ ____ ____.

Answer 16

pump inlet restriction

pump drive speed

Question 17

The most common cause of hydraulic pump aeration is:

a) air leakage on the outlet side of the pump
b) air leakage on the inlet side of the pump.
c) inlet pressure that is too low.
d) outlet pressure that is too high.

Answer 17

b) air leakage on the inlet side of the pump

Question 18

When a three-stage telescoping hydraulic cylinder is operated, the greatest force is generated when the:

a) first stage is extended
b) second stage is extended.
c) third stage is extended.
d) cylinder is retracted.

Answer 18

a) first stage is extended

Question 19

Double-acting hydraulic cylinders differ from single-acting cylinders in that they ________________.

Answer 19

hydraulically extend and retract.

Question 20

Identify the inlet and outlet ports of the external gear pump.
Left is _____. Right is _____.

Answer 20

Left is inlet

Right is outlet

Question 21

In its normal position, a normally closed pressure controlled valve blocks oil flow from its inlet port to its outlet port. (True or False)

Answer 21

True.

Question 22

The term that describes the pressure when a direct-acting, normally closed pressure relief valve initially begins to open is:

a) cracking pressure.
b) full flow pressure.
c) pressure override.

Answer 22

a) cracking pressure.

Question 23

The term that describes the pressure when a direct-acting, normally closed pressure relief valve is fully open is:

a) cracking pressure.
b) full flow pressure.
c) pressure override.

Answer 23

b) full flow pressure.

Question 24

Single-acting hydraulic cylinders:

a) hydraulically actuate in one direction.
b) hydraulically actuate in two directions.
c) have two work ports.
d) have three work ports.

Answer 24

a) hydraulically actuate in one direction.

Question 25

Single-acting hydraulic cylinders are returned by:

a) hydraulic power.
b) air pressure.
c) some external force.
d) vacuum.

Answer 25

c) some external force.