Alberta Individual Learning Modules - 190103i Flashcards
Test
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?
94%
135 cm³ x 2000 rpm
_____________________ = 270
1000 (metric constant)
1000 cm³ = 1 Litre
254/270 = 0.94 = 94%
As pump outlet pressure increases, the pump’s internal leakage decreases. (True or False)
False.
As pump outlet increases, the pump’s internal leakage also increases.
Why is some internal leakage necessary within all hydraulic pumps?
Internal leakage lubricates moving pump parts.
The two (2) factors that determine the amount of internal leakage in a pump are:
1) the pressure between the pump inlet and outlet ports.
2) the amount of internal clearances within the pump.
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
d) cavitation
The hydraulic pump converts __________ energy to __________ energy.
mechanical
hydraulic
A hydraulic pump creates pressure. (True or False)
False.
The hydraulic pump does not create pressure; it creates FLOW. The resistance to pump flow creates pressure.
The most important characteristic of a non-positive displacement pump is that ____________.
inlet and outlet pressure ports are hydraulically connected.
Which of the following is a non-positive displacement pump?
a) gear pump
b) vane pump
c) piston pump
d) engine water pump
d) engine water pump
The main advantage of a positive displacement pump over a non-positive displacement pump is that ____________.
flow does not decrease significantly as pressure increases.
The two (2) factors that affect pump flow rate are ______ ______ and ______ ______ ______.
pump displacement
input shaft speed
Pump displacement refers to ______________.
the volume of liquid that a pump delivers in one revolution.
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
c) 150 L/min
100 cm ³ x 1500 rpm
_____________________ = 150
1000 (metric constant)
1000 cm³ = 1 Litre
The term used to express the amount of power required to overcome a pump’s internal friction is _______ _______ .
mechanical efficiency
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
c) 262.2 L/min
285 x 0.92 = 262.2
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.
a) inlet pressure fall too low.
Pump inlet pressure is affected by ____ ____ ____ and ____ ____ ____.
pump inlet restriction
pump drive speed
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.
b) air leakage on the inlet side of the pump
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.
a) first stage is extended
Double-acting hydraulic cylinders differ from single-acting cylinders in that they ________________.
hydraulically extend and retract.
Identify the inlet and outlet ports of the external gear pump.
Left is _____. Right is _____.
Left is inlet
Right is outlet
In its normal position, a normally closed pressure controlled valve blocks oil flow from its inlet port to its outlet port. (True or False)
True.
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.
a) cracking pressure.
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.
b) full flow pressure.
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.
a) hydraulically actuate in one direction.
Single-acting hydraulic cylinders are returned by:
a) hydraulic power.
b) air pressure.
c) some external force.
d) vacuum.
c) some external force.
