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HET3 Hydraulics 190301 > 190301h > Flashcards

Flashcards in 190301h Deck (20):
1

List three (3) sources of information that can be used as resources for technicians
troubleshooting hydraulic systems:

a) manufacturer service manuals
b) manufacturer service bulletins
c) operator's manuals

2

What is the best source of information about how a machine had been performing
prior to a failure?

the operator

3

List four (4) conditions that should be looked at when performing a visual inspection
of a hydraulic system.

a) hydraulic oil level and type
b) hydraulic oil condition
c) hydraulic oil leaks
d) signs of overheating

4

Hydraulic oil temperature is not an important factor to consider when performing
hydraulic tests.T/F

false;

5

It is useful to operate the machine as part of the troubleshooting process. List three
things that you should be looking for while operating:

a) machine response (slow, jerky)
b) smoothness of the controls (no binding)
c) unusual noises

6

Define the term actuator cycle time. ______

Actuator cycle time refers to the amount of time required for the actuator to complete
one cycle. For example, the time taken for an excavator bucket to move from the
fully dumped to the fully curled position is known as the bucket curl cycle time.

7

Actuator cycle times that are longer than manufacturers specifications normally
indicate:

excessive internal leakage.

8

You found that engine speed dropped excessively when performing a hydraulic stall
test on an open centre hydraulic system. The cause could be:
a) increased engine power.
b) lack of engine power.
c) the system relief valve is set too low.
d) none of the above responses are correct

lack of engine power.

9

List four (4) safety precautions that must be observed before installing hydraulic test
equipment.

a) Lower or mechanically secure all suspended loads.
b) Relieve the pressure from the hydraulic tank if the system is equipped with a
pressurized reservoir.
c) Relieve any static pressure that is trapped in the system.
d) Depressurize any accumulators in the system.

10

What is a snubber?

A snubber is an orifice that is placed in the inlet of a pressure gauge to dampen
pressure spikes that could damage the internal mechanism of the gauge.

11

Excessively low pressures measured at the pump inlet indicates that:
a) the pump inlet is restricted.
b) the pump driveshaft speed is too high.
c) the wrong oil is being used.
d) all of the above responses are correct.

all of the above responses are correct.

12

Excessively high neutral pressure in an open centre hydraulic system indicates that:

Excessive resistance in lines, fittings, directional control valve, filter or other return
line components.

13

When pressure testing a hydraulic system, you found working pressure to be
abnormally high. One cause for the high reading could be:

excessive friction or binding in the actuator or connecting linkages.

14

Low charge pressure in a closed circuit hydrostatic transmission could cause
_________________ damage to the hydrostatic pump

cavitation

15

The problem with a cylinder that heats up more rapidly than normal is:

the piston seals are leaking.

16

Internal leakage in a hydraulic motor can be quickly checked by measuring the
amount of oil flowing from the drain line when the motor is at full load.T/F

true

17

Three (3) disadvantages of testing a hydraulic system with a flowmeter are

a) Flowmeter testing of a hydraulic system is often more time consuming than
performing operational tests.
b) Connecting a flowmeter into a system requires that the system be opened up,
running the risk of contamination entering the system.
c) If the flowmeter was last used to test a system that has experienced a serious
failure, contamination may be passed on to other systems being tested.

18

When testing pump efficiency with a flowmeter, no load flow is found to be
significantly lower than specification. The most likely cause is that:

the pump inlet is restricted.

19

In order to perform circuit leakage tests with a flowmeter, the inlet of the flowmeter
is connected in series in the pump outlet line.T/F

false;

20

Why is it important to determine the root cause of a hydraulic system fault?

Determining the root cause of a hydraulic system fault and repairing it will prevent
the system from failing again shortly after the initial repair.