301H: Hydraulic System Testing & Service Flashcards
List three sources of information that can be used as resources for technicians troubleshooting hydraulic systems:
- Manufacturer service manuals
- Manufacturer service bulletins
- Operator’s manuals
301H Pg. 3
What is the best source of information about how a machine had been performing prior to a failure?
The operator
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What conditions should be looked at when performing a visual inspection of a hydraulic system?
- Hydraulic oil level and type
- Hydraulic oil condition
- Hydraulic oil leaks
- Signs of overheating
- Damaged cylinders
301H Pg. 4
It is useful to operate the machine as part of the troubleshooting process. List three things that you should be looking for while operating:
- Machine response (slow, jerky)
- Smoothness of the controls (no binding)
- Unusual noises
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Actuator cycle times that are longer than manufacturers specifications normally indicate:
Excessive internal leakage.
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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
B) Lack of engine power
301H Pg. 11
List four safety precautions that must be observed before installing hydraulic test equipment.
- Lower or mechanically secure all suspended loads.
- Relieve the pressure from the hydraulic tank if the system is equipped with a pressurized reservoir.
- Relieve any static pressure that is trapped in the system.
- Depressurize any accumulators in the system.
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What is a hydraulic snubber?
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.
Three Types:
- Porous Element
- Metering Pin
- Threaded Plug
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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.
D) All of the above responses
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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.
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When pressure testing a hydraulic system, you found working pressure to be abnormally high. One cause for the high reading could be:
a) excessive internal leakage
b) slow cycle time
c) excessive friction or binding in the actuator or connecting linkages
d) system refief valve is set too high
c) Excessive friction or binding in the actuator or connecting linkages
301H Pg. 18
Low charge pressure in a closed circuit hydrostatic transmission could cause what type of damage?
Cavitation
301H
The problem with a cylinder that heats up more rapidly than normal is:
a) Operating at excessive pressure
b) Return line restricted
c) System relief valve is set too high
d) Piston seals leaking
D) Piston seals are leaking
301H Pg. 22
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
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Three disadvantages of testing a hydraulic system with a flowmeter are:
- Flowmeter testing of a hydraulic system is often more time consuming than performing operational tests.
- Connecting a flowmeter into a system requires that the system be opened up, running the risk of contamination entering the system.
- 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.
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When testing pump efficiency with a flowmeter, no load flow is found to be significantly lower than specification. The most likely cause is that:
a) Pump inlet restricted
b) Pump is overloaded
c) Flowmeter needs calibrating
d) Oil temperature is too low
A) Pump inlet is restricted
301H
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
In parellel for Tee Test
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How is pump efficiency calculated?
Full load flow rate / No load flow rate
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Flowmeters can be connected to a hydraulic system to test pump efficiency. What two connection configurations could be used?
Bypass: Pump oil bypasses all other system components
Inline: Pump oil through flowmeter continues through the regular system
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What pump efficiency test connection method has the flowmeter inlet receive all the system’s oil flow and has the outlet connected directly to the reservoir?
Bypass Connection
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What pump efficiency test connection method has the oil flow through the flowmeter and return back to the system to be used?
Inline Connection
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How would a flowmeter be connected into a hydraulic system to measure circuit leakage?
Tee Test / Parallel
301H Pg. 29