Hydraulics Advanced

The difference between an unbalanced vane pump and a balanced vane pump is the

direction of rotation.

type of oil used.

inlet and outlet vanes.

number of inlet and outlet ports.

Correct! Wrong!

A pneumatic accumulator for most hydraulic systems is commonly pre-charged with

argon

air

nitrogen

oxygen

Correct! Wrong!

An open center hydraulic system can best be described as one in which

pump oil flow is not circulated until a demand is imposed with operator controls.

pump oil flow recirculates freely to the reservoir with controls in the neutral position.

pump oil flow is not unloaded to the reservoir in the neutral position.

the hydraulic storage tank does not have filters inside the tank.

Correct! Wrong!

In the illustration below, what type of hydraulic system is being illustrated?

An open center system.

a closed center system.

a non-positive displacement system.

a fixed displacement system.

Correct! Wrong!

A hydraulic system seems to be functioning normally in all other circuits within the system. However, a noticeably decreased free load hydraulic motor speed would most likely be caused by worn pump housing. What other possible cause must be checked?

low supply tank fluid level.

low of pump pressure.

decreased oil flow.

excessive pump pressure.

Correct! Wrong!

To evaluate a hydraulics system, when flow and pressure testing a piece of equipment, the flow rate is best defined as

a measure of the volume of fluid that passes a given point in a given time.

a measure of the speed of fluid that passes a given point in a given time.

the average speed of a fluid past a given point.

a rating of the viscosity of hydraulic oil while in motion past a given point.

Correct! Wrong!

In a system with a variable displacement pump, the volume of the fluid moved by the pump will

decrease when the system pressure drops.

stay the same when the system pressure drops.

decrease when system demand drops.

stay the same when system demand increases.

Correct! Wrong!

When replacing a hydraulic pump you should

make certain the new pump has the same rotation, flow and pressure ratings.

make sure the threaded holes are compatible or that adapters are available.

pour oil into the outlet of the pump to pre-charge and ensure initial lubrication.

all the above are correct.

Correct! Wrong!

Flow rate is best defined as

a measure of the volume (G.P.M.) of fluid that passes a given point in a given time.

a measure of the speed (velocity) of fluid that passes a given point in a given time.

the average speed of a fluid past a given point.

viscosity of liquids in motion.

Correct! Wrong!

The figure below indicates

gas charged accumulator.

air charged accumulator.

weight loaded accumulator.

spring loaded accumulator.

Correct! Wrong!

Causes of a "lack of hydraulic power to do the work" problem might well be the fault of

hydraulic pump, hydraulic motor or directional control valves.

engined, hydraulic pump or drive.

hydraulic pump, hydraulic motor or hydraulic actuators.

hydraulic pump , hydraulic actuators or directional control valve.

Correct! Wrong!

When testing a hydraulic system, technicians will monitor and test for

hydraulic fluid flow and pressure.

hydraulic fluid flow, temperature and cycle times.

hydraulic fluid flow and temperature.

hydraulic fluid flow, pressure, and temperature.

Correct! Wrong!

Flow meters have a load valve on them. Before starting the equipment to run tests, the load valve should be

turned to the fully applied position.

turned to the fully released position.

it depends on what you are testing for.

it can be left half way to be safe.

Correct! Wrong!

On most gear or vane hydraulic pumps, when checking the pumps efficiency, satisfactory pump flow at the rated pressure should be ___________ as high as the pump flow at zero pressure.

55%

65%

75%

85%

Correct! Wrong!

If a loader bucket drops slightly while holding a load, with control valve in neutral position, it might be caused by

control valve not centering properly.

oil leaking past cylinder packing''s or O-rings.

oil leaking past control valve or a relief valve.

all of the above

Correct! Wrong!

If pump is cavitating, it may be an indication of

a clogged inlet screen.

an improperly installed canister filter.

a damaged filter O-ring.

all of the above.

Correct! Wrong!

An indication of an internal hydraulic leak caused by an improperly seated main relief valve may show up as

lower fluid operating temperature.

normal fluid operating temperature.

increased system pressure.

decreased system pressure.

Correct! Wrong!

Hydraulic flow is created by:

gravity

difference in pressure.

resistance in the lines.

velocity of the fluid.

Correct! Wrong!

The device included in many hydraulic systems to help reduce noise, vibrations and shocks to the system is

an oil cooler.

a reservoir.

an accumulator.

a cylinder.

Correct! Wrong!

Most oil-to-water hydraulic coolers use the coolant from engine cooling system.

True

False

Correct! Wrong!

A certain level of internal leakage is permissible in some components of a hydraulic system.

True

False

Correct! Wrong!

To make a generalization, fixed displacement pumps are usually used in open-centre systems, while variable displacement pumps are used in closed-centre systems.

True

False

Correct! Wrong!

In a variable displacement axial piston pump, the distance the pistons can travel back and forth in their bores is controlled by

the volume of oil pumped

the angle of the swash-plate.

inlet check valves.

manual spring settings.

Correct! Wrong!

The three most common types of hydraulic motors are

fixed, variable, positive.

gear, vane, piston.

external, internal, radial.

positive, non-positive, radial.

Correct! Wrong!

The technical name for the rotary output of a hydraulic motor is

force.

load.

energy.

torque.

Correct! Wrong!

Which of the following is the most common cause of hydraulic pump and motor failure?

leaks in the system.

bad repair.

reducing operating limits.

dirty or poor quality fluid.

Correct! Wrong!

What is the effective area of the rod end of a hydraulic cylinder piston if the the piston diameter is 4 1/2" and the rod diameter is 1.125"?

14.9 sq. in.

10.59 sq. in.

8.94 sq. in.

13.18 sq. in.

Correct! Wrong!

The function of the bucket kick-out on a wheeled loader is to hold the bucket control lever in the rollback location position until the bucket reaches the correct digging position.

True

False

Correct! Wrong!

The main disadvantage of electricity controlled hydraulic systems is that they are

very expressive.

not able to provide variable speed control.

not very energy efficient.

operated on less than full system voltage.

Correct! Wrong!

Proximity switches are commonly used in wheel loader bucket kick-out and lift height control systems. When the detector plate is in close proximity to the switch, the switch is

energized.

grounded.

open.

closed.

Correct! Wrong!

The function of input devices in an electronically controlled hydraulic system is to

be the brain of the control system.

actuate the hydraulic components.

send electronic signal information to the ECU.

provide system self diagnosis.

Correct! Wrong!

An example of a typical reference voltage sensor that sends a constant voltage signal when energized is a

switch.

joystick.

potentiometer.

solenoid.

Correct! Wrong!

Proportional solenoids use a pulse width modulated signal to actuate because it

provides the most accurate action.

can move the solenoids to energize the hydraulics to partial flow.

provides an oscillating or dithering solenoid action.

is compatible with the signal generated by the joystick.

Correct! Wrong!

The main advantage of a pilot operated pressure control valve is that it

allows higher operating pressures.

allows higher flow rates.

provides minimum pressure override.

provides maximum pressure override.

Correct! Wrong!

A relief valve that limits the pressure in one branch of a hydraulic system is called a

pilot operated relief valve.

system relief valve.

pressure regulator valve.

circuit relief valve.

Correct! Wrong!

Which of the following components is NOT usually used in a closed centre hydraulic system that is supplied with a variable displacement pump?

a system relief valve.

an counter-balance valve.

an accumulator.

a closed centre directional control valve.

Correct! Wrong!

One of the primary purposes of a lock valve is to prevent the load from drifting due to leakage.

True

False

Correct! Wrong!

The flow control valve that splits a single flow among two or more circuits is called a

restrictor type flow control valve.

non-compensated flow control valve.

meter out flow control valve.

proportional flow control valve.

Correct! Wrong!

Auxiliary closed center directional control valves can be connected into an existing circuit closed centre system by connecting the auxiliary valve in

series.

parallel.

series-parallel.

tandem.

Correct! Wrong!

Constant horsepower open centre hydraulic systems maintain a constant power draw from the engine by varying

pump displacement proportional to the load on the system.

the pressure proportional to the load on the system.

the speed of the engine proportional to the load on the system.

pump flow rate proportional to actuator speed.

Correct! Wrong!

The identifying characteristic of a closed centre hydraulic system is

they are always equipped with a fixed displacement pump.

they are always equipped with a pressure compensated pump.

they are always equipped with an accumulator.

the directional control valves always block pump flow when it is in neutral.

Correct! Wrong!

Closed centre systems can be designed with either fixed or variable displacement pumps.

True

False

Correct! Wrong!

The difference between an open and closed circuit HST is that the path of oil flow between the pump and motor is interrupted by the reservoir in the open circuit.

True

False

Correct! Wrong!

The most commonly used form of HST in mobile equipment is a/an

open circuit system with a fixed displacement pump.

open circuit system with a variable displacement pump.

closed circuit system with a variable displacement, reversible pump.

closed circuit system with a fixed displacement pump.

Correct! Wrong!

On HST systems that are equipped with variable displacement motors, motor torque generation will

remain the same regardless of motor displacement.

be reduced as motor displacement is reduced.

be increased as motor displacement is reduced.

be reduced as motor displacement is increased.

Correct! Wrong!

A pilot control circuit is a low-pressure hydraulic circuit used to remotely operate a directional control valve.

True

False

Correct! Wrong!

Hydraulic oil temperature is not an important factor to consider when conducting hydraulic tests.

True

False

Correct! Wrong!

Actuator cycle times that are longer than manufacturers specifications normally indicate

excessive internal leakage.

excessive pressure drop.

excessive pressure.

insufficient pressure.

Correct! Wrong!

You found that engine speed dropped excessively when performing a hydraulic stall test on an open centre hydraulic system. The cause could be

increased engine power.

lack of engine power.

the system relief valve is set too low.

none of the above.

Correct! Wrong!

If you wanted to measure the maximum pressure in a hydraulic system that is designed to operate at a maximum pressure of 18MPa (2610 psig), you should use a pressure gauge with a range of:

0-18 MPa (2610 psig)

0-22 MPa (3142 psig)

0-30 MPa (4285 psig)

0-36 MPa (5142 psig)

Correct! Wrong!

Excessively low pressures measured at the pump inlet indicates that

the pump inlet is restricted.

the pump drive-shaft speed is to high.

the wrong oil is being used.

all of the above are correct.

Correct! Wrong!

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

excessive internal leakage.

slow cycle times.

excessive friction or binding in the actuator or connecting linkages.

system relief is set too high.

Correct! Wrong!

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

it is operating at excessive pressure.

the return line is restricted.

the system relief is set too high.

the piston seals are leaking.

Correct! Wrong!

When testing pump efficiency with a flow meter, the no-load flow is found to be significantly lower than specifications. The most likely cause is that

the pump inlet is restricted.

the pump is overloaded.

the flowmeter needs to be calibrated.

oil temperature is too low.

Correct! Wrong!

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

True

False

Correct! Wrong!

The difference between an unbalanced vane pump and a balanced vane pump is the

A pneumatic accumulator for most hydraulic systems is commonly pre-charged with

An open center hydraulic system can best be described as one in which

In the illustration below, what type of hydraulic system is being illustrated?

A hydraulic system seems to be functioning normally in all other circuits within the system. However, a noticeably decreased free load hydraulic motor speed would most likely be caused by worn pump housing. What other possible cause must be checked?

To evaluate a hydraulics system, when flow and pressure testing a piece of equipment, the flow rate is best defined as

In a system with a variable displacement pump, the volume of the fluid moved by the pump will

When replacing a hydraulic pump you should

Flow rate is best defined as

The figure below indicates

Causes of a "lack of hydraulic power to do the work" problem might well be the fault of

When testing a hydraulic system, technicians will monitor and test for

Flow meters have a load valve on them. Before starting the equipment to run tests, the load valve should be

On most gear or vane hydraulic pumps, when checking the pumps efficiency, satisfactory pump flow at the rated pressure should be ___________ as high as the pump flow at zero pressure.

If a loader bucket drops slightly while holding a load, with control valve in neutral position, it might be caused by

If pump is cavitating, it may be an indication of

An indication of an internal hydraulic leak caused by an improperly seated main relief valve may show up as

Hydraulic flow is created by:

The device included in many hydraulic systems to help reduce noise, vibrations and shocks to the system is

Most oil-to-water hydraulic coolers use the coolant from engine cooling system.

A certain level of internal leakage is permissible in some components of a hydraulic system.

To make a generalization, fixed displacement pumps are usually used in open-centre systems, while variable displacement pumps are used in closed-centre systems.

In a variable displacement axial piston pump, the distance the pistons can travel back and forth in their bores is controlled by

The three most common types of hydraulic motors are

The technical name for the rotary output of a hydraulic motor is

Which of the following is the most common cause of hydraulic pump and motor failure?

What is the effective area of the rod end of a hydraulic cylinder piston if the the piston diameter is 4 1/2" and the rod diameter is 1.125"?

The function of the bucket kick-out on a wheeled loader is to hold the bucket control lever in the rollback location position until the bucket reaches the correct digging position.

The main disadvantage of electricity controlled hydraulic systems is that they are

Proximity switches are commonly used in wheel loader bucket kick-out and lift height control systems. When the detector plate is in close proximity to the switch, the switch is

The function of input devices in an electronically controlled hydraulic system is to

An example of a typical reference voltage sensor that sends a constant voltage signal when energized is a

Proportional solenoids use a pulse width modulated signal to actuate because it

The main advantage of a pilot operated pressure control valve is that it

A relief valve that limits the pressure in one branch of a hydraulic system is called a

Which of the following components is NOT usually used in a closed centre hydraulic system that is supplied with a variable displacement pump?

One of the primary purposes of a lock valve is to prevent the load from drifting due to leakage.

The flow control valve that splits a single flow among two or more circuits is called a

Auxiliary closed center directional control valves can be connected into an existing circuit closed centre system by connecting the auxiliary valve in

Constant horsepower open centre hydraulic systems maintain a constant power draw from the engine by varying

The identifying characteristic of a closed centre hydraulic system is

Closed centre systems can be designed with either fixed or variable displacement pumps.

The difference between an open and closed circuit HST is that the path of oil flow between the pump and motor is interrupted by the reservoir in the open circuit.

The most commonly used form of HST in mobile equipment is a/an

On HST systems that are equipped with variable displacement motors, motor torque generation will

A pilot control circuit is a low-pressure hydraulic circuit used to remotely operate a directional control valve.

Hydraulic oil temperature is not an important factor to consider when conducting hydraulic tests.

Actuator cycle times that are longer than manufacturers specifications normally indicate

You found that engine speed dropped excessively when performing a hydraulic stall test on an open centre hydraulic system. The cause could be

If you wanted to measure the maximum pressure in a hydraulic system that is designed to operate at a maximum pressure of 18MPa (2610 psig), you should use a pressure gauge with a range of:

Excessively low pressures measured at the pump inlet indicates that

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

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

When testing pump efficiency with a flow meter, the no-load flow is found to be significantly lower than specifications. The most likely cause is that

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

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Heavy-Duty Mechanic - Trucks & Equipment