Practice Questions Flashcards
The displacement of a pump refers to?
The discharge rate per minute
Discharge rate per hour
Discharge rate per revolution
Discharge rate per cycle
Discharge rate per revolution
A Gear type hydraulic motor
Is not reversible
Has more shaft seal protection due to dual rotation
Is similar to a gear pump but contains three pressure plates
Will damage the shaft seal if reversed
Has more shaft seal protection due to dual rotation
A piston pump that has the pistons parallel to the drive shaft is called?
Non positive displacement pump
Axial Pump
Radial Pump
Bent Axis Pump
Axial Pump
Tandem section gear pumps
Always use two sections of equal size
are two pumps mounted together
always contain two inlets and outlets
Use adjustable gear sections to control output
Are two pumps mounted together
Variable Displacement pumps are
The volume can be altered per cycle
The speed of the pump can be altered
The pressure can be altered
The flow rate is fixed
The volume can be altered per cycle
Vane pumps may be
Positive displacement
Fixed displacement
Variable Displacement
All of the above
All of the above
The pressure that will just open a valve is called
Opening pressure
Main pressure
high pressure
cracking pressure
Cracking pressure
A valve section regenerative position
Allows a fast drop of crawler loader boom
Supplies the oil to rear mounted equipment
Connects the becket cylinder rod ends to the head ends for a fast dump
Returns the bucket cutting edge to a digging position
Connects the bucket cylinder rod ends to the head ends for a fast dump
A spool valve is used to control
Direction of oil flow
System Pressure
Accumulator pressure
None of the above
Accumulator Pressure
When installing hydraulic pumps, the inlet lines should be kept?
As long as possible
Have at least one bend to relieve pressure
As short and as straight as possible
In a slight curve to prevent cavitation
As short and as straight as possible
A Pump of unbalanced design is so named because
Its disproportioned weight will cause it to vibrate
There is a side load on the rotor and drive shaft
The design is not balanced to system needs
None of the above
There is side load on the rotor and driveshaft
Gear pumps
Use pressurized wear plates
Are variable displacement
Are always non positive displacement
Always use tapered bearings on the shaft
Use pressurized wear plates
What is the purpose of a cushion in a cylinder?
Provide a reserve of air
Eliminate fluctuation of pressure
Reduce mechanical shock
Prevent back pressure
Reduce mechanical shock
What is used for overload protection in a hydraulic system
The pump
The directional Control
the pressure control
The actuator
The pressure control
In any hydraulic circuit if only the actuator area is changed
the speed of operation will be changed
the minimum force exerted will be changed
the maximum pressure obtainable will be changed
the input horsepower will be changed
The speed of operation will be changed
Leakage from the housing drain port on axial piston pumps may not be caused by
Damaged drive shaft seal
Scored valve plate or cylinder block face
Cylinder Block Lifting
Return oil from a yoke control unit
Damaged drive shaft seal
In a variable radial piston pump, what controls the stroke of the pistons?
System Pressure
Case Pressure
Spring Pressure
Centrifugal Force
System Pressure
The maximum safe working pressure of a hydraulic system is reduced by
Installing a smaller pump
Changing relief valve setting
Installing a check valve
Installing a smaller motor
Changing a relief valve setting
If two directional control valves are connected in series in a hydraulic system
Both valves must be operated simultaneously
only one can be operated at a time
either one or the other or both can be operated
can not be hooked in series
Either one or the other or both can be operated
A detent mechanism is used to
Alert the operator be feel that they are in a certain position
Hold the spool in certain positions
hold the auxiliary valve in the raise position
none of the above
Hold the spool in certain positions
Fixed displacement motors have
Variable speed, variable torque
fixed torque fixed speed
fixed torque fixed displacement
fixed torque and speed controlled by system
Fixed torque
Fixed displacement
A stop tube
Allows fluid to move in one direction only
overrides pressure relief in case of reservoir loss
minimizes actuator side loads
limits swash plate angle in an axial piston pump
Minimizes actuator side loads
A valve that is used to coordinate the times of actuation is
Pressure Relief
Unloading Valve
Sequence Valve
Pressure Reducing
Sequence Valve
Hydraulic motors may be of the style
Variable speed
Fixed speed
Reversible speed
All of the above
All of the above
The purpose of a lift check is
To allow a fast drop of a cylinder
Prevent cavitation of the pump
Trap flow spikes in the valve
Stop a function from settling just before it starts to move
Stop a function from settling just before it starts to move
Piston type pumps
Have the lowest volumetric efficiency
May require supercharging in some applications
if variable displacement should not be operated too near the centre position when the inlet is pressurized
Are not used in high pressure applications
May require supercharging in some applications
A style of pump that has a device called a crescent is a?
Gear
Vane
Piston
Centrifugal
Gear Pump
The type of pump that cannot be made variable is?
Gear
Vane
Piston
All of the above
Gear Pump
Bent Axis Pump is a?
Gear
Vane
Piston
Centrifugal
Piston Pump
If you work on or replace a directional control valve you must
Be careful when tightening he mounting bolts
Drain and replace the hydraulic fluid
Also replace the pump
Use a lower viscosity oil during the break in period
Be careful when tightening the mounting bolts
The difference between the cracking pressure and the full flow is called
Pressure reducing
Pressure override
Pressure Relief
none of the above
Pressure override
Pressure compensated axial piston pumps have the following characteristics
Their displacement is automatically changed to meet system demands
They generate more heat in a system
Always require another relief valve
Displacement is controlled on both sides of the yoke position
Their displacement is automatically changed to meet system demands
A directional control valve is rated at 3/4”, this means that the valve is
3/4” High
Mounted with 3/4” Bolts
To be piped with a 3/4” Pipe
All of the above
To be piped with a 3/4” Pipe
When a restriction is placed on the return line of an advancing Cylinder, the results would be
System pressure on piston decreases
Tank PRessure increased
Force output of cylinder decreases
Force output of cylinder increases
Force output of cylinder decreases
The results of closing off the discharge side of a positive displacement pump would be?
Pump motor would stall
pump casing would split
pump discharge line would burst
all of the above
All of the above
In a valve section float position
The pump is connected to the piston end of a cylinder
The pump is connected to the rod end of a cylinder
Work ports, pump supply and return are connected so the cylinder may move freely
Both ends of the cylinder area are connected together to increase its extension speed
Work ports, pump supply and return are connected so the cylinder may move freely
An anti cavitation check valve
Stops a function from settling just before it starts to move
Opens to allow oil to fill an actuator when the pump supply is unavailable
Limits pressure peaks in the control valve then the circuit relief valve sticks
B and C
Opens to allow oil to fill an actuator when the pump supply is unavailable
A Minimum starting speed of 600 RPM is recommended for vane pumps
To avoid cavitation
to push the vanes into the rotor
To start pumping action
To prevent aeration
To start pumping action
Vane motors used on most industrial equipment
Do not contain spring loaded vanes
never use double edged vanes
usually use a replaceable cartridge
all of the above
Usually use a replaceable cartridge
A double vane cylinder exhausts oil through
External Drain lines
one way check valves
internal passages
directional control valves
Internal Passages
When two identical motors are connected in series they will develop
Same torque but different speeds
Same torque same speed
Different torques same speed
Different torques different speeds
Different torques
Same Speed
if a system is unable to function with full force the problem could be caused by
broken pump drive shaft
low pump flow
relief valve set too low
none of the above
Relief valve set too low
Shock Loads imposed upon motors may be safeguarded by?
Deceleration valves
Pressure relief valves
Accumulators
All of the above
All of the above
A valve used to divery oil to alternate end of a cylinder is
Pressure reducing valve
Check valve
Four Way Valve
Quick Drop Valve
Quick drop valve
Methods of varying the displacement of variable pumps is?
Moving the pressure ring in respect to the rotor
Varying the angle of bent axis pumps
Varying the stroke of piston pumps
All of the above
All of the above
Gear pumps are
Fixed displacement
Hydraulically unbalanced
Positive Displacement
All of the above
All of the above
An anti cavitation valve
Stops a function from settling just before it starts to move
Opens to allow oil to fill a cylinder when the pump supply is unavailable or inadequate
Limits pressure peaks in the control valve when the system relief valve sticks
B and C
Opens to allow oil to fill a cylinder when the pump supply is unavailable or inadequate
Centrifugal pumps are classed as?
Rotary pumps
Non positive displacement pumps
Axial Flow Pumps
Ram Pumps
Non Positive Displacement Pumps
According to your module a simple check valve can be considered a
Pressure Relief Valve
Directional Control Valve
None of the above
Both A and B
Directional control valve
Hydraulic pumps are usually rated in terms of their?
Mechanical and Hydraulic output
Volumetric input and pressure
Volumetric output and pressure
Mechanical input and pressure
Volumetric output and pressure
A defective shaft seal in an internally drained vane pump will
Leak oil when the pump is running
Have no effect on pump operation
keeps air from entering the system
Make the pump noisy
Makes the pump noisy
Directional Control Valves may be operated
Manually
Mechanically
Electrically
All of the above
All of the above
The relief valve in a hydraulic system relieves excess pressure by
Venting to atmosphere
By-passing the fluid to the reservoir
By-passing the fluid to the pump discharge
Venting to the fluid cooler
Venting to the fluid cooler
When a lower than main pressure is required in a secondary circuit the type of valve that would be used is a
Relief valve
sequence valve
Check valve
Pressure reducing valve
Pressure reducing valve
To vent a pressure relief valve means that
The valve is uncoupled from the circuit
The valves pilot pressure is increased
The valves pilot pressure is decreased
The valves pilot pressure is returned to tank
The valves pilot pressure is returned to tank.
An unloader valve
is always set at least 150 psi above relief
is held open by spring pressure
is the only valve that can replace a relief valve
controls slowing down of the load
Is the only valve that can replace a relief valve
The speed at which a cylinder moves is controlled by?
The pump
the pressure control
the pump or flow control
the flow control
The pump or flow control
Reversing drive shaft rotation of axial piston pumps
May require a relative change in the valve plate or sub assembly
Will change oil flow direction through the pump unless yoke is moved to opposite side of centre
Should not be tried ever
Can only be done on variable displacement units
May require a relative change in the valve plate or sub assembly
The swash plate pump is a?
Gear
Vane
Piston
Centrifugal
Piston Pump
The time taken for a cylinder to make a definite stroke is dependent upon the
Pump output and piston area
pump pressure output and length of stroke
pump volume output stroke length and piston area
pump volume output and length of stroke
Pump volume output stroke length and piston area
Flow direction through a variable displacement piston type pump is affected by
Direction of drive rotation
Angle of degrees of yoke displacement from centre position
Yoke position one side to the other of centre
Drive shaft speed in RPM
Yoke position one side to the other of centre
Single section gear pumps do not
contain a driving gear
contain an idler gear
contain pressure plate
have external drains
Have external drains
Which of the following pumps could not be operated as a variable displacement pump with a fixed speed?
Vane
Radial Piston
Gear
Axial Piston
Gear Pump
Circular grooves cut around the valve spool
Serve no purpose
Allow lubrication and sealing of the spool
allow metering of a function
Match the edges of the bore lands to decrease pressure peaks
Allow lubrication and sealing of the spool
A Fixed Displacement Motor
Provides a variable torque regardless of speed
Provides constant torque regardless of pressure
May be reversed by reversing oil flow to and from motor
Should not be used in a closed loop
May be reversed by reversing oil flow to and from motor
When it is required to allow flow in one direction and prevent flow in the opposite direction we would use a
Relief Valve
Sequence Valve
Check Valve
Reducing Valve
Check Valve
The main pressure relief valve in a hydraulic system is located
in the main line to the cylinder
in the oil return line
in the pump suction line
between the pump and the control valve
Between the pump and the control valve
Air in a hydraulic pump causes?
Smoother operation
Cooler operation
Better operation
Noisy operation
Noisy Operation
What type of valve is used to control a double acting cylinder?
Two Way Valve
Glove Valve
Four Way Valve
Three Way Valve
Four way Valve
Oil flow through an open centre control valve when in the neutral position
Returns to the reservoir
is at a pressure as low as possible
is routed through the valve so that all spools can recieve oil
All of the above
All of the above
A Meter in valve is classified as
Pressure control device
Flow control device
Both flow and pressure control device
None of the above
Flow control device
Hydraulic pumps are devices used to?
Convert mechanical energy to electrical
Convert Hydraulic energy to electrical
Convert Hydraulic energy to mechanical energy
Convert mechanical energy into hydraulic energy
Convert mechanical energy into hydraulic energy
Balanced Vane Pumps rated output flow in fallons per minute is determined by
Rise in cam ring
Width of pumping cartridge
Drive shaft rated speed
All of the above
All of the above
Where fixed output pumps are used, a method of controlling the speed of actuators is by means of?
Meter in valves
Meter out valves
Bleed off valves
All of the above
All of the above
A Non positive displacement pump refers to a type of pump
Where the inlet must be higher than the outlet
Where the outlet must be lower than the inlet
Which will slip the liquid at a certain pressure
Which will not slip the liquid at a certain pressure
Which will slip the liquid at a certain pressure
A Pressure relief valve will operate because
Pressure are equal over equal areas
Pressures are unequal over unequal areas
Pressures are unequal over equal areas
A spring setting has been reached or overcome
A spring setting has been reached or overcome
A pump that could be used without a pressure relief valve is?
vane pump fixed displacement
Manually controlled variable displacement vane pump
Fixed displacement Gear Pump
Pressure Compensated, Variable displacement, Piston Pump
Pressure Compensated, Variable Displacement Piston Pump
A Hydraulic cylinder is known as
Torque Converter
Rotary Actuator
Linear Actuator
All the above
Linear Actuator
As the speed at which a pump is driven changes
Its displacement changes
its pressure changes
its swash plate angle changes
its volume changes
Its volume changes
A Directional control valve is categorized in two types
Low and medium pressure
medium and high pressure
Spool and Rotary
Check and Relief
Spool and rotary
The purpose of the swash plate in an axial piston pump is
to adjust pump pressure
to open and close the discharge ports
Change pump displacement
Change pump speed
Change Pump Displacement
Horsepower required at 83% to drive a hydraulic pump is?
Gallons Per Min X PSI X 0.000583
Gallons Per Min X PSI X 0.00583
Gallons Per Min X PSI X 0.007
Gallong Per Min X PSI X 0.0007
All of the above
A Power beyond feature
Allows a second control valve to receive oil when the system control is in neutral
Allows a second control valve to receive oil through the main system control valve at all times
Supplies pressure oil to the crawler dozer selected valve
None of the above
Allows a second control valve to receive oil when the system control is in neutral
Two gear pumps placed in series will
Affect the pressure
Affect the flow
Not work unless mounted within 2” of tank
None of the above
Affects the pressure
A Piston pump that has the pistons arranged at right angles to the drive shaft is called?
Non Positive Displacement Pump
Axial Pump
Radial Pump
Bent Axis Pump
Radial Pump
A Positive displacement pump refers to a type of pump where?
The liquid is discharged by a flexible delivery hose
The inlet of the pump is sealed from pump discharge
The inlet of the pump is a flexible hose
The inlet is not sealed from the outlet
The inlet of the pump is sealed from pump discharge
Single direction hydraulic motor is usually controlled by
Two way two position
Two way four position
Four way two position
Four way four position
Four way
Two Position
When two identical hydraulic motors on the same output shaft are connected in parallel with each other they will develop
Twice the speed and twice the torque
Half the speed and half the torque
Twice speed half torque
Half speed Twice torque
Half the speed
Twice the Torque
When a telescoping cylinder actuates it usually has
The smallest diameter piston first
The largest diameter piston first
All the pistons at the same time
None of the above
The largest piston first
When it is required to allow a pump to run when the system is not being used, it is useful to fit a ___________ valve in the system
Relief
Sequence
Unloading
Reducing
Unloading
Jerky or erratic motion in a hydraulic cylinder is usually due to
Presence of water in system
Presence of air in system
presence of oil in system
synthetic fluids are being used
Presence of water in system
An accepted point of control valve leakage is
Between the valve spool and its bore
relief valve seats
anti cavitation check valve seats
circuit relief valve o rings
Between the valve spool and its bore
On a axial piston pump, which statement does not apply?
Excessive valve plate or cylinder block wear may cause cylinder block lift
Replenishing pumps are required on all piston unit circuits
The housing drain port should be piped in such a way that the case is always full of oil
The housing or case of a piston unit should be filled with oil before it is operated
Replenishing pumps are required on all piston unit circuits
A reversible hydraulic motor that is required to coast or free wheel in the neutral position is usually controlled by
Three position, four way open centre valve
Four position, four way closed centre valve
Four position, three way tandem centre valve
Three position, four way tandem centre valve
Three position
Four way
Open centre valve
The force output of a conventional cylinder is the greatest when
The piston is advancing
the piston is retracting
the cylinder is mounted horizantally
the cylinder is mounted vertically
The piston is advancing
The volumetric efficiency of a vane pump
Increases with an increase in drive shaft RPM within recommended operation range.
remains constant under all operating conditions
decreases as oil temperature decreases
Increases with an increase in drive shaft RPM within
Delivery in a Gallons per minute of a variable displacement piston type pump is affected by?
Direction of driveshaft rotation
Angle of degrees of yoke displacement from centre position on the same side
Yoke position, one side or other of centre on same angle
The size of the drain line hose
Angle of degrees of yoke displacement from centre position on the same side
A restricted hydraulic pump suction line
Cut down pump oil intake without damage
Damages the pump
Causes excessive oil back pressure
Blow out the filter gasket
Damages the pump
Notches or holes in a valve spool land
Allow the operator to precisely meter or feather oil to a cylinder
Restrict the flow of oil to a circuit relief valve
Allows the gradual stoppage of oil through the valve center which limits pressure peaks
All of the above
Allow the operator to previsely meter or feather oil to a cylinder
