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Question 1

From the list below, select two (2) classifications that apply to pressure control
valves.

Answer 1

b) normally open

d) normally closed

Question 2

A normally closed pressure control will block the flow of oil through the valve when
system pressure overcomes valve spring force.T/F

Answer 2

false;

Question 3

For a pressure control valve, the difference between cracking and full flow pressure
is known as _________

Answer 3

pressure override.

Question 4

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

Answer 4

provides minimum pressure override.

Question 5

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

Answer 5

circuit relief valve.

Question 6

State three (3) safety precautions that must be observed when installing a pressure
gauge into a hydraulic system.

Answer 6

a) Depressurize the system before installing the gauge.
b) Select a pressure gauge approximately twice maximum system pressure.
c) Be sure all lines and fittings will withstand at least twice maximum system
pressure.

Question 7

A hand pump is sometimes used to test system relief valve pressure setting.T/F

Answer 7

false;

Question 8

Hydraulic accumulators perform the following four functions. They are:

Answer 8

a) energy storage
b) shock absorption
c) gradual pressure buildup
d) constant pressure maintenance

Question 9

List two (2) safety precautions that must be observed when working on hydraulic
systems that contain accumulators.

Answer 9

a) never use oxygen or compressed air in gas-charged accumulators
b) always discharge systems equipped with accumulators prior to performing
service

Question 10

State the function of an unloader valve.

Answer 10

An unloader valve allows full pump flow to return to the reservoir while maintaining
minimum pressure at the pump outlet.

Question 11

Which of the following components is not used in a closed centre hydraulic system
that is supplied with a fixed displacement pump?

Answer 11

a relief valve

Question 12

The unloader valve in a demand type hydraulic system that is supplied by tandem
fixed displacement pumps is open when:

Answer 12

the load on the system is high.

Question 13

A pressure reducing valve will block oil flow through the valve when pressure
upstream of the valve overcomes the valve spring.T/F

Answer 13

false;

Question 14

Two (2) functions of a sequence valve are:

Answer 14

a) to cause actions in a hydraulic system to occur in a certain order and
b) to maintain a predetermined minimum pressure in a primary function while a
secondary function is in operation.

Question 15

All backpressure valves are located in the:

Answer 15

the actuator return line.

Question 16

Care must be taken not to excessively restrict the flow from the rod end of a doubleacting
cylinder because

Answer 16

Pressure intensification may result in damage to system components.

Question 17

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

Answer 17

true

Question 18

A pressure compensated flow control valve maintains constant flow through the
valve by:

Answer 18

maintaining a constant pressure drop across its orifice.

Question 19

State the most appropriate flow control valve circuit for an application where the
actuator load changes direction and strength.

Answer 19

a meter out flow control circuit

Question 20

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

Answer 20

proportional flow control valve.

Question 21

What is the function of the priority flow control valve used in heavy equipment
steering systems?

Answer 21

The priority flow divider provides a relatively constant flow rate to the steering
system regardless of fluctuations in steering pressure or engine speed

Question 22

The 3 back pressure valves in the module are?

Answer 22

Counterbalance
Brake valve
Lock valves

Question 23

Counterbalance valve is a safety device used to control?

Answer 23

The lowering of a vertical load so it does not fall freely

Question 24

Counter balance valves do not work well with varying loads because?

Answer 24

Power is wasted opening valve when load is lighter than maximum
Static oil pressure in actuator may hold the valve open if max load is exceeded

Question 25

What is the purpose of the spring-loaded poppet valve in a bladder style gas accumulator?

Answer 25

Prevents the rubber bladder from being pushed through the port if the gas pressure becomes too high in relation to oil pressure in the oil chamber.

Question 26

What are 4 reasons accumulators are installed in heavy equipment hydraulic systems?

Answer 26

• energy storage,
• shock absorption,
• gradual pressure buildup and
• constant pressure maintenance.

Question 27

Unloader valves differ from relief valves in 2 ways:

Answer 27

• are always used in conjunction with a check valve and

* pilot pressure to open the unloader is sensed from the high pressure side of the check valve.

Question 28

What determines the actuator speed?

Answer 28

The internal capacity of the actuator and the input flow rate supplied to the actuator

Question 29

Define flow rate.

Answer 29

The function of the displacement and driveshaft speed of the hydraulic pump. Can be determined with a mathematical formula. Flow rate=Volume/Time.

Question 30

With an orifice in a circuit, where is pressure the lowest?

Answer 30

Pressure is always the lowest in the orifice.

Question 31

What is meant by the greater the drop, the greater the flow?

Answer 31

This is the pressure drop across the orifice.

Question 32

There are 3 things in total that determine the amount of oil that will flow through an orifice, name them.

Answer 32

The orifice size and shape.
The pressure drop across the orifice.
The viscosity of the oil.

Question 33

An orifice can be adjusted. T/F

Answer 33

True.

Question 34

What is required when you ned an accurate control of the actuator speed?

Answer 34

A pressure compensated flow control.

Question 35

Define compensator.

Answer 35

Normally closed pressure sensitive valve installed in parallel to carry away any flow that exceeds the regulated flow through the orifice.