Hydraulic Valve II Part A

Question 1

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

a. open center
b. normally open
c. normally closed
d. pressure compensated

Answer 1

b. normally open

c. normally closed

Question 2

For a pressure control valve, the difference between cracking and full flow pressure is kown as ______.

Answer 2

pressure override.

Question 3

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

Answer 3

d. circuit relief valve.

Question 4

A hand pump is sometimes used to test system relief valve pressure setting.
True
False

Answer 4

false

Question 5

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

Answer 5

Never use oxygen or compressed air in a gas charged accumulator.
Always discharge systems equipped with an accumulator prior to performing service.

Question 6

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

a. fixed displacement pump
b. a relief valve
c. an unloader valve
d. an accumulator
e. a closed center directional control valve.

Answer 6

b. a relief valve.

Question 7

A pressure reducing valve will block oil flow through the valve when pressure upstream of the valve overcomes the valve spring.
True
False

Answer 7

False

Downstream

Question 8

All backpressure valves are located in the:

a. pump delivery line.
b. system return line.
c. actuator return line.
d. actuator inlet line.

Answer 8

c. actuator return line.

Question 9

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

Answer 9

True

Question 10

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

Answer 10

A meter out flow control circuit.

Question 11

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

Answer 11

Priority flow divider provides a constant flow rate to the steering system regardless of fluctuations in steering pressure or engine speed.

Question 12

A normally closed pressure control will block the flow of oil through the valve when system pressure overcomes valve spring force.
True
False

Answer 12

False

Question 13

The main advantage of using a pilot operated pressure control valve is that it:
A. allows higher operating pressures/
B. allows higher flow rates.
C. Provides minimum pressure override.
D. Provides maximum pressure override.

Answer 13

C. Provides minimum pressure override.

Question 14

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

Answer 14

1. Depressurize the system.
2. Select pressure gauge twice the operating system pressure.
3. Be sure hoses and fittings will withstand maximum system pressure.

Question 15

Hydraulic accumulators perform the following four functions:
a.
b.
c.
d.

Answer 15

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

Question 16

State the function of an unloader valve.

Answer 16

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

Question 17

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

a. the load on the system is low.
b. the load on the system is high.
c. the load on the engine is low.
d. more flow is required.

Answer 17

b. the load on the system is high.

Question 18

State the function of an unloader valve.

Answer 18

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

Question 19

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

a. the load on the system is low.
b. the load on the system is high.
c. the load on the engine is low.
d. more flow is required.

Answer 19

b. the load on the system is high.

Question 20

Two functions of a sequence valve are:

Answer 20

a. To cause actions in a hydraulic system to occur in order.

b. Maintain minimum pressure in a primary function while a secondary function is in operation.

Question 21

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

Answer 21

Pressure intensification may damage the system.

Question 22

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

a. maintaining a constant pressure drop across its orifice.
b. changing the pressure drop across it orifice as load pressure changes.
c. varying load pressure.
d. maintaining a constant inlet flow rate.

Answer 22

a. maintaining a constant pressure drop across its orifice.

Question 23

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

a. restrictor type flow control valve.
b. non-compensated flow control valve.
c. meter out flow control valve.
d. proportional flow control valve.

Answer 23

d. proportional flow control valve.