Final Prep 1

Question 1

F: The local atmospheric pressure is 14.7 psia. Is it possible that the gage pressure of a container can be -20 psig?

Answer 1

No

Question 2

F: What is viscosity?

Answer 2

A magnitude of internal friction. Thickness.

Question 3

F: What happens to viscosity as temperature increases and decreases?

Answer 3

Viscosity decreases as temperature increases and increases as temperature decreases.

Question 4

F: What kind of viscosity index (VI) indicates a high rate of change with temperature?

Answer 4

A low viscosity index (VI) indicates a high rate of change with temperature

Question 5

F: If the viscosity of the hydraulic fluid increases, what happens to the leakage of the system?

Answer 5

The leakage decreases

Question 6

F: At a given flow rate, the inside diameter of the pipe is increased, how will this effect the fluid velocity?

Answer 6

Increasing the inside diameter of the pipe causes the fluid velocity to decrease

Question 7

F: At a given inside diameter of the pipe, how will increasing the flow rate effect the fluid velocity?

Answer 7

Increasing the flow rate will cause the velocity to increase

Question 8

F: What is the purpose of hydraulic fluid?

Answer 8

To transmit power, lubricate moving parts, seal clearances between mating parts, dissipate heat, and remove contaminants.

Question 9

F: How can you increase responsiveness of a hydraulic system?

Answer 9

You can increase responsiveness of a hydraulic system by increasing bulk modulus.

Question 10

F: What does low bulk modulus indicate?

Answer 10

A high compressibility of fluids.

Question 11

F: As the pressure of a hydraulic system increases, what will happen to the volumetric efficiency of the pump?

Answer 11

The volumetric efficiency will decrease

Question 12

F: Gear pumps give…

Answer 12

constant output with constant RPM

Question 13

F: Increasing the angle of the swashplate in a variable displacement piston pump will do what to the displacement of the pump?

Answer 13

It will increase the displacement of the pump

Question 14

F: How do variable displacement piston pumps change the output flow?

Answer 14

By changing either the pumps RPM and/or swashplate

Question 15

F: How do variable displacement piston pumps increase the flow?

Answer 15

By increasing the angle of the swash plate

Question 16

F: Are vane pumps always fixed displacement?

Answer 16

No, they can be variable displacement

Question 17

F: Why are centrifugal pumps not used as hydraulic pumps?

Answer 17

Because their output (flow rate) is reduced as system pressure increases

Question 18

F: Name all the types of pumps, if they are positive displacement or not, if they are always fixed displacement.

Answer 18

Gear pump, yes PD, yes always fixed displacement.
Vane pump, yes PD.
Piston pump, yes PD.
A centrifugal pump, not PD.

Question 19

F: What is a positive displacement pump’s output flow rate almost independent of?

Answer 19

It is almost independent of the system pressure.

Question 20

F: Will changing the flow rate to an actuator have an effect on the actuator speed?

Answer 20

Yes.

Question 21

F: With the same pressure, when will a double acting single rod cylinder produce more force? (extending or retracting)

Answer 21

It will produce more force on extending.

Question 22

F: What are hydraulic motors rated according to?

Answer 22

displacement, torque capacity, and maximum pressure.

Question 23

F: At a given flow rate to a variable displacement piston motor, how will increasing the angle of the swashplate effect the rotation speed of the motor?

Answer 23

It will decrease the rotation speed of the motor.

Question 24

F: Hydraulic gear motors give

Answer 24

constant rpm with constant input flowrate

Question 25

F: At the same input flow rate, will a double acting single rod cylinder run faster on extension or retraction?

Answer 25

On retraction.

Question 26

F: For a double acting double rod cylinder, does regeneration increase the extension speed?

Answer 26

No, regeneration does not increase the extension speed.

Question 27

F: What does a relief valve control?

Answer 27

Maximum system pressure

Question 28

F: What is the first stage of a pilot operated relief valve?

Answer 28

A small direct acting relief valve

Question 29

F: What normally state is a sequence valve?

Answer 29

A sequence valve is normally closed.

Question 30

F: A 4-way valve has how many ports?

Answer 30

4 ports

Question 31

F: What happens when an unloading valve opens?

Answer 31

It directs flow directly back to the tank.

Question 32

F: What is used to control the rate of a cylinder with an overrunning load?

Answer 32

A counterbalance valve

Question 33

F: What is the two purposes of the brake valve?

Answer 33

It prevents a load from overrunning the motor, and when the directional control valve is centered, it brings the motor to a stop at a controlled rate of speed.

Question 34

F: How is dynamic braking achieved?

Answer 34

When the directional control valve is centered, the brake valve allows a controlled amount of back pressure to build in line between the motor and the brake valve to achieve dynamic braking.

Question 35

F: When does flow through a needle valve vary?

Answer 35

If the differential pressure across the valve varies

Question 36

F: How does a pressure compensated flow control valve maintain a constant flow?

Answer 36

by maintaining constant pressure upstream from the valve.

Question 37

F: Check valves are classified as what?

Answer 37

Directional control valves

Question 38

F: Pilot operated check valves use what to do what?

Answer 38

use an external pilot to allow reverse flow to pass through a valve

Question 39

F: What is the concern with Meter-out? Is it the same with Meter-in?

Answer 39

Meter-out flow control will have a safety concern about the pressure intensification. Meter-in does not have this concern.

Question 40

F: Regardless of type of pump, pumps generate flow. The output pressure of the pump is the result of what?

Answer 40

Resistance to flow.

Question 41

F: High-low systems operate at what?

Answer 41

High pressure and low flow rate or high flow rate and low pressure.

Question 42

F: What do reservoirs do?

Answer 42

Help to condition hydraulic fluid (such as cooling the hydraulic fluid, removing air and water from the fluid) and store the fluid.

Question 43

F: Does the return line to the reservoir need to be above the fluid level in the reservoir?

Answer 43

No

Question 44

F: What are two common applications for accumulators?

Answer 44

To store energy in a hydraulic circuit and to absorb the shock

Question 45

F: What hydraulic conduits should be used if the components being connected move relative to each other?

Answer 45

Hoses

Question 46

P: When installing a flow control in circuit to control the speed of a pneumatic cylinder, how is it best to connect it in the line?

Answer 46

To meter the air out.

Question 47

P: What does 5/2 valve mean?

Answer 47

5 ways and 2 positions

Question 48

P: By what percent is a pneumatic receiver usually oversized?

Answer 48

By 50%

Question 49

P: Why is pneumatic cylinder speed considerably more difficult to predict?

Answer 49

Because of the high compressibility of air.

Question 50

P: Atmospheric air needs to be conditioned before use in a pneumatic system. What conditioning does this entail?

Answer 50

Removal of entrapped dirt, removal or water vapor, removal of heat, and incorporating oil for component lubrication.

Question 51

P: As the temperature increases, what happens to gas viscosity?

Answer 51

gas viscosity increases as temperature increases