Midterm

Question 1

Advantages of Fluid Power

Answer 1

Ease and Accuracy of Control
Control can be Automated by PLC or Microporcessor
Multiplication of Force
Very large forces can be generated and reversed quickly

Question 2

Disadvantages of Fluid Power

Answer 2

Hydraulic Oil is Messy and will leak
Conductors not as easy to route as “wire”
Efficiency -> Not always the most efficient
Hazards to manage
- Fire
- Noise
- High pressure oil weak

Question 3

Pressure Units

PSI

Answer 3

This is fairly intuitive to US one pound of force applied to one square inch

Question 4

Pressure Unit

Pascal

Answer 4

The force of one Newton applied to the area of one square meter

Question 5

Pascal’s Law

Answer 5

Pressure applied to a confined liquid is transmitted undiminished in all directions and acts with equal forces on all equal areas and at right angles to those areas

Question 6

How is the Pascal Law the Basis for Hydrostatics

Answer 6

Static part implies that the fluid is confined and at rest or nearly so

Question 7

Most Common Source of Contamination

Answer 7

Solid or Particle
Heat or Thermal
Air and Gas
Water
Chemical and Radiation
Microbial Growth
Bulit-In
External
Internally Generated
Maintenance Generated

Question 8

Benefits of Cartridge Valves

Answer 8

Greater Design Flexibility
Lower Installed Cost
Smaller Package Size
Alleviated External Leakage
Easier Troubleshooting
Easier Maintenance
Better Organized Plumbing
Lower Noise Level

Question 9

Laminar Flow

Answer 9

A condition of flow in a passage that is typified by slow movement of fluid in a relatively straight path alon gthe cneterline of a passage

Question 10

Turbulent Flow

Answer 10

A condition of flow in a passage that is typified by rapid movement of fluid in a passage where the fluid is churning and bouncing off the passage walls

Question 11

“Meter-In” Flow Control

Answer 11

To regulate the amount of fluid flow into an actuator or system

Question 12

“Meter-Out” Flow Control

Answer 12

To regulate the flow of discharge fluid out of an actuator or system

Question 13

Cavitation

Answer 13

A localized gaseous condition within a liquid stream which occurs where the pressure is reduced to the vapor pressure

Question 14

Torque Efficiency

Answer 14

A function of speed and fluid viscosity

Question 15

Volumetric Efficiency

Answer 15

A function of clearance spaces, system pressure and pump speed

Question 16

Pressure Intensification

Answer 16

Occurs on the Annular (rod end) side of the double acting cylinder when in “meter-out” control

Question 17

What can cause Cavitation at a Pump

Answer 17

• Can occur in overrunning loads
• Can have same negative effects in both pumps and cylinders
• May need to protect the load from falling
• Typically use some type of “meter-out” control to manage

Question 18

Schematic

Answer 18

Vented Reservoir

Question 19

Schematic

Answer 19

Reservoir
- Fluid Container
- Allow air to separte out

Question 20

Schematic

Answer 20

Relief Valve
- Provide protection to hydraulic system so components dont seize or burst

Question 21

Schematic

Answer 21

Filter
- Removing solid contamination

Question 22

Schematic

Answer 22

Fixed Displacement Pump
- Providing a constant flow

Question 23

Schematic

Answer 23

Variable Displacement Pump
- Providing only what the system needs

Question 24

Schematic

Answer 24

Directional Control Way
(3 positions,4 ways)
- Direct fluid to specific location

Question 25

# Schematic

Answer 25

Double Acting Cylinder - Moves force in both directions

Question 26

# Schematic

Answer 26

Single Acting Cylinder - Moves force in one direction and relying on gravity to retract

Question 27

# Schematic

Answer 27

Fixed Displacement **Motor** - Provides constant torque

Question 28

# Schematic

Answer 28

Variable Displacement **Motor** Reversible

Question 29

# Schematic

Answer 29

Working Line

Question 30

# Schematic

Answer 30

Pilot Line (Drain)

Question 31

# Schematic

Answer 31

Variable Displacement **Motor** - Range of torque/speed wanted

Question 32

# Schematic

Answer 32

Adjustable Orifice - Restricting flow (able to adjust)

Question 33

# Schematic

Answer 33

Check Valve - Allowing flow in one direction & not in the other way

Question 34

# Schematic

Answer 34

Flow Meter - Measures the volume of fluid moving through

Question 35

# Schmetic

Answer 35

Pressure Gauge

Question 36

Breakout Torque*

Answer 36

How much torque is required to start a part's rotation from a stationary position - Ex. Grain Auger (stopped when fully loaded)

Question 37

How does breakout torque relate to running torque?

Answer 37

Breakout torque can be **considerably less** than running torque

Question 38

Cylinder Stop Tube

Answer 38

- Limit Extension - Can also control buckling in long cylinders

Question 39

Where would a cylinder stop tube be used?

Answer 39

Scissor Lift Telehandler

Question 40

Where can **Accumulators** be used?

Answer 40

On sprayer booms for shock absorption

Question 41

Purpose of a Accumulator

Answer 41

Can store or temporarily absorb, hydraulic energy in the form of fluid under pressure

Question 42

# Most Common Types Spring Loaded Accumulator

Answer 42

Spring provides the force on the pistion - Combination of the force and pistion area determines the pressure on the fluid in the accumulator

Question 43

# Most Common Types Gas Charged Accumulator

Answer 43

Fluid is forced into the accumulator, gas that occupies the space is compressed

Question 44

# Most Common Types Piston Accumulator

Answer 44

A free piston separating the gas from the fluid in a cylinder

Question 45

Pilot Operated Relief Valve

Answer 45

Design of relief valve have a significantly lower pressure override characteristics - used in hydraulic systems where the amount of pressure overrides is critical to protecting circuit components and hydraulic lines

Question 46

Direct Acting Relief Valve

Answer 46

Either a ball or a poppet is held in the closed postion by an adjustable spring - Blocks the flow path to the tank

Question 47

Possible Effects of Cavitation on a Hydraulic Pump

Answer 47

- Pump Performance Deterioriation - Mechanical Damage - Noise & Vibration

Question 48

Pseudo-Cavitation

Answer 48

Air is entering the inlet side of a pump

Question 49

Symptoms of Entrained Air

Answer 49

- Increased Heat-Load - Increased Noise Levels - Decreased Efficiency

Question 50

Where to look for the source of air in Hydraulic Systems

Answer 50

- Pump Seals - Pipe Fittings - Low Reservoir Fluid Level

Question 51

How to confirm entrained air in a circuit

Answer 51

Placing a small drop of oil or grease around the leak site area

Question 52

Pressure Compensated Flow Valve

Answer 52

A constant output flow rate into a branch circuit regardless of system input pressure or load pressure

Question 53

# Schematic

Answer 53

Pressure Compensated Flow Valve

Question 54

# Directional Control Valve

Answer 54

2 Positions, 2 Ways

Question 55

# Directional Control Valve

Answer 55

2 Position, 3 Ways

Question 56

# Directional Control Valve

Answer 56

2 Position, 4 Ways

Question 57

# Directional Control Valve

Answer 57

3 Position, 4 Ways

Question 58

# Directional Control Valve

Answer 58

3 Position, 4 Ways