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Fluid Power > Midterm > Flashcards

Midterm Flashcards

1
Q

Advantages of Fluid Power

A

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

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2
Q

Disadvantages of Fluid Power

A

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

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3
Q

Pressure Units

PSI

A

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

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4
Q

Pressure Unit

Pascal

A

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

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5
Q

Pascal’s Law

A

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

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6
Q

How is the Pascal Law the Basis for Hydrostatics

A

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

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7
Q

Most Common Source of Contamination

A

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

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8
Q

Benefits of Cartridge Valves

A

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

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9
Q

Laminar Flow

A

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

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10
Q

Turbulent Flow

A

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

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11
Q

“Meter-In” Flow Control

A

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

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12
Q

“Meter-Out” Flow Control

A

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

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13
Q

Cavitation

A

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

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14
Q

Torque Efficiency

A

A function of speed and fluid viscosity

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15
Q

Volumetric Efficiency

A

A function of clearance spaces, system pressure and pump speed

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16
Q

Pressure Intensification

A

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

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17
Q

What can cause Cavitation at a Pump

A
  • 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
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18
Q

Schematic

A

Vented Reservoir

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19
Q

Schematic

A

Reservoir
- Fluid Container
- Allow air to separte out

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20
Q

Schematic

A

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

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21
Q

Schematic

A

Filter
- Removing solid contamination

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22
Q

Schematic

A

Fixed Displacement Pump
- Providing a constant flow

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23
Q

Schematic

A

Variable Displacement Pump
- Providing only what the system needs

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24
Q

Schematic

A

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

25
Q

Schematic

A

Double Acting Cylinder
- Moves force in both directions

26
Q

Schematic

A

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

27
Q

Schematic

A

Fixed Displacement Motor
- Provides constant torque

28
Q

Schematic

A

Variable Displacement Motor
Reversible

29
Q

Schematic

A

Working Line

30
Q

Schematic

A

Pilot Line (Drain)

31
Q

Schematic

A

Variable Displacement Motor
- Range of torque/speed wanted

32
Q

Schematic

A

Adjustable Orifice
- Restricting flow (able to adjust)

33
Q

Schematic

A

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

34
Q

Schematic

A

Flow Meter
- Measures the volume of fluid moving through

35
Q

Schmetic

A

Pressure Gauge

36
Q

Breakout Torque*

A

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

37
Q

How does breakout torque relate to running torque?

A

Breakout torque can be considerably less than running torque

38
Q

Cylinder Stop Tube

A
  • Limit Extension
  • Can also control buckling in long cylinders
39
Q

Where would a cylinder stop tube be used?

A

Scissor Lift
Telehandler

40
Q

Where can Accumulators be used?

A

On sprayer booms for shock absorption

41
Q

Purpose of a Accumulator

A

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

42
Q

Most Common Types

Spring Loaded Accumulator

A

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

43
Q

Most Common Types

Gas Charged Accumulator

A

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

44
Q

Most Common Types

Piston Accumulator

A

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

45
Q

Pilot Operated Relief Valve

A

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

46
Q

Direct Acting Relief Valve

A

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

47
Q

Possible Effects of Cavitation on a Hydraulic Pump

A
  • Pump Performance Deterioriation
  • Mechanical Damage
  • Noise & Vibration
48
Q

Pseudo-Cavitation

A

Air is entering the inlet side of a pump

49
Q

Symptoms of Entrained Air

A
  • Increased Heat-Load
  • Increased Noise Levels
  • Decreased Efficiency
50
Q

Where to look for the source of air in Hydraulic Systems

A
  • Pump Seals
  • Pipe Fittings
  • Low Reservoir Fluid Level
51
Q

How to confirm entrained air in a circuit

A

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

52
Q

Pressure Compensated Flow Valve

A

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

53
Q

Schematic

A

Pressure Compensated Flow Valve

54
Q

Directional Control Valve

A

2 Positions, 2 Ways

55
Q

Directional Control Valve

A

2 Position, 3 Ways

56
Q

Directional Control Valve

A

2 Position, 4 Ways

57
Q

Directional Control Valve

A

3 Position, 4 Ways

58
Q

Directional Control Valve

A

3 Position, 4 Ways

Fluid Power (2 decks)

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