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Fluid Power > Final > Flashcards

Final Flashcards

1
Q

Advantages of Fluid Power

A
  • Easy and accuary of control
  • Control can be automated by PLC or microprocessor
  • Multiplication of Force
  • Very large forces can be generated and reversed quickly
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2
Q

Drawbacks of Fluid Power

A
  • Hydraulic oil is messy and it will leak
  • Conductors not as easy to route as “wires”
  • Efficiency
  • Hazards to Manage –> Fire, Noise, Hight pressure oil leak
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3
Q

Pressure Units

PSI

A

One pound of force applied to one square inch

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4
Q

Pressure Units

Pascal

A

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

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5
Q

Definition

Pascal’s Law

A

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

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6
Q

Pascal’s Law the basis of Hydrostatics

A

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

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7
Q

Definiton

Laminar Flow

A

A condition of flow in a passage that’s typified by slow movement of fluid in a relatively straight path along the cneterline of a passage

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8
Q

Definition

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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9
Q

Definition

Meter In

A

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

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10
Q

Definition

Meter Out

A

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

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11
Q

Definition

Accumulator

A

A vessel, normally cylindrical, whihc is used to store fluid and gas for future release of the energy in the compressed fluid and gas

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12
Q

Schematic

A

Line
Working Main

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13
Q

Schematic

A

Pressure Compensated

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14
Q

Schematic

A

Reservoir

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15
Q

Schematic

A

Vented Reservoir

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16
Q

Schematic

A

Hydraulic Pump
Fixed Displacement

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17
Q

Schematic

A

Hydraulic Pump
Variable Displacement

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18
Q

Schematic

A

Hydraulic Motr
Fixed Displacement

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19
Q

Scehmatic

A

Hydraulic Motor
Variable Displacement

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20
Q

Schematic

A

Hydraulic Motor
Bi-directional

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21
Q

Schematic

A

Single Acting Cylinder

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22
Q

Schematic

A

Double Acting Cylinder

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23
Q

Schematic

A

Electric Motor

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24
Q

Schematic

A

Nonelectric Prime Mover

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25
Q

Scehmatic

A

Spring Load Accumulator

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26
Q

Schematic

A

Gas Charged Accumulator

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27
Q

Schematic

A

Heater

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28
Q

Schematic

A

Cooler

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29
Q

Schematic

A

Temperature Controller

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30
Q

Schematic

A

Filter, Strainer

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31
Q

Schematic

A

Pressure Gauge

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32
Q

Schematic

A

Flow Meter

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33
Q

Schematic

A

Temperature Indicator

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34
Q

Schematic

A

Direction of shaft rotation
(assume arrow on near side of shaft)

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35
Q

Schematic

A

Air Bleed

36
Q

Schematic

A

Check Valve

37
Q

Schematic

A

Pressure Relief

38
Q

Schematic

A

Pressure Reducting
(No drain shown)

39
Q

Schematic

A

Sequence Valve

40
Q

Schematic

A

Counterbalance Valve

41
Q

Schematic

A

Unloading Relief Valve

42
Q

Schematic

A

Flow Control
Adjustable, Non-compensated

43
Q

Schematic

A

2 Position/2 Way Directional Control Valve

44
Q

Schematic

A

2 Position/3 Way Directional Control Valve

45
Q

Schematic

A

2 Position/4 Way Directional Control Valve

46
Q

Schematic

A

3 Position/4 Way Directional Control Valve

47
Q

Schematic

A

3 Position/4 Way Directional Control Valve

48
Q

Whats the purpose of an accumulator

A
  • Energy source (supplement pump)
  • Emergency Power
  • Shock absorption (see on sprayer booms)
  • Thermal expansion protection
  • Leakage compensation
  • Pulsation dampening
49
Q

Types of Contamination

A
  • Solid or Particle
  • Heat or Thermal
  • Air and Gas
  • Water
  • Chemical and Radiation
  • Microbial Growth
  • Built-in
  • External
  • Intermally Generated
  • Maintenance Generated
50
Q

Functions of an Reservoir

A
  • Fluid container
  • Cooling
  • Allow air to separate out
  • Allow debris to settle out
  • Provide good inlet conditions to the pump
51
Q

Why a resevoir may need to be pressurized

A
  • High altitude operation
  • Pump located above reservoir
  • Cold weather start up
52
Q

Benefits of utilizing Cartridge Valves

A
  • Greater design flexibility
  • Lower installed cost
  • Smaller package size
  • Alleviated external leakage
  • Easier troubleshooting
  • Easier maintenance
  • Better organized plumbing
  • Lower noise levels
53
Q

Definition

Relief Valve

A

A valve that limits the pressure at its inlet port by exhausting flow present at its inlet port to another chamber of lower pressure potential its outlet port

54
Q

Definition

Unloading Valve

A

A valve that’s normally closed and opens from a separte fluid source on rising pressure thats balanced against a precision spring

55
Q

Definition

Simple Needle Valve

A

A two-way valve that may be opened or closed to block the flow of fluid in a passage

56
Q

Definition

Pressure Reducing Valve

A

A valve that decreases the downstream pressure (at the valve outlet) to control the flow and therefore the outlet pressure to some present level

57
Q

Definition

Sequence Valve

A

A valve that is normally closed or normally open and changes to the opposite state when pilot pressure is applied to its spring chamber at a present pressure level

58
Q

Definition

Counterbalance Valve

A

A valve used to balance the weight of a machine or dead load by causing a back pressure in the system cylinders of sufficient magnitude to support the weight

59
Q

Definition

Pilot Operated Check Valve

A

A special check valve that may be opened against a check load by applying pilot pressure from a secondary source to open the check to free reverse flow

60
Q

Definition

Flow Divider

A

A mechanical device used to divide the fluid in a passage into two or more separate fluid streams

61
Q

Definition

Flow Meter

A

An analog device which indicates the volume of fluid passing through its interior passage

62
Q

Definition

Pressure Gauge

A

A visual indicator of pressure that is set for “zero” psi at atmospheric pressure and includes a dial which will continue to indicate the level of pressure above atmospheric pressure

63
Q

Definition

Pressure Compensated Flow Control Valve

A

A valve used to cause a variable pressure drop in a fluid passage, thus reducing the amount of fluid that may pass through the passage regardless of pressure level at the inlet of the valve

64
Q

Definition

Directional Control Valve

A

A valve whose primary function is to direct or prevent flow through selected channels

65
Q

Definition

Cavitation

A

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

66
Q

Definition

Starting Torque

A

Friction is the resistance to relative motion between two materials in contact with each other
Ex. Grain auger, grain has static to it dont want to stop an auger full of grain

67
Q

Definition

Entrained Air

A

Any air present in excess of the saturation level of the fluid at a given pressure

68
Q

Closed Circuit Hydrostatic Transmission

A

A provision for sensing the motor speed and using this signal to adjust the pump displacement to increase or decrease the motor speed until it reaches the set point

69
Q

Open Circuit Hydrostatic Transmission

A

No feedback of the motor speed

70
Q

Open Center Circuit

A

Have a passage designed in the casting that allows all inlet flow when the spool is in the neutral or cenmter position to pass through a bypass area at the low pressure drop

71
Q

What happens to pump system pressure when DCV is active

A

When all valve spools are in neutral position (no work is being performed) the power consumed by the hydraulic system is at its lowest

72
Q

Closed Center Circuit

A

Do not have a bypass passage and block all flow through the valve when the spool is in the neutral or center position

73
Q

Standby Condition Closed Center Circuit

A

Closed center valves are used with variable displacement pumps where system flow in the neutral position does not exist as the pump will be in its “cut off” or “standby” position

74
Q

Regenerative Flow

A
  • Pressure is equal on both ends of cylinder
  • Cylinder is effectively reduced to rod size
  • Speed is increased
  • Force capability is reduced
  • Only applies in extension
75
Q

Draw the concept of pressure override in a pressure relief valve

A
76
Q

Direct Operated Relief Valve

A

Where either a ball or a poppet is held in the closed position by an adjustable spring
- This blocks the flow path to the tank

77
Q

Pilot Operated Relief Valve

A

Used in hydraulic systems where the amont of pressure override is critical to protecting components and the hydraulic lines

78
Q

How to achieve Pressure Compensated Flow

A

Piston or Spool Type
- By using springs to maintain a constant pressure drop across the metering orifice

79
Q

What limits the allowable pressure for pressure compensated flow

A

An input pressure increases, output flow is restricted as either the piston or spool is closed off. This prevents an increase in output flow as the increase of input system pressure tries to force more flow through the valve

80
Q

Simple Orifice

A

Conveniently be inserted into a hydraulic line as a stand alone valve or more typically into a hydraulic fitting as a means of restricting the flow into a branch circuit

81
Q

Pressure Override

A

The measure of pressure increase over the nominal setting of a device when additional fluid flow is passed over the device after it initially opens

82
Q

Pressure Intensification

A

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

83
Q

When do you see Pressure Intensification

A

Piston seal failure in meter out control

84
Q

Volumetric Efficiency

A

A function of clearance spaces, system pressure and pump speed

85
Q

Torque Efficiency

A

A function of speed and fluid viscosity

86
Q

Temperature Contamination Effects on Hydraulic Fluid

A

Hydraulic fluid running over 140F effectively doubles the oxidation rate of the hydraulic fluid cutting its useful life in half

87
Q

Causes for Cavitation

A
  • Restrictions in the flow of the hydraulic fluid to the inlet
  • Excessively clogged inlet screens or flters
  • Running pump too fast

Fluid Power (2 decks)

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