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MK3 > Hydraulics > Flashcards

Hydraulics Flashcards

1
Q

The engineering science pertaining to the use of liquid pressure and flow to transmit power, multiply force, and modify motion

A

Hydraulics

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2
Q

Pressure applied to a confined fluid is transmitted undiminished an all direction and acts with equal force on equal areas and at right angles to them

A

Pascal’s Law

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3
Q

Three parts of the formula triangle for Pascal’s law

A

Force, Area, Pressure

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4
Q

What is at the top of the formula triangle for Pascal’s law?

A

Force

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5
Q

The measure of a bounded region or plane

A

Area

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6
Q

Anything that tends to produce or modify motion

A

Force

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7
Q

Force per unit area

A

Pressure

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8
Q

Area is usually expressed in ___

A

Square inches

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9
Q

Force is usually expressed in ___

A

Units of weight

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10
Q

Pressure is measured in ___

A

PSI

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11
Q

Two working surface areas inside a cylinder

A

Cap or blind end area

Net or rod end area

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12
Q

Hydraulic pressure working on the cap end forces the piston rod to ___

A

Extend

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13
Q

Hydraulic pressure working on the net area forces the piston rod to ___

A

Retract

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14
Q

Cap end area =

A

D^2 x .7854

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15
Q

The amount of weight a cylinder will push or pull

A

Working force

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16
Q

Scientific unit of pressure roughly equal to the atmospheric pressure on earth at sea level

A

Bar

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17
Q

psi =

A

bar x 14.5

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18
Q

bar =

A

psi / 14.5

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19
Q

The ability or capacity to do work

A

Energy

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20
Q

Two types of energy

A

Potential

Kinetic

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21
Q

Also known as stored energy

A

Potential energy

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22
Q

This form of energy is present in a hydraulic system in the form of fluid pressure

A

Potential energy

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23
Q

Also known as energy in motion

A

Kinetic energy

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24
Q

This form of energy is present in a hydraulic system in the form of fluid flow

A

Kinetic energy

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25
Q

Energy can neither be created nor destroyed, but instead will simply be changed from one energy form to another

A

Law of conservation of energy

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26
Q

In hydraulics the ___ provides the mechanical advantage

A

Difference in piston areas

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27
Q

Hydraulic symbols are authorised and controlled by ____ under ___

A

International Standards Organisation (ISO)

ISO Code 1219-2

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28
Q

Establishes principles for the use of symbols and specifies basic symbols and rules for devising functional symbols

A

ISO Code 1219-2

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29
Q

ANSI

A

American National Standards Institute

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30
Q

ISO

A

International Standards Organisation

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31
Q

NFPA

A

National Fluid Power Association

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32
Q

Provide a graphic depiction of hydraulic systems

A

Hydraulic symbols

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33
Q

Symbols shall be drawn to show the ___ position

A

At rest or neutral

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34
Q

The basic component for a rotating component

A

A circle

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35
Q

One triangle indicates

A

Unidirectional

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36
Q

Two triangles indicate

A

Bidirectional

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37
Q

Half circle indicates

A

A rotating component with a limited angle of rotation

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38
Q

The basic component for a control component

A

Square

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39
Q

The basic symbol of a conditioning apparatus

A

Diamond

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40
Q

Shown by a continuous solid line

A

Working line

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41
Q

Carries fill system flow, and includes suction line, pressure lines, and return lines

A

Working line

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42
Q

Shown by a dashed line

A

Pilot line

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43
Q

Used to send a signal or to control a valve or other component. These lines carry system pressures, but very little flow

A

Pilot line

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44
Q

Shown by a dashed line, small dashes

A

Drain line

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45
Q

Used to carry internal leakage fluid from a component to the reservoir. Very low pressure

A

Drain line

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46
Q

Shown by a short and long dashed line

A

Component enclosure line

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47
Q

Used to enclose two or more components to indicated close grouping

A

Component enclosure line

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48
Q

Shown by a double line

A

Mechanical connection line

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49
Q

Used to indicate mechanical connection

A

Mechanical connection line

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50
Q

Variable displacement for pump symbol

A

Arrow across the circle at a diagonal

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51
Q

Stores system fluid

A

Reservoir

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52
Q

Energy source for the pump

A

Prime mover

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53
Q

Provides fluid flow

A

Hydraulic pump

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54
Q

Protects system from over pressurisation

A

Pressure relief valve

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55
Q

Directs fluid flow

A

Directional control valve

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56
Q

Convert hydraulic energy to mechanical energy

A

Actuator

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57
Q

Removes contaminates from the fluid

A

Filtering device

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58
Q

Carry the fluid flow throughout the system

A

Conductors

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59
Q

Two types of hydraulic circuits

A

Open loop

Closed loop

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60
Q

Most common type of hydraulic circuit

A

Open loop

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61
Q

The main characteristic of this hydraulic circuit is that atmospheric pressure forces fluid from the reservoir up the pump, and the pump creates flow for the circuit

A

Open loop

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62
Q

Hydraulic circuit where neither the inlet port nor outlet port of the pump or motor is connected to the reservoir

A

Closed loop

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63
Q

Fluid in a hydraulic system has four main requirements

A

Transmit power
Cool
Seal
Lubricate

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64
Q

Viscosity is measured in ___

A

Saybolt Seconds Universal (SSU)

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65
Q

Most commonly used hydraulic fluid

A

Navy standard hydraulic oil series 2 and 8

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66
Q

Numbering system used to measure a fluid’s resistance to viscosity changes with changes in temperatures

A

Viscosity Index

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67
Q

A VI of ___ is preferred in most hydraulic systems

A

90 or above

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68
Q

Three general groups that hydraulic fluids can be placed in

A

Petroleum oils
Fire-resistant
Biodegradable

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69
Q

Most common group/category of hydraulic fluid

A

Petroleum oils

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70
Q

This hydraulic fluid can be blended with synthetic fluids

A

Petroleum oils

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71
Q

Three types of fire-resistant hydraulic fluids

A

Water in oil emulsion
Water-based
Synthetics

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72
Q

This hydraulic fluid is made of vegetable oil

A

Biodegradable

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73
Q

This fluid is comparable to petroleum based hydraulic fluids

A

Biodegradable

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74
Q

Any material foreign to a hydraulic fluid that has a harmful effect on system performance

A

Contamination

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75
Q

Approximately ___ of all hydraulic system failures result from contamination

A

80%

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76
Q

Filters may be made of many materials except ___

A

Wire screen

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77
Q

Filters are rated by __

A

Micron size

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78
Q

A micron is ___

A

1-millionth of a metre, or 39-millionths of an inch

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79
Q

The smallest particle visible to the naked eye is about ___

A

40 microns

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80
Q

A simple wire screen or wire strainer is rated for filtering fineness by ____

A

Mesh number or standard sieve number

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81
Q

The higher the mesh of sieve number ___

A

The finer the screen

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82
Q

When a filter is specified as so many microns, it usually refers to the filter’s ____

A

Nominal rating

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83
Q

The size of the largest opening or pore in the filter

A

Absolute rating

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84
Q

Installed on the pump inlet side of the reservoir and may be located internally or externally

A

Strainer

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85
Q

Use a relatively coarse filtering element constructed of fine mesh wire

A

Inlet strainers

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86
Q

Should only be expected to prevent large particles from entering the pump and causing catastrophic failure

A

Inlet strainers

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87
Q

Two important requirements for any inlet strainer

A
  • The strainer must be capable of passing the full pump volume within the permitted inlet pressure drop for that pump
  • The strainer must provide bypass flow which is still within that limit if the strainer element is blocked
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88
Q

Remove contamination from hydraulic fluid, and is accomplished by forcing the fluid stream to pass through a porous filter element which traps the contaminants

A

Function of a filter

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89
Q

Filter elements are divided into two classifications

A

Surface-type elements

Depth-type elements

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90
Q

The fluid stream has a straight flow path through the element, and contamination is trapped on the surface of the element

A

Surface-type elements

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91
Q

In this type of element, the fluid flow is forced to pass through a multiple layer element, and the multiple layers trap the contamination

A

Depth-type elements

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92
Q

The location of the filtering device is usually determined by the ___

A

Manufacturer

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93
Q

Two primary locations for filters

A

Pump discharge side

Return side

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94
Q

Filters the fluid before is does the work

A

Pump discharge side

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95
Q

Filters the fluid before it returns to the reservoir

A

Return side

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96
Q

Used to measure the performance of filter elements

A

Filter ratings

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97
Q

Three types of filter ratings

A

Micron rating
Flow rate
Filter pressure rating

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98
Q

Filter’s ability to effectively allow fill system flow to pass through the filter without causing undesired pressure increase

A

Flow rate

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99
Q

Filter’s ability to remove contamination at a specified micron size

A

Micron rating

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100
Q

Filter’s ability to function properly regardless of system pressure

A

Filter pressure rating

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101
Q

Provide a visual means of detecting filter condition while the system is operating

A

Filter condition indicators

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102
Q

Indicators with green, yellow, and red visuals react to the ____

A

Pressure differential

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103
Q

Reacts to the position of the bypass check valve

A

Mechanical indicator

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104
Q

Installed in a filter to ensure an uninterrupted flow of fluid

A

Bypass check valves

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105
Q

Symbol for filtering device

A

Conditioning component symbol with dashed line through the middle

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106
Q

Three general categories of contamination in a system

A

Built-in contamination
Ingress contamination
Internally generated contamination

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107
Q

Also referred to as environmental contamination

A

Ingress contamination

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108
Q

Occurs when there are solid particles present in the hydraulic fluid

A

Abrasion

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109
Q

Refers to repeated stressing of a surface

A

Fatigue

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110
Q

Caused by dynamic pressure reduction on hydraulic fluid, typically occurring in both the pump inlet and in an actuator

A

Cavitation

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111
Q

Indications of cavitation can be ___

A

Pump noise and fluid temperature rise

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112
Q

The presence of air or gas bubbles in the fluid

A

Aeration

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113
Q

Spongy actuator operation may be due to __

A

Aeration

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114
Q

Mechanical clearances within hydraulic components can be divided into two principle zones

A
  • Up to 5 micrometers

- 10 - 20 micrometers

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115
Q

Mechanical clearances are generally measured in ___

A

thousandths of an inch, ten thousandths of an inch, or fractions of a mm

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116
Q

Provides information on hydraulic systems that shall be tested and frequency of testing. Also provides information on sampling procedures

A

NEM, Chapter 262

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117
Q

Samples taken from a non operating system

A

Thief samples

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118
Q

Thief samples should only be taken when ___

A

The system cannot be operated

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119
Q

Sampling intervals on hydraulic systems that do not have a defined oil change interval shall be taken ____

A

Quarterly

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120
Q

Oil will be darker than original oil

A

Oxidation

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121
Q

Fluid will be cloudy or water droplets will be present

A

Water

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122
Q

Air will be visible when the sample is first drawn

A

Air

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123
Q

If you can see particles in the fluid, then is is very dirty

A

Contaminants

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124
Q

Store and supply hydraulic fluid for a system

A

Primary function of a reservoir

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125
Q

Transfer heat and allow for contamination settling and de-aeration of the system

A

Reservoirs

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126
Q

Sometimes referred to as a non pressurised reservoir

A

Vented reservoir

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127
Q

Most common type of reservoir used in the CG

A

Vented reservoir

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128
Q

In the event sea level atmospheric pressure is not available or the environment is extremely dirty, a ___ is used

A

Pressurised reservoir

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129
Q

Act as heat exchangers by allowing waste heat to dissipate through the walls

A

Reservoirs

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130
Q

Reservoirs are usually mounted in a location that is ___

A

2 to 6 inches above the deck

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131
Q

Constructed of welded steel plates with legs on all four corners to elevate it off the deck

A

Reservoir

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132
Q

Allows for easy fluid removal

A

Drain plug

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133
Q

Allows for air exchange

A

Breather assembly

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134
Q

In the case of pressurised reservoirs, a ___ replaces the air breather

A

Schrader-type

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135
Q

Used to check the fluid level to avoid exposing the system to contamination

A

Sight gauge

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136
Q

The filler opening is normally incorporated into the ___

A

Breather assembly

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137
Q

Separates the inlet line from the return line, forcing the fluid to slow down and allowing time for cooling, contamination settling, and air purging

A

Baffle plate

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138
Q

Removable plate normally installed on the ends of the reservoir, allowing access to the inside of the tank for maintenance and cleaning

A

Clean-out/access plate

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139
Q

Suction lines begin and return lines end ___ above the bottom of the reservoir

A

2 inches

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140
Q

Drain lines terminate just below ___

A

The low fluid level in the reservoir

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141
Q

A reservoirs capacity should be __

A

2 to 3 times pump flow

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142
Q

When fluid pressure increases, fluid temperature

A

Increases

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143
Q

Can be installed to supplement the cooling effects of the reservoir

A

Heat exchanger coolers

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144
Q

Type of heat exchanger used for hydraulic fluid

A

Shell and tube

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145
Q

May be installed in the reservoirs where the ambient temperatures are low

A

Heaters

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146
Q

The fluid temperature in the reservoir should be maintained above ___

A

110 degrees F

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147
Q

Component that absorbs hydraulic shock and stores fluid under system pressure as an auxilary energy source

A

Accumulator

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148
Q

Used in an accumulator to maintain pressure

A

Springs, weights, compressed gas

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149
Q

Absorbs a quantity of fluid above a preset pressure and releases it when the pressure reduces, thereby reducing pressure spikes or surges in some systems

A

Accumulator

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150
Q

Hydraulic shock absorber

A

Accumulator

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151
Q

Two types of accumulators commonly found in the CG

A

Spring loaded

Gas charged

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152
Q

Two most common types of gas-charged accumulators

A

Piston-type

Bladder or diaphragm-type

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153
Q

What kind of gas must not be used in a gas-charged accumulator

A

Oxygen or air

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154
Q

Most common accumulator in the CG

A

Gas-charged

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155
Q

Most common gas used for gas-charged accumulator

A

Nitrogen

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156
Q

Connect the hydraulic pump to the rest of the system

A

Hydraulic hoses

157
Q

Conductor or passage used to transport fluid between components in a fluid power system

A

Flexible hose

158
Q

Hydraulic hose construction

A

Multiple layers of rubber or other synthetic materials interlaced with wire mesh

159
Q

Flexible rubber hose is identified by three things

A

Inside diametre
Service
Pressure class or working-pressure rating

160
Q

The inside diametre of a hose is expressed in __

A

16ths of an inch

161
Q

Three layers of hydraulic hose

A

Inner tube
Reinforcement layer
Outer cover

162
Q

Hydraulic hoses with an overall length greater than ___ must be supported

A

30 inches

163
Q

Support clamps should not be placed more than ___ apart

A

24 inches

164
Q

About ___ of the total length of the hydraulic hose must be allowed as slack to provide freedom of movement under pressure

A

5% to 8%

165
Q

When a flexible hose is under pressure, it:

A

Contracts in length and expands in diametre

166
Q

Selecting the correct connector or fitting depends upon three things

A

Type of circulatory system
Fluid medium
Maximum operating pressure of the system

167
Q

Most commonly used hydraulic connector in CG applications

A

JIC 37* Flare

168
Q

Permanent hose fitting are ___ when the hose is damaged or defective

A

Discarded

169
Q

Reusable hoses installed for flexible connections typically utilise one of five methods for attachment of the fitting to the hose

A
  • One-piece reusable socket
  • Segmented, bolted socket
  • Segmented socket, ring and band attached
  • Segmented socket, ring and bolt attached
  • Solid socket, permanently attached
170
Q

The socket component is fabricated as a single piece. Screwed or rocked onto the hose OD, followed by insertion of the nipple component

A

One-piece reusable socket

171
Q

Consists of two or more segments which are bolted together on the hose after insertion of the nipple component

A

Segmented, bolted socket

172
Q

Consists of three or more segments. As with the bolt-together segments, the segments, ring and band are put on the hose after insertion of the nipple. A special tool is required to compress the segments

A

Segmented socket, ring and band attached

173
Q

Consists of three or more segments. As with the other segmented socket type fittings, the segments ring, nuts, and bolts are put on the hose after insertion of the nipple

A

Segmented socket, ring and bolt attached

174
Q

This type of socket is permanently attached to the hose by crimping or swaging

A

Solid socket, permanently attached

175
Q

Do not use what to cap open hydraulic hoses

A

Rags or paper

176
Q

Shelf life for all synthetic rubber flexible hoses and prefabricated assemblies shall not exceed ___

A

10 years

177
Q

Bulk storage of hoses or hose assemblies should be in a ___

A

Cool dry area, never exceeding 100 degrees F

178
Q

Never stack hoses ___

A

Too high

179
Q

PMS for flexible rubber hose may be determined independently for each class of cutter, except for ___

A

Fleet system equipment

180
Q

A second-level hose inspection should include a thorough examination of the hose for

A

Soft spots
Bulges
Accelerated deterioration

181
Q

Long hoses should be inspected with the hoses __

A

Pressurised and under operating conditions

182
Q

Inspections of long hoses should include

A

Alignment
Hose movement
Chafing

183
Q

Replace any hoses past their __ year service life

A

8

184
Q

It is recommended that ___ of all hoses be changed each quarter to eliminate the need to change all hoses at one time

A

5%

185
Q

All hoses that are included in paper-based hose logs shall be identified with __

A

Individual hose tags

186
Q

Hose tags for hoses identified in a hose log shall include three pieces of information

A

Hose log item number
Hydro test procedure and test date
Service life

187
Q

Hose tags shall be attached using materials that ___

A

Will not damage the hose assembly

188
Q

Apply what over the area of the hose to be cut

A

Electrical tape

189
Q

Use what to cut hydraulic hose

A

Fine-tooth hacksaw or cut off wheel

190
Q

Install fitting socket on end of hose by ___

A

Threading it counterclockwise with the appropriate open end wrench and slight downward pressure with thumb

191
Q

Back the hose socket of ___ after it bottoms

A

1/4 turn

192
Q

Install fitting into socket by applying light pressure in a downward direction while turning fitting in a ____ rotation

A

Clockwise

193
Q

Leave ____ clearance between nut and socket to allow nut to swivel freely

A

1/32” to 1/16”

194
Q

An assembly mandrel is required for all single-wire hoses in sizes ___

A

1/4” through 3/4”

195
Q

Ensure the flexible hose has not backed out of the fitting more than __

A

1/16”

196
Q

Flexible hose assemblies which are assembled shall be ___ before the hose assembly is installed

A

Hydrostatically tested

197
Q

Hydrostatic testing procedures require a test pressure of ___, for approximately ___

A

Twice the rated working pressure of the hose

Five minutes

198
Q

Low pressure system

A

Less than 150 psi

199
Q

Those hose assemblies identified as ___ do not have to be hydrostatically tested

A

Condition-Based Maintenance

200
Q

Takes mechanical energy from a prime mover, and converts it into hydraulic energy

A

Pump

201
Q

Heart of the hydraulic system

A

Pump

202
Q

Any energy source used to drive any hydraulic pump

A

Prime mover

203
Q

Symbol for prime mover, electric motor

A

Circle, M inside, mechanical connection line coming off

204
Q

Symbol for prime mover, heat engine

A

Square within a square, mechanical connection line coming off

205
Q

Symbol for prime mover, reduction gear

A

Circle, R/G inside, mechanical connection line coming off

206
Q

Symbol for prime mover, manual

A

TT shape

207
Q

Complete absence of pressure

A

Absolute vacuum

208
Q

Unit of measure for vacuum

A

Inches of mercury (Hg)

209
Q

Two basic classifications of pumps

A

Nonpositive displacement pump

Positive displacement pump

210
Q

The output from this pump is reduced as restriction to flow increases

A

Nonpositive displacement pump

211
Q

Designed mainly for low pressure high volume systems, such as fluid transfer systems

A

Nonpositive displacement pump

212
Q

Designed to deliver a set amount of hydraulic fluid with minimal delivery loss regardless of discharge pressure

A

Positive displacement pump

213
Q

The amount of flow a pump produces in a given amount of time

A

Delivery

214
Q

The amount of fluid that passes through a pump in one revolution, stroke, or cycle

A

Displacement

215
Q

A positive displacement pump whose displacement cannot be changed

A

Fixed displacement pump

216
Q

A positive displacement pump whose displacement can be changed

A

Variable displacement pump

217
Q

The pump’s suction and discharge ports can be shifted without changing the pump’s direction of rotation

A

Bi-directional pump

218
Q

Used to create fluid flow

A

Pumps

219
Q

Resistance to flow creates ___

A

Pressure

220
Q

Operate on the theory of increasing and decreasing volumes within the pump

A

Positive displacement pump

221
Q

Three categories of positive displacement pump

A

Gear
Vane
Piston

222
Q

A ___ is created when the teeth of a gear pump unmesh

A

Vacuum

223
Q

Method through which the vanes are forced out of the rotor slots

A

Tracking

224
Q

Tracking is accomplished in three ways

A

Springs
Centrifugal force
Hydraulic fluid

225
Q

Almost all hydraulic vane pumps are __

A

Balanced vane pumps

226
Q

Two designs of piston pumps

A

Radial

Axial

227
Q

Has the pistons arranged radially in a cylinder block

A

Radial piston pump

228
Q

Has the pistons arranged parallel to each other and to the axis of the cylinder block

A

Axial piston pump

229
Q

Axial piston pumps may be further divided into ___

A

Inline (swash plate)

Bent axis types

230
Q

The pistons are connected to a swash plate that has a reaction ring which rotates within itself

A

Inline (swash plate) axial piston pump

231
Q

The pistons are fitted to bores in the cylinder block, and the piston shoes ride against an angled swash plate

A

Inline axial piston pump

232
Q

The ___ creates the reciprocating motion in the pistons and controls the displacement of the pump by controlling the piston stroke length (Inline axial piston pump)

A

Angled swash plate

233
Q

There are changes in velocity and pressure when pipe diametres change, as long as there is a constant flow rate

A

Bernoilli’s principle

234
Q

Two types of gear pumps

A

External gear pump

Internal gear pump

235
Q

Two types of vane pumps

A

Unbalanced vane pump

Balanced vane pump

236
Q

In a balanced vane pump, rotating the cam ring 180 degrees ___

A

Reverses the direction of rotation

237
Q

Taking the swash plate back past 0 degrees will create ___

A

Fluid flow in the opposite direction

238
Q

Created whenever fluid flow is resisted

A

Pressure

239
Q

In hydraulic systems, resistance may come from ___

A

Load on an actuator

Restrictions in the system piping

240
Q

An important characteristic of fluid is that it will always take ___

A

The path of least resistance

241
Q

The conductor and the components through which the fluid passes create two types of fluid flow

A

Laminar flow

Turbulent flow

242
Q

The most desirable type of flow; has minimal friction, low velocity, and occurs in straight piping

A

Laminar flow

243
Q

Fluid particles do not move smoothly parallel to the flow direction

A

Turbulent flow

244
Q

This flow is caused by a drastic change in direction of flow, reduced cross-section pipe size, or fluid velocity that is too high

A

Turbulent flow

245
Q

This flow causes increased friction, increased operating pressure, wasted power, and increased heat generation

A

Turbulent flow

246
Q

Limit system pressure, regulate system pressure, or control a load

A

Pressure control valves

247
Q

Operate on the principle of a balance between pressure and spring force

A

Pressure control valves

248
Q

Only open or close enough to maintain the required or set pressure

A

Infinite position

249
Q

Pressure control valves are classified by four things

A

Pressure operating range
Size (flow rating)
Type of connections or mounting
Design

250
Q

Pressure control valves are normally named for ___

A

Their primary function

251
Q

In pressure control valves, there are three terms used in reference to pressure

A

Cracking pressure
Full flow pressure
Pressure override

252
Q

The pressure at which the valve just begins to open

A

Cracking pressure

253
Q

Maximum pressure when the valve is fully open and full system flow is going through the valve

A

Full flow pressure

254
Q

The difference between cracking pressure and full flow pressure

A

Pressure override

255
Q

In high-pressure/high-volume systems, a high-pressure override can cause ___

A

A loss of power and efficiency

256
Q

Most common types of pressure control valves

A

Pressure relief valves

257
Q

Limits the maximum operating pressure for the entire system, thereby protecting the system from overpressurisation and overload

A

Pressure relief valves

258
Q

Pressure relief valves are located __

A

Off the main line coming from the pump

259
Q

Two types of pressure relief valves

A

Direct-acting

Compound

260
Q

Two advantages of a direct-acting pressure relief valve

A

Inexpensive

Easy to maintain

261
Q

Two disadvantages of a direct-acting pressure relief valve

A

Does not respond well to constant pressure changes

Large pressure override

262
Q

This type of pressure relief valve is used to alleviate high-pressure override

A

Compound

263
Q

This pressure relief valve contains two stages: An upper stage, which contains a pilot valve, and a lower stage, which is the main valve

A

Compound

264
Q

Contains ports connecting the valve to the system, a spool (also known as a balanced piston), and a 20-psi light spring that holds the balanced piston in position

A

Compound pressure relief valve

265
Q

How large is the orifice in the piston in a compound pressure relief valve

A

.040-inch

266
Q

The spring for the main spool is a light spring rated at ___ (Compound pressure relief valve)

A

20 psi

267
Q

DCVs

A

Directional Control Valves

268
Q

Direct the fluid flow in a system

A

Directional control valves

269
Q

By opening and closing ports, these valves can bypass, start, and stop actuator movement

A

Directional control valves

270
Q

Flow paths in DCVs known as ___

A

Ways

271
Q

Allow fluid flow in one direction but will block flow in the opposite direction

A

One-way check valves

272
Q

Two types of check valves

A

Ball type

Poppet type

273
Q

A ball is held against the seat by a light spring (usually 5 psi)

A

Ball-type check valve

274
Q

Instead of a ball, it will have a poppet held against the seat by a light spring

A

Poppet-type check valve

275
Q

Usual psi of spring in check valve

A

5 psi

276
Q

Used to prevent hydraulic fluid in the pump from draining into the reservoir while the system is secured

A

One-way DCVs

277
Q

Used to allow fluid to bypass the filter

A

Bypass check valve

278
Q

Also known as load lock valves and are commonly used in steering systems

A

Pilot to open check valve

279
Q

In a two-way DCV, the spool position in the valve determines whether ___

A

The valve is open or closed

280
Q

The symbol for DCVs are broken down into several important parts

A

Positions
Ways
Center-type
Actuation

281
Q

To determine the number of DCV positions ___

A

Count the number of boxes

282
Q

Refers to the number of active porting connections

A

Ways

283
Q

To determine the number of ways ___

A

Count the number of connections or lines attached to the valve

284
Q

The ports on a DCV are labeled as ___

A

P - pressure
T - tank
A
B

285
Q

Have three ports and maybe two or three position valves

A

Three way DCVs

286
Q

This type of DCV will be used to reverse the direction of an actuator

A

Four-way DCVs

287
Q

On most three position, four-way DCVs the end positions are ___

A

Parallel ported

Cross-ported

288
Q

With a three position valve, the center position may be one of the following

A

Closed
Open
Float
Tandem

289
Q

Determines the center position of the DCV

A

Application of the system

290
Q

All ports are blocked, stop the actuator at any position and hold it there

A

Closed center

291
Q

When in the center position, system pressure before the valve will be at ___

A

Relief pressure

292
Q

All ports are open to each other, will move the actuator, they do not have control of the load

A

Open center

293
Q

Open centers are not used in systems with ___

A

More than one DCV

294
Q

A, B, & T ports are open to each other

A

Floating center

295
Q

Used mainly with linear actuators, used in systems with more than one DCV, will not have control of he load

A

Floating center

296
Q

P & T ports are open to each other while A & B ports are blocked

A

Tandem center

297
Q

Used to unload the pump in the center position, not used in systems with more than one DCV, stop the actuator at any position and hold it there, can be reversed for other operations

A

Tandem center

298
Q

Two-way and three-way DCVs can have ___ on one or both ends of the spool to return it to the neutral position

A

Springs

299
Q

On two-position DCVs, the spring is called ___

A

Spring-offset

300
Q

On three-position DCVs, the spring is called ___

A

Spring-centred

301
Q

The spool is either spring-centred or ___

A

Detented

302
Q

Means to lock the sliding spool valve in one position

A

Detent

303
Q

Uses a spring and steel ball in a cylinder with the ball riding in a groove on the spool

A

Detenting

304
Q

Shifts the spool or rotating element of a direct-acting directional valve

A

Operator or actuator

305
Q

The means through which the valve is shifted from one position to another

A

Actuation

306
Q

The five categories of actuators (operators)

A 
Mechanical actuators
Pneumatic actuators
Manual actuators
Electrical actuators
Hydraulic actuators
307
Q

Are either plunger or wheel type, device such as a cam or cylinder will move the spool into position

A

Mechanical actuators

308
Q

Use air pressure from an external source to shift the spool

A

Pneumatic actuators

309
Q

Are usually levers attached to the spools through some kind of linkage. Includes hand lever, foot pedal, push button, or other mechanical means

A

Manual actuators

310
Q

Known as solenoid actuators, are on/off solenoids. Upon receiving an electrical signal, the solenoid is either fully shifted or off

A

Electrical actuators

311
Q

Three-position DCVs will have a solenoid ___

A

One each end

312
Q

Produce a limited amount of force and will only move short distances, so this type of actuation is used only on smaller, low-flow valves

A

Solenoids

313
Q

Use pilot pressure and flow to shift the spool. An additional directional valve (pilot valve) normally controls this pilot pressure and flow

A

Hydraulic actuators

314
Q

Often referred to as two-stage valves, and are normally electrically operated

A

Pilot valves

315
Q

Causes and symptoms of valve failure include the following

A

Broken springs
Fluid contamination
Bound spool/piston
Fluid leakage

316
Q

If the spring for the main spool is broken, the spool would not be able to ___. Fluid could then flow into the reservoir or actuator at the wrong time resulting in the system operating ___

A

Return to a neutral position

At a slower than normal pace

317
Q

Result of contamination wearing down sealing areas inside control valves

A

Fluid leakage

318
Q

Malfunctioning valves cause a system to:

A

Operate at the wrong pressure
Operate at the wrong speed
Operate at the wrong time
Not operate at all

319
Q

Pressure control valves use ___ to control their operation

A

System pressure

320
Q

Flow control valves use ___ to control their operation

A

The rate of flow or, more specifically, the size of the path through which fluid flows into and out of the valve

321
Q

Setting the size of the path controls the amount of flow exiting the valve

A

Flow control valve

322
Q

By controlling the rate of flow within a hydraulic system, we can control the ___

A

Speed of an actuator

323
Q

Disadvantage of the simple flow control valve is that when changing a load on the system to maintain the same actuator speed, you must ___

A

Adjust the valve

324
Q

Three factors that affect flow rate through an orifice or restriction

A

Fluid temperature/viscosity
Orifice size
Pressure drop

325
Q

The ___ the fluid, the faster the flow rate

A

Thinner

326
Q

The __ the hole, the more fluid can pass through

A

Bigger

327
Q

If a ___ exists in the system, the pressure preceding that orifice will rise

A

Restriction

328
Q

The pressure downstream of the orifice will be ___

A

Lower

329
Q

The ___ the pressure drop, the faster fluid will move through the restriction

A

Larger

330
Q

Two types of flow control valves

A

Fixed orifice

Variable orifice

331
Q

Symbol for Flow control valve

A

Line, with two arcs on either side, apex facing the line

332
Q

Simplest type of flow control

A

Fixed orifice flow control valve

333
Q

Consists of a restriction, non adjustable

A

Fixed orifice flow control valve

334
Q

Contains an orifice that can be adjusted

A

Variable orifice flow control valve

335
Q

Major disadvantage of variable orifice flow control valve

A

Fluid pressure preceding the valve will be at or near the setting of the pressure relief valve

336
Q

Over-running creates ___

A

Wasted power and heat

337
Q

Most common flow control circuits

A

Metre-out
Metre-in
Bleed-off

338
Q

Fluid leaving the actuator must pass through the flow control valve in order to return to the tank

A

Metre-out circuit

339
Q

This arrangement will allow the system to control an over-running load

A

Metre-out circuit

340
Q

Fluid entering the actuator will first go through the flow control valve

A

Metre-in circuit

341
Q

This design is useful to control the speed but will not have any control over an over-running load

A

Metre-in circuit

342
Q

Fluid is bled off to the reservoir prior to the actuators, thus controlling the speed on an actuator. This design is less accurate

A

Bleed-off circuit

343
Q

Similar in design to pumps, the main difference is that it converts hydraulic energy, created by the pump to mechanical energy/force

A

Actuators

344
Q

Two categories of actuators

A 
Linear actuators (hydraulic cylinders)
Rotary actuators
345
Q

Deliver their force in a straight line

A

Linear actuator

346
Q

Deliver their force in a rotary motion

A

Rotary actuator

347
Q

Convert the hydraulic energy created by the pump back into mechanical energy

A

Rotary and linear actuators

348
Q

Where the work is completed

A

Actuator

349
Q

The force that is created by a hydraulic motor

A

Torque

350
Q

The turning effort of the output shaft

A

Torque

351
Q

If torque is sufficient enough to overcome the resistance, ___ will occur

A

Rotary motion

352
Q

Force x radius =

A

Torque

353
Q

Hydraulic motors are rated by ___

A

Maximum pressure
Displacement
Torque

354
Q

Three basic types of hydraulic motor designs

A

Gear (internal & external)
Vane (balanced & unbalanced)
Piston (inline and radial)

355
Q

The angle of the swash plate determines ___

A

The speed and the amount of torque created by the motor

356
Q

At a given pressure, a greater swash plate angle will provide ___ torque and a ___ shaft rpm

A

Higher

Lower

357
Q

A lower swash plate angle will provide a ___ torque, but a ___ shaft rpm

A

Lower output

Higher

358
Q

Difference in symbol of motor from pump

A

The triangle points inward on the motor symbol

359
Q

Two basic types of linear actuators

A

Single-acting linear actuator

Double-acting linear actuator

360
Q

Retraction of a single-acting linear actuator is accomplished by ___

A

Gravity
The weight of the abject being moved
Manually

361
Q

Retraction of a double acting linear actuator is accomplished with ___

A

Hydraulic fluid pressure

362
Q

Similar to hydraulic rams

A

Single-acting linear actuator

363
Q

Apply force in one direction only and rely on gravity or a counterforce to retract

A

Single-acting linear actuator

364
Q

The main difference between a single-acting cylinder and a ram is that the ___

A

Cylinders use pistons

365
Q

Most common type of actuator used in industrial hydraulics. Hydraulic pressure and flow are used to extend and retract the cylinder rod

A

Double-acting linear actuator

366
Q

Two types of double-acting linear actuators

A

Double-acting differential linear actuator

Double-acting nondifferential linear actuator

367
Q

Refers to the different piston areas (net and cap) within the actuator

A

Differential

368
Q

A double rod cylinder is an example of a ___

A

Nondifferential linear actuator

369
Q

This design makes the speed and force equal in both directions

A

Nondifferential linear actuator

370
Q

A device that converts fluid power into linear mechanical force and motion

A

Hydraulic linear actuator

371
Q

Houses the piston and rod

A

Body (cylinder tube)

372
Q

The body is connected to the head and end caps by ___

A

Tie rods and nuts

373
Q

Prevent leakage between the cylinder body and head ends

A

Static seals

374
Q

The ___ contain the fluid ports

A

Ends

375
Q

The rod head end contains a ___ which prevents external leakage along the rod

A

Rod seal

376
Q

The main body of the cylinder and is used with the cylinder end cap and cylinder head to create the cylinder chamber

A

Cylinder tube

377
Q

Cylinder tube construction

A

Brass, steel, or aluminium

378
Q

Determines the construction of the cylinder tube

A

Intended working pressure and use

379
Q

The inside of the cylinder tube may be ___ to improve wear characteristics and to reduce corrosion

A

Plated or anodised

380
Q

Used to create a sealed chamber on each side of the piston and are usually constructed from rolled steel or cast iron

A

Cylinder heads and end caps

381
Q

Two types of seals found in hydraulic linear actuators

A

Static seal

Dynamic seal

382
Q

Primarily used to join two mating parts that remain stationary. Used in a linear actuator to prevent fluid leakage between the cylinder tube and cylinder head/end cap

A

Static seal

383
Q

Used to prevent fluid leakage between a stationary and a nonstationary part

A

Dynamic seal

384
Q

Two dynamic seals in a linear actuator

A

Rod seals

Piston seal

385
Q

Prevent fluid leakage between the cylinder head and the cylinder rod

A

Rod seals

386
Q

Used to separate the cap end fluid from the rod end fluid

A

Piston seal

387
Q

Usually constructed of cast iron and are the primary components that allow for the conversion of hydraulic energy to mechanical energy

A

Cylinder pistons

388
Q

Installed to prevent hydraulic fluid from leaking past the piston. Used to separate one side of the piston from the other; usually cast iron or steel. Create two different chambers within the cylinder, and are designed to fir into slots around the circumference of the piston

A

Piston rings

MK3 (10 decks)

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