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Millwright Third Year Compressors > Millwright Third Year Compressors > Flashcards

Millwright Third Year Compressors Flashcards

1
Q

Does a liquid ring compressor need an aftercooler?

A

No

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2
Q

What does an axial compressor use to remove fluid?

A

Baffle or Cyclone Separator

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3
Q

On a Screw Compressor or a Lobe Blower, Labyrinth Seals prevent oil from getting back to the:

A

rotor(s)

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4
Q

On a Lobe Blower most of the clearance is on the:

A

Timing Gear side

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5
Q

Lobe Rotors have lands that are also known as:

A

Wear Strips

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6
Q

Before you take off gears:

A

Match mark them

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7
Q

Vein, Screw, and Liquid ring compressors:

A

20-2300 CFM, 30-100psi, can draw 29” ov vacuum

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8
Q

cone and port plates in a liquid ring compressor are for:

A

gas entry and exit

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9
Q

baffles, and cyclone separators remove

A

fluid

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10
Q

Liquid Ring compressors need oil:

A

for the bearing areas only

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11
Q

The inlet port on a liquid ring compressor is:

A

larger than the discharge port

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12
Q

air pressure entering a liquid ring compressor must be:

A

below atmospheric pressure if first stage

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13
Q

on a liquid ring compressor a heat exchanger:

A

cools bearing oil

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14
Q

Clean fluid is admitted through a pipe over the lantern ring to

A

direct cooling oil to the packing

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15
Q

Bypassing High Pressure back to the intake is a method of unloading a:

A

liquid ring compressor

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16
Q

bearing caps should be:

A

1/4-1/3 full of grease

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17
Q

Lantern ring aligns with

A

fluid water

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18
Q

1/16”

A

belt tension

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19
Q

If the amount of liquid in a liquid ring compressor is altered so is the:

A

amount of gas

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20
Q

proper seal face may have a

A

preload*

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21
Q

Mechanical efficiency:

A

actual torque delivered by the motor compared to the theoretical in a percentage without any friction loss

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22
Q

Volumetric efficiency

A

the volume that comes out of the discharge compared with the volume that enters the motor inlet

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23
Q

overall efficiency=

A

mechanical efficiency X volumetric efficiency

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24
Q

Overall efficiency is

A

how much power you get out of a motor compared to how much power you put into it.

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25
Q

speed in a hydraulic motor is

A

flow rate + Volume

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26
Q

The bigger the fluid chambers the:

A

slower the engine

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27
Q

pressure depends on: (2)

A

load and displacement

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28
Q

the maximum pressure rating is maximum recommended inlet pressure for continuous operation for a:

A

specified time

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29
Q

bias piston must have:

A

2-400 psi on it at all times to return the pump to full stroke

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30
Q

load sensor reduces flow during a change in load and during metering of flow through the:

A

flow control valve

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31
Q

the pressure limiting compensator maintains set operating pressure: (3)

A

when the closed centre directional control is centred, when the actuator stalls on overload, and when the cylinder is at the end of it’s stroke

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32
Q

in line piston pumps have to be:

A

below the lowest level of fluid in the reservoir

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33
Q

bent axis piston pumps can be

A

above level of reservoir

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34
Q

vane pumps need to rotate

A

at 600 rpm to begin pumping, unless they have springs in the vanes in which case they can pump at any rpm

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35
Q

balanced vane pumps need

A

smaller bearings

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36
Q

what can be changed in a balanced vane pump?

A

the camrings

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37
Q

tandem center valve

A

brake valve with cross port relief valves (load runs the motor when breaking so check valves are added to prevent cavitation. A vacuum will create condition for anti-cavitation check valve to open.

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38
Q

which ports are connected in a tandem style envelope?

A

pressure and tank

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39
Q

in a float control valve which is the only port that is not connected to other three connected ports?

A

pressure is not connected, A B and T are.

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40
Q

pressure compensation setting is always:

A

lower than the relief valve setting

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41
Q

the pressure compensator could not work if the

A

relief valve blows

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42
Q

Relief valve should be set at %10 above

A

max system pressure

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43
Q

Pressure limiting piston:

A

Bias piston, limits maximum pressure in the system, prevents excess oil from going across the relief valve, the pump is a flow control valve because it maintains a pressure differential.

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44
Q

Load and pressure compensated:

A

pump has two valves, flow control valves can be eliminated, the load sensing part maintains a correct flow at all times irrespective of what the load is. Correct flow at all times.

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45
Q

bent axis piston pumps have no

A

swash plate

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46
Q

bent axis piston pump piston is attached to

A

drive shaft with ball joints, it can be load and pressure compensated and can go both directions

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47
Q

rotary piston pump

A

pistons move in a bore, pump displacement is the size of the pistons, pintle is the inlet and outlet, they have a reaction ring, pressure from the piston is used to move the stator ring

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48
Q

radial piston pump

A

a camshaft moves pistons in and out

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49
Q

radial piston pumps

A

odd number of pistons

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50
Q

vane pumps are:

A

reliable, 300psi (midrange for pumps), 1200 RPM MAX, Unbalanced has alot of side load so balanced can handle higher pressure, but unbalanced can have varied displacement

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51
Q

vane pumps

A

flow controlled by flow control valves, pressure by pressure compensation,

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52
Q

balanced vane pumps can produce what pressure?

A

up to 3000psi

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53
Q

Intravane, or balanced vane, some pressure is used to:

A

keep the vanes pressed out on stator

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54
Q

Vane trailing edge is on the side with

A

feed notches

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55
Q

Death pots allow gas to expand out so:

A

cavitation does not happen in wear area

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56
Q

gear pumps are?

A

tough

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57
Q

you can change the output on a gear pump by:

A

changing the gear

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58
Q

gear pumps are

A

unbalanced (not hering bone)

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59
Q

gear pumps have a provision for leakage oil to:

A

inlet and bearings with grooves

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60
Q

diaphragm compressors are considered to be:

A

a reciprocating compressor

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61
Q

Scroll

A

positive displacement

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62
Q

ejector, centrifugal and axial compressors

A

Dynamic, NonPositive Displacement

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63
Q

Radial:

A

Using one flow to compress another

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64
Q

an Ejector is a?

A

non mechanical compressor (venturi principle, needs a motive fluid)

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65
Q

Dynamic Compressors are not as good for:

A

pressure as they are for flow

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66
Q

horizontally split axial compressors are

A

easiest to disassemble

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67
Q

Horizontally split

A

800 psi, most popular

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68
Q

dynamic multi stage compressors use diffusers to:

A

create pressure?

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69
Q

diaphragms are located

A

between stages

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70
Q

Impellers in different stages have the same Diameter but different

A

thicknesses

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71
Q

Balance drums are on the:

A

discharge side

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72
Q

plain bearings are

A

friction, or hydrostatic. They get oil jacked before a large dynamic compressor is turned on.

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73
Q

stators are:

A

stationary

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74
Q

diffusers

A

speed gas up and then slow it down

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75
Q

diffuser vanes are an option that

A

increases pressure ratio

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76
Q

The large gear on a speed increase is the driver or driven gear?

A

driver

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77
Q

Gas is drawn into?

A

the eye of the impeller

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78
Q

sectional casing attributes (2)

A

low pressure ratios, small volumes

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79
Q

axial compressors must have:

A

several stages, typically 12 is max

80
Q

dynamic compressors can provide low pressure air for:

A

combustion, aeration, vacuum pump

81
Q

Impellers are keyed for:

A

rotor shaft

82
Q

impeller rotors are balanced with:

A

all components in place

83
Q

open impellers:

A

single stage, simplest

84
Q

semi closed impellers:

A

single or multi stage, final stage in an axial compressor

85
Q

closed impellers:

A

on shafts, slight curvature on blades, you can not see the blades, gas is thrown out radially

86
Q

single stage

A

impellers are straight

87
Q

adjustable diffusers slow down gas and

A

increase pressure

88
Q

2 stage vane

A

125psi max

89
Q

dry sliding vane cannot sustain high temperatures so max pressure is:

A

50 psi

90
Q

oil pressure acts on servo valve and controls how much?

A

air gets into the compressor

91
Q

oil reservoir pressure matches

A

compressor pressure

92
Q

the oil servo valve matches compressor output to ?

A

system requirement

93
Q

hearing bone style is great for:

A

fluid flow, however if it turn in reverse it will break

94
Q

internal gear pump

A

fixed displacement, oil carried internally through the pump, crescent between gear teeth of two gears, oil provides lubrication and prevents metal to metal contact, has an internal gear and a small external gear

95
Q

lobe pump

A

same principle as a gear pump

96
Q

gerotor

A

generated rotor, inner gear has one less tooth,

97
Q

internal gear

A

small gear drives bigger gear

98
Q

in a hydraulic system load does not change

A

cylinder speed

99
Q

double rod cylinders are

A

not differential, force and speed are equal

100
Q

tandem cylinder

A

double the force on one rod

101
Q

hydraulic cylinders are formed

A

on a piercing roll, they are seamless pipe, they have great strength

102
Q

cushion flow control

A

has a ball valve for allowing flow to bypass small adjustable cushioning hole so cushioning effect does not slow down retraction

103
Q

cup seals push

A

out and seal

104
Q

an o ring groove should be

A

135-150% of o ring width

105
Q

o ring crush

A

%10

106
Q

flush mounted cylinders

A

the bottom of the rod and cap ends are drilled and tapped

107
Q

o ring boss threads are

A

straight threads

108
Q

bleed ports are for

A

getting rid of air

109
Q

main cause of cylinder wear is

A

misalignment

110
Q

main cause of cylinder failure is

A

contamination

111
Q

internal leaks create

A

hot spots, jerky movements, squealing, aeration

112
Q

binding in cylinders

A

misalignment betwen rod and load

113
Q

mechanical efficiency is reduced by:

A

the internal friction of the motor

114
Q

low speed high torque

A

radial piston, cam type, rotary, roller vane

115
Q

high speed low torque

A

inline piston, bent axis, vane, gear

116
Q

limited rotation motors

A

open and close large valves, alot of torque

117
Q

how do you speed up a hydraulic motor?

A

increase pressure differential

118
Q

pressure is biggest determining factor on?

A

torque

119
Q

motor performance rating:

A

rated service life= hours of operating life at a rated displacement, pressure and torque

120
Q

venturi output

A

Velocity down and pressure up

121
Q

ejector pump

A

not mechanical, one flow,

122
Q

each stage in an axial compressor has:

A

one rotor and one stator

123
Q

diaphragms are between

A

stators on an axial compressor

124
Q

axial thrust is always

A

going towards low pressure from HP

125
Q

every impeller has some:

A

hp gas acting on it to reduce axial force, a balnce piston handles the rest.

126
Q

dynamic seals

A

j strip or interlocking labyrinth

127
Q

low pressure differentials used as the final sealing element are

A

carbon ring

128
Q

mechanical seals are only for

A

low shaft speed

129
Q

dry gaskets

A

plastic turning on plastic

130
Q

beam type

A

rotor supported by bearings on both sides

131
Q

variable stators are used on

A

constant speed drives

132
Q

easiest way to control an axial compressor

A

vary the speed

133
Q

variable stators may require

A

constant speed drives

134
Q

stator blades cane be two types:

A

adjustable or fixed

135
Q

adjustable stator blades that work during operation are called

A

continuously adjustable type

136
Q

combination flow

A

axial and centrifugal compression

137
Q

stator blades in axial compressors can get fouled by

A

dirt

138
Q

surge point is when pressure is

A

high and discharge pushes towards suction

139
Q

stonewall point

A

low quantity of gas moves towards discharge

140
Q

a compressor control module

A

takes pressure reading from inlet and discharge

141
Q

stonewall happens

A

at the speed of sound

142
Q

compressor speed is varied to

A

prevent stonewalling

143
Q

direct drive gear pumps

A

sharper form teeth

144
Q

the bias spring straightens out yoke on pressure:

A

compensated variable displacement axial pump

145
Q

synthetic piston rings do not allow

A

creep

146
Q

cast iron rings can handle

A

higher temperatures and higher pressures

147
Q

stop tubes provide stability for

A

long cylinders

148
Q

the most common cylinder mounts are

A

tie rod mounts

149
Q

amperage cards control

A

speed

150
Q

radial

A

centre moves on a cam

151
Q

carbon ring seals keep bearing housing oil from

A

getting into the compression chamber

152
Q

low pressure carbon seals go between the

A

casing and the bearing housing

153
Q

dry gas seals use

A

centripedal force

154
Q

mechanical seals

A

cooled with liquid or gas

155
Q

rotor drum type consist of

A

discs flanged to fit each other, fur tree, bulb type dove tail, t-root,

156
Q

Fixed stator blades have a shroud for

A

supporting the blades and they provide a gas seal

157
Q

stator blades get more_____ than rotator blades during fouling

A

punishment

158
Q

transducers convert

A

energy from one state to another

159
Q

surge is

A

low flow, not enough flow going into the system so the compressor works harder

160
Q

surge pressure can destroy

A

thrust bearings

161
Q

fan pressure comes from

A

resistance to flow

162
Q

u tube manometer

A

measures very small changes in pressure

163
Q

u tube manometer

A

add sum of readings above and below zero

164
Q

coil fired plants use

A

squirrel cage fan(large quantities of air for combustion and for removing exhaust so natural draft can happen)

165
Q

induced fan location

A

furnace stack

166
Q

air foil blades are

A

backward inclined

167
Q

straight blades are

A

strongest, faster, can handle high speeds

168
Q

straight blades are

A

self cleaning

169
Q

if we speed up a fan we can create

A

higher pressure

170
Q

the best Induced Draft fan is

A

straight because dirt will not stick to the blades

171
Q

backward blades

A

use less horsepower and are more efficien than forward curved blades

172
Q

airfoil blades have

A

a backward incline

173
Q

airfoil backward incline

A

operate like an airplane wing, they are the most efficient fan blades, %85 high pressure and high capacity, but expensive to make

174
Q

forward curved blades are the most

A

common, ash particles do not stick, so it can be used as an ID fan,

175
Q

forward curved veins can handle the high

A

air velocities at moderate blade speeds

176
Q

axial flow fans are common in

A

exhaust conditions where airborne particles are small

177
Q

axial fans must rotate at a higher rpm than

A

centrifugal fans to produce the same airflow

178
Q

propeller fans can turn

A

both directions

179
Q

propeller fans use

A

electric bearings with increased axial thrust capabilities

180
Q

axial flow fans are used for

A

air cooled condensors, unit heaters and exhaust fans for ventilation purposes

181
Q

the tube axial fan

A

heavier duty, can be mounted in a duct, create swirl, channels can stop swirl, they create alot of noise, not good for residential or commercial air conditions.

182
Q

vane axial fans,

A

outlet and guide veins, vanes eliminate swril, used to induce draft for boiler exhaust, mounted overhead in a crawl space, difficult to maintain because of limited access.

183
Q

mixed flow

A

axial and tubular

184
Q

cooling towers

A

reject hear to atmosphere

185
Q

Atmospheric uses

A

a natural draft

186
Q

mechanical

A

forced and induced draft

187
Q

fan performance curves

A

done by running unit and restricting flow by varying outlet sizes

188
Q

suction throttling

A

having louvres at inlet

189
Q

impellers on centrifugal fans are often called

A

wheels

190
Q

outlet damper controls are used with constant speed motors and are

A

the least expensive and the least efficient control

191
Q

variable inlet vane control

A

uses radial vanes installed in the fan inlet. The vane shafts interconnect so that all the vanes rotate open and close in unison

192
Q

Fan Volume Controls

A

PLC, FD,ID

193
Q

air inlet silencers

A

used on centrifugal fans to muffle loud inlet sound generated by increased air velocity and air shock as it flows into the eye of the fan wheel

194
Q

vibration isolators

A

between casing base and concrete foundation to absorb vibrations caused by mechanical and air imbalances. some use springs, oil dampening, rubber, wool or cork

195
Q

spring type isolators

A

absorb vibration and allow for large thermal movements

196
Q

Rubber disk

A

more compact than spring type isolators

197
Q

liquid ring

A

built in pressure ratio

Millwright Third Year Compressors (2 decks)

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