Millwright Third Year Compressors Flashcards
1
Q
Does a liquid ring compressor need an aftercooler?
A
No
2
Q
What does an axial compressor use to remove fluid?
A
Baffle or Cyclone Separator
3
Q
On a Screw Compressor or a Lobe Blower, Labyrinth Seals prevent oil from getting back to the:
A
rotor(s)
4
Q
On a Lobe Blower most of the clearance is on the:
A
Timing Gear side
5
Q
Lobe Rotors have lands that are also known as:
A
Wear Strips
6
Q
Before you take off gears:
A
Match mark them
7
Q
Vein, Screw, and Liquid ring compressors:
A
20-2300 CFM, 30-100psi, can draw 29” ov vacuum
8
Q
cone and port plates in a liquid ring compressor are for:
A
gas entry and exit
9
Q
baffles, and cyclone separators remove
A
fluid
10
Q
Liquid Ring compressors need oil:
A
for the bearing areas only
11
Q
The inlet port on a liquid ring compressor is:
A
larger than the discharge port
12
Q
air pressure entering a liquid ring compressor must be:
A
below atmospheric pressure if first stage
13
Q
on a liquid ring compressor a heat exchanger:
A
cools bearing oil
14
Q
Clean fluid is admitted through a pipe over the lantern ring to
A
direct cooling oil to the packing
15
Q
Bypassing High Pressure back to the intake is a method of unloading a:
A
liquid ring compressor
16
Q
bearing caps should be:
A
1/4-1/3 full of grease
17
Q
Lantern ring aligns with
A
fluid water
18
Q
1/16”
A
belt tension
19
Q
If the amount of liquid in a liquid ring compressor is altered so is the:
A
amount of gas
20
Q
proper seal face may have a
A
preload*
21
Q
Mechanical efficiency:
A
actual torque delivered by the motor compared to the theoretical in a percentage without any friction loss
22
Q
Volumetric efficiency
A
the volume that comes out of the discharge compared with the volume that enters the motor inlet
23
Q
overall efficiency=
A
mechanical efficiency X volumetric efficiency
24
Q
Overall efficiency is
A
how much power you get out of a motor compared to how much power you put into it.
25
speed in a hydraulic motor is
flow rate + Volume
26
The bigger the fluid chambers the:
slower the engine
27
pressure depends on: (2)
load and displacement
28
the maximum pressure rating is maximum recommended inlet pressure for continuous operation for a:
specified time
29
bias piston must have:
2-400 psi on it at all times to return the pump to full stroke
30
load sensor reduces flow during a change in load and during metering of flow through the:
flow control valve
31
the pressure limiting compensator maintains set operating pressure: (3)
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
32
in line piston pumps have to be:
below the lowest level of fluid in the reservoir
33
bent axis piston pumps can be
above level of reservoir
34
vane pumps need to rotate
at 600 rpm to begin pumping, unless they have springs in the vanes in which case they can pump at any rpm
35
balanced vane pumps need
smaller bearings
36
what can be changed in a balanced vane pump?
the camrings
37
tandem center valve
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.
38
which ports are connected in a tandem style envelope?
pressure and tank
39
in a float control valve which is the only port that is not connected to other three connected ports?
pressure is not connected, A B and T are.
40
pressure compensation setting is always:
lower than the relief valve setting
41
the pressure compensator could not work if the
relief valve blows
42
Relief valve should be set at %10 above
max system pressure
43
Pressure limiting piston:
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.
44
Load and pressure compensated:
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.
45
bent axis piston pumps have no
swash plate
46
bent axis piston pump piston is attached to
drive shaft with ball joints, it can be load and pressure compensated and can go both directions
47
rotary piston pump
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
48
radial piston pump
a camshaft moves pistons in and out
49
radial piston pumps
odd number of pistons
50
vane pumps are:
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
51
vane pumps
flow controlled by flow control valves, pressure by pressure compensation,
52
balanced vane pumps can produce what pressure?
up to 3000psi
53
Intravane, or balanced vane, some pressure is used to:
keep the vanes pressed out on stator
54
Vane trailing edge is on the side with
feed notches
55
Death pots allow gas to expand out so:
cavitation does not happen in wear area
56
gear pumps are?
tough
57
you can change the output on a gear pump by:
changing the gear
58
gear pumps are
unbalanced (not hering bone)
59
gear pumps have a provision for leakage oil to:
inlet and bearings with grooves
60
diaphragm compressors are considered to be:
a reciprocating compressor
61
Scroll
positive displacement
62
ejector, centrifugal and axial compressors
Dynamic, NonPositive Displacement
63
Radial:
Using one flow to compress another
64
an Ejector is a?
non mechanical compressor (venturi principle, needs a motive fluid)
65
Dynamic Compressors are not as good for:
pressure as they are for flow
66
horizontally split axial compressors are
easiest to disassemble
67
Horizontally split
800 psi, most popular
68
dynamic multi stage compressors use diffusers to:
create pressure?
69
diaphragms are located
between stages
70
Impellers in different stages have the same Diameter but different
thicknesses
71
Balance drums are on the:
discharge side
72
plain bearings are
friction, or hydrostatic. They get oil jacked before a large dynamic compressor is turned on.
73
stators are:
stationary
74
diffusers
speed gas up and then slow it down
75
diffuser vanes are an option that
increases pressure ratio
76
The large gear on a speed increase is the driver or driven gear?
driver
77
Gas is drawn into?
the eye of the impeller
78
sectional casing attributes (2)
low pressure ratios, small volumes
79
axial compressors must have:
several stages, typically 12 is max
80
dynamic compressors can provide low pressure air for:
combustion, aeration, vacuum pump
81
Impellers are keyed for:
rotor shaft
82
impeller rotors are balanced with:
all components in place
83
open impellers:
single stage, simplest
84
semi closed impellers:
single or multi stage, final stage in an axial compressor
85
closed impellers:
on shafts, slight curvature on blades, you can not see the blades, gas is thrown out radially
86
single stage
impellers are straight
87
adjustable diffusers slow down gas and
increase pressure
88
2 stage vane
125psi max
89
dry sliding vane cannot sustain high temperatures so max pressure is:
50 psi
90
oil pressure acts on servo valve and controls how much?
air gets into the compressor
91
oil reservoir pressure matches
compressor pressure
92
the oil servo valve matches compressor output to ?
system requirement
93
hearing bone style is great for:
fluid flow, however if it turn in reverse it will break
94
internal gear pump
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
lobe pump
same principle as a gear pump
96
gerotor
generated rotor, inner gear has one less tooth,
97
internal gear
small gear drives bigger gear
98
in a hydraulic system load does not change
cylinder speed
99
double rod cylinders are
not differential, force and speed are equal
100
tandem cylinder
double the force on one rod
101
hydraulic cylinders are formed
on a piercing roll, they are seamless pipe, they have great strength
102
cushion flow control
has a ball valve for allowing flow to bypass small adjustable cushioning hole so cushioning effect does not slow down retraction
103
cup seals push
out and seal
104
an o ring groove should be
135-150% of o ring width
105
o ring crush
%10
106
flush mounted cylinders
the bottom of the rod and cap ends are drilled and tapped
107
o ring boss threads are
straight threads
108
bleed ports are for
getting rid of air
109
main cause of cylinder wear is
misalignment
110
main cause of cylinder failure is
contamination
111
internal leaks create
hot spots, jerky movements, squealing, aeration
112
binding in cylinders
misalignment betwen rod and load
113
mechanical efficiency is reduced by:
the internal friction of the motor
114
low speed high torque
radial piston, cam type, rotary, roller vane
115
high speed low torque
inline piston, bent axis, vane, gear
116
limited rotation motors
open and close large valves, alot of torque
117
how do you speed up a hydraulic motor?
increase pressure differential
118
pressure is biggest determining factor on?
torque
119
motor performance rating:
rated service life= hours of operating life at a rated displacement, pressure and torque
120
venturi output
Velocity down and pressure up
121
ejector pump
not mechanical, one flow,
122
each stage in an axial compressor has:
one rotor and one stator
123
diaphragms are between
stators on an axial compressor
124
axial thrust is always
going towards low pressure from HP
125
every impeller has some:
hp gas acting on it to reduce axial force, a balnce piston handles the rest.
126
dynamic seals
j strip or interlocking labyrinth
127
low pressure differentials used as the final sealing element are
carbon ring
128
mechanical seals are only for
low shaft speed
129
dry gaskets
plastic turning on plastic
130
beam type
rotor supported by bearings on both sides
131
variable stators are used on
constant speed drives
132
easiest way to control an axial compressor
vary the speed
133
variable stators may require
constant speed drives
134
stator blades cane be two types:
adjustable or fixed
135
adjustable stator blades that work during operation are called
continuously adjustable type
136
combination flow
axial and centrifugal compression
137
stator blades in axial compressors can get fouled by
dirt
138
surge point is when pressure is
high and discharge pushes towards suction
139
stonewall point
low quantity of gas moves towards discharge
140
a compressor control module
takes pressure reading from inlet and discharge
141
stonewall happens
at the speed of sound
142
compressor speed is varied to
prevent stonewalling
143
direct drive gear pumps
sharper form teeth
144
the bias spring straightens out yoke on pressure:
compensated variable displacement axial pump
145
synthetic piston rings do not allow
creep
146
cast iron rings can handle
higher temperatures and higher pressures
147
stop tubes provide stability for
long cylinders
148
the most common cylinder mounts are
tie rod mounts
149
amperage cards control
speed
150
radial
centre moves on a cam
151
carbon ring seals keep bearing housing oil from
getting into the compression chamber
152
low pressure carbon seals go between the
casing and the bearing housing
153
dry gas seals use
centripedal force
154
mechanical seals
cooled with liquid or gas
155
rotor drum type consist of
discs flanged to fit each other, fur tree, bulb type dove tail, t-root,
156
Fixed stator blades have a shroud for
supporting the blades and they provide a gas seal
157
stator blades get more_____ than rotator blades during fouling
punishment
158
transducers convert
energy from one state to another
159
surge is
low flow, not enough flow going into the system so the compressor works harder
160
surge pressure can destroy
thrust bearings
161
fan pressure comes from
resistance to flow
162
u tube manometer
measures very small changes in pressure
163
u tube manometer
add sum of readings above and below zero
164
coil fired plants use
squirrel cage fan(large quantities of air for combustion and for removing exhaust so natural draft can happen)
165
induced fan location
furnace stack
166
air foil blades are
backward inclined
167
straight blades are
strongest, faster, can handle high speeds
168
straight blades are
self cleaning
169
if we speed up a fan we can create
higher pressure
170
the best Induced Draft fan is
straight because dirt will not stick to the blades
171
backward blades
use less horsepower and are more efficien than forward curved blades
172
airfoil blades have
a backward incline
173
airfoil backward incline
operate like an airplane wing, they are the most efficient fan blades, %85 high pressure and high capacity, but expensive to make
174
forward curved blades are the most
common, ash particles do not stick, so it can be used as an ID fan,
175
forward curved veins can handle the high
air velocities at moderate blade speeds
176
axial flow fans are common in
exhaust conditions where airborne particles are small
177
axial fans must rotate at a higher rpm than
centrifugal fans to produce the same airflow
178
propeller fans can turn
both directions
179
propeller fans use
electric bearings with increased axial thrust capabilities
180
axial flow fans are used for
air cooled condensors, unit heaters and exhaust fans for ventilation purposes
181
the tube axial fan
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
vane axial fans,
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
mixed flow
axial and tubular
184
cooling towers
reject hear to atmosphere
185
Atmospheric uses
a natural draft
186
mechanical
forced and induced draft
187
fan performance curves
done by running unit and restricting flow by varying outlet sizes
188
suction throttling
having louvres at inlet
189
impellers on centrifugal fans are often called
wheels
190
outlet damper controls are used with constant speed motors and are
the least expensive and the least efficient control
191
variable inlet vane control
uses radial vanes installed in the fan inlet. The vane shafts interconnect so that all the vanes rotate open and close in unison
192
Fan Volume Controls
PLC, FD,ID
193
air inlet silencers
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
vibration isolators
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
spring type isolators
absorb vibration and allow for large thermal movements
196
Rubber disk
more compact than spring type isolators
197
liquid ring
built in pressure ratio
