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Test Review > Rotary compressors Screw, vane, dynamic liquid ring > Flashcards

Rotary compressors Screw, vane, dynamic liquid ring Flashcards

1
Q

rotary screw compressors are positive displacement compressors designend to deliver_____________ with a specific built in ___________

varying volume, pressure ratio

constant volume, pressure drop

constant volume, pressure ratio

varying volume, safety valve

A

Constant Volume, Pressure ratio

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2
Q

if you saw a screw compressor apart, how would you know it was a dry screw compressor

it would have no oil lubrication entering the screw

it would have extra sealing between the screws and bearings

it would have timing gears

all the above

A

All of the above

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3
Q

the location of the discharge port determines the pressure ratio of the screw compressor

true

false

A

True

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4
Q

leakage in the screw compressor can happen ____________ and can be partly eliminated by _____________

between stages, decreasing the rpm

between the rotors, increasing the rpm

between the rotor and housing, injecting oil

both the 2nd and 3 option are correct

A

Both second and third options are correct

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5
Q

if you wanted to produce a high pressure and low volume out of the screw compressor you would use a ___________________

4+6

3+4

6+8

they all would work

A

6+8

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6
Q

6.a single screw compressor has 1 main rotor and 2 star rotors on opposite sides

true

false

A

True

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7
Q

The fixed bearing in a screw compressor must be located at the intake end of the compressor

true

false

A

False

Must be installed at the outtake end to maintain the proper clearance of the screw and the end plate

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8
Q

oil flooded screw compressors use oil to cool the compressed air and ___________between the rotors

wash

seal

purge

vent

A

Seal

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9
Q

proper maintenance of the screw intake air filter will help

improve the efficiency of the compressor

extend the temperature range the compressor can operate at

decrease the pressure drop across the filter

all the above

A

Improve the efficiency of the compressor

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10
Q

on a wet screw compressor the purpose of the minimum pressure valve is to help get the oil flowing in the lubrication system on start up bu building up pressure to 20 -50 psi

true

false

A

True

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11
Q

.the main purpose of the blow down valve is to vent the pressure from the separator on a shutdown, to prevent oil from beng pushed out the compressor inlet and inet filter

true

false

A

True

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12
Q

displacement control for a screw compressor can be done by

turn valves

poppet valves

slide valves

all the above

A

All of the above

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13
Q

variable capacity control can be achieved by moving slide valves and slide stop controls together or independently

true

false

A

True

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14
Q

when maintaining compressor separators, the gasket must have the staples left in to prevent over-pressuring the sump

true

false

A

False.

Staples are to ground and reduce risk of explosion

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15
Q

for every 18 degrees F in crease in mineral oil temperature above 135 degrees F, the oxidation rate doubles.

true

false

A

true

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16
Q

if your screw compressor has low air delivery, it could mean that

the inlet is restricted

the blowdown valve is stuck

the air / oil separator is plugged

all the above

A

All of the above

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17
Q

2 and 3 lobe blowers are considered to be ______________ volume , _______________ pressure machines

low, high

high, high

high, low

low, low

A

High. Low

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18
Q

2 and 3 lobe blowers _____________ (inside the casing)

compress air

do not compress air

A

Do not compress air

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19
Q

lobe blowers must have _________________ to maintain the clearances inside the unit

oil

seals

pressure differential

timing gears

A

Timing Gears

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20
Q

any leakage from the discharge back to the inlet on a blower is known as

negative flow

effciency

slip

positive flow

A

Slip

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21
Q

the 3 lobe blower has a higher efficiency that 2 lobe blowers

true

false

A

True

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22
Q

helical lobe blowers

compress air in side the housing

create operating pressure of 20 - 50 psi

have an unequal number of lobes on the 2 rotors (2+4)

all the above

A

All of the above

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23
Q

timing gears should be of a high quality and have excessive backlash in the gears to keep the rotors in proper mesh

true

false

A

False

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24
Q

oil seals on blowers are usually labyrinth with some type of lip seal

true

false

A

True

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25
Q

when maintaining lobe blowers, you should always turn it over by hand to make sure it rotates freeely and than bump start motor to find the correct ________________ before running the system

clearances

mate marks

rotation

position

A

Rotation

26
Q

when checking clearances, it is important to rotate the impellers thru 360 degrees and obtain at least the minimum specified clearance

true

false

A

True

27
Q

impeller to impeller cleanance on lobe blowers is usully taken at a ____________ degree position

25

35

45

90

A

45

28
Q

A 16.38 lobe blower size – tells us it has a

16” length rotor, 38”, timing gear

16” diameter timing gear, 38” length rotor

this number does not tell us anything about a blower

16” timing gear driving a 38” timing gear

A

16” diameter timing gear, 38” length rotor

29
Q

if a knocking sound is heard inside the blower, it may mean the unit _____________

has to much oil in the gear housing

is out of time

has excessive rotor clearances

has worn shaft seals

A

Out of time

30
Q

vane compressors work on the principle of an inceasing area on the intake cycle and a decreasing area on the compression cycle.

true

false

A

True

31
Q

if the vane compressor is oil free, you would need to use

vanes made of cast steel

vanes made of teflon compounds

vanes made of graphite compounds

both the 2nd and 3rd answers are correct

A

Both second and third answers are correct

32
Q

there is an extra cut in the stator of the vane compressor, that matches the rotor diameter. this is to help

increase the clearances between rotor and stator

decrease clearances between rotor and stator

increase the sealing area between rotor and stator

increase clearances and increase the volume of the trapped air between the vanes

A

increase the sealing area between rotor and stator

33
Q

in the minimum pressure valve / non-return valve, the check valve helps prevent reverse flow of the air flow.

true

false

A

True

34
Q

automatic air control is accomplished by the use of the unloading valve and the ______________

pressure relief valve

servo valve

oil return valve

sump valve

A

Servo valve

35
Q

oil relief valves are used to help stop ______________

moisture build up

oil hydraulic lock

high air pressure

none of the above

A

oil hydraulic lock

36
Q

when overhauling sliding vane compressors, careful attention should be paid to

positioning of the shims

new vane end clearances

O-ring seating

all the above

A

All if the above

37
Q

when match marking the end cover to stator, do NOT use ________________ as this will damage the sealing serfaces

hammer and punch

etching tool

felt pen

both the 1st and 2nd answer is correct

A

Both 1st and second answers are correct

38
Q

multi-stage centrifugal compressors increase the volume and overall pressure ratio to achieve higher discharge pressures

true

false

A

True

39
Q

casing styles for centrifugal compressors are sectional, horizontal split and vertical split. the one that is used for high pressure is

sectional

horizontal split

vertical split ( barrel casing)

all can be used for high pressure

A

Vertical split (barrel casing)

40
Q

impellers can be of the open, semi-open, and closed design. the design that is used for rough service environments is the

open

semi-open

closed

all can be used for rough service environments

A

Open

41
Q

guide elements (stationary or adjustable diffusers) direct gas flow from one stage to the next in a multi-stage centrifugal compressor

true

false

A

True

42
Q

labryrinth seals are installed on the diaphragm assembly in axial flow compressors to minimize internal leakage along the shaft between stages

true

false

A

True

43
Q

thrust control on dynamic compressors can be accomplished by

balance pistons or drums

thrust bearings

impeller arrangements

all the above

A

All of the above

44
Q

carbon seals are where there are low pressure differentials

true

false

A

True

45
Q

a common axial thrust bearing is the tilting pad type

true

false

A

True

46
Q

in an axial compressor, the rotors ____________ and the stators ________________-

increase the gas velocity, converts velocity to pressure

decrease the gas velocity, converts pressure into velocity

increases gas pressure, converts pressure to velocity

none of the above

A

Increase the gas velocity, converts velocity to pressure

47
Q

an example of a rotor dixc blade mounting style is the fir tree

true

false

A

True

48
Q

to correct blade fouling in axial compressors you can

add crushed walnut shells while still running

use special non-stick coatings

increase the RPM until material loosens

all the above

A

All of the above

49
Q

the best operating range of all dynamic compressors is

at balancing points

between the surge point and the stonewall point

at the surge point

at the stonewall point

A

Between the surge wall and stone wall point

50
Q

surge control is resolved by closing off the discharge valve and then redirecting some of the discharge air back to the inlet

true

false

A

True

51
Q

the liquid ring compressor is an oil-free positive displacement pump that uses a ring of liquid to seal the spaces between the impeller vanes

true

false

A

True

52
Q

air-flow into and out of the liquid ring compressor is thru a set of cones ( or port plates ) that surround the shaft

true

false

A

True

53
Q

cooling of the compressed air in a liquid ring compressor is done by the

oil

cone

liquid ring

all the above

A

Liquid ring

54
Q

when repacking a liquid ring compressor bearings with grease, you should pack the bearing full of grease and then fill the housing__________ with grease

1/2 full

full

1/4 to 1/3 full

to the bottom of the bottom rolling element

A

1/4 to 1/3 full

55
Q

if you are repacking the packing gland, make sure you stagger the joints______ and mount the ____________in the proper position

45 degrees, end cap

90 degrees, end cap

45 degrees, lantern ring

90 degrees, lantern ring

A

90degrees , to the lantern ring

56
Q

there are 2 main compressor classifications. they are

dynamic and axial

rotary and reciprocating

reciprocating and dynamic

non-positive and positive displacement

A

Non-positive and positive displacement

57
Q

positive displacement works on the principle that

Option 1there is an increasing area and a decreasing area that lets in and compresses the air

air flows from low pressure to high pressure after the compressor

velocity increases in the volute and then pressure decreases in the lines

velocity increases thru the compressor and then slows down in the volute where pressure increases

A

There is an increase area and a decreasing area that lets in and compresses the gas

58
Q

a dynamic compressor works on the principle that

the velocity is slowed down thru the compressor to create a pressure drop

the air velocity is sped up thru the compressor and slowed down in the volute to increase the pressure

the pistons create the pressure by allowing air flow into the intake and decreasing the pressure out the out feed

the pistons create the pressure with the stroke of compression

A

the air velocity is sped up thru the compressor and slowed down in the volute to increase the pressure

59
Q

compressors are used for boosting pressure and gas gathering in the oil and gas industry

true

false

A

True

60
Q

compressor unloading can be

start/stop

variable speed

inlet unloading

all the above

A

All of the above

61
Q

heat always travels from hot to cold

true

false

A

True

Test Review (17 decks)

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