Rotary compressors Screw, vane, dynamic liquid ring

Question 1

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

Answer 1

Constant Volume, Pressure ratio

Question 2

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

Answer 2

All of the above

Question 3

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

true

false

Answer 3

True

Question 4

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

Answer 4

Both second and third options are correct

Question 5

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

Answer 5

6+8

Question 6

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

true

false

Answer 6

True

Question 7

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

true

false

Answer 7

False

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

Question 8

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

wash

seal

purge

vent

Answer 8

Seal

Question 9

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

Answer 9

Improve the efficiency of the compressor

Question 10

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

Answer 10

True

Question 11

.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

Answer 11

True

Question 12

displacement control for a screw compressor can be done by

turn valves

poppet valves

slide valves

all the above

Answer 12

All of the above

Question 13

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

true

false

Answer 13

True

Question 14

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

true

false

Answer 14

False.

Staples are to ground and reduce risk of explosion

Question 15

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

true

false

Answer 15

true

Question 16

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

Answer 16

All of the above

Question 17

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

low, high

high, high

high, low

low, low

Answer 17

High. Low

Question 18

2 and 3 lobe blowers _____________ (inside the casing)

compress air

do not compress air

Answer 18

Do not compress air

Question 19

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

oil

seals

pressure differential

timing gears

Answer 19

Timing Gears

Question 20

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

negative flow

effciency

slip

positive flow

Answer 20

Slip

Question 21

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

true

false

Answer 21

True

Question 22

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

Answer 22

All of the above

Question 23

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

true

false

Answer 23

False

Question 24

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

true

false

Answer 24

True

Question 25

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

Answer 25

Rotation

Question 26

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

Answer 26

True

Question 27

impeller to impeller cleanance on lobe blowers is usully taken at a ____________ degree position 25 35 45 90

Answer 27

45

Question 28

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

Answer 28

16" diameter timing gear, 38" length rotor

Question 29

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

Answer 29

Out of time

Question 30

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

Answer 30

True

Question 31

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

Answer 31

Both second and third answers are correct

Question 32

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

Answer 32

increase the sealing area between rotor and stator

Question 33

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

Answer 33

True

Question 34

automatic air control is accomplished by the use of the unloading valve and the ______________ pressure relief valve servo valve oil return valve sump valve

Answer 34

Servo valve

Question 35

oil relief valves are used to help stop ______________ moisture build up oil hydraulic lock high air pressure none of the above

Answer 35

oil hydraulic lock

Question 36

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

Answer 36

All if the above

Question 37

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

Answer 37

Both 1st and second answers are correct

Question 38

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

Answer 38

True

Question 39

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

Answer 39

Vertical split (barrel casing)

Question 40

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

Answer 40

Open

Question 41

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

Answer 41

True

Question 42

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

Answer 42

True

Question 43

thrust control on dynamic compressors can be accomplished by balance pistons or drums thrust bearings impeller arrangements all the above

Answer 43

All of the above

Question 44

carbon seals are where there are low pressure differentials true false

Answer 44

True

Question 45

a common axial thrust bearing is the tilting pad type true false

Answer 45

True

Question 46

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

Answer 46

Increase the gas velocity, converts velocity to pressure

Question 47

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

Answer 47

True

Question 48

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

Answer 48

All of the above

Question 49

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

Answer 49

Between the surge wall and stone wall point

Question 50

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

Answer 50

True

Question 51

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

Answer 51

True

Question 52

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

Answer 52

True

Question 53

cooling of the compressed air in a liquid ring compressor is done by the oil cone liquid ring all the above

Answer 53

Liquid ring

Question 54

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

Answer 54

1/4 to 1/3 full

Question 55

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

Answer 55

90degrees , to the lantern ring

Question 56

there are 2 main compressor classifications. they are dynamic and axial rotary and reciprocating reciprocating and dynamic non-positive and positive displacement

Answer 56

Non-positive and positive displacement

Question 57

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

Answer 57

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

Question 58

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

Answer 58

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

Question 59

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

Answer 59

True

Question 60

compressor unloading can be start/stop variable speed inlet unloading all the above

Answer 60

All of the above

Question 61

heat always travels from hot to cold true false

Answer 61

True