Vane compressor

Question 1

What is pressure ratio?

Answer 1

Ratio of the absolute incoming air pressure to the absolute

compressor discharge pressure.

Question 2

What is the casing?

Answer 2

Metal outside structure that holds all the components in place.

Question 3

What is a stator?

Answer 3

Stationary inner metal cylinder that the vanes contact and slide
across as they turn within the unit. Machined as a separate unit and
contains inlet & outlet ports, oil relief valves and oil release valves..

Question 4

What is a rotor?

Answer 4

Only rotating part in a vane compressor.

Question 5

What is the purpose of the bearing carriers?

Answer 5

Locate the rotor in the correct position

Question 6

What are vanes?

Answer 6

Metal or composite sliding parts that fit into rotating block slots

Question 7

What purpose do the bearings serve?

Answer 7

Support and position the rotor in the off centre position within
the stator ring so no metal to metal contact takes place.

Question 8

What types of valves are found on vane compressors?

Answer 8

Min. pressure valve, check valves, unloader valves, servo

valves, oil relief, oil return, oil release, safety relief and vacuum

Question 9

What is the purpose of the minimum pressure valve and where

is it found?

Answer 9

Allows the wet sliding vane compressor to build enough
pressure to get oil lubrication system working 1st before sending any
air out into they system. Located at compressor discharge.

Question 10

What is the purpose of the check valve and where is it found?

Answer 10

Prevent back flow of compressed air into the compressor on
shutdown. Located at discharge. On wet vane it is located in the
minimum pressure valve assembly, plus another in the unloader
valve to prevent compressor air and oil mixture from discharging
though the inlet on shutdown.

Question 11

What is the purpose of the unloader valve and where is it

found?

Answer 11

Regulates incoming air and matches it to the system

requirements. Found after the inlet are filter but before the rotor.

Question 12

What is the purpose of the servo valve and where is it found?

Answer 12

When opened, allows oil pressure to reach the unloader valve
and move it to the closed position. Found in the oil reservoir just
before the unloader valve.

Question 13

What is the purpose of the oil relief valve and where is it found?

Answer 13

Allows trapped oil an escape route to prevent hydraulic lock.
Found on Stator near the compressor discharge.

Question 14

What is the purpose of the oil return valve and where is it

found?

Answer 14

Allows separated oil, but not air, to be fed back into the

compressor intake.

Question 15

What is the purpose of the oil release valve and where is it

found?

Answer 15

Allows oil to drain back into the reservoir to prevent hydraulic
lock. Found on bottom of the stator.

Question 16

What is the purpose of the safety relief valve and where is it
found?

Answer 16

Prevents over pressure of the casing and to unload the
compressor for ease of starting. Found on the casing between the
rotor and minimum pressure valve.

Question 17

What is the purpose of vacuum valve and where is it found?

Answer 17

Used to break the vacuum that causes blade instability, found
near the compressor intake.

Question 18

What are internal valve ports and where are they found?

Answer 18

Allow air into the inlet or out of the outlet chamber at the correct
time during the cycle. Cast into the stator ring at specific locations.

Question 19

Roughly how often should you change vane compressor oil and

grease?

Answer 19

10,000 hours and grease every 6 months

Question 20

What is a common problem with the servo/unloader valve

modulation control?

Answer 20

Valves get stuck and blow relief valve.

Question 21

In a sliding vane compressor, explain the position of the rotor,
which enables it to compress air.

Answer 21

Set in the stator off centre.

Question 22

What type of compressor requires the vanes be made from a
special material with a low coefficient of friction such as teflon or
graphite?

Answer 22

Dry Vane

Question 23

What type of compressor is flooded with oil all the time that it is
running?

Answer 23

Wet vane.

Question 24

How do vane compressor systems often eliminate the need for

an air receiver?

Answer 24

By using an inlet throttling system

Question 25

What is the only major moving part in a sliding vane

compressor?

Answer 25

Rotor Assembly.

Question 26

What does it mean for a compressor to have a built in pressure
ratio?

Answer 26

The pressure ratio is not adjustable as are reciprocating

compressors.

Question 27

482. What prevent the high pressure discharge air from leakage
     back into the low pressure suction area?

Answer 27

Centrifugal force along with an oil seal on the vanes.

Question 28

How is compressor capacity determined on a vane

compressor?

Answer 28

By calculating the volume of air between the two sets of vanes
at maximum volume multiple by the number of vanes multiplied by
the rpm of the motor.

Question 29

Why do non-lubricated vane designs generally produce air at

low pressures?

Answer 29

They cannot sustain high temperatures generated when high
pressures are required and they have increased friction from vanes
sliding on the cylinder surface.

Question 30

What is the purpose of the oil in the wet vane compressors?

Answer 30

Cool, seal, lubricate, prevent corrosion and operate the servo
valve.

Question 31

What is the principle involved with designing a vane

compressor system without and air receiver?

Answer 31

The air pressure being produced inside the casing is used to
control the position of the inlet unloader valve, which matches
compressor output to system requirements.

Question 32

On a wet vane compressor, what part gets rid of the majority of
oil as soon as it passes through the discharge port on a stator?

Answer 32

The labyrinth seal.

Question 33

Which valve on a wet vane serves the purpose of ensuring that
the oil circulation system is satisfied first, before the compressor
sends any air into the system?

Answer 33

The minimum pressure valve located on the pressure

discharge.

Question 34

Under what condition does the minimum pressure valve open?

Answer 34

As long as system pressure is above 60psi

Question 35

How is the reverse flow of air, along with condensed water
vapor and other contaminants prevented from entering the
compressor?

Answer 35

The check valve portion of the minimum pressure valve slams
shut or on larger compressors, there is a check valve in the
discharge line.

Question 36

On the wet vane, which valve is normally open on startup and

which is normally closed?

Answer 36

The unloader is normally open and the servo is normally

closed.

Question 37

Why must you have a good seal on the vanes while they rotate

and compress air?

Answer 37

As compression is occurring, each blade is at a slightly higher
pressure so the air is always trying to leak back towards the suction.

Question 38

Within a wet vane compressor, why must you remove the oil

vapour while the air/oil mixture is still quite warm?

Answer 38

If the moisture in the air were allowed to cool too much, the
water vapour could condense and contaminate the oil.

Question 39

Whats the purpose of an oil relief valve?

Answer 39

To prevent hydraulic lock or overpressure and breakage.

Question 40

What stops the oil from going to the cooler and warms up up

quicker to get it to the proper temperature for proper lubrication?

Answer 40

Oil bypass valve.

Question 41

Why does a safety relief valve need to be installed on the

casing of the wet vane compressor?

Answer 41

If the minimum pressure valve were to get blocked off, the

compressor could blow itself apart.

Question 42

Which valve could cause high pressure air to leak into lower
pressure areas of the compressor causing the compressor to work
harder and trip the breaker?

Answer 42

Oil relief valves if they are not seating properly.

Question 43

What happens if the inlet unloader is stuck in the closed

position?

Answer 43

No air can be pulled so no air can be delivered.

Question 44

Vane compressors are

Answer 44

Positive displacement constant volume compressors with built in pressure ratio