DETAIL STUDY ON TYPES OF AIR COMPRESSOR (POSITIVE & DYNAMIC ) WITH ITS WORKING PRINCIPLE AND MAINTENANCE PROCEDURE. ADVANTAGE OF DYNAMIC COMPRESSURE, ADVANTAGE OF POSITIVE DISPLACEMENT COMPRESSOR,DRAWBACK OF SINGLE STAGE AIR COMPRESSOR OVER MULTISTAGE COMPRESSOR

1. Air Compressors

2. An air compressor is a mechanical device that is used to compress the incoming
air and provide a fast speed and compressed air on the outgoing side.
Air Compressor – 1) Takes in atmospheric air,
2) Compresses it, and
3) Delivers it to a storage vessel ( i.e. Reservoir ).
Air
Compressors
Compressor must be driven by some sort of Prime Mover ( i.e. Engine )

3. PARTS OF AIR
COMPRESSOR

4.  On top of the cylinder, there is an air inlet valve. Inside the cylinder is a
piston, the air inlet valve is initially open so that as the piston goes down air
can fill the cylinder.
 As the piston reaches the bottom of the cylinder, the air inlet valve shuts and
the air outlet valve opens
Working principle of air compressor

5.  The piston then pushes the air out of the cylinder up and out of the air outlet
valve into the air storage tank. The air outlet valve shuts as the piston reaches
the top again, in turn, the air inlet valve opens and the process starts again.
 As the storage tank starts to fill up with compressed air a sensor in the tank
monitors it so that it knows when it is at capacity or at the maximum amount of
bar or PSI of pressure for the compressor.
 Once that happens the electric motor driving the piston up and down switches
off. As air is used from the compressor by power tools, etc the motor will start
up again to keep the storage tank full and under pressure.
 There is an oil pan that the crankshaft (attached to the piston) sits in, keeping
all of the moving parts lubricated and cooling the moving parts. Compressing
air generates a lot of heat and so it is important to keep the oil levels correct.
 There is also a filter that removes moisture from the air, as moisture build-up
inside the compressor would start to rot the compressor and cause rust
Working principle of air compressor

6. Compressors have many everyday uses, such as in :
 Air conditioners, (car, home)
 Pneumatic devices
 Home and industrial refrigeration
 Hydraulic compressors for industrial machines
 Air compressors for industrial manufacturing
Applications

7. Compressor classification can be described by following flow chart:
Classification of Compressor

8. The dynamic compressor is continuous flow compressor is characterized by
rotating impeller to add velocity and thus pressure to fluid.
It is widely used in chemical and petroleum refinery industry for specific services.
There are two types of dynamic compressors
 Centrifugal Compressor
 Axial Flow Compressor
Dynamic Compressors

9.  Achieves compression by applying inertial forces to the gas by means of
rotating impellers.
 It is multiple stage ; each stage consists of an impeller as the rotating
element and the stationary element, i.e. diffuser
 Fluid flow enters the impeller axially and discharged radially
 The gas next flows through a circular chamber (diffuser), where it loses
velocity and increases pressure.
Centrifugal Compressors

10.  Working fluid principally flows parallel to the axis of rotation.
 The energy level of air or gas flowing through it is increased by the
action of the rotor blades which exert a torque on the fluid
 Have the benefits of high efficiency and large mass flow rate
 Require several rows of airfoils to achieve large pressure rises making
them complex and expensive
Axial Flow Compressor

11. Positive displacement Compressors
Reciprocating Rotary
Single – acting
Double - Acting
No. of Sides of Piston
in operation
No. of Stages
for Compression
Centrifugal
Single – stage
Multi - stage
Positive displacement
Compressor

12. Positive displacement compressors causes movement by trapping a fixed
amount of air then forcing (displacing) that trapped volume into the
discharge pipe.
It can be further classified according to the mechanism used to move air.
 Rotary Compressor Reciprocating compressor
Positive displacement Compressor

13.  The gas is compressed by the rotating action of a roller
inside a cylinder.
 The roller rotates off-centre around a shaft so that part
of the roller is always in contact with the cylinder.
 Volume of the gas occupies is reduced and the
refrigerant is compressed.
 High efficient as sucking and compressing refrigerant
occur simultaneously.
Rotary Compressor

14. It is a positive-displacement compressor that
 Uses pistons driven by a crankshaft to deliver
gases at high pressure.
 The intake gas enters the suction manifold, then
flows into the compression cylinder
 It gets compressed by a piston driven in a
reciprocating motion via a crankshaft,
 Discharged at higher pressure
Reciprocating Compressor

15. Principle of Operation
 Fig. shows single-acting piston actions in
the cylinder of a reciprocating compressor.
 The piston is driven by a crank shaft via a
connecting rod.
 At the top of the cylinder are a suction valve
and a discharge valve.
 A reciprocating compressor usually has two,
three, four, or six cylinders in it.
Reciprocating Compressor - Detailed Analysis

16. Reciprocating Compressor - Working

17. WHY MULTISTAGE COMPRESSOR?
 High temp rise leads into limitation for the maximum achievable pressure rise.
 Discharge temperature shall not exceed 150ºC and should not exceed 1350C for
hydrogen rich services
 A multistage compressor compresses air to the required pressure in multiple
stages.
 Intercoolers are used in between each stage to removes heat and decrease the
temperature of gas so that gas could be compressed to higher pressure without
much rise in temperature

18. Series arrangement of cylinders, in which the compressed air from earlier cylinder
(i.e. discharge) becomes the intake air for the next cylinder (i.e. inlet).
Intercooler :
Compressed air is cooled
between cylinders.
L.P. = Low Pressure
I.P. = Intermediate
Pressure
H.P. = High Pressure
L.P.
Cylinder
I.P.
Cylinder
H.P.
Cylinder
Intercooler
Intercooler
Air Intake
Air Delivery
Reciprocating Compressor – Multistage

19. When High Pressure is required by Single – Stage
1. Requires heavy working parts.
2. Has to accommodate high pressure ratios.
3. Increased balancing problems.
4. High Torque fluctuations.
5. Requires heavy Flywheel installations.
This demands for MULTI – STAGING…!!
The drawbacks of single stage Reciprocating
Compressor

20. Table showing operating conditions of various compressors

21. Advantages Disadvantages
Dynamic Compressors
Centrifugal •Wide operating range
•High reliability
•Low Maintenance
•Instability at reduced flow
•Sensitive to gas composition change
Axial •High Capacity for given size
•High efficiency
•Heavy duty
•Low maintenance
•Low Compression ratios
•Limited turndown
Advantages and Disadvantages of Dynamic compressors

22. Advantages Disadvantages
Positive displacement compressor
Reciprocating •Wide pressure ratios
•High efficiency
•Heavy foundation required
•Flow pulsation
•High maintenance
Diaphragm •Very high pressure
•Low flow
•No moving seal
•Limited capacity range
•Periodic replacement of diaphragm
Screw •Wide application
•High efficiency
•High pressure ratio
•Expensive
•Unsuitable for corrosive or dirty gases
Advantages and Disadvantages of Positive
displacement compressors

23. Maintenance
•Visually Inspect Air Compressor
•Check and Log Drive Motor Bearing Temps
•Check and Log Fan Motor Bearing Temps
•Inspect Coupler, Hub and Shaft Seal
•Check and Log Oil Cooler Temps
•Check and Log After Cooler Temps
•Inspect Scavenge Line Check Valve
•Check Drive Belt condition if applicable
•Log load and unload pressure settings

24. •Check moisture trap or autodrain
•Perform An Oil Sample Analysis
•Change Oil Filter
•Blow Out Coolers
•Change Air Filter
•Change Oil/Water Separator
•Check and log ambient condition
•Change Oil Separator O-Ring if necessary
•Change Oil if necessary
Maintenance

25. Thank You