The need to move gases has been a The need to move gases has been a requirement of industry.In virtually all requirement of industry.In virtually all systems that require the movement of gas, systems that require the movement of gas, there must be a means of producing a there must be a means of producing a driving force, the higher pressure. driving force, the higher pressure. The equipment that raises a gas to a higher pressure is called a compressor..

Pressure in gas is developed by pressing Pressure in gas is developed by pressing molecules of gas.molecules of gas.

FAN AND BLOWERFAN AND BLOWER

Low pressure (1 atm) Low pressure (1 atm) and low and low P (0.01-0.15 P (0.01-0.15 kg/cm2) for FAN.kg/cm2) for FAN.

Blower Blower P (0.15-1.5 P (0.15-1.5 kg/cm2)kg/cm2)

High volume flow to High volume flow to 500 std m500 std m33/s/s

Efficiencies of 65-80%Efficiencies of 65-80%

Principle of operationPrinciple of operation:-:-

(a) (a) Compression by decreasing volumeCompression by decreasing volume:-:- Required pressure is developed by trapping a gas in a Required pressure is developed by trapping a gas in a

chamber, reducing the volume of the chamber and chamber, reducing the volume of the chamber and increasing the pressure of the gas by the ratio of initial increasing the pressure of the gas by the ratio of initial chamber to the final volume.chamber to the final volume.

(b) (b) Compression by accelerating fluidCompression by accelerating fluid :- :- The second method of compressing gases is based on The second method of compressing gases is based on

the conversion of kinetic energy into the potential the conversion of kinetic energy into the potential energy. Accelerating fluid to a higher velocity and then energy. Accelerating fluid to a higher velocity and then decelerating it by changing its direction of flow decelerating it by changing its direction of flow transforms the accumulated energy into potential energytransforms the accumulated energy into potential energy

Classification of Compressors:-Classification of Compressors:-

DATA REQUIRED FOR SELECTION OF DATA REQUIRED FOR SELECTION OF COMPRESSOR:COMPRESSOR:

Capacity Suction pressure Suction temperature Discharge pressure Gas composition Type of driver Utilities like cooling water, steam, N2,

electricity etc.

Selection results in calculation

Type of compressor Number of casing / phases Number of impellers in each phase Speed of compressor Compressor BKW Driver rating Operating range

Application Range of Various Application Range of Various CompressorsCompressors

Inlet Flow (Acfm)

Dis

char

ge P

ress

ure

(Psi

a)

Reciprocating

Axial

102 103 104 105 106

101

102

103

104

105

Centrifugal

CENTRIFUGAL COMPRESSORS:CENTRIFUGAL COMPRESSORS: Centrifugal compressor works on the principle i.e. Centrifugal compressor works on the principle i.e.

accelerating a gas to a high velocity and converting its accelerating a gas to a high velocity and converting its KINETIC ENERGY (velocity) into POTENTIAL KINETIC ENERGY (velocity) into POTENTIAL ENERGY (pressure) by decelerating the gas. The gas ENERGY (pressure) by decelerating the gas. The gas enters the eye of the impeller and is accelerated to the enters the eye of the impeller and is accelerated to the outward edge of the impeller as it rotates. It then enters outward edge of the impeller as it rotates. It then enters a diffuser where its direction is changed, causing a diffuser where its direction is changed, causing deceleration. This deceleration converts the KE into the deceleration. This deceleration converts the KE into the PE, pressure. If the gas is to be further compressed, PE, pressure. If the gas is to be further compressed, then a return chamber directs it from the diffuser to the then a return chamber directs it from the diffuser to the eye of the next impeller in series. The gas enters a eye of the next impeller in series. The gas enters a collector or volute when it is to leave the compression collector or volute when it is to leave the compression stage. It is discharged to the process through a stage. It is discharged to the process through a discharge nozzle.discharge nozzle.

DESIGN FEATURESDESIGN FEATURES:-:- Based on the type of casing design,centrifugal compressors are Based on the type of casing design,centrifugal compressors are

classified into two types:classified into two types:

1)1) Horizontally split casing design(MCL/MCH type):-Horizontally split casing design(MCL/MCH type):- This design is This design is used for low working pressure below 40ata.These casings are in two used for low working pressure below 40ata.These casings are in two halves with horizontal parting plane.halves with horizontal parting plane.

DMCL Compressor have two stages of compression in parallel in a DMCL Compressor have two stages of compression in parallel in a single casing.The solution is most balanced.The other aspects of single casing.The solution is most balanced.The other aspects of construction are the same as for the MCL Compressor.construction are the same as for the MCL Compressor.

2) 2) Verically Split Casing design (BCL/BCH type):-Verically Split Casing design (BCL/BCH type):-This design is This design is made of barrel construction closed on the sides by end covers with made of barrel construction closed on the sides by end covers with help of studs.This type of construction is suitable for high pressure help of studs.This type of construction is suitable for high pressure operations upto 750kg/cm2operations upto 750kg/cm2

Another type of compressor is the PCL(Pipeline compressor),which Another type of compressor is the PCL(Pipeline compressor),which has casing in the form of a cup with a single closing flange in the has casing in the form of a cup with a single closing flange in the vertical plane instead of two as with the BCL.vertical plane instead of two as with the BCL.

Horizontally split type Horizontally split type CompressorCompressor

Vertically Split Type CompressorVertically Split Type Compressor

Example of Designation of BCL Example of Designation of BCL CompressorCompressor::

Example : 2BCL407/b

2 BCL 40 7 / b

Pr. rating (up to 350 ata)

No. Of impellers(7 impellers on rotor)

Nominal dia. of impeller(Impeller dia. of 40 cms appx.)

Constructional feature(Barrel design)

Functional feature(2 Compressor stages in series)

CompressorCompressor ComponentsComponents CasingCasing Counter Casing (If Applicable)Counter Casing (If Applicable) DiaphragmDiaphragm End Cover (If Applicable)End Cover (If Applicable) ShaftShaft ImpellersImpellers Shaft SealsShaft Seals Journal BearingJournal Bearing Thrust BearingThrust Bearing CouplingCoupling

COMPONENETS OF BCL COMPONENETS OF BCL COMPRESSORCOMPRESSOR

Construction of centrifugal compressor:Construction of centrifugal compressor:

Every centrifugal compressor consist of Every centrifugal compressor consist of two parts:- An impeller which forces the two parts:- An impeller which forces the gas into the rotary motion by the action of gas into the rotary motion by the action of blades, and the casing which directs the blades, and the casing which directs the gas to the eye of the impeller and then gas to the eye of the impeller and then leads it away from the impeller perimeter leads it away from the impeller perimeter at a higher pressure. For most multistage at a higher pressure. For most multistage compressors, shaft end seals are located compressors, shaft end seals are located inboard of the bearings. The internal inboard of the bearings. The internal passages are formed by a set of passages are formed by a set of diaphragms.diaphragms.

Cross-section of a BCL Cross-section of a BCL CompressorCompressor

BARREL PULLING BARREL PULLING ARRANGEMENTARRANGEMENT

Rotor AssemblyRotor Assembly

Assembly of Diaphragms in Assembly of Diaphragms in Counter CasingCounter Casing

Assembly of Journal BearingAssembly of Journal Bearing

Assembly of Thrust BearingAssembly of Thrust Bearing

BALANCING DRUMBALANCING DRUM There exists some amount of thrust generated at each There exists some amount of thrust generated at each

impeller because of the differntial pressure prevailing across impeller because of the differntial pressure prevailing across it. The cumulative thrust generated across all the impellers it. The cumulative thrust generated across all the impellers is huge and it needs to be supported by the thrust bearing. is huge and it needs to be supported by the thrust bearing. The thrust bearing size becomes huge if all the gas thrust The thrust bearing size becomes huge if all the gas thrust has to act on the bearing. For this purpose a rotating has to act on the bearing. For this purpose a rotating element called “Balancing Drum” is incorporated on the element called “Balancing Drum” is incorporated on the rotor. The drum is acted upon by a pressure differential rotor. The drum is acted upon by a pressure differential which pushes the rotor in a direction opposite to that of the which pushes the rotor in a direction opposite to that of the gas thrust. The thrust so generated balances the thrust gas thrust. The thrust so generated balances the thrust produced by the impellers. Amount of balancing depends produced by the impellers. Amount of balancing depends upon the size of the drum and pressure differential created upon the size of the drum and pressure differential created across it. The pressure differentiated is maintained by an across it. The pressure differentiated is maintained by an efficient seal placed over the balancing drum.efficient seal placed over the balancing drum.

Types of Compressor EndTypes of Compressor EndSealing SystemsSealing Systems

Labyrinth Sealing Labyrinth Sealing Floating Oil SealsFloating Oil Seals Oil Mechanical SealsOil Mechanical Seals Air Injection Sealing SystemAir Injection Sealing System Injection / Extraction SealingInjection / Extraction Sealing Dry Gas SealsDry Gas Seals

Compressor DrivesCompressor Drives

STEAM TURBINESTEAM TURBINE For variable speed operationFor variable speed operation In process plants like fertilizers and refineries In process plants like fertilizers and refineries

ELECTRIC MOTORELECTRIC MOTOR For constant speed operationFor constant speed operation Wherein uninterrupted electricity from captive power Wherein uninterrupted electricity from captive power

plants is ensured plants is ensured GAS TURBINEGAS TURBINE

For variable speed operation For variable speed operation Applications where gas availability is ensuredApplications where gas availability is ensured

Advantages of Centrifugal Advantages of Centrifugal CompressorsCompressors

High degree of balancingHigh degree of balancing Pulsation free deliveryPulsation free delivery Easy maintenanceEasy maintenance Standby not required Standby not required Best suited for part load operationsBest suited for part load operations Lower noise levelLower noise level Compact Compact

Type of PlantType of Plant Gas Compressed Gas Compressed

FertilisersFertilisers Syn Gas, NHSyn Gas, NH33, Air, Nat gas, , Air, Nat gas,

COCO22, Nitrogen , Nitrogen

RefineriesRefineries Air, Wet Gas, HydrogenAir, Wet Gas, Hydrogen

Petrochemical Plants Petrochemical Plants Propane, Propylene, Propane, Propylene,

Ethylene.Ethylene.

Metallurgical PlantsMetallurgical Plants OO22, Air, Gas, Air, Gas

Industrial Applications of Industrial Applications of Centrifugal CompressorsCentrifugal Compressors