Compressors and Application

Compressor :

Compressor is basically used for increasing the pressure of a fluid by compressing the fluid in a closed chamber for compressible fluids OR by imparting Kinetic energy in it and subsequently changing Kinetic Energy into Pressure Energy for incompressible fluids.

Types of Compressors :

The compressors are classified as follows.

Depending on the construction :

Hermetically sealed compressors Semi sealed compressors Open type compressors

Depending upon working principle :

Reciprocating compressors Rotary compressors Screw compressors Scroll compressors

Hermetic Compressor :

When the motor, the gas pump assembly and other parts are placed in side the dome OR housing and completely sealed , is called Hermetic Compressor.

Application of Hermetic Compressors :

Hermetic Compressors are generally used in the Refrigerators , Air - Conditioners , Water coolers and Chillers.

Generally Reciprocating compressors are used in Refrigerators and Rotary compressors are in Air - conditioners.

Role of the compressor in the Refrigerator / Air conditioner / Water cooler / Chiller is vital and the entire functioning and efficiency of the system depends on the working and efficiency of the Compressor.

Cost of the compressor is around 50 % of the Refrigerator / Air -Conditioner / Water cooler / Chiller.

Hence the Compressor is the heart of the system / product.

Function of compressor in Refrigeration :

Elevating the temperature of the refrigerant gas and pressure to such values at which the vapor refrigerant change its phase from vapor to liquid at room temperature.

Returning the evaporated liquid from the evaporator maintaining the mass flow of the gas in the system.Importance of Refrigeration :

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There are few phases of modern living untouched by refrigeration and air conditioning. business operations, manufacturing processes, storage, and shipping are almost always carried out today under controlled temperature conditions.

The refrigeration and air conditioning industry helps make possible this system of living. Air conditioning has improved business and industrial efficiency, while adding to human comfort .

More and more factories and heavy industries are being air conditioned.

Many fruits and vegetables are refrigerated immediately upon being harvested the quality of such products is much better for this reason.

Cooling and freezing of meat and meat products makes possible their handling in a much sanitary way than would be possible without mechanical refrigeration.

Beverages, desserts , and even staple foods are all at least partially processed by refrigeration equipment.

Who's who in refrigerator industry:

GE Whirlpool Electrolux Maytag LG Samsung Matsusitha / Panasonic Haier Kelon

Refrigerator demand in India :

Estimated Sale for 2003 - 2004 is 3.4 Mln - 3.65 Mln units.

Almost 60% of sales are in from refrigerators priced betweenRs 12,000 - Rs 16,000.

The 165 - 225 litre segment comprises 75% of the total demand.

Expected growth rate at 10-15% for 2004 - 2005.

Expected growth in 2004 - 2005 is 4.1 Mln - 4.2 Mln units.

Average growth rate from 1999 is 5%

Future Trends of Refrigerator : Fuzzy logic Power Saving Freshness

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Coolness User Friendly

Who's who in compressor industry :

The three largest manufacturers over 15 Million annual production are: Matsushita (Malaysia, Japan, Korea) Electrolux (Italy, Austria, Spain, US, China, Egypt, India) Whirlpool (Brazil, Italy, China, France) Tecumseh ( USA )

World Compressor demand :

The installed capacity of Compressor Manufacturers is 80 MillionActual Annual production is 65 Million

Compressor demand in India : Installed capacities is 8.1 Million whereas actual production is around 3 Million

Technology changes :

Environmental Friendly Technology Low Energy Consumption Low Noise Level Very Compact size High Efficiency

B asic principle of Refrigeration :

The simplest form of a vapor compression system is an open vessel containing any liquid which has a boiling point well below surrounding space temperature. The liquid picks up heat ( latent heat ) required for its change of phase from liquid to vapor. And lowers the temperature of the vessel wall and surrounding air.

This method of refrigeration is uneconomical since the recovery of evaporating liquid is not possible. Therefore an economical refrigeration system must consists of a method of refrigerant recovery back into the form of liquid for continuous evaporation. In all the refrigerant systems, the process of evaporation take place in the evaporator and the conversion of vapor to liquid achieved by the compressor and condenser.

Function of compressor :

Elevating the temperature of the refrigerant gas and pressure to such values at which the vapor refrigerant change its phase from vapor to liquid at room temperature.

Returning the evaporated liquid from the evaporator maintaining the mass flow of the gas in the system.

Function of condenser :

The condenser aids the recovery by receiving the refrigerant at high pressure and high temperature and lowers it temperature up to the condensing temperature for converting it to liquid dissipating the heat to the surrounding atmosphere.

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Expansion device ( Capillary tube ) :

The main function of a capillary tube is to reduce the temperature of refrigerant from condensing temperature to below evaporate temperature ( by the principle of cooling and throttling ) to enable heat removal from evaporator. Capillary divides the system into a high side and low side. The low side is for lowering the boiling point of the refrigerant below the conditioned space temperature and the high side for conversion of vapor to liquid. Another function of the capillary tube in a system is to meter the flow of refrigerant at the same rate as of its evaporation in the evaporator.

Refrigerant :

Refrigerant are heat carrying mediums which during their cycle in the refrigeration system absorb heat at low temperature level and discard the heat so absorbed at a higher temperature. Refrigerants have boiling points much below ordinary room temperature and so they exist as gases and are only held as liquids by keeping them under pressure, such as in a refrigerant cylinder.

Types of Refrigeration :

Refrigerator is basically a reversible heat engine. It follows the theoretical 'Carnot' cycle. 'Carnot' cycle comprises of two ' Isotherm ' processes and two 'Adiabatic ' processes. Different techniques are practiced to achieve this. They are Vapor compression refrigeration. Vapor absorption refrigeration.

The most common type used in household refrigeration is Vapour Compression Refrigeration .The two isotherms of ' Carnot ' cycle are the two heat exchange process, viz. Condensation and Evaporation and two Adiabatic are throttling valve expansion and compression by Compressor.

In Isotherm process, the system temperature is always constant but pressure varies. In Adiabatic process , the pressure is always constant but Temperature varies.

Vapor compression refrigeration cycle :

As the refrigerant circulates through a vapor compression refrigeration system , it passes through a number of changes in state or condition in a definite sequence and returns to the initial condition to complete a cycle. This cycle is made up of fundamental processes viz. Expansion, vaporization, compression, condensation.

Vapor compression refrigeration circuit diagram is shown in the next page.

Thus, the vapor compression refrigeration system can briefed as follows:

(1)– (2) Adiabatic compression by a reciprocating compressor.(2) - (3) Condensation. (3) - (4) Throttle and expansion.(4) - (1) Evaporation.

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So, compressor is the heart of refrigerator. It takes the refrigerant vapor at low pressure low temperature and delivers it at high pressure high temperature. By taking up the refrigerant vapor from evaporator, it also maintains the flow in the refrigeration circuit. The performance of a compressor is measured by C.O.P value and it varies from 3.1 to 5.4 BTU / Watt Hr.

C.O.P is co-efficient of performance. For a refrigerator it is defined as the ratio of refrigerating effect obtained and compressor work input to the system.

E.E.R – Energy efficiency ratio.

Range of Compressors :

Based on the capacities the compressors are categorised into Low back pressure, Medium and High back pressures. The L.B.P range varies from 98 to 148 Kcal/Hr. The M.B.P ranges from 148 to 300 Kcal/Hr. The H.B.P ranges from 340 Kcal/Hr and above.

Ton of Refrigeration :

The method for rating refrigeration equipment goes back to the days when ice was used as the source for removing heat.

One Ton of refrigeration is the amount of heat required to melt 1 ton(2000 lbs.) of ice in a 24 hour period.

It takes 144 Btu of heat to melt 1 pound of ice. It would take 2000 times that much heat to melt a ton of ice.

144 Btu / lb X 2000 lb = 288,000 Btu / 24 hours

12,000 Btu / Hour = 1 Ton

Types Refrigerants :

Refrigerants commonly used today are classified into four areas : Chlorofluorocarbons -- CFC Hydrochlorofluorocarbons -- HCFC Hydrofluorocarbons -- HFC Refrigerant blends.

Properties of Refrigerants :

It must follow the standards set by environmental protection agency. It should be nontoxic. It should be non explosive. It should be non corrosive it should be nonflammable. It should make leaks easy to detect and locate. It should operate under low pressure. It should be a stable gas. It should permit refrigerator or compressor parts moving in the fluid to be easily lubricated. It should have high liquid volume per pound to provide durable refrigerant controls.

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It should have a low vapor volume per pound. It should have high latent heat.

CFC Refrigerants :

These refrigerants are composed of Chlorine, Fluorine, and Carbon and are called Chlorofluorocarbons.

Common CFCs are R-11 R-12 R-113 R-114 R-115These are one of the major cause of ozone depletion.

HCFC Refrigerants :

These are composed of Methane or Ethane in combination with Halogens. the common HCFCs are

R-22 R-123

HFC refrigerants :

This contains one or more hydrogen atoms and no chlorine atoms. Common HFCs are

R-134a. R-124.

Refrigerant blends :

There are two types of blends :

Azeotropic blend1. Zeotropic blend.

R600a R290

Ozone layer :

The ozone layer is a fairly thin layer of the earth‘s upper atmosphere .(stratosphere ) it is approximately thirty five miles above the ground. The ozone layer functions as a filter for the sun‘ s ultra violet rays .This protects human, plant, and sea life from the damaging effects of sun .

Scientists have found that releasing Chlorofloro carbons ( cfc ) from refrigerants can harm the ozone layer . the chlorene content in the cfc is the cause for depletion of ozone layer. This concern has developed into what we refer as the EPA ( Environmental Protection Agency ) regulations. these regulations identify types of refrigerants that can be produced and used. and

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define the phase out program of these cfcs. Countries through out the world have passed legislation preventing the use of chemicals that effect this layer .

Ozone Depleting potential : This measures the capacity of the refrigerant to destroy the ozone layer by reacting with the ozone gas.

Global warming potential :

This measures the capacity of the refrigerant to cause global warming.

Montreal protocol :

Montreal protocal on substances that deplete the ozone layer was agreed to on september 16, 1987. the montreal protocal obligates all parties to phase out ozone depleting substances according to a specified time table and was so designed that the phase out schedules could be revised on the basis of periodic scientific and technological assessments.

As per Montreal protocol provisions for article 5 countries, the Indian industries have to phase out the production and / or use of Ozone depleting substances by the year 2010.

Earth's outer atmosphere is having a thick layer of ozone gas, which protects us from different ultra violet and cosmic rays. It has been found that in some areas this ozone layer is being depleted because of many reasons, use of CFCs is one of them. Chlorine of CFC reacts with ozone and thus destroys the ozone layer.

Thus for refrigerator industry, the immediate alternative for R12 is R134a which is Hydrofluoro carbon ( HFC ). As there is no chlorine atom, hence it does not react with ozone.

But this changeover requires a lot of change in system design and manufacturing of refrigerator.

These change overs can be listed as follows :-

Displacement of Compressors.

Changes to counter the flammable nature of gases used.

High degree of cleanliness and process for removal of contaminants.

High degree of moisture removal by Dehydration and Evacuation system. Changes in the material used like Mineral oils, coating and insulation of wires.

More use of Aqua / Alkali cleaning agents.Manufacturing of Hermetic Compressors

Compressor :Compressors are basically used for increasing the pressure of a fluid by compressing the fluid in a closed chamber for compressible fluids OR by imparting Kinetic energy in it and subsequently changing Kinetic Energy into Pressure Energy for incompressible fluids.

Types of Compressors :

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The compressors are classified as follows.

1. Depending on the construction :

Hermetically sealed compressors Semi sealed compressors Open type compressors

Hermetically sealed compressors :

When the motor and the compressor are placed in side the dome OR Housing and completely sealed, is called Hermetic Compressor.

2. Depending upon it's working principle :

Reciprocating compressors Rotary compressors Screw compressors Scroll compressors

Among these types the most common type of compressor used for Refrigeration is Reciprocating compressor.

Working principle of Reciprocating Compressor :

Basically, this type of compressor belongs to the positive displacement class machines. Generally reciprocating compressors are driven by means of a electric motor.

The rotary motion is converted into reciprocating motion by means of Slider -Crank mechanism. (i.e. Piston - Connecting rod-Crank shaft ).

Reciprocating compressors works on '' Brayton cycle '' , in which one cycle completes in each 360 degrees of crank rotation. Thus there are two strokes in each cycle. ( i.e Suction and Compression ).

During downward movement of piston, the refrigerant vapour is taken in through suction line via intake valve. During upward movement, vapour is compressed and passed through a small diameter pipe and subsequently through expansion valve.

Gas pump Assembly :

Gas pump assembly is a critical part of the compressor which facilitates the function of pumping the refrigerant gas for circulating in the closed loop cycle of refrigeration. The refrigerant has to be in continuous circulation in the system at different temperatures and pressure to complete the refrigeration cycle. This is achieved by continuous compression and pumping of the same with the help of gas pump assembly. The gas pump assembly consists of the following components:

Compressor block Piston Connecting Rod

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Piston pin

The piston operates in a reciprocating motion in the cylinder bore, which is an integral part of the compressor block. The connecting rod which is connected to crank shaft - upper bearing- rotor group , helps in transmitting the rotary motion generated by stator & rotor, into the reciprocating motion of the piston. By the reciprocating motion of the piston, it sucks refrigerant gas into the cylinder and pumps the same into the system after compression. The refrigerant gas is sucked into the pump assembly through suction muffler assembly, valve plate and suction valve. After compression in the cylinder the same is pumped into the system through valve plate, discharge valve and discharge muffler of the block and discharge pipe connecting the compressor to the system.

The pump assembly will be seated on the springs in the compressor body and it forms the frame for all other components.

Critical parts of reciprocating compressor . Compressor block :

Compressor block castings are made up of grey cast iron by the sand moulding process. The cast iron must be dense enough to prevent seepage. Some Nickel is usually added to give the casting the desired density.

Usually the crank case is part of the same casting. This practice cuts down number of joints that might leak. It also permits close alignment between crank shaft and cylinder.

Piston :

Pistons castings are usually made up of cast iron by the sintering process. Smaller sizes do not have piston rings. The temperature of piston seldom goes higher than 250 degree F. Thus there is not much expansion of either piston or cylinder. Smaller pistons have oil grooves cut in them.

Piston pin :

Piston pins are made up of Special alloy steel and made through machining process and accurately ground to size. Usually they are hollow to reduce weight. They are usually of full floating type. This means the pin is free to turn both connecting rod bushing and piston bushing.

Connecting rod :

The connecting rod castings are made up of aluminium alloy by pressure die casting process . It holds the piston rigidly by a piston pin and connected to the crank shaft.

Crank shaft :

Crankshaft is made up of grey cast iron and by sand moulding process. The reciprocating motion is achieved by the crankshaft/ connecting rod / piston assembly.

Upper bearing :

Upper bearing is usually made up of Aluminium alloy and by pressure die casting process. It is placed in between Crank shaft collar and rotor. It acts as a bearing.

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Rotor :

It is Basically an assembly of lamination stack and aluminum counter weights. Rotor is made by Die casting process by pouring the Aluminium in the slots of the lamination. It is the part of the motor which rotates under the action of the magnetic field created by stator.

Split pin :

Split pins are made up of hardened and tempered steel and made through machining process. This split pins are used to lock the piston pin.

Cylinder head :

Cylinder head castings for Hermetic compressor are usually made of cast iron/ Aluminium and these castings are made by sand moulding process for cast iron and by pressure die casting process for Aluminium. The head serves as a pressure plate. It supports and holds valves and valve plates in position. It also provides vapour passage into and out of compressor. The pressure of compression may amount as much as 300 psi. These pressure depends on type of refrigerant used. The valve plate must have good support. There must be no leakage at the gaskets on either side of the valve.

Cylinder head gasket :

Cylinder head gaskets are made up of rubber by rubber moulding process.

Cylinder head fixing screws :

Cylinder head fixing screws are made up of tensile strength steel and through machining process.

Valve plate :

Valve plates are made up of cast iron by sintering process. It supports the suction valve and discharge valve.

Discharge valve pins :

Discharge valve pins are made up of steel with copper coating and through machining process.

Discharge valve :

Discharge valves are made up of carbon steel and by blanking and piercing process.

Suction valve :

Suction valves are made of made up of carbon steel and by blanking and piercing process.

Valve reed :

Valve reed is made up of carbon steel and by blanking and piercing process.

Valve stop :

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Valve stops are made of cold rolled steel and by of blanking and piercing Process.

Valve guide pin :

Valve guide pin is made up of steel and by cold drawing process.

Oil pump:

Oil pump is made up of steel (C75) and by blanking, piercing and forming process.

Rotor :

It is Basically an assembly of lamination stack and aluminium counter weights. Rotor is made by Die casting process by pouring the Aluminium in the slots of the lamination. It is the part of the motor which rotates under the action of the magnetic field created by stator.

Rotor Lamination :

Rotor lamination is made up of low silicon steel semi processed through blanking and piercing process.

Stator :

It is Basically an assembly of lamination stack , copper wire wound on the lamination stack with the mylor film for insulation. It creates the magnetic field for rotation of the Rotor.

Stator lamination :

Stator laminations are made up of low silicon steel, semi processed and by blanking and piercing process .Mylar film :

Mylar film is made up plastic material of polyester film, and by process of plastic extrusion process .

Copper wire :

Winding wire is made up Copper ,and by drawing process .

Stack cleats :

Stack cleats are made up of cold rolled steel and by drawing process

Heat shrink tube :

Heat shrink tube is made up plastic material of polyester film, and by injection moulding process .

Connector :

Connector is made up plastic material, and by injection moulding process .

Stator fixing screws :

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Stator fixing screw is made up of high tensile strength steel and by machining process.

Upper shell :

Upper Shell is made up of cold rolled steel EDD quality, and by blanking and forming process.

Crankshaft stop :

Crankshaft stop is made up of cold rolled steel EDD quality, and by blanking and forming process.

Lower shell :

Lower Shell is made up of cold rolled steel EDD quality, and by blanking and forming process .

Machining of compressor components :

The following compressor components will undergo the machining on various SPM / GPM / CNC machines to get the accuracy of the parameters /dimensions of the components as per the specifications.

Accuracy of the critical parameters / dimensions :

Compressor block: Tolerance on cylinder bore -- 10 microns Surface finish of cylinder bore -- 0.33 Ra Flatness of cylinder head face -- 25 microns

Piston: Tolerance on outer diameter -- 10 microns Surface finish of outer diameter -- 0.25 Ra Tolerance on piston pin hole -- 10 microns Surface finish of piston pin hole -- 0.5 Ra

Connecting rod: Tolerance on big end hole diameter -- 5 microns Tolerance on small end hole diameter -- 8 microns Surface finish of big end diameter -- 0.4 Ra Surface finish of small end diameter -- 0.4 Ra

Crank shaft: Tolerance on main axis diameter -- 8 microns Tolerance on eccentric axis diameter -- 8 microns Surface finish on main axis -- 0.2 Ra Surface finish on eccentric axis -- 0.2 Ra

Upper bearing: Tolerance on shaft hole diameter -- 8 microns Surface finish of shaft hole -- 0.4 Ra Flatness of block seating face -- 10 microns

Valve plate:

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Surface finish of both the faces -- 0.16 Ra Flatness of both the faces -- 10 microns

Gauges:

Machined compressor components will undergo in-process/ final inspection on various gauges like

On- line gauges - Marposs / Tespa make

Air gauges with dial type display units with 0.5 micron accuracy - Baker / Accurate make

Electronic gauges with digital type display units with 0.5 micron accuracy - Baker / Accurate make

Mechanical gauges :

Plug gauges

Snap gauges

Thread plug gauges

Multi gauging fixtures

Relational gauges

Cutting Tools:

The following type of cutting tools are used in the machining of compressor components to the accuracy of the components as per the specifications.

Turning - Standard tools / Special brazed tools Drilling / CSK - Standard / Special - HSS drills Reaming - Special - Carbide reamers Final boring - Special - Diamond boring tools Milling - Standard / Special cutters Honing - Special honing tools Grinding (Rough) - Special grinding wheel - 38A46 2 L8 V11 Grinding (Finish) - Special grinding wheel - 38A150L8V11 / SA120L6VF8

- Special regulating wheel - A80 RR 51

Lapping (Rough) - Special grinding wheel - GC 801 TDR 801 Lapping (Finish) - Special grinding wheel - C320 TDR 757

Diamond dressers - Special multi point - 1R6 - J7 - Special Single point - 4 / 1.5 carat

Vibro finishing - Ceramic abrasive granules - PI - Elliptical shape 14 x 14 x 5

Oils:

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The following oils are used in the manufacturing of Hermetic Compressors :

Hydraulic oil - Emkarate RL 68 - non CFC grade - Servo 68

Spindle oil - High spin SW 100 Coolant oil - grinding - Servo cut - S Coolant oil - Lapping - Cimtech - D14 - non CFC grade

- Shell Adrina - non CFC grade Washing chemical - Oakite - 445 NNF - non CFC grade Compressor oil - Emkarate RL 22 H - non CFC grade

Manufacturing process for Compressor Block :

The Cast Iron castings of Compressor block will undergo the following Machining and cleaning operations.

1. SPM - I :The following operations are performed on the stator seating side of the compressor block .

Rough & Finish milling of stator seating face Rough milling of cylinder head face Core drilling of Cylinder bore Rough boring of cylinder bore Rough facing of upper bearing seating face Rough boring of upper bearing locating hole Drilling of Upper bearing fixing holes Drilling of stator fixing holes Drilling of locating holes Reaming of locating holes. Taping of stator fixing holes

2. SPM - II : The components are turned and positioned to perform the operations on suspension spring supports side of the compressor block.

Rough boring of cylinder bore Rear side chamfering of cylinder bore Trepaning of suspension spring supports Drilling of cylinder head fixing holes Taping of cylinder head fixing holes3. SPM - III :

The following finishing operations performed on the compressor block.

Finish milling of cylinder head face Finish facing of upper bearing seating face Finish boring of upper bearing locating hole Finish boring of cylinder bore Counter boring of cylinder bore Milling of half moon

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Drilling of valve plate locating holes

4. Automatic rotary table Honing machine :

The Honing operation for the cylinder bore is performed on the Automatic rotary table honing machine in 10 stations with the Increment of 2 to 3 microns in the ID of the cylinder bore.

5. Automatic brushing machine :

The brushing operation for cylinder head face is performed on theAutomatic brushing machine.

6. Washing machine :

The machined compressor blocks are sent for the cleaning inThe high pressure washing machine with OKAITE - 445, Non - CFC grade chemical.

After cleaning the components will go to the pre assembly.

Manufacturing process for Piston :

The Sintered Cast Iron piston will undergo the following process before sending into the Pre - assembly.

Rough grinding of outer diameter on Center less grinder

Drilling of retaining pin hole and chamfer on SPM

Drilling of piston pin hole on Deep hole drilling machine

Chamfering of piston pin hole on Drilling machine

Honing of piston pin hole on Rotary table Honing machine

Finish grinding of outer diameter on Center less grinding machine

Vibro finishing on Thumbler machine

Cleaning of the machined pistons in the high pressure washing Machine with OKAITE - 445, non - CFC grade chemical.

After cleaning the components will go to the pre assembly.

Manufacturing process for connecting rod :

The aluminum castings will under go the following process before Sending into the pre assembly.

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Rough boring of Big end hole and Small end hole on rough Boring machine.

Drilling of oil hole on Automatic drilling machine

Finish boring of Big end hole and Small end hole on final Boring machine.

Cleaning of machined components on screw washing machine.

After washing these components will be going to pre assembly.

Manufacturing process of Crankshaft :

The Cast iron castings will undergo the following machining and Cleaning operations before being sent to pre assembly.

Facing and centering operation on SPM.

Turning of Main axis on Auto lathe / CNC lathe

Reference face milling on SPM

Eccentric axis turning on SPM

Oil hole drilling / Helical grooving on SPM

Rough grinding of main axis on Centerless grinder

Finish grinding of main axis on Centerless grinder

Finish grinding of eccentric axis on Cylindrical grinder

Vibro finishing of crank shaft on Thumbler

Cleaning of machined crank shafts in the High pressure washing Machine with OKAITE - 445, non - CFC grade chemical.

After cleaning crank shafts will be sending to Pre - assembly.Manufacturing process of Upper bearing :

The Aluminum castings will undergo the following manufacturing process before being sent to pre - assembly.

Rough boring , rough turning of outer diameter, chamfering , facing of the Upper bearing on Auto lathe.

Drilling , Counter sinking , Taping of block fixing holes and Milling of notch on the automatic rotary drilling machine.

Finish boring, finish turning of outer diameter on final boring machine.

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Brushing of block seating face on Brushing machine.

Cleaning of machined upper bearings in the High pressure washing machine with OKAITE - 445 grade , non - cfc chemical.

After cleaning these upper bearings will be sending to pre- assembly.Manufacturing process for Valve plates :

The Sintered Cast Iron casting valve plate will undergo the following Process before sending it in to the pre - assembly / assembly.

Rough grinding of both the faces of valve plates on lapping machine with rough grade grinding wheels.

Finish grinding of both the faces of valve plates on lapping machine with finish grade grinding wheels.

Cleaning of ground valve plates in the ultrasonic washing Machine with OKAITE - 445 grades chemical.

After cleaning the components will go to the pre - assembly / assembly.

Manufacturing process for Upper shell :

1. Shell fabrication :

Steel strip coil for the Upper shell will undergo the following Process before sending it to the welding line.

De coiling of strip on de coilerBlanking of sheet from strip on pressDeep drawing of upper shell on pressTrimming of shell on pressFinal forming of shell on press

2. Shell welding :

The fabricated shell will undergo the following process before sending it in to the pre - assembly / assembly.

Crank shaft stop is welded on fabricated upper shell on the projection welding machine. Cleaning of the welded shell in the washing machine. Pre treatment of upper shell

After pre treatment these upper shells will be going to the assembly.

Manufacturing process for Lower shell :

1. Shell fabrication :

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Steel strip coil for the Upper shell will undergo the following Process before sending it to the welding line.

De coiling of strip on decoilerBlanking of sheet from strip on pressDeep drawing of lower shell on pressTrimming of shell on pressFinal forming of shell on pressPiercing of holes on the press

2. Shell welding :

The fabricated shell will undergo the following process before Sending it in to the assembly.

Welding of Suspension spring pins on projection welding machine Welding of Bracket mounting on projection welding machine Welding of Relay guard on projection welding machine Welding of Relay terminal on projection welding machine Brazing of connector tubes and oil cooler tubes on Brazing furnace Bending of tubes on Bending fixture Cleaning of the welded shell in the washing machine. Pre treatment of Lower shell

After pre treatment these Lower shells will be going to the assembly.

Manufacturing process for Stamping :

Silicon steel sheet is fed into high speed press through a de coiler for auto feed and blanking of the bore , slots for rotor are made .

Stator slots & stator lamination blanks

Stacking of rotor lamination Stator laminations are sent for blueing operation

Stamping treatment:

Loading of stator / rotor packets on pallet/ trolley

Removing of lubricants from surface by burn in operation

Soaking to extract carbon from the material

Cooling down the load to lower temperature

Injection of steam at controlled temperature & pressure

Holding the material with steam at controlled temperature & pressure to required duration

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Unloading the material

Cooling down to the normal atmosphere temperature

Stator/Rotor stampings are ready for next process

Then the stator lamination is sent for stator assembly line and rotor lamination is sent for Rotor line.

Manufacturing process for Stator :

Lamination will undergo the following process before sending it to pre assembly.

Stacking , cleating and insulation on stacking machine Run winding of stator on main winding machine. Run winding forming on forming machine. Start winding on Aux. winding machine. Start winding forming on forming machine. Connection of connector on work bench. Welding of connector on connector welding machine. Insertion of connector leads done on the work bench. Pre forming will be on forming m/c. Lacing will be done on lacing m/c. Visual inspection of stator on work bench. Final forming on forming m/c Burnishing of Stator ID on Roller burnishing m/c. After completion of all the operation the stator will go for Final Testing.

After completion of the process the component will go to main assembly.

Hermetic system motor :

The motor is placed inside housing. The motor must drive the compressor directly. It should have good leak proof electrical connections and must be of an induction type. Motors using rotor windings requiring either brushes or slip rings cannot be used.

To calculate the motor speed, the formula is: N = 120 * f / p.

Where, N = RPM f = Frequency p = No. of pole.

Problems associated with Hermetic motors :

Special cooling provisions must be made.

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Wiring insulation must be resistant to oil and chemicals in the refrigerant. Manufacturing standards must provide exact alignment of stator, rotor and compressor. Electrical connections through the housing must be electrically perfect and leak proof.

Hermetic motor types :

Hermetic motors are generally single phase induction motors. They are of four types Split phase Induction motor Capacitor Start, Induction Run (CSIR ). Capacitor start, Capacitor run (CSCR). Permanent split phase Capacitor ( PSC ). Resistance start Induction run ( RSIR ). Resistance start capacitor run (RSCR ).

Hermetic Split Phase Induction Motor :

It is the basic type of motor for all Hermetic compressor.

The principle of operation is There are two windings – one for starting and one for running. Since starting torque is low such motors must be used on systems with low starting load.This motor is very popular for capillary tube refrigerant control. Pressure in this system balanced in the off cycle. Thus compressor is not required to start under load.Compressors use this type of motor must have some outside starting relay, which might be a Thermal, Current, or Potential relay.

Motor Capacitor:

Capacitors changes current flow in A.C circuit. It is changed from a single phase to a two phase current flow. Capacitors are used in both starting and running windings.

Capacitor start induction run motor ( CSIR ) :

It has good starting torque, which is obtained by placing a capacitor in series with the starting winding. It can use current relay, potential relay or thermal relay.

Hermetic capacitor start and capacitor run motor ( CSCR )

This generally uses two motors. Both are in the starting winding circuit but only the start capacitor is controlled by the relay switch.When motor is started, the capacitors turn the motor power surges into two phase power and produces a high starting torque. After the motor reaches 60% load or 75% of its rated speed, the relay opens the circuit to the starting capacitor. The running capacitor is left in the circuit.This action produces a two phase motor that is very efficient. The power factor is improved. Large Hermetic units in commercial systems use this type of motor.

Permanent split capacitor motor ( PSC ) :

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The permanent split phase capacitor is popular for air conditioning systems. It does not use relay. Current flows through both the running winding and the starting winding when power is on . A running capacitor is connected in series with the starting windingsuch motors are sensitive to line voltage. A 5% drop in line voltage will cause starting difficulty and over heating.Starting torque is low . Thus, if the motor tries to start when the system is not balanced , the motor will over heat.

Resistance start induction run ( RSIR ) :

In motors for resistance start, the start winding is made of wire of a smaller dimension than that of the main winding. The result is a large difference in the ohmic resistance, causing the current in the start winding to be less inductive than the current in the main winding, and the required phase displacement is obtained.

Resistance start capacitor run ( RSCR )

These type of motor are having start winding as resistance start, and the run winding as capacitor run.

Hermetic Motor Terminals :

The electrical terminals that carry current through the dome must be electrically insulated from the dome or housing. They also must be leak proof. Most motor terminals are fused to glass. The glass, in turn fused to a metal disk . This assembly may be welded to the hermetic dome or housing . The terminal must be leak proof after thousands of heating and cooling and expansion and contraction cycles. Further more, it must have a high insulating value ( 50kv )

Manufacturing Process of Pre - assembly :

After machining of each and every component of compressor as per specifications, they are sent for grouping in pre - assembly . This grouping is a selective.

Grouping / Selective assembly :

Grouping is an important feature of hermetic compressors.

The clearance between cylinder bore and piston is 10 microns. The clearance between crank shaft and upper bearing is 18 microns. Manufacturing the mating parts exactly with the dimensions to get this clearance is not practical in mass production and every machining process requires some tolerance on the sizes of the component. Hence in order to overcome this problem, the components like cylinder block, piston, connecting rod , piston pin , crank shaft, upper bearing are made within a specified range of dimensions. Then these components are classified in different classes like A, B, C etc. based on the size defined for each class.

In the selective assembly mating parts of each group are selected such that the difference between OD & ID is as per the specification.

In the pre - assembly the grouping is done mainly in three different lines. They are

Oil pump -Crank shaft - Upper bearing - Rotor group Cylinder block - Piston - Connecting rod - Piston pin group

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Valve plate assembly.

Manufacturing process of crank shaft - upper bearing - rotor assembly :

The following sequence of operations are performed in the assembly of oil pump , crank shaft, upper bearing and rotor.

Oil pump is fitted at the small end of the crank shaft .

Classification of upper bearing on Air / Electronic gauge

Classification of crank shaft on Air / Electronic gauge

Selection and coupling of crank shaft and upper bearing such that clearance between both is as per the specification.

Placing the thrust washer in the rotor and positioning the rotor in the fixture of the hot fitting machine.

Insertion of the crank shaft in the rotor on hot fitting machine.

After the hot fitting the rotor group assembly will be sent to assembly.

Manufacturing process of Block- piston - con rod - piston pin assembly:

The following sequence of operations are performed in the assembly of block , piston, connecting rod and piston pin assembly.

Classification of piston on Air /Electronic gauge

Classification of connecting rod small end on Air /Electronic gauge

Classification of piston pin on Air /Electronic gauge

Selection and coupling of Piston and connecting rod

Selection and insertion of piston pin in the piston and con rod small end holes

After the insertion of piston pin , this block- piston - con rod group will be sent to assembly.

Manufacturing process of Valve plate assembly :

The following sequence of operations are performed in the assembly of valve plate.

Insertion of discharge valve pins in the valve plate

Assembly of discharge valve , valve reed , valve stop

Fixing of spring

Leak testing of valve plate assembly on leak testing equipment

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After the leak testing , the valve plate assembly will be sent to assembly.

Manufacturing process of Suction Muffler assembly :

The following sequence of operations are performed in the assembly of Suction muffler.

Assembly of suction muffler on the cylinder head

Fixing of retaining stop

After spring fixing , this suction muffler assembly will be sent to assembly.

Manufacturing process of Compressor :

Various sheet metal parts like Spring pins , Foot brackets , Hermetic terminal , Relay guard will be projection welded on the lower shell on special purpose projection welding machines.

Connectors / Tubes of different sizes will be brazed manually to the welded lower shell.

Crank shaft stop will be welded to the upper shell.

The upper shell and lower shell will be sent for pre-treatment in a pre- treatment plant and sent to Compressor assembly.

Various machined parts / selectively assembled parts will be assembled in the lower shell on a continuous assembly conveyor with pneumatic nut runners. After this assembly it is passed through Dehydration oven for a period of 4 hrs and taken out and Moisture level is checked ( < 150 mg )

After placing the upper shell on the lower shell, the compressor is welded on a MIG welding machine and leak tested at 17 kg / sq. cm.

After leak testing it is sent on conveyor for painting and baking. The painted compressors will be unloaded and tested for various parameters on final testing machine.

After testing , the compressors will be sent for packing and then to finished goods stores for despatch.

The detailed description of process for Assembly of compressors / sub assemblies / manufacturing of components , that goes into Compressor are as follows.

Sequence of operations for the assembly of Compressor :

On Block - Piston - Con rod assembly, Crank shaft - Upper bearing - Rotor assembly are placed.

The following components / sub assemblies are placed on the above assembly before the next stage.

Stator. Valve plate assembly. Cylinder head & Suction muffler assembly. Discharge muffler cover assembly.

The spring bushes and spring fittings are placed on the lower shell.

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The discharge muffler is then brazed to the discharge tube.

Then it is open tested in a open test bench and placed in a Dehydration oven for dehydration by hot air injection.

After taking lower shell assembly from dehydration oven the upper shell assembly is kept on the top. Then it is sent for MIG welding.

After the welding it is leak tested pneumatically.

Then it is painted in a paint dipping tank and it is baked.

On the final testing the following operations are performed.

Vaccumising. Oil charge. Run test. Compression & Absorption test. Noise test. Marking.

High voltage tested and injected with dry air. Packing and OK compressors will be sent to the finished goods stores.

INDEX

Compressors and Application :

What is Compressor Types of Compressors Hermetic Compressor Application of Compressors Function of Compressor in Refrigeration

Refrigeration :

Importance of Refrigeration Global and Indian market - Refrigerator Global and Indian market - Compressor Principle of Refrigeration Types of Refrigeration Vapor compression refrigeration cycle Types of Refrigerants Ozone layer Montreal Protocol

Manufacturing of Compressors :

Working principal of Reciprocating Compressor Critical parts of Reciprocating Compressor

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Machining of compressor components Accuracy of critical parameters / dimensions Gauges Cutting tools Oils

Process flow charts / sequence of operations for machining of

Compressor block

Piston

Connecting rod

Crank shaft

Upper bearing

Valve plate

Process flow charts / sequence of operations for press components like

Upper shell

Lower shell

Lamination

Process flow chart / sequence of operations for assembly

Stator

Hermetic system motor

Hermetic motor types

Manufacturing process of pre-assembly Process flow charts / sequence of operations for selective assembly of

Block- Piston - Connecting rod - Piston pin group

Oil pump -Crank shaft - Upper bearing - Rotor group

Valve plate assembly

Manufacturing process of Compressor Process flow chart / sequence of operations for Compressor assembly

Gauges :

Machined compressor components will undergo in-process/ final inspection on various gauges like

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On- line gauges - Marposs / Tespa make

Air gauges with dial type display units with 0.5 micron accuracy - Baker / Accurate make Electronic gauges with digital type display units with 0.5 micron accuracy - Baker / Accurate make

Mechanical gauges :

Plug gauges

Snap gauges

Thread plug gauges

Multi gauging fixtures

Relational gauges

Cutting Tools :

The following type of cutting tools are used in the machining of compressor components to the accuracy of the components as per the specifications.

Turning - Standard tools / Special brazed tools Drilling / CSK - Standard / Special - HSS drills Reaming - Special - Carbide reamers Final boring - Special - Diamond boring tools Milling - Standard / Special cutters Honing - Special honing tools Grinding (Rough) - Special grinding wheel - 38A46 2 L8 V11 Grinding (Finish) - Special grinding wheel - 38A150L8V11 / SA120L6VF8

- Special regulating wheel - A80 RR 51

Lapping (Rough) - Special grinding wheel - GC 801 TDR 801 Lapping (Finish) - Special grinding wheel - C320 TDR 757

Diamond dressers - Special multi point - 1R6 - J7 - Special Single point - 4 / 1.5 carat

Vibro finishing - Ceramic abrasive granules - PI - Elliptical shape 14 x 14 x 5

Oils :

The following oils are used in the manufacturing of Hermetic Compressors :

Hydraulic oil - Emkarate RL 68 - non CFC grade - Servo 68

Spindle oil - High spin SW 100 Coolant oil - grinding - Servo cut - S Coolant oil - Lapping - Cimtech - D14 - non CFC grade

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- Shell Adrina - non CFC grade Washing chemical - Oakite - 445 NNF - non CFC grade Compressor oil - Emkarate RL 22 H - non CFC grade

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