final md.golam kabir

MD. GOLAM KABIRPRIMEASIA UNIVERSITY

Welcome

Spinning, Dyeing & Utilities

Viyellatex Spinning Ltd

SPINNING

Viyellatex Spinning has a well developed quality assurance lab equipped with modern sophisticated machineries for raw material and finished material testing. All the machineries are imported from USA , Switzerland ,Italy, Germany & India. Produce100% export oriented a very high quality yarn.

At a glance Viyellatex Spinning Ltd.

Viyellatex Spinning Ltd is a sister concern of Viyellatex Group. It equipped with all brand new state of the art European machines. It was established in the year 2004.

Position hold Mr. K. M. Rezaul Hasanat (David), Chairman & CEO

No. of Spindle 40320 spindle in Ring unit. 1280 spindle in Rotor unit.

Capacity 700 Tons per month (Ring Spinning) 200 Tons per month (Rotor Spinning)

Project Cost More than 200 crore.

Project area 7.50 Acres

Total Manpower 1140 person (Management Staff -37, Non-Management Staff-127 & Worker-980)

Department wise Present Manpower Status

Section MS NMS WORKERPlant Head 1 0 0

Production & Planning 17 14 845

Human Resources 06 68 N/A

Plant Maintenance (Maintenance)

2 6 85

Plant Maintenance (Utility) 3 11 50

Quality Management 2 18 N/A

Material Management 2 6 N/A

Sales & Distribution 2 4 N/A

Accounts & Finance 1 0 0

ISS 1 0 0

Total 37 127 980

Machine specification

Blow room : Blendomat , SPMF , CLP, MX-I , CLC-3, SP-F

Preparatory : Carding , Breaker drawing , Unilap , Comber ,Finisher Drawing , Simplex

Ring Section : Ring Frame

Finishing section : Autoconer , Heat setting

Production types

In Viyellatex Spinning we produce two different types of yarn . They are –

1. Combed yarn.2. Carded yarn .

We have required different machine for producing the above two types of yarn and their processing is also different . The process flow chart for combed and Carded yarn are given in the next.

Combed yarn

Combed yarn is most precious, finer and thiner than the carded yarn. Because the Carded Yarn is produced by following some less manufacturing steps than the Combed Yarn.

Process flow chart of combed yarn

Input Processing Machineries

Output

Raw Cotton Blow Room Lap

Lap Carding Carded Sliver

Carded Sliver Pre-Comb Drawing Pre-comb drawn sliver

Pre-comb drawn sliver Super Lap Former Mini Lap

Mini Lap Comber Combed Sliver

Combed Sliver Post Comb Drawing Post Comb Drawn Sliver

Post Comb Drawn Sliver

Speed Frame/ Simplex Roving

Roving Ring Frame Yarn

Yarn Winding Yarn in large package

CLC-3 CL-PMX-I SPMF BLENDOMATE

UNILAP COMBER

RING SIMPLEX POST COMBED DRAWING

SP-F CARDING PRE COMBED DRAWING

HEAT SETTING

AUTOCONE

PROCESS FLOW CHART FOR COMBED YARN

Carded Yarn

Carded Yarn needs less steps to follow to make a yarn than the Combed yarn. The main purpose of Combed yarn manufacturing is to create a yarn which is highly finer and highly qualified.Here i will give you a chart from where you will be able to know about How A Yarn is made by the combed yarn manufacturing process”

Process flow chart of carded yarn

Input Processing Machineries

Output

Raw Cotton Blow Room Lap

Lap Carding Carded Sliver

Carded Sliver Drawing-1 drawn sliver

Breaker Sliver Drawing-2 Finish draw sliver

Finisher Drawn Sliver Speed Frame/ Simplex Roving

Roving Ring Frame Yarn

Yarn Winding Yarn in large package

PROCESS FLOW CHART FOR KARDED YARN

CLC-3 CL-PMX-I SPMF BLENDOMATE

RING SIMPLEX

FINISHER DRAWING

SP-F CARDING BREAKER DRAWING

HEAT SETTING

AUTOCONE

PROCESS FLOW CHART FOR CARDED YARN

Name of wastage Generated from Standard wastage percentage

Types of wastage

01 Blow room dropping (BW) Blow room machines 2%~3% Usable

02 Card Dropping (CD) Carding 3%~4% Usable

03 Flat Strips (FS) Carding 1%~2% Usable

04 Sliver Wastage Carding , drawing, comber 0.25% Usable

05 Noil Comber 15%~16% Usable

06 Roving wastage Simplex, Ring 0.25% Usable

07 Pnueumafil Ring 2.0%~2.5% Usable

08 Hard wastage Autocone, Ring 0.50% Saleable

09 Filter wastage All machine 0.75% Unusuable

10 Microdust Blow room machines 0.50% Unusable

Different wastage of Ring Unit

Information in Rotor Unit

Back Section of Plant 1200 - Rotor

ROTOR MACHINE

1,Drafting 2,Twisting 3,Winding the yarn on the paper tube .

Quality Management

Viyellatex Spinning has a well developed quality assurance lab equipped with modern sophisticated machineries for raw material and finished material testing. All the machineries are imported from USA , Switzerland ,Italy, Germany & India.

Different Lab QC machine

No. Machine name Model No. Origin Number of M/c

1 USTER HVI SPECTRUM Spectrum 1 USA 1

2 USTER AFIS PRO Pro USA 1

3 SLIVER & ROVING REEL

SRR:001 USA 1

4 PORTABLE SCALE LBP:001 USA 1

5 ELECTRONIC YARN REEL

YRL:001 Italy 1

6 USTER AUTO SORTER 4 Switzerland 1

7 ELECTRONIC TWIEST TESTER

002 Italy 1

8 LEA STRENGTH TESTER

MAG- Y 0251 India 1

9 USTER TESTER 4sx Switzerland 1

10 MOISTURE TESTER HMT:001 USA 1

11 TECHOMETER LSR:103 UK 1

12 TENSION METER DTMB:500 Germany 1

Picture of lab machine

Quality control strategy

The quality department of Viyellatex spinning ensures standard quality of yarn as per buyer’srequirement . We always try to maintain quality in every steps of yarn manufacturing process.Besides, we implement the standard norms to achieve quality product. For this , we prepare a yarnengineering plan according to fibre properties and types of yarn. Then we send this plan to thetop management. Then the top management purchase raw cotton through different cottonsupplier . When the raw cotton arrives to the factory premises from the various cotton growingcountry , at first we take sample from every bale according to invoice lot. Then these samples areconditioned at 20~22c temp for 72 and above hours. After that we test these samples and preparebale management according to fibre properties . During bale management we consider all fibreproperties . Then we prepare lay down plan. When the fibre goes in the process we fix upprocess parameter according to the production plan given by production department. Analyze andcontrol yarn fault and take corrective action in process while deviation found in case of urgent andcritical situations. QAD discuss with the related department to reduce wastage.

We have certification in “FLO Fair Trade “ , “CMIA”, “Organic”, “Okeo-Tex” CCI (Cotton councilInternational ) . So, only Viyellatex Spinning can produce this kind of certified yarn.

In a word QA department always try to produce qualityful yarn to keep the reputation of ViyellatexSpinning in the textile sector.

This is the end About Spinning

Villatex Dyeing Unite.

Dyeing

Dyeing is the process of adding color to textile products like fibers, yarns, and fabrics. Dyeing is normally done in a special solution containing dyes and particular chemical material. After dyeing, dye molecules have uncut Chemical bond with fiber molecules. The temperature and time controlling are two key factors in dyeing. There are mainly two classes of dye, natural and man-made.

Different types of dyeing

Reactive dyeDisperse dyeAzoic dyeAcid dyeBasic dyeVat dye.

About Villatex dyeing pocess

Viyellatex Dyeing is covered by the 22 dyeing machines & 2 Turning machines and every machines are German branded and we have 30 tons per day dyeing capacity. 24 hours running our dyeing section by the three shift 3 hundred workers are working in our dyeing section. This is 100% export oriented knit dyeing plant.

Lay out of dyeing floor

About the machine of Viyellatex

Total number of machine: 22Sample machine: 7Bulk Machine : 15

Total CapacityMachine no Capacity

Machine 1 Machine 2. Machine 3. Machine 4. Machine 5.

Machine 6.Machine 7.Machine 8.Machine 9.

Machine 10.Machine 11Machine 12.Machine 13Machine 14.Machine 15Machine 16Machine 17Machine 18Machine 19Machine 20Machine 21Machine 22.

Total Capacity

50010001000

252525050075025120200250750

112084030560

1680840

112060

60 11705

Production Per Day (100% loading)

At a time loading capacity = 11705kg

Production per day(100% loading)= (11705*2.5)kg

= 29262kg

(Approx 30 ton)

Production Per Day (80% loading)

At a time loading capacity = 9364kg

Production per day(80% loading)= (9364*2.5)kg

= 23410kg (Approx

25 ton)

Machine SpecificationNo. Name Type Model No. Origin Capacity No. of Nozzle

1 FONG’S Bulk 28015002 China 500kg 2

2 THIES Bulk 45505 Germany 1000kg 4

3 THIES Bulk D-48653 Germany 1000kg 4

4 FONG’S Sample 28015001 China 25kg 1

5 THIES Sample D-48653 Germany 25kg 1

11 FONG’S Bulk ECO-6-IT China 200kg 1

12 FONG’S Bulk ECO-6-IT China 250kg 1

Process flow chart of Knit dyeing.

Batching/Grey Fabric Inspection↓

Sewing or Stitching↓

Scouring↓

Bleaching↓

Mercerizing↓

Dyeing↓

Printing↓

Finishing↓

Final Inspection↓

Delivery

MACHINE DESCRIPTION

There is two types of dyeing machine use in Viyellatex,

Thise Fongs

Different production capacity of machine.Machine NO. Machine name Machine

capacity Origin

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

Fong’sThies.ThiesThiesThiesFong’sFong’sFong’sFong’sFong’sFong’sFong’sFong’sFong’sFong’s

50010001000500750120200250750

1120840560

1680840

ChinaGermanyGermanyGermanyGermany

ChinaChinaChinaChinaChinaChinaChinaChinaChinaChina

Different parts of dyeing machine..

Stairs Unload reel Unloader

Lid Reel motor

Light Reel

Nozzle Dyeing chamber

Main pump Chemical tank 1. Chemical tank 2.

Water bulb

Steam tank Drain line

Pressure bulb Chemical tank filter

Chemical tank mixtuture.

Reel switch board. Chemical tank switch

board. Panel board.

Heat exchanger Filter

Water line Steam line

Thies machine.

Feature of Thies machine.

Filter is at the inside of the machine. Need more time & water for machine wash. Chamber size is fixed not adjustable. Nozzle size is manually adjustable. The chamber is half round shaped. There is a heat chamber in vertically. Nozzle is situated at the top of the machine. There is a pressure bulb in the lid. The chemical are manually mixed with the help of stirrer. No need to clean the filter of the machine. Origin at Germany.

Fong’s machine.

Feature of Fong’s machine.

Filter is at the inside of the heat exchanger of the machine. Need small time & water for machine wash with the help of

spray rod. Chamber size is adjustable. Nozzle size is automatically adjustable. The chamber is fully round shaped. There is a heat chamber in horizontally at the back side of the

machine . Nozzle is situated at the side of the machine. There is a pressure bulb in the lid if the machine is HTTP. The chemical are automatically mixed with the help of mixture. Filter need to clean. Origin at China.

The technique of dyeing.

Difference between Thies & Fong’s machine

No Thies Fong’s1 Filter is at the inside of the machine. Filter is at the inside of the heat exchanger of the

machine.

2 Need more time & water for machine wash. Need small time & water for machine wash with the help of spray rod.

3 Chamber size is fixed not adjustable. Chamber size is adjustable.

4 Nozzle size is manually adjustable. Nozzle size is automatically adjustable.

5 The chamber is half round shaped. The chamber is fully round shaped.

6. There is a heat chamber in vertically. There is a heat chamber in horizontally.

7 Nozzle is situated at the top of the machine. Nozzle is situated at the side of the machine..

8 No need to clean the filter of the machine. Filter need to clean.

9 The chemical are manually mixed with the help of stirrer.

The chemical are automatically mixed with the help of mixture.

10 Origin at Germany. Origin at China

Calculation of Winch Speed

Let,Fabric weight = 1000kgPer nozzle fabric weight =250kgFabric Diameter (open) = 56 inchCycle time or Dwell time = 2.5-3.0 m per minute G.S.M =180We know, GSM = gram / meter2

= gram / (Length × Diameter)Or, Length = gram / (GSM × Diameter)

= (250×1000× 100) / (56×2.54× 180)

= 976 meters.So, Winch or Reel Speed = Per nozzle Fabric length / Cycle time

= 976 / 3 meter/minute= 325 meter/minute.

Calculation of Linear Density:Linear Density = (Diameter×GSM×2.54) / 100 gram/meter

Dyeing process flow chart

Grey fabric receive from knitting section↓

Batching↓

Turning of fabric (only for Single Jersey)↓

Selection machine no↓

Fabric loading↓

Select production program↓

Select recipe for dyeing↓

Pretreatment↓

Dyeing↓

After treatment↓

Fabric Unload

Production Parameters

PHScouring PH – 12.5During H2O2 bleaching PH 10.5-11

Enzyme PH – 4.5Before dyeing (Leveling) PH – 6.5Salt PH – 7-8During reactive dyeing PH 10.5-11.5 During disperse dyeing PH 4.5-6.0Softener PH – 6.5

Time:For white fabric 4-5hrsFor 100% cotton 8-10hrsFor 100% polyester 5hrsCVC 2 parts 13-14 hrs.

Production Parameters

Temperature:For cotton fabric scouring: 105ºCDuring NaOH addition 65oCDuring H2O2 addition 70oCPeroxide killing at 80oC Sequestering at 90oCBio-polishing at 55oCFor cotton dyeing:Low brand – 45oCMedium brand - 600CHot brand – 80oC Migration for turquoise color at – 90oCOptical brightening agent (OBA) at – 80oC Polyester dying: 1000-1300C

Softener at – 45oC M: L ratio:

For reactive dyeing M: L ratio maintained between 1:6

Pretreatment process

Typical recipe for scouring: (all in g/l) Felson NOF – 0.7 Kapazon H53 – 0.5 Caustic – 2 H2O2 – 2.5 Recorit wez/Peroxide killer – 0.75 Acetic acid – 0.8 Biopolish B-11 – 1.5 Securon 540 – 0.5

Pretreatment flow chart

Fresh water and fabric Load at 45oC

Temperature raise to 60oC

Detergent, Peroxide Stabilizer inject

Run for 5 min

Inject Caustic and run 5 min

Raise temperature to 70oC

H2O2 inject and run 5 min

Temperature raise to 105oC

Run for 30 min

Lower the temperature to 80oC

Bath drain

Peroxide killer inject and run 10 min

Rinsing and unload the fabric.

Curve for scouring of fabric

Types of shade

LightMedium DarkWhite

Curve for black shade (dark) cotton dyeing

Curve for Cotton part Dyeing

Curve for White shade

Curve for Polyester dyeing

Curve for dyeing with turquoise color

Common dyeing faults with their remedies

Uneven dyeingCauses:

Uneven pretreatment (uneven scouring & bleaching).Rapid addition of Dyes and Chemicals.Improper color dosing.Using dyes of high fixation property.Uneven heat-setting in case of synthetic fibers.Lack of control on dyeing m/c

Remedies:By ensuring even pretreatment.By ensuring even heat-setting in case of synthetic fibers.Proper dosing of dyes and chemicals.Proper controlling of dyeing m/c

Batch to Batch Shade variation Causes:

Fluctuation of temperature.Improper dosing time of dyes & chemicals.Batch to batch weight variation of dyes and chemicals.Dyes lot variation.Improper reel speed, pump speed, liquor ratio.Improper pretreatment.Liquor ratio changed.Different dyeing procedure for each batch.

Remedies:Use standard dyes and chemicals.Maintain the same liquor ratio.Follow the standard pretreatment procedure.Maintain the same dyeing cycle.Identical dyeing procedure should be followed for the same depth of the Shade.Make sure that the operators add the right bulk chemicals at the same time and temperature

in the process.The pH, hardness and sodium carbonate content of supply water should check daily.

Dye SpotsCauses:

Not proper agitation of dyestuffs.Dye bath hardness.Operators ignorance about mixing and dissolving the

dyestuffs and chemicals.Remedies:

Proper agitation of dyestuffs.Use adequate amount of sequestering agent to minimize

hardness.

Remarks

I have seen that in dyeing different production parameters like temperature, time, PH, M:L ratio etc. are strictly followed. Sometimes the original dyeing process may not be found according to dyeing curve as they produce some complicated shade. One thing is clearly noticeable that production manager and officers are committed to try their best for reducing production time.

Viyellatex Utilities

Boiler

Introduction:A boiler is a closed vessel in which water under

pressure is transformed into steam by the application of heat. In the boiler furnace, the chemical energy in the fuel is converted into heat, and it is the function of the boiler to transfer this heat to the contained water in the most efficient manner. The boiler should also be designed to generate high quality steam for plant use. A flow diagram for a typical boiler plant is presented in Figure.

Boiler Plant Flow Diagram

The source of heat for a boiler is combustion of any of several fuels, such as: wood,

A. Coal, B, Oil, C. Natural gas.

Electric steam boilers use resistance- or immersion-type heating elements. Nuclear fission is also used as a heat source for generating steam. Heat recovery steam generators (HRSGs) use the heat rejected from other processes such as gas turbines.

Classification of steam boiler1. According to the contents in the tube.2. According to the position of the furnace.3. According to the axis of the shell.4. According to the number of tube.5. According to the method of circulation of water &

steam.6. According to the use.7. According to the source of heat.

Pot boiler or Haycock boiler

"Pot boiler" or "Haycock boiler": a primitive "kettle" where a fire heats a partially-filled water container from below. 18th century Haycock boilers generally produced and stored large volumes of very low-pressure steam, often hardly above that of the atmosphere. These could burn wood or most often, coal. Efficiency was very low.

Fire-tube boiler Fire-tube boiler. Here, water partially fills a boiler barrel with a small volume left

above to accommodate the steam (steam space). This is the type of boiler used in nearly all steam locomotives. The heat source is inside a furnace or firebox that has to be kept permanently surrounded by the water in order to maintain the temperature of the heating surface just below boiling point. The furnace can be situated at one end of a fire-tube which lengthens the path of the hot gases, thus augmenting the heating surface which can be further increased by making the gases reverse direction through a second parallel tube or a bundle of multiple tubes (two-pass or return flue boiler); alternatively the gases may be taken along the sides and then beneath the boiler through flues (3-pass boiler). In the case of a locomotive-type boiler, a boiler barrel extends from the firebox and the hot gases pass through a bundle of fire tubes inside the barrel which greatly increase the heating surface compared to a single tube and further improve heat transfer. Fire-tube boilers usually have a comparatively low rate of steam production, but high steam storage capacity. Fire-tube boilers mostly burn solid fuels, but are readily adaptable to those of the liquid or gas variety.

Water-tube boilerWater-tube boiler. In this type, the water tubes are arranged inside

a furnace in a number of possible configurations: often the water tubes connect large drums, the lower ones containing water and the upper ones, steam and water; in other cases, such as a monotone boiler, water is circulated by a pump through a succession of coils. This type generally gives high steam production rates, but less storage capacity than the above. Water tube boilers can be designed to exploit any heat source and are generally preferred in high pressure applications since the high pressure water/steam is contained within small diameter pipes which can withstand the pressure with a thinner wall.

Flash boilerA flash boiler is a type of water-tube boiler, whose tubes

are strong and close together with water pumped through the tubes. The tubes are kept very hot so the water feed is quickly flashed into steam and superheated. The flash boiler was invented by Léon Serpollet, who used the design in his steam-powered cars.

Compared to other kinds of boilers, they have the advantages of being lighter and less bulky and taking less time to raise steam from a cold start. On the other hand, a flash boiler is much easier than an ordinary boiler to overheat, as there is no large reservoir of water to cool the tubes in case the water flow is interrupted or inadequate

Fire-tube boiler with Water-tube firebox

Fire-tube boiler with Water-tube firebox. Sometimes the two above types have been combined in the following manner: the firebox contains an assembly of water tubes, called thermic siphons. The gases then pass through a conventional firetube boiler. Water-tube fireboxes were installed in many Hungarian locomotives, but have met with little success in other countries.

Sectional boiler

In a cast iron sectional boiler, sometimes called a "pork chop boiler" the water is contained inside cast iron sections. These sections are assembled on site to create the finished boiler.

Steam Utilization

Steam is generated for the following plant uses:

1. Turbine drive for electric generating equipment, blowers and pumps

2. Process for direct contact with products, direct contact sterilization and noncontact for processing temperatures

3. Heating and air conditioning for comfort and equipment

Supercritical Steam Generators

Supercritical steam generators (also known as Benson boilers) are frequently used for the production of electric power. They operate at "supercritical pressure". In contrast to a "subcritical boiler", a supercritical steam generator operates at such a high pressure (over 3,200 psi/22.06 MPa or 220.6 bar) that actual boiling ceases to occur, and the boiler has no water - steam separation. There is no generation of steam bubbles within the water, because the pressure is above the "critical pressure" at which steam bubbles can form. It passes below the critical point as it does work in the high pressure turbine and enters the generator's condenser. This is more efficient, resulting in slightly less fuel use. The term "boiler" should not be used for a supercritical pressure steam generator, as no "boiling" actually occurs in this device.

Different parts and function of boiler

Boiler fittings and accessories

Safety valve: It is used to relieve pressure and prevent possible explosion of a boiler.Water level indicators: They show the operator the level of fluid in the boiler, also known as a sight glass, water gauge or water column is provided.Bottom blowdown valves: They provide a means for removing solid particulates that condense and lie on the bottom of a boiler. As the name implies, this valve is usually located directly on the bottom of the boiler, and is occasionally opened to use the pressure in the boiler to push these particulates out.Continuous blowdown valve: This allows a small quantity of water to escape continuously. Its purpose is to prevent the water in the boiler becoming saturated with dissolved salts. Saturation would lead to foaming and cause water droplets to be carried over with the steam - a condition known as priming. Blowdown is also often used to monitor the chemistry of the boiler water.Flash Tank: High pressure blowdown enters this vessel where the steam can 'flash' safely and be used in a low-pressure system or be vented to atmosphere while the ambient pressure blowdown flows to drain.

Different parts and function of boilerAutomatic Blowdown/Continuous Heat Recovery System: This system allows the boiler to blowdown only when makeup water is flowing to the boiler, thereby transferring the maximum amount of heat possible from the blowdown to the makeup water. No flash tank is generally needed as the blowdown discharged is close to the temperature of the makeup water.Hand holes: They are steel plates installed in openings in "header" to allow for inspections & installation of tubes and inspection of internal surfaces.Steam drum internals, A series of screen, scrubber & cans.Low- water cutoff: It is a mechanical means (usually a float switch) that is used to turn off the burner or shut off fuel to the boiler to prevent it from running once the water goes below a certain point. If a boiler is "dry-fired" (burned without water in it) it can cause rupture or catastrophic failure.Surface blowdown line: It provides a means for removing foam or other lightweight non-condensible substances that tend to float on top of the water inside the boiler.Circulating pump: It is designed to circulate water back to the boiler after it has expelled some of its heat.Feedwater check valve or clack valve: A non-return stop valve in the feedwater line. This may be fitted to the side of the boiler, just below the water level, or to the top of the boiler.Top feed: A check valve (clack valve) in the feedwater line, mounted on top of the boiler. It is intended to reduce the nuisance of limescale. It does not prevent limescale formation but causes the limescale to be precipitated in a powdery form which is easily washed out of the boiler.Desuperheater tubes or bundles: A series of tubes or bundles of tubes in the water drum or the steam drum designed to cool superheated steam. Thus is to supply auxiliary equipment that does not need, or may be damaged by, dry steam.Chemical injection line: A connection to add chemicals for controlling feedwater pH.

Steam accessories• Main steam stop valve:• Steam traps:• Main steam stop/Check valve: It is used on

multiple boiler installations.

Combustion accessories:Fuel oil systemGas systemCoal systemSoot blower

Other essential items:Pressure gaugesFeed pumpsFusible plug Inspectors test pressure gauge attachmentName plateRegistration plate

Diagram of a boiler

Production of a boiler.

Production/hr = 6 ton..’. Production /day, 6 * 24 = 144 tonViyella tex need 144 ton steam for

regular production.

Steam required different section

Dyeing =Garments =Fabric =Printing =Fashion & plastic = Others =

Difference between water tube & faire tube boiler.

NO Water tube boiler Fire tube boiler

1 The water circulates inside the tubes which are surrounded by hot gases from the finance.

The hot gases from the furnace pass through the tubes which are surrounded by water.

2 It generates steam at a higher pressure upto165 bar.

It can generate steam only upto 24.5 bar.

3 The rate of generation of steam is high, i.e. upto 450 tons per hour.

The rate of generation of steam is low, i.e. upto 9 tons per hour.

4 Overall efficiency with economizer is upto 90%.

It overall efficiency is only 75%.

5 It is preferred for widely fluctuating loads. It can also cope reasonably with sudden increase in load but for a shorter period.

6 The direction of water circulation is well defined.

The water does not circulate in a definite direction.

7 The operating cost is high. The operating cost is less.

8 The bursting chances are more. The bursting chances are less.

9 It is use for large power plants. It is not suitable for large plants.

An air compressor is a m/c to compress the air & to raise its pressure. The air compressor sucks air from the atmosphere, compresses it & then delivers the same under a high pressure to a storage vessel. From a storage vessel, the pipeline to a place where the supply, of compressed air is required.

AIR COMPRESSOR

Type of air compressor

Reciprocating air compressors are positive displacement machines, meaning that they increase the pressure of the air by reducing its volume. This means they are taking in successive volumes of air which is confined within a closed space and elevating this air to a higher pressure. The reciprocating air compressor accomplishes this by a piston within a cylinder as the compressing and displacing element.

Single-stage and two-stage reciprocating compressors are commercially available. Single-stage compressors are generally used for pressures in the range of 70 psig to 100 psig. Two-stage compressors are generally used for higher pressures in the range of 100 psig to 250 psig. Note that 1 HP ~ 4 CFM at 100 psi and that 1 to 50 HP are typically for reciprocating units. Compressors 100 hp and above are typically

Rotary Screw or Centrifugal Compressors. The reciprocating air compressor is single acting when the compressing is accomplished using only

one side of the piston. A compressor using both sides of the piston is considered double acting. Load reduction is achieved by unloading individual cylinders. Typically this is accomplished by

throttling the suction pressure to the cylinder or bypassing air either within or outside the compressor. Capacity control is achieved by varying speed in engine-driven units through fuel flow control.

Reciprocating air compressors are available either as air-cooled or water-cooled in lubricated and non-lubricated configurations and provide a wide range of pressure and capacity selections.

Reciprocating Air Compressors

Rotary air compressors are positive displacement compressors. The most common rotary air compressor is the single stage helical or spiral lobe oil flooded screw air compressor. These compressors consist of two rotors within a casing where the rotors compress the air internally. There are no valves. These units are basically oil cooled (with air cooled or water cooled oil coolers) where the oil seals the internal clearances.

Since the cooling takes place right inside the compressor, the working parts never experience extreme operating temperatures. The rotary compressor, therefore, is a continuous duty, air cooled or water cooled compressor package.

Rotary screw air compressors are easy to maintain and operate. Capacity control for these compressors is accomplished by variable speed and variable compressor displacement. For the latter control technique, a slide valve is positioned in the casing. As the compressor capacity is reduced, the slide valve opens, bypassing a portion of the compressed air back to the suction. Advantages of the rotary screw compressor include smooth, pulse-free air output in a compact size with high output volume over a long life.

The oil free rotary screw air compressor utilizes specially designed air ends to compress air without oil in the compression chamber yielding true oil free air. Oil free rotary screw air compressors are available air cooled and water cooled and provide the same flexibility as oil flooded rotaries when oil free air is required.

Rotary Screw Compressors

The centrifugal air compressor is a dynamic compressor which depends on transfer of energy from a rotating impeller to the air.

Centrifugal compressors produce high-pressure discharge by converting angular momentum imparted by the rotating impeller (dynamic displacement). In order to do this efficiently, centrifugal compressors rotate at higher speeds than the other types of compressors. These types of compressors are also designed for higher capacity because flow through the compressor is continuous.

Adjusting the inlet guide vanes is the most common method to control capacity of a centrifugal compressor. By closing the guide vanes, volumetric flows and capacity are reduced.

The centrifugal air compressor is an oil free compressor by design. The oil lubricated running gear is separated from the air by shaft seals and atmospheric vents.

Centrifugal Compressors

There are three parts of an air compressor:-

Main compressorAir heater.Air reserver.

Different parts of an air compressor.

final md.golam kabir

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