cement project new

7/31/2019 Cement Project New

1/73

PREFACE

Industrial Training is one of the most important aspects ofDegree in Mechanical engg.. Theoretical knowledge is notsufficient to give complete grip and confidence over the basicfundamentals. So, Four years in Degree course has includedIndustrial training for the students for increase the knowlwdgewhat kind of equipment uses industry.so

According my branch(Mechanical)what kind ofswitchgear,motors,relays,transformers,Power Plant etc.use the

industry.

So,I took training in ASSOCIATED CEMENT COMPANY (ACC)LIMITED, LAKHERI from 01.05.2012 to 30.06.2012. Succeedingchapters give details about what I have learnt in this prestigiousorganization.

SHOHEB ALI BHUTTO Roll No. SHOHEB ALI BHUTTO Roll No. 09EPEME05309EPEME053

44thth Year 7Year 7thth Sem,Sem, Mechanical Page No. Page No.

PACIFIC INSTITUTE OFPACIFIC INSTITUTE OFENGINEERING,UDAIPUR(RAJASTHAN)ENGINEERING,UDAIPUR(RAJASTHAN)

Rajasthan Technical University,KotaRajasthan Technical University,Kota

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------


2/73

AKNOWLEDGEMENT

I take this opportunity to express my deep sense of

gratitude to The Professor & Head Department ofTraining And Placement, PACIFIC INSTITUTE OFPACIFIC INSTITUTE OFENGINEERING,UDAIPUR(RAJASTHANENGINEERING,UDAIPUR(RAJASTHAN)For organizingmy training at Associated Cement Works (ACC) Limited,Lakheri.

Also, I am very gratefull to Mr. Yatindra Sharma,Mr. PrashantPandey & Mr. Anurag Singh and all other staff for their valuableguidance.



---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

INDEX


3/73

S. No. Description

1. Introduction

2. Cement Plant

3. Different stages of Cement Plant

4. Departments

5. Transformer

6. Motors



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

INTRODUCTION


4/73

The ACC Lakheri Cement Works Limited is ideally locatedbetween the Aravalli Mountain Ranges. It is situated betweenKota and sawaimadhopur train and bus route. It is just 78kmaway from kota and 55 km away from sawai madhopur.

Basic Reasons For Choosing Lakheri To Install TheCement Plant:-

Avalability of large amount of raw material (Limestone)required for Cement Plant.

Easy access to the site. It is situated between Kota and sawai madhopur train and

bus route.it just 78km away from kota and 55km awayfrom sawai madhopur.

Avalability of two grid power first one is kota ans secondone is sawai madhopur.

Company Profile

ACC Limited established in the year 1936, is the largestproducer of CEMENT in India. With the annual installed capacityof 18.5 million tones. In addition to the domestic operations,ACC extends its services to various parts of the world including

operations and management of cement plants. The companyscorporate office is located at Mumbai.

PACIFIC INSTITUTE OFPACIFIC INSTITUTE OF

ENGINEERING,UDAIPUR(RAJASTHAN)ENGINEERING,UDAIPUR(RAJASTHAN)Rajasthan Technical University,KotaRajasthan Technical University,Kota

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------


5/73

ACC Lakheri Cement Works An Outline

Lakheri Cement Works was established in the year1917 by adopting wet process Technology for manufacturing

Portland Cement. This was the best conventional Technologyavailable at that point of time. Since then Lakheri CementWorks extended its services to Rajasthan State as well asneighbouring States and contributed towards the nation inbuilding a modern India.

Lakheri Cement Works kept on marching ahead and inthe year 1997 as a part of modernization programmeconverted wet process technology into the energy efficient dryprocess technology. Lakheri Cement Works is manufacturing

Cement ; namely PPC ( Portland Pozzolna Cement),OPC(33/43 grade) type at Lakheri town, District of Bundi,Rajastnan . Plant has been expanded to a production capacityof 50 lac. Tons per annun ( LTPA) and a 25 MW Captive PowerPlant . Now ACC is recently entering into the field of windEnergy. So ACC will become the first Company whichintroduces wind energy first in Rajasthan.


Rajasthan Technical University,KotaRajasthan Technical University,Kota--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

LAKHERI CEMENT WORKS:-


6/73

Cement manufacturing plant of Bundi district in Rajasthanis one of the earliest unit set up for the manufacturing ofcement in India.

Lakheri Cement Works (LCW) celebrated its PlatinumJubilee of operations in 1992, LCW has been pioneeringindustry in industrial development of Rajasthan and since itsinception has undergone various stages of up gradation and iscurrently producing about 3200 TPD of clinker.

The Lakheri cement works was established in 1905 forproducing hydraulic lime and was converted into a cementplant in 1917 using wet process kilns. The mining operationsusing manual methods began in 1905 at mines located near

Lakheri Mines which has continued unto 1980, mechanizedmining was commenced at Lakheri Mines which has continuedto the present days.

In 1996-97, the unit was converted into modernized dryprocess kiln with installed clinker capacity of 1200 tons per day(TPD). Then, the first phase of expansion was completed inMarch 2000 where the clinker capacity was increased to 1600

TPD.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------


7/73

In the folklore of Rajasthan, a Gujjar named Lakha is creditedwith establishing the town of Lakheri several hundred yearsago. It was an ideal grazing spot. Well protected from storms,nestling in the hills of the north eastern span ofAravalli range

in Bundi district, this patch of green, covered thick withbamboo trees attracted Lakha who raised two temples asprelude to building the town.

Since the beginning of this century other structures havecome up to challenge Lakheris traditional skyline of ruggedhills and embattled walls. A cluster of four cylindrical, pill boxshaped vertical kilns of a plant set up in 1905 to producehydraulic lime, stand like grizzled sentinels on a Cliffside. It wasthis primitive plant, which was converted into a cement factory

in the year 1917 that makes the Lakheri Cement Factory theoldest cement factory in India. Lakheri works is credited withmanufacturing the first branded cement. It was the mostpopular cement of the times and known as BBB Cement or Bundi Bagh Brand Cement

Commencing operations with two 100 tpd kilns, Lakhericement works expanded to three kilns with an aggregatecapacity of 3.2 lakh per annum.




8/73

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

About RUGGED HISTORYLakheri Cement Plant

The rugged Aravalli hills which have shaped andinfluenced the history of this region, as well as the character ofits people, have proved to be the source of livelihood to theinhabitants. The limestone quarried from these hills is theprincipal raw material. Its distinctive feature is that thelimestone by itself is naturally occurring and known as cement-rock.

Originally mining operations at the limestone quarrieswere totally manual. Nearly 2500 people were employed in themining of limestone, In 1930, mechanization was introducedwith steam-driven excavators - replaced in 1935 with battery-operated ones. By the 1950s, quarry operations at Lakheriwere fully mechanized.

At present the limestone is being mined about ten

kilometers southwest of the factory. A higher quality limestoneis being obtained to be used as a sweetener from nearbysources.


9/73



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

In the sweltering heat of Rajasthans summer, registering

50C at times, our employees go to work in the mines with the

same zeal and fortitude which their ancestors displayed when

facing overwhelming odds in battle. The 18 meter yellow

beaked pare (turban) - which characterized the headgear of

their ancestors - has now been replaced by safety helmets. The

limestone (enriched by wobblers process) in transported from

the quarries to the works on a broad-gauge railway system,

owned and operated by ACC. This limestone is unloaded from

wagons into Primary Crusher.

DEPARTMENT AT LAKHERI CEMENT WORKS PROCESS DEPARTMENT

1. QUARRY

2.CRUSHER

3. RAW MEAL PREPARATION STAGE/ KILN FEED STAGE

4. FUEL PREPATION STAGE

5. PYRO PROCESSION STAGE

6. CEMENT MILL

7.CEMENT DISPATCH STAGE

8. LABORATORIES


10/73



----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Besides, there are other supporting important

units such as

1. Electrical & Instrumentation

2. Workshop

3. CPP

4. DG set

5. Motor Vehicle Department

6. Stores & Purchase

7. Human Resource & Time office

8. Accounts

9. Safety & Environment

10. Hospital

11. SAFETY DEPARTMENT


11/73



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

1. QUARRY:-

Lakheri Cement Works has 687.46 hectares captive

mining lease extending over 17.2 kms. strike length along

Bundi road. The mining area is divided into many parts by

natural NALAS and known as various hill nos. (from 1 to 31).

The thickness of the limestone deposits is also defined as name

of various series as follows:

1. bottom or lower series

2. middle series

3. upper series

Generally middle series is not rich with the quality

limestone, so mainly limestone is taken from the lower or

upper series. Upper series are used in the rainy season

elsewhile the lower series is used to mine outlimestone.

Limestone deposit ratio of lower and upper series is around

60:40 approximately. The quality of limestone in chemicalparameters in various series is shown in table below:


12/73



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

RAW MATERIAL ANALYSIS

TC%(Maxupto)

CaCO3%

MgCO3%

SiO2%

Al2O

3%Fe2O3%

CaO%

MgO%

LOI%

LOWER 77.2 75.8 1.1 16.

3

2.7 1.3 42.

6

1.3 34

.1MIDDLE 69.3 67.9 1.1 23.

93.3 2.1 38.

01.2 30

.5UPPER(HIGHGRD.)

76.0 74.4 1.3 16.6

2.2 1.3 41.7

1.2 34.8

UPPER(LOWGRD.)

73.9 72.2 1.4 17.2

2.2 1.8 41.5

1.3 34.0

The various series can also be described as below:

Series Average thickness Overburdenratio

Lower 17 Mts.(dips approx. 18-25deg. towards NW)

1 : 1.13

Middle 60-65 Mts. -Upper Uniform(dips approx. 20-25

deg. in NW)

1 : 1.22


13/73



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------As usual in any limestone quarry, ACC Lakheri has open cast

mines and uses various mining methods as follows:

1. Manual

2. Semi mechanized

3. Fully mechanized

The details of the various processes in quarry is given below:

DRILLING

Before drilling the operation of cleaning of the place to

drill is done by using dozers. After the cleaning of the place,

the drilling is started at specified point for specified varying

depths. Wet drilling process is employed to avoid

environmental pollution caused by the dust coming out.

Generally the drilled hole diameter is taken 115 mm.

drilling machine is used with tungsten tip to bore the earth and

pneumatic and hydraulic pressure used to drill the earth.

Various drilled material samples are sent to test in laboratory.

The drilling rate of the hydraulic machine employed,

Prithvi is 11m/hr with a fuel consumption rate of 22 l/ton oflimestone drilled. The rated pressure used is 10.5kg/cm2 with

the help of 180 hp motor.


14/73



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

BLASTING

Blasting is done very carefully and according the norms of

mines safety. For blasting either cap sensitive or non-cap

sensitive explosives are used as follows:

1.TOE BLAST

2. INNERGEL

3. AMMONIUM NITRATE + FUEL OIL (ANFO) (mostly

used)

During the blasting a fixed pattern is used to economize

the blasting process, so the maximum limestone can be

obtained from consuming minimum explosive. First the holes

are dug and filled with explosive (20kg/hole) upto certain

depths. These all holes are connected to detonators and

circuited to be blasted. Around 1 kg. Of explosive is needed to

blast 10 tones of limestone. ANFO contains 70% Ammonium

nitrate & 30% other explosive of which 6% is fuel oil.

The spacing of the holes is kept 5m & burden 3 m. The

whole depth is 6m of which lower 1 m is filled with explosives,the next 1.5 m is filled with sand & stone for stemming. The

whole dia is kept 115 mm.


15/73


Rajasthan Technical University,KotaRajasthan Technical University,Kota--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

LOADING

This process deals with the operation of loading the

limestone obtained by blasting into the transport vehicles. This

can be done either by hand (at manual mines) or by

mechanical means.

The principle mechanical loading appliances used in quarry are

1) Excavators- 3 nos. (model EX400)

2) Shovel- 2 nos. of capacity 2.88T

3) Backhoe- 1 no of cap 2.28T

4) Dumpers- 5 nos.; capacity 40T (4 nos.) & 35T (1 no.)

5) Dozer- 1 no.

6) Drilling machine- 3 nos.

TRANSPORTATION

This transportation comprises the transport of limestone

(1) From mines to the Wobbler &

(2) From quarry to crusher


16/73



----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

WOBBLING

Wobbling process is a quality enrichment process of

limestone at quarry, because limestone mined from the mines

is not as per the requirement of the plant to produce quality

cement. This process is assuring quality enrichment of around1-1.5% of total carbonate (TC) by removing shale. Wobbling

process takes place through the two machine units named as

Wobbler

Wobbler

It consists of set of transverse bars rotating in the same

direction with the spacing between the bars remaining

constant. These bars are of elliptical cross-section with the

major axis at 90 degree to each respective adjacent bar. The

action of rocking and tumbling forward motion is started when

bars rotate. The material placed on it is then scalped and

screened.


17/73



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

WASHING

It is a newly applied technique for quality enrichment atquarry. It enhances the quality of limestone by removing the

undesired sticky sand particles and excess clay

contents.Washing is done with water and as a result of this TC

of LS is increased by 0.25%. After the washing operation,

limestone is transported to the crusher at the plant in tipping

wagons by loco. One Loco (No. 9) hauls 40 trolleys, capacity of

each are 10 tons.


18/73



------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

2. CRUSHER:-

The raw material brought to the plant in the form of the

large lumps containing their natural ingredients of max.

Permissible size 1.2(m)*1.2(m)*0.25(m) is subjected to size

reduction process.

The material is first unloaded from trippling wagons or

payloader/dumper into the crusher-unloading hopper by means

of winch. It is fed to the jaw crusher by laminated conveyor in

controlled fashion by a motormanwho intermittently feeds

the material in the jaw.

The primary crushed material is conveyed to the secondary

crusher which is an open circuit hammer crusher with 36/ 42

hammers. Here the size is reduced to below 3. Hammer crusher

has no grid bar arrangement- only set of Mn-steel impact plates

have been used. It is directly coupled to the drive motor. The

crushed stone is then conveyed to either the limestone stockyard or

the vertical roller mill (VRM) hoppers depending on requirement by

an arrangement of belt conveyors.


19/73



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

The primary crushed material is conveyed to the secondary

crusher which is an open circuit hammer crusher with 36/ 42hammers. Here the size is reduced to below 3. Hammer

crusher has no grid bar arrangement- only set of Mn-steel

impact plates have been used. It is directly coupled to the drive

motor. The crushed stone is then conveyed to either the

limestone stockyard or the vertical roller mill (VRM) hoppers

depending on requirement by an arrangement of belt

conveyors.

The purchased stones & stones from manual mines are stocked

at site near unloading hopper & at top crusher area. Crushed stone

stocked at crusher can be extracted by an arrangement of

underground belt and chute arrangement.


20/73



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

VRM

Lime stone fluxes are mixed in desired proportions and

fed to VRM for grinding. The pulverized raw meal is of the size

24 - 28 % on 170-sq. mesh & less than 2.5 % on 72-sq. mesh.

This is fed into silo through an airlift pump along with air

obtained from PD blowers. Further, there are small air slides

inside the silo. The air for blending is supplied by 3 separate PD

blowers.

The air for lifting & blending the material requires to be

evacuated in the same rate otherwise this will pressurize the

silo. So 1 no. Of dust collector of appropriate capacity has been

installed at silo top for de-pressuring the silo.

Sample boy takes the sample of VRM output, physical/chemical analysis is done. Feed back is given to the DM - Q &

PC who guides the CCR operator for taking the necessary

corrective actions (If required). The material stored in C.F. silo

is fed into kiln through a suspension pre-heater.


21/73

Since ours is DCS Control Process, all the equipments are

started/stopped from DCS in-group start mode. All the drives

attached to particular group starts one by one in preset

sequence and stops in the reverse order.

After the crusher is started, the crusher operator opens

and regulates the valve for water spraying inside the secondary

crusher and closes the valve when the crusher is stopped.

Material of construction of bearing = white metal bearing.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Magnetic separators

These pull the pieces of iron out of the stream of the

material and remove them. Magnetic separators are not able toextract all iron and specially not the larger and more bulky

object such as large balls, hammers, excavator, and bucket

teeth etc. which constitute a particularly serious hazard to the

crushing machinery.

Metal detectors:They do indicate the presence of any metal object with

complete certainty.Here there is one metal detector used

before the feed line of VRM.If it indicates the presence of metal

in the feed line then another line through divertor opens and


22/73

removed by magnetic separator and rest of the material is

recycled into feed line.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

3. RAW MEAL PREPARATION STAGE/KILN

FEED STAGE

At this stage for maintaining the quality of the product

some additives are added in raw materials. Generally these

additives are as follows:

1. Silica(Sio2)

2. Lime(Cao)

3. Ferric oxide(Fe2O3)

4. Alumina(Al2o3)And these additives are taken by using various compounds as

follows:

1. Silica: Sandstone

2. Alumina: Laterite, Bauxite


23/73

3. Ferric oxide: Laterite, Iron ore

4. Lime: higher grade / chemical grade lime stones

These all raw materials are stored in three hoppers, aftercrushing, as one hopper of low-grade limestone, second one of

chemical grade limestone and the third one of iron ore or

Laterite (called as Flux). These all three hoppers are feeding on

the weigh-feeder, which supplies proportionate quantities of

various raw materials as per the desired quality of raw

materials.


ENGINEERING,UDAIPUR(RAJASTHAN)ENGINEERING,UDAIPUR(RAJASTHAN)


--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

4. FUEL PREPARATION STAGE :-

There are many types of fuels are available for the firing in the

kiln as follows:

1. Coal

2. Coke/pet coke

3. Natural gas

4. Crude oil

5. Diesel

6. Lignite


24/73

Here we are using coal (especially imported coal) along

with little amount of petroleum coke (upto 5%).

Fine coal is fired into the kiln along with air. Coal is first

crushed in hammer crusher having 16 hammers. The details of

hammer crusher is as:

No. Of hammers = 16.

Feed size = 1.5(max.)

Product size = 1.0(max.)

Capacity = 50.0 TPH.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Crushed coal obtained from crusher is ground in the three-

compartment air swept ball mill. Hot air is passed through the

coal mill for drying. Air is heated in the Pulverized Hot Air

Furnace, inside temperature of which is in range 1200-13000c.

There are two coal mills. Dimension of which is as:

No. 1 coal mill = 2.2(m)*7.6(m)

No. 2 coal mill = 1.98(m)*8.6(m).


25/73

Coal mill no.1 is used for pet. Coke grinding & no. 2 is used for

imported coal.

Different chambers of coal mill are as:

1. Drying chamber

2. First chamber containing large balls

3. Second chamber containing pebbles.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

As process, coal is used as fuel in the cement

industry in the form of the powder i.e. fine coal. Then the coal

is tested in general for the following parameters to decide

quantity and process parameters to be maintained for burning

the raw mix:

1. % moisture

2. % ash

3. % volatile matter

4. % inherent moisture


26/73

5. % fixed carbon.

Coal is crushed in crusher and ground in mill to a required

fineness i.e. residue percentage retention on 170 SQ mesh and

72 SQ mesh for better fuel efficiency and to produce product of

good quality.

Normally the retention on 170 SQ mesh and 72 SQ mesh

is maintained 21-24% and less than 4% respectively which is a

function of the percentage volatile matter present in the coal.

& the percentage retention on 172 SQ mesh is maintained 60-

80% of the volatile matter. Now this pulverized coal is ready to

fire in kiln.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

5.PYRO-PROCESSING STAGE :-

Pyro-processing is the heart of a cement plant. Primarily

clinker is produced here. This process starts with the feeding of

kiln feed from the silo. Ground raw material is stored in the CF

silo. After silo there are two nos. of shut gate and flow control

gate respectively. Raw mix flow from silo is as: -it passes

through shut gate and flow gate material from that goes into


27/73

control bin whose set point is 58 T-65 T. When stored material

in the control bin exceeds 58T, it starts flow from bin through

solid flow meter, Air- slide, and Air lift to the single string six

stages preheater. Whenever material in the control bin exceeds

65T flow through it stops. The kiln system consists of a six

stage single stream preheater for preheating/ precalcination of

the kiln feed, before it enters into the kiln. The kiln feed is

conveyed to the preheater by an air lift pump with a cyclone

cum bag filter arrangement for separating the conveying air

from the kiln feed before feeding to the preheater. The partiallycalcined material is converted into clinker in the burning zone

of the kiln at a temperature of about 1350-degree centigrade.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Sintered material discharged from the kiln in the form of

small, hard gray pallets is called clinker. The clinker is then

cooled in a grate cooler and transported by the deep bucket

conveyor to the covered storage gantry; from where two

electrically operated overhead cranes deliver it to cement mill

hoppers.


28/73

PREHEATER

In ACC Lakheri, before kiln the kiln feed is to be passed

through the six-stage single string preheater. Here,

precalcination of the kiln feed is occurred. After preheater the

60% calcination of kiln feed is completed. For the next 40 %

calcination the material is fed to the kiln.

This preheater consists of a system of cyclones, with

connecting pipes, through which the exit gases of the rotary

kiln at 10000

c are drawn by means of PH fan of 820 rpm. Theraw meal, which passes through the system in the opposite

direction to the gas is separated from the gas stream in each

cyclone and is introduced into the stream in the next stage.

Separation is taking place in the cyclones and heat

transfer in the ducts and in this way material reaches the

rotary kiln in a partially calcined condition.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

The preheater achieves the most rapid transfer of the

heat from the hot gases to the powdered material, because in

the suspended state each particle is totally enveloped by the

gas. The raw meal does not have to be nodulized; it is fed


29/73

completely dry to the preheaters. This method offers the

special advantage that it yields dry exit gases, which may be

further, utilized for drying raw material or coal.

Rotary kiln is used for clinker production. It consists of a slowly

revolving cylindrical tube, which is inclined to the horizontal by

a little amount. The material to be burned enters the kiln at the

feed end and the firing system is installed at the lower or

discharge end i.e. the counter flow principles are employed by

pulverized coal which is used as fuel. Rotary kiln is of not too

much length because it has only the calcining zone and hereonly remaining 40% calcination is occurred.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Due to the variation in the temperature, kiln can be

described in three main zones as follows:

1. Cooling zone(900-1200 deg. Celsius)


30/73

2. Burning zone(1200-1600 deg. Celsius)

3. Calcining zone(1000 deg. Celsius)

The reaction taking place is given as: -

CaCO3 Cao +CO2

AUXALLARIES

Loss of the heat from the kiln due to radiation can be

reduced to a minimum by providing the refractory lining with

refractory bricks.

Coolers are also used in conjunction with the kiln, for the

purpose of fast cooling the clinker discharged from the kiln.

Here the grate cooleris employed with the kiln for that

purpose. The clinker from the rotary kiln is fed on to the grate,

uniformly distributed over the width throughout.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

The grate consists of plates, of which every alternate are

in connected to a moving frame which performs a to and fro


31/73

motion causing the clinker to slide down along the grate

towards the outlet end of the cooler. The grate is totally

enclosed. Air for cooling the clinker is forced into the space

under the grate by a fan. The air passes through the interstices

of the grate and permeates the bed of clinker lying on it. The

clinker gives off its heat to the air. Clinker coming from cooler

is at temperature of 100-130 0c.

Then these clinkers are stored at the cement mill hoppers

from where these are fed to the cement mills in the desiredproportion with the gypsum and flyash (in case of PPC

production).



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

6.CEMENT MILL :-


32/73

Cement mill is an important part of any cement industry.

In ACC Lakheri, there are five cement mills at this stage to

meet with the desired production of the cement. These five ball

mills are very old but are working competitively.

During this stage clinker from the cement mill hoppers

and required proportion of the gypsum and fly ash are fed to

five cement mills through the feed table, where they are

grounded to produce cement. The mixture of the clinker, fly

ash and gypsum is called Pozzolana Portland Cement (PPC).

Finally this produced cement is pneumatically conveyedthrough three fluxo to the storage silos, from where it is

conveyed to the packing plant by screw conveyor and elevator.

There are four silos, three for PPC and one for OPC. At the time

of conveying of cement by fluxo, to avoid the dust the dust

collector is attached with the unit.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

CEMENT BALL MILL :


33/73

All the five-cement ball mills are identical and are quite

old. Each ball mill is a 12 meters long shell as whole, which is

divided into two chambers by a diaphragm. Here the setting of

two chambers is done for 4 meters and 8 meters as primary

grinding chamber and secondary grinding chamber

respectively.

Primary chamber contains high chrome balls as grinding

media. The size of the balls in primary chamber is more

comparative to the size of he balls of the secondary chamber.

Generally sizes of the balls of this chamber are 90 mm. 80 mm.or 70 mm.

Secondary chamber also contains high chrome balls as

grinding media but of smaller sizes than the primary chamber.

This section provides more surface finish to the cement. The

surface of cement depends on the sizes of balls used in the

primary chamber and secondary chamber. Generally secondary

chamber contains the balls of diameters of 17 mm. 20mm. 25

mm. and 40 mm.

Each cement mill produces about 20 TPH as standard. Main

quality parameter of the cement received from the cement mill

is the specific surface area (SSA). It is standardized as 2400-

2600 cm2/gm and 3300-3500 cm2/gm for OPC and PPC

respectively





34/73

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

7. CEMENT DISPATCH STAGE :-

This stage is connected with the process of packing of the

cement in bags. The packing of any product is an important

part of any industry in current business world. The packing

work of cement is very dusty and hazardous.

In ACC Lakheri, first the cement from the silos comes over

the vibrating screens through the screw conveyors and bucket

elevators. The bucket elevators are used to elevate the cement

to certain height above the vibrating screens. Vibrating screen

is used to avoid the nibs from the cement. Then the cement is

passed to the packer machines to pack the cement in the bags

of weight 50 kgs. Currently the rotary packer machine is also

installed to enhance the packing capacity, which takes 30

seconds to pack a 50 kgs bag.

Now there are three types of the packers in ACC Lakheri, as:

1. Pneumatic packer,

2.Mechanical packer &

3.Rotary packer

Then the packaged cement bags are inspected visually

and loaded to the railway wagons for dispatching to RMO or theclients. Automatic wagon loaders are used to load the cement

bags to the railway wagons.




35/73


--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

8. LABOURATRY:-

Laboratory provides a CO-plant activity right from theextraction of the limestone from the quarry and purchase ofraw materials and continuously goes beyond the dispatch ofthe cement to the market. Laboratory is the breath of a cementplant.As the quality cost system development, the laboratorycosts have great impact on the appraisal costs. This cost is ofgreat amount in the quality costs because in the processindustry the quality parameters are always the properproportion of the chemical constituents.

In ACC Lakheri, the work distribution is like that all the

performance reporting in terms of the quality are done by

laboratory, else that all complaints handling is also done by

laboratory. Here the laboratory is divided in three small units

as:

1. Main lab.

2. Side lab.

3. Top lab.




36/73


--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Quality control system is fully operated by laboratory as the daily

testing of various key parameters of the cement samples like:

1. Lime(Cao)

2. Insoluble residue (IR)

3. SO3

4. Loss on ignition (LOI)

5. Surface

And with these, it also engaged in the full analysis of the

cement in following terms:

i. SiO2

ii Al2O3

iii. Fe2O3

iv. CaOv. MgO

vi. LOI





37/73

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

vii. IR

viii. SO3

ix. Surface

HOW THE QUALITY OF CEMENT IS DEFINED

Quality of cement from the construction point of view is

defined through the following quality parameters:

1. Fineness

2. Setting time(initial & final setting time)

3. Expansion

4. Compressive strength at various ages

3days

7days

28days

5. Heat of hydration

6. Durability




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------


38/73

AUXILLARY DEPARTMENT

Electrical & Instrumentation:This department basically concern with electrical and

instrument items. Their main jobs are:-motors repairing, weirfittings, motors assembling etc. electrical instruments arerepair by this department to stop breakdown when company isin production process. They check all instruments on daily basisand replace by new device.

GOVT. POLYTECHNIC COLLEGE, SAWAIMADHOPUR (RAJ.)GOVT. POLYTECHNIC COLLEGE, SAWAIMADHOPUR (RAJ.)Board of Technical Education, JodhpurBoard of Technical Education, Jodhpur

Abdul HamidAbdul Hamid SPN No. EE 2006SPN No. EE 2006374/14374/14II Year, ElectricalII Year, Electrical Page No. Page No.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Workshop:

All maintenance work is doing by this department on daily

basis .but sometime suddenly breakdown and shut down

occurs in plant then they repair that part which is responsible

for breakdown. These are the main work of this department:-

welding, machine assembling, water pump repairing etc.

CPP Captive power plant total power generation is 1, 75,

77,000 units and total power exported is 1,48,70,142 units.

Achievements

100 % protection & interlocks in line to ensure equipment

& process safety.

Accident free erection, commissioning & operation of the

plant.


39/73

Successful erection commissioning & operation of plant

with minimum consultants

Assistance which resulted into higher confidence amongst

CPP crew.


Abdul HamidAbdul Hamid SPN No. EE 2006SPN No. EE 2006

374/14374/14II Year, ElectricalII Year, Electrical Page No. Page No.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

D.G.SET :-

ACC has 6mw D.G.set but it is use only when it is

needed.Key functional area

1 Running during Peak Load Hours for cement mill operation

2. Power shortage especially during winter period.

3. Bad climatic condition.

4. Sudden grid disturbance.

Motor Vehicle Department :-

This is the department handle all those vehicle which use

in production process of cement.

The principle mechanical loading appliances used in quarry are


40/73

1. Excavators- 3 nos. (model EX400)

2. Shovel- 2 nos. of capacity 2.88T

3. Backhoe- 1 no of cap 2.28T

4. Dumpers- 5 nos.; capacity 40T (4 nos.) & 35T (1 no.)

5. Dozer- 1 no.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Apart from this wagons are use to dispatch cement to

different location and wagons use for to bring raw material

from different location. All responsibility of transportation of

acc handles this department.

Stores & Purchase :-

Stores & Purchase department where the company can

store their main equipment. If suddenly there is any breakdown

then they can change parts of machine with the help of stored

item. In purchase department 5 managers are their a they

estimate how much raw material company has to purchase?

Where should they porches these raw material. And tw0 staff

members are also working there to help them

Human Resource & Time office people are the major

resource. One of ACC corporate core value is concern for


41/73

people. All policies and strategies of Human Resource

Development are aligned to this core value.

ACC strive to build the competencies and upgrade the

knowledge and capabilities of people by orgning training

interventions. Unit training based on standard operation and

maintenance practices, basis engineering skills traning, specific

equipment training, and laboratory base training in basic as

well as advanced skills are some of examples.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Special training programmers are held to enhance peoples

capabilities at various points these includes supervisory

development program, management development program

and enhancing managerial effectiveness program. Thrust is

giving for enabling the front line and middle management to

successfully lead the changes. The center has a very good

infrastructure with fully equipped workshop for imparting

training in various trades like marching, welding.

Time office :-

Time office is the sub department of H.R. department.

There is one officer and 8 staff members. Provident fund,

employee wages and mgt staff salary, implementation of


42/73

company policies etc are the work of time office department.

Only Qualified employee can sit there. Who should have

knowledge about company policies

Accounts: account is that section where all transactions of the

company are recorded .9 management staff are working there

and 6 staff members are working under them. They analysis all

the financial data on regular and daily basis.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Hospital:-

ACC has a modern hospital with an emergency unit with a

total of.beds to take care of a population of over thousand

over.. Patients report to the hospital outdoor on an average

daily. Around.. Persons get admitted in the wards annually.

There is.staff to look after health of the employees. One

occupational healthy service commonly known as plant medical

unit is located within the plant. Facility like pathology,

biochemistry,x-rasy are provided in the hospital

Total quality management:-

Total quality management in order to bring about a significant

improvement in its system and process; lakheri cement plant


43/73

decided to develop and install quality management system

through out the organization.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

OFFICER-SECURITY :-

To maintain record of maintenance, repairs of various firefighting equipment of the Plant and quarry.

To carry out routine inspection, maintenance / repairs of

water hydrants, pumps, refilling of used fire extinguishers

and maintaining records of such inspections / repairs.

Assist fire chief in fighting fire.

Training of the employees of plant and mines in fire fighting.

Organize mock drill rehearsals at periodic intervals at

different locations of the Plant.

To assist fire chief and departmental heads in investigating

the incidences of fire and


44/73

Maintain record of such fires in fire logbook.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

FACILITIES AT ACC :-

Welfare Activities

ACC The necessity of social welfare was recognized bymanagement even before the introduction of various SocialWelfare Legislation which has created a sense of belongingnessamong employees as well as people in the surroundingvillages.

Keeping the above in view, a Village Welfare Center wasstarted in the year 1956. This is an arid area with scanty rainfall, infertile land with lack of irrigation facility. The people inthe neighboring rural hamlets, at that time were mostly

superstitious, uneducated and prone to dependence uponothers. The main objective of the Village Welfare Center was toignite the spirit of self and independence and to initiateactivities for the enlistment of the area.

Health And Hygine


45/73

Money, health and education are the three pre-requisitesof progress of any society. Modern Medical Care was broughtby ACC to this remote villages long back. Every year we havebeen organizing various camps such as Family Welfare, Eye

Camp, and Anti Malaria Camp at our Works Hospital with thehelp Government Authorities. These camps include freedescription.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Education And Sports -

The company has given importance to the rural education.We have an English Medium School unto 12th standard affiliatedto CBSC and Hindi Medium School unto 8th standard affiliated

the Rajasthan Board. These schools have produced verycitizens / officials of very high rank.

Company has always been championing the cause ofeducation whether it may be in case of its employees orotherwise, with this objective, company has constructed aschool building in the premise of ACC Colony and donated toGovernment of Rajasthan.

Apart from this, company has gone to interior of villagesand have constructed number of schools in villages ofChamaoli, Guntha, Sakhoda etc.

Company also organizes sports meet every year forchildren studying in village schools in ACC Gymkhana Ground.

Rest And Lunch Room-


46/73

Spacious rest and lunch room are provided in eachdepartment. These rooms are used by the worker to take foodand rest after work. In departments like C.P.P. wheretemperature is very high air conditioned rest room are provided


Abdul HamidAbdul Hamid SPN No. EE 2006SPN No. EE 2006374/14374/14

II Year, ElectricalII Year, Electrical Page No. Page No. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Safety & Environment -

Systematic, well structured and comprehensive SafetyOrganization is very essential for effective management ofhealth and safety for an establishment. Salient features of

safety organization at Lakheri Cement Works which isindicative of top managements commitment for safety andhealth of employees and surrounding vicinity is given as under.

To take round of the plant in shifts to locate unsafe

actions of the employees / unsafe conditions and if found any

report the same to the concerned department head shift

supervisor and Asst. Manager Safety.

Environment Protection -

At ACC Lakheri Cement Works mining operation arecarried out based on mines plan approved by appropriate


47/73

authorities. In order to maintain ecological balance, LakheriCement Works Mines have planted in total 93000 plants withsurvival rate of 90 %. The majority of plantation in mines hasbeen done in the abandoned mines, which are filled with over

burden. The other areas selected in mines for plantation is theland where mining activities are not there.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Performance Rating System at ACC Cement Works

The prime role of Management Staff is to Make Things

Happen. To performhis / her role successfully, he / she is required to imbibe,

sustain and improve upon a series ofcritical factors withoutwhich any management process remains incomplete andineffective.

The Overall Performance level of the employee will bebased on the total score obtained. The guidelines for rating theoverall performance is as follows :

Score Outstanding : 91 & aboveVery Good : 81 - 90Good : 71 - 80Acceptable : 61 - 70Unsatisfactory : Below 60


48/73




--------

Important factor are consider in performance rating scale:

When reviewing the performance of your employee, recallinstances, which are typical of his / her behavior. Do not getinfluenced by unusual situations, which are not typical.

Do not allow your personalfeelings/emotions/perception/past impression to govern theperformance review as far as possible.

No attempt should be made to arrive at any pre-determinedscore. Each critical factor should be considered separately.

The value of the performance rating lies in the

impartiality/unbiased ness and sound judgment of theperformance reviewer.

Detailed reports in cases of Outstanding / Unsatisfactoryratings should be forwarded to Head Office along with thePerformance Appraisal Form for review. The report must


49/73

mention about the performance of the employee in objectiveand verifiable terms.

The Review Committee at the Head Office will review thesecases across all ACC basis and this Committee will decide

the final rating.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

TRANSFORMER

A Transformer is essentially a static electromagneticdevice consisting of two or more windings. Which link with acommon magnetic field. One of these windings, the primary, isconnected to an alternating voltage source, and the anotherwinding, the secondary, is connected to an load.

It must be understood that a transformer is not anenergy conversion device but a device that transforms electricalenergy from one or more primary a.c. circuits to one or more

secondary a.c. circuits with changed values of voltage andcurrent.

Presently, most of the electric power for industrial andutility purposes, is generated by large hydro-electric plants andsteam power stations in the form of three phase a.c. at afrequency of 50 Hz. The voltages of the generators installed at


50/73


51/73

7. Bushings8. Conservator and Breather9. Explosion Vent10. Temperature Indicators

11. Buchholz Relay

CoreMagnetic circuit is three limbed core the construction,

each limb has inter left- metered points with top & bottomyokes. The three limb have windings. The lamination is madeup of high-grade non-agreeing cold grain oriented silicon steel.

The yokes are clamped by means of end plates, with bolts andmeans plates with regi glass clamp lugs.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

WindingThe inner most coil near to the 3 core forms the L V

winding. This is spiral coil. Axial coil ducts are provided inside &outside the coil. Outside the L V winding, HV winding has beenwould which is also disc type winding & provided with axial &radial ducts. Line load is taken out from the tap of the coilstatic rings has been provided at the lines ends of HV coils forbetter impulse distribution

Across the coil, outer most winding is disc type winding(tapping winding). Tapping winding stop to made up of A coilsconnected in parallel. Tapping winding is connected in serieswith main HV winding with 15 taps to vary on load tap changerhas been provided on H V side.


52/73

Transformer Oil

One of the most important factors which determine thelife and satisfactory operation of a transformer is the oil in

which it is immersed.

The transformer oil has two prime functions:i) To create an acceptable level of insulation inconjuction with insulated conductors and coils.ii) To provide a cooling medium capable ofextracting quantities of heat without deterioration asan insulating medium

Transformer oil is mineral oil (clean hydrocarbon oil)

obtained by refining crude petroleum . Vegetable and animalsoils are not used in transformers as they form fatty acids thatattach the fibrous insulating insulating materials used.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Some of the important characteristics necessary ordesirable in transformer oil are described below:

1. Electric Strength The transformer oil should have ahigh dielectric strength in order to minimize clearancesbetween coils and from windings to tank. The minimumelectric strength of new oils should be 3 kv/mm (rms) .

The resistivity of new transformer oils is morethan 13 x 10 ohm.m. However, if dust andsmall fibres are present in oil, they tend to alignthemselves along electric lines of force therebyforming paths of low resistivity which maycause electric failure.


53/73

2. Resistance to emulsion - The oil should have a highresistance to emulsion in order to prevent holding water insuspension in it. This is because even a small trace ofmoisture severely reduces the electric strength of oil. The oil

should not to be allowed to come in contact with moisture.

3. Viscosity - The viscosity of transformer oil should be small topermit

rapid circulation of oil.

4. Purity - The oil must not contain any acid, alkali, andsulphur compounds as these cause corrosion of metal partsand insulation.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

5. Flash Point - The flash point is the temperature atwhich oil vapour ignites spontaneously. The flash point of anoil characterizes its tendency to evaporate. The lower theflash point the greater is the vaporization of oil. When an oilvapourises it loses in volume, its viscosity rises, and anexplosive mixture may be formed. The flash point oftransformer oil should be higher than 104 degree centigrade.

6. Sludge Formation - Sludging means the slow formationof solid hydrocarbons due to heating and oxidation. Thesludge deposits itself on windings, tank walls and in coolingducts. Sludge is a poor conductor of heat and therefore itproduces temperature gradients across winding insulation


54/73

causing overheating of conductors. The deposition of sludgein the oil duct does not allow the oil to circulate freelythereby impairing cooling. The resultant increasedtemperature produces more sludge. This process of sludge

formation and consequent overheating will continue till thetransformer becomes unserviceable. Therefore, contact of oilwith air should be avoided in order to prevent sludgeformation ( since oxygen in air causes oxidation).

Transformer oil tends to deteriorate in service, but thistendency can be greatly reduced by paying attention totransformer operating condition and to oil itself when this isshown to be necessary as the result of regular tests. Themost important factors are :

i) Operating temperature, ( ii) atmospheric conditionsparticularly inside stations (iii) electric strength, (iv)moisture, and other contamination, (v) sludge formation.




--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

If the oil is found to contain moisture or suspendedcontaminants it should be filtered or if this treatment isconsidered to be inadequate, the oil should be replaced byfresh charge. Transformer oil is normally tested once everyyear and, if found below standard, may be treated by acentrifuge or filter unit.

Terminals and LeadsThe connection to the winding are of insulated copper

rods or bars. The shape and size of leads is important in highvoltage transformers. Owing to dielectic stress and corona


55/73

which are caused at bends anhd corners. Sharp edges andcorners should be avoided.

Bushings

Transformers are connected to high voltage lines, andtherefore, care must be taken to prevent flashover from thehigh voltage connection to the earth bank. Connections forcables are made in cable boxes, but overhead connectionsmust be brought through bushings specifically designed forvarious voltage classes.

The bushing consist of a current carrying part in the form ofa conducting rod, bus or cable, a porcelain cylinder installed in ahole in the transformer cover and used for isolating the currentcarrying part.

The simplest bushing is a moulded, high quality glazedporcelain insulator with a conductor through its centre. Thisbushing is used for voltages upto 33 kv. The porcelain bushingsused for indoor use have a smooth surface or slightly finnedsurface. The outside (upper part) of the bushing used fortransformers working outdoors is made with petticoats toprotect the lower fins against water in rainy weather.

GOVT. POLYTECHNIC COLLEGE, SAWAIMADHOPUR (RAJ.)GOVT. POLYTECHNIC COLLEGE, SAWAIMADHOPUR (RAJ.)

Board of Technical Education, JodhpurBoard of Technical Education, JodhpurAbdul HamidAbdul Hamid SPN No. EE 2006SPN No. EE 2006374/14374/14II Year, ElectricalII Year, Electrical Page No. Page No.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------


56/73

The bushing used for transformers having voltages above36 kv are either oil filled or capacitor and type. The oil filledbushings consist of a hollow two paret porcelain cylinder with aconductor, usually a cylinder, passing through its axis. The

space between the conductor and the inner surface of theporcelain is filled with oil. The oil is contained separately fromthe oil in the transformer tank. The top of the bushings isconnected to a small expansion chamber required toaccommodate variations in the volume of the oil due to changein operating temperature. There is a provision for currenttransformer at the lower end of the bushings. The arrangementis such that bushings can be removed without disturbing thecurrent transformer. The capacitor bushing is made up oflayers of synthetic resin bonded paper (s.r.b.p.) interleaved

with thin layers of metal foil or paper impregnated withconducting material. The result is a series of capacitors with acapacitor formed by two layers of metals foil with s.r.b.p.cylinder inbetween. The variationin length of metal foils andthe thickness of s.r.b.p. cylinders is so arranged that there is auniform distribution of dielectric stress throughout the radialdepth i.e. along the radius of the bushing.



57/73


--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Conservator and breather

The satisfactory operation of transformer depends so largelyon the condition of oil and therefore devices and methods for keepingthe oil clean and dry are of prime importance.

The oil level of a transformer changes with changes the temperature

rise of oil which in turn depends upon the load on the transformer. Theoil expands if the load increases and contracts when it decreases.

Therefore, provision must be made to take up this expansion andcontraction of oil.

Smaller transformers are not totally filled with oil and some space isleft between oil level and the tank cover. This space is taken by air.

The tank is connected the atmosphere through a vent pipe. When theoil expands, air is expelled out while if it contracts air is drawn in from

the atmosphere. This is called breathing of transformer. The airentering the transformer is passed through an apparatus calledbreather for the purposes of extracting moisture from it. A breatherconsists of a small container connected to the vent pipe and contains adehydratingmaterials like silica gel crystals impregnated with cobalt chloride. Thematerial is blue when dry and a whitish pink when damp. The colourcan be observed through a glass window provided in front of thecontainer.


58/73




--------

Breathers alone are not sufficient for protection of large andimportant power transformers because:

i) These transformers are liable to overloads which mayoverheat the oil and consequently there is sludge formationif air is present.

ii) Occasionally such transformers also suffer short circuitsand temperature rise becomes very high. This causesvapourization of a part of the oil. The oil vapours fromexplosive mixture with air which ignites and can causeconsiderable damage.

For these reasons oil is prevented from having contact withair as well as moisture. Conservators are used for this

purpose. The function of the conservator is to take up airfrom which it might absorb moisture.

The conservator is an airtight cylindrical drum mounted onor near the cover of the transformer and connected to itthrough a small pipe . The oil is set so that the transformertank is entirely full with oil and the conservator is about halffull. The interior of the conservator above the oil level isconnected to the atmosphere through a breather havingdehydrating material.

With the use of conservators, interchange of oil betweenconservator and main tank as a result of temperaturechanges is slow. Also dry is in contact with much smallersurface of relatively cool oil. Hence the sludge formation isconsiderably reduced and whatever sludge is formedremains in the conservator there being no sludge formation


59/73

in the main tank. This is a great improvement over theordinary tank with air space above the oil.

GOVT. POLYTECHNIC COLLEGE, SAWAIMADHOPUR (RAJ.)GOVT. POLYTECHNIC COLLEGE, SAWAIMADHOPUR (RAJ.)

Board of Technical Education, JodhpurBoard of Technical Education, JodhpurAbdul HamidAbdul Hamid SPN No. EE 2006SPN No. EE 2006374/14374/14II Year, ElectricalII Year, Electrical Page No. Page No.

--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Explosion Vent

In order to guard against the possibility of a sudden highpressure caused by a breakdown or a short circuit in thetransformer winding, a diaphragm relief device is used. Thisdevice consists of a large opening to the atmosphere coveredby a thin non-metallic diaphragm. The diaphragm bursts if thepressure inside the tank becomes excessive. The relief devicemust be above the level of oil in the conservator in order toprevent an overflow of oil in case the device operates.

Temperature Indicators

The most obvious indicator of transformer temperature isthe temperature of the hot oil. The oil temperature ismeasured by a dial type thermometer. The bulb of thethermometer is mounted in the oil and the dial is mountedoutside the tank.

However, oil temperature is not a reliable measure of the

winding temperature especially under sudden over-loads whichcause the winding temperature to rise more rapidly than the oiltemperature. Therefore, it is desirable to use an indicator whichwill show the actual temperature of hot spot in the windings.

Winding temperature indicator is a thermometer with abulb . The thermometer is immersed in oil and the bulb is


60/73

heated by heaters which carry a current proportional to thewinding current. Therefore, the reading of the thermometer isan analogue indication of winding temperature.



--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

--------

Buchholz Relay

It is a gas and oil actuated protective device and is usepractically in all oil immersed transformers with the exceptionof smaller distribution transformers. Buchholz relay is used forprotection of transformer against faults developed in side thetransformer. The device relies on th

cement project new

Documents