Manufacturing process of Insulators At

Bharat Heavy Electricals Limited-IPJagdishpur (U.P.)

Under Guidance of - Presented by-Gaurav Pandey Anushreya Gupta Engineer (Manufacturing/Production) EE- 4th Year 1309020020

BHEL- An IntroductionJagdishpur unit of BHEL is the leading manufacturer of high tension porcelain insulators and distribution insulators like Bobbin, Shakle, Guy/Stay/Strain, Pin, Cap and pin type Post insulators in the country. The plant is equipped with highly sophisticated plant and machinery. This division also offers wear resistance high alumina ceramic lining materials for power, steel, cement and mining industries as well as a wide range of industrial ceramics.

The product portfolio can be divided into three categories:-•LT type insulators•Disk type insulators•Ceralins

Major customers

 Major customers of BHEL IP Jagdishpur are

• NTPC• Power Grid Corporation of India Ltd.• State Electricity Boards• R.P. Goenka group of industries• Export to Middle East and African countries 

The total plant capacity is 6000 CMT (Excluding the weight of metal parts)

Insulators• The insulators for overhead

lines provide insulation to the power conductors from ground.

• The insulators are connected to cross arms of the supporting structures of the power conductors and the power conductors pass through a clamp of the insulators.

• The insulators are mainly made of either glazed porcelain or toughened glass.

Types of Insulators

• Basically there are three types of insulators used for overhead lines.

They are:-

• Pin type• Suspension type• Strain type

Pin Type

Strain Type

Suspension Type

Nomenclature for Disc type insulators

• BHEL IP has its own nomenclature for the disc type insulators.

• They are named on the basis of the strength they can withstand.

Materials used Mainly made of either glazed porcelain or toughened glass. Porcelain-

▫ materials used for porcelain are silica 20%, feldspar 30% and clay 50%. ▫ should be ivory white, sound and free from defects. ▫ should be vitrified because the presence of air lowers the dielectric strength.▫ dielectric strength should be 15 to 17 KV for every 1/10th inch of thickness.▫ Is mechanically strong, less affected by temperature and has minimum leakage

problem.

Toughened glass -▫ Has higher dielectric strength (35 KV for1/10th inch thicknesses) which makes it

possible for single piece construction, whatever be the operating voltage.▫ As glass is transparent, flaws like trapping of air can be detected. ▫ has a disadvantage that moisture condenses very easily on its surface, limiting

its use to about 33KV.

Manufacturing Process

The various manufacturing units at BHEL IP are

• Storage• Slip House• Jiggering Unit• Finishing Unit• Glazing Unit• Firing Unit• Assembly Unit• Testing Unit• Dispatch Unit

StorageThe different raw materials for manufacture of insulators are stored in the identified bins.

The raw materials are:- • Calcined Chaibasa clay• Dolomite• Manganese dioxide• Chrome ore• Calcite• Talc• Ellur Clay• Than Clay• Quartz for brown glaze• Quartz• Feldspar• Bikaner clay• Pyrophyllite• Felcite• Sericite• Japan ball Clay

Samples of different raw materials used

Slip House The input to slip house is Raw Material + Water

Following operations are performed

1. WeighingDifferent raw materials from the storage bins are collected and weighed according to the percentage composition and according to ball mill capacity to be charged.

A sample data for preparation of suspension body slip in a 5 ton ball mill for the first charge are as follows:

2. Grinding of raw materials in ball mills for first charge body slip

•Weighed quantity of raw materials are charged into the ball mill.• River pebble is also charged in the specified amount . It is used as a binder.•Specified amount of water is also charged.•Little quantity of slip is collected for checking slip parameters.•Ballmill runs for 14-16 hours.

3. Preparation of second charge body slip

•Same process is repeated and then ball mill is stopped.•Then the slip is discharged into mixing tanks and is agitated continuously

4. Slip Filtration

• Slip is returned to storage tank by passing it through vibro screen.•It removes coarser residue from insulator slurry.

5. Preparation of Cake

•Slip passed into filter press which removes excess water from it.•Slip is converted into cakes.•Hardness of cake is checked.•Stored in specified area in stacks.

Slip house work ends here and the output is Cake.

Filter Press

Stacks of Cake

Jiggering UnitThis unit is divided into two processes

1. Pugging Process which is an extrusion process.

2. Jiggering Process in which final shape is given to the cake after which it is dried.

Pugging:-• This is done in a pug mill.• Cake is fed into the pug mill• Mixed and a pug(cylindrical) or blank is formed.

Cake fed into pug mill

Pug formation

Jiggering:-

• This is done by automatic jiggering machine.• It is completed in two steps.

1. Primary station/Primary turn table/pre shaping station

•The pugs are assembled on the automatic jiggering machine .

•Initial shape is given to them by pressing them as shown in the picture.

2. Secondary turn table/forming station

•Has two dies which gives the article its final shape.

• 1. Primary dieAs shown in the picture, after giving the primary shape the articles are then transferred to the secondary turn table where they are given the initial shape along with the introduction of some kerosene oil on top .

•2.Secondary dieThe secondary die gives the final shape to the article after which they are kept in chain dryer for drying.Articles are kept in chain dryer for 2-3 hours and then released for finishing process.

Secondary Die

Primary Die

Chain Dryer

Finishing Unit• Articles checked for defects and the defective ones are discarded.• Article is placed on the MCBL (Multi Cutting Blade Lathe)• Three tools are used for finishing process.

▫ Jantar:- for finishing the top or B part▫ Finishing plate:- for finishing the curved surface or C part▫ Head finishing tool:- for finishing top or A part

Finished Article

Drying

• Articles are left for minimum of 8 hours to naturally dry.• After that kept in tunnel dryer for 39- 52 hours depending upon the type of

the insulator and the number of articles in each wagon• Tunnel dryer has five different zones and the articles are subjected to 5

different temperatures , zone 4 having the highest temperature.• Articles are then unloaded for glazing operation.

Glazing Unit• Visual inspection is done for defects• Brown glaze is applied on the G portion of the insulator• Sanding grog is applied on the F & B portion.• Stamping Operation is done and glazing ends.

Firing Unit• Done in kiln.• Continous process, kiln is fired 24/7.• One wagon enters kiln ,anothers exits.• Temperature is maintained as per the standards.

Assembly

The various operations performed are:-

• Application of bituminous paint.• Preparation of cement mortar.• Cement mortar is poured inside

the cap as well shell portion.• Cap and pin are placed in their

respective places.• Insulators are water and air cured

for 24-36 hours.

Testing SectionTesting of insulators is of three types namely:

1. Routine test 2. Acceptance test 3. Type test.

Routine test:-

Contains three sub-tests

•Physical Verification test•Routine mechanical test•Routine electrical test.

Routine Mechanical Test

Routine Electrical test

Acceptance test

• Also called performance test.• Consists of following tests:-

1.Verification of standard dimensions 2.Temperature Cycle Test (TCT):- Entire trolley is dipped in hot and cold water for

15 minutes . 3.Mechanical Performance Test (MPT):- 24 hour test,60% of rated mechanical load

is applied. 4.Electro mechanical test:- 50-60% of rated voltage is applied. 5.Puncture Test:- Done to verify the puncture voltage of insulators which should not

be less than the specified voltage. 6.Galvanizing test:- done to ensure proper coating of zinc on metal parts to avoid

corrosion.

Dispatch Unit

The insulators are then packed and dispatched to respective customers according to the demand & specifications.