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BP 23796PLANT PURCHASING SPECIFICATION

BHOPAL Rev No. 05

PAGE 1 OF 5

SUPERSEDESBP 23796 Rev.04SEMI -CONDUCTING WOVEN FABRIC TAPE

1. GENERAL:

This specification governs the quality of semi-conducting tape manufactured fromplain woven fabric e.g. Rayon, Cotton, Nylon or Polyester impregnated with semi-conducting varnish of graphite base. The material has temperature index of atleast 105.

NOTE: Type of base material shall be as stated on order.

2. APPLICATION:

Used as semi-conducting layer in primary windings of Instrument Transformers etc.

3. COMPLIANCE WITH NATIONALSTANDARDS:

There is' no Indian Standard covering this type of material..

4. DIMENSIONSANDTOLERANCES:

Thickness (Treated), width and length shall be as stated on the order.

4.1 Preferred Thickness (Treated) and Tolerances: 0.13,0.25 mm with tolerance oft 15 %.

However any other thickness can also be ordered.

4.2 Preferred Width and Tolerances: 12,20,25 mm with tolerance of t 1 mm.

4.3 Length I Roll : 50 meters.

However any other length can also be ordered.

5. FINISH:

The tape shall be flexibl~. The surface and edges shall be smooth and any loose fibershall not be present.

6. TEST METHODS:

Unless otherwise specified, the tests shall be conducted in accordance with therelevant methods of 15:5351.

Revision: Reviewed & brought upto date Issued by : ~

-Rev. 05

STANDARDS AND MATERIALS GROUPTECHNICAL SERVICES DEPARTMENT

1 Date: 04.01.20081 Date of first Issue: 25.06.1983

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BP 23796PLANT PURCHASING SPECIFICATION

BHOPALRev No. 05

PAGE 2 OF 5

7. SAMPLE FOR TEST: 1 Roll of tape shall be supplied for tests and approval.

8. MECHANICAL PROPERTIES :

8.1 BreakinQ StrenQth (As Received Condition) : 5 N I mm width, Min.

8.2 ElonQation (As Received) : 3%, Min.

Shall be measured on 100 mm gauge length.

9. ELECTRICAL PROPERTIES: -

9.1 Surface Resistance: 0.5 to 1.5 K Q I s.q.

The resistance shall be measured with 250 volt megger on a tape sample of lengthequal to the width of the tape.

10. CHEMICAL PROPERPTIES:

.10.1 Identification of Material:

The base material shall be identified by Infra -red spectrophotometer or by anyconventional method.

11.0 TYPE TESTS:

11.1 BreakinQ StrenQth after Aaeina in Oil:

11.1.1 Effect of A~ in Oil :

The breaking strength shall not be less than 4N/mm width, when tested onspecimens which have been aged in insulating oil to 15:335 for 168:!: 1 hours at100 :!:2 Deg.C and allowed to cool down to atmospheric temperature before testing.-

11.2 Effect of material on Insulatina Oil: (Annexure - I) -(Type Test)

11.2.1 Increase in acidity: 0.1 mg KOH I g. Max.

11.2.2 Increase in sludge content: 0.05 % Max.

12. TEST CERTIFICATE:

Three copies of test certificates shall be supplied alongwith each consignment.

In addition, the supplier shall ensure to enclose one copy of the test certificatealongwith their dispatch documents to facilitate quick clearance of the material.

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BP 23796PLANT PURCHASING SPECIFICATION

BHOPAL Rev NQ. 05PAGE 3 OF 5

The test certificate shall bear the following information:

BP 23796- Semi-Conducting Woven Fabric-Tape.(Rev.05)

Our Order No.

Batch I Lot No.

Test values obtained for compliance for clause 4,5 & 8 to 11.

13. PACKING AND MARKING:

13.1 The tape shall be wound on a hollow core of suitable material, the length of whichshall not b~ less than the full width of the tape.

13.2 The core shall have an inside diameter of approx 40 mm and be sufficiently strongto support the tape without collapsing.

13.3 The tape rolls shall be packed so as to be well protected from dust, dirt, moistureand mechanical damage.

13.4 Each package shall be marked with the following information:

BP 23796 : Semi-Conducting Woven Fabric Tape.

BHEL Order No.

Batch I Lot No.

Manufacturer's and I or Supplier's Name and Grade.

Thickness, Width and Length.

No. of Rolls.

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BP 23796PLANT PURCHASING SPECIFICATION

BHOPALRev No. 05

PAGE 4 OF 5

ANNEXURE-I

SLUDGE AND OIL ACIDITY TEST

1. Conditioning:

Condition the test specimen at 65 :!::5 % relative humidity at a temperature of 27 :!::2deg.C for 18 to 24 hours.

2. Procedure:

Into a 150 mmx 25 mm test tube weigh 25 g of transformer oil complying with therequirements of 15:335. Cut a sample of the material under test with lineardimensions such that the surface area including both sides is 25 cm 2 e.g. 25 mm x50 mm weigh it and introduce it into the oil. Lightly plug the mouth of the tube withcotton wool and place it in a constant temperature bath maintained at 100 :!::0.5 deg.Cfor 164 h.

Place a similar quantity of the oil above in a second tube and maintain this under thesame conditions as a 'blank' sample.

At the end of the specified heating period remove the tubes from the bath and allowthem to cool to room temperature. Determine the sludge content of the oil in whichthe sample has been immersed as follows.

pour the oil into a 600 ml beaker and wash the test tube and sample with n-heptaneuntil oil-free, adding the washings to the oil in the beaker. Make the contents of thebeaker up to approximately 300 ml with n-heptane. Cover the beaker with a watchglass and allow to stand in the dark for 24 h at room temperature.

Filter the solution through a tared, dried, sintered glass filter, complying with therequirements of a No.4 filter as specified in 85:1752 transferring all the sediment tothe filter with the aid of n-heptane from a wash-bottle. Dry the filter at 110 deg.C toconstant mass. Express the amount of 'sediment as a percentage of the originalsample mass.

Make th filtrate upto 500 ml in a measuring cylinder with nheptane. Make the 'blank'sample up to 500 ml in a second cylinder. Determine the acid values of the n- heptanesolutions are follows.

Place 60 ml toluene and 40 ml industrial methylated spirits (66 O.P) in a 600 ml conicalflask.

Add 2 ml alkali blue 6 8 indicator solution (2% mass in I.M.5.)and one drop of 0.1Nhydrochloric acid. Neutralize this mixture with 0.1N alcoholic potassium hydroxide togive a red colour which persists for 15. Add 100 ml of the above filtrate to theneutralized solvents and titrate to the same end point with the 0.1N alcoholic KOH.Repeat the titration on 100 ml of the 'blank' solution.

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BP 23796PLANT PURCHASING SPECIFICATION

BHOPAL Rev No. 05PAGE 5 OF 5

Calculate the acid value of the oil in mg KOH/g from the expression.

( t 2 -t 1 ) x 5~61x 5A.V= -------------------------

11Where,t 1 is the number of MLO.1 N KOHrequired to neutralize 100 ML n-heptane in the'blank' solution.

t 1 is the number of MLO.1N KOH required to neutralize 100 ML above filtrate.N is the mass of & Sample in gms.

Result:

Report the acid value of the 'blank' oil together with that of the sample oil andthe percentage 'sludge' produced in the latter. (Note that the sludge may in fact not be oiloxidation products alone but may also contain particles of the sample material orbreakdown products of it).

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