IS : 3513 ( Part 1 ) - 1989 REAFFIRMED Indian Standard 2009 SPECIFICATION FOR RESIN TREATED COMPRESSED WOOD LAMINATES (COMPREGS) ,PART 1 FOR ELECTRICAL PURPOSES ( First Revision) First Reprint AUGUST 2001 UDC 674.812.2 : 678.632 : 621.315.619 © BIS 1989 BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH Z A F A R MAR G NEW DELHI 110002 October 1989 Price Group 4 AMENDMENT NO. 1 NOVEMBER 1998 TO IS 3513 ( PART 1 ) : 1989 SPECIFICATION FOR RESIN TREATED COMPRESSED WOOD LAMINATES (CO MPREGS) PART 1 FOR ELECTRICAL PURPOSES ( FirstRevision) ( Page S, Table 3, SI No. 1 and 2, col 2 ) the end. Insert 'aloDI tbe pain din:cciOD' at (CED20) Reproarapby Unit,51S. NewDelhi,India AMENDMENT NO. 2 JULY 2005 TO IS 3513 (PART 1): 1989 SPECIFICATION FOR RESIN TREATED COMPRESSED WOOD LAMINATES (COMPREGS) PART 1 FOR ELECTRICAL PURPOSES ( Fir. Revision) ( Page 3, clauses 7.1 and 7.1.1 ) existing: Substitute the following for the "7.1Boards The dimensions of resin treated compressed wood laminate boards shall be as follows: Length in nun Width in nun 2 400, 2 100, 1 800, 1 500, 1 200, 900 and 600 1 200, 900, 600, 300 and 150 NOTE - Any other dimension as agreed to between the manufacturer and the purchaser may also be used. ' ( Page 4, clause 7.1.2 ) following for the existing: ' '7.1.1 Thickness Renumber the clause and substitute the Unless otherwise specified the thickness of resin treated compressed wood laminate boards shall be 3 mm, 4 mm, 5 mm,6 mm, 8 mm, 12 DUn, 16 mm, 20 mm, 25 nun, 32 mm, 40 mm, SO mm, 60 mm and 70 nun. t ( Page 4, clause 7.t.3 ) following for the existing: Renumber the clause and substitute the 1 Amend No.2 to IS 3513 ( Part 1 ) : 1989 '7.1.2 Tolerances The toleranceon the nominal sizes offinished boards shall be as follows: Dimensions Length Width Tolarance +6mm -O'mm +3rnm -0 IDJD Thickness: i) Less than 6 nun ii) 6 mm andabove 10 percent 5 percent 2 mmper 1 000 nun or 0.2 percent 2 nun per 1 000 nun or 0.2 percent' Edge straightness Squareness (CEO 20) Repropphy Unit, BIS, New Delhi, India 2 AMENDMENT NO. 3 FEB~UARY ·1009 TO IS 3513 (PART 1)': 1989 SPECIFICATION FOR RESIN TREATED COMPRESSED WOOD LAMINATES (COMPREGS) PART 1 FOR ELECTRICAL PURPOSES ( First Revision) (Page 2, clause 5.2) Substitute the following for the existing: 'The synthetic resins used for impregnation and bonding of veneers shall be of phenol or cresol formaldehyde type and the resultant resin adhesive shall conformto the requirements specified in IS 848 : 2006.' . (Page 4, Table 1) Substitute the following for the existing table: Table 1 Physical Properties 01 Compress (All Types) (Clause 8.1) SI No. . Property Requirement Method or Test r A Types I, 11, III and IV i) Types V andVl 1.2S 4 IS 1708 (Part 2) : 1986 IS 1708 (part I): 1986 " Specific gravity, Min Moisture content and volatile matter, percent, Max 1.25 4 ii) jii) Waterabsorption at 27 ~ 2°C, . percent, Max Sporadicworkingtemperature, Max 1.2 1.5 IS 3513 (part 4) : 1966 IS 3513 (part 4) : 1966 iv) 900C 90°C [Page 5, Table 3, (see also Amendment No. 1)]- Substitute the following for the existing table: AmeDd No. 3513 (part I) : 1989 Table 3 Mechaaleal Properties (Clause 8.3) Sl No. Tat Valt ,'/ Requlremeat Method of Tat ~ TypeV (4) 140 TypeVI (S) 70 50 (1) i) (2) Tensilestrenath, Min: a) Along the POI b) Across the grains Staticbendingstrenath, Min: a) Along the grains (3) MPa (6) IS 1734 (Part 9): 1983 MPa ii) b) Acrossthe grains iii) MPa MPa MPa MPa 185 90 IS 1998 : 1962 6S 160 110 170 IS 1708 (puts 8 tit 9) : 1986 Compressive strength. Min: a) Parallel to laminae b) Perpendicular to laminae Shear strength, Min: a) Parallel to grains &: laminae iv) . MPa b) Perpendicular to grains &. laminae v) MPa 12 SO 70 IS 40 IS 1708 (Part II) : 1986 Hardness, Rockwell, MIn, M scale 70 IS 1586 : 2000 I) vi) Impac(strenath, Izod, Un-notched, Min: a) Perpendicular to laminae k&'mz kglm2 0.45 0.30 0.20 IS 1998: 1962 b) Parallel to laminae I) 0.25 Rockwell hardness in M scale shall be determined using an indenterof diameterof 6~3SO 0.002 S mm and with Minor load of 10kg and M~ loadof 100kg. * (Page 6, Annex A) - Substitute the following for the existing entries: 'IS 848 : 2006 IS 1586 : 2000 Synthetic resin adhesives for plywood (phenolic and aminoplastic) - Specification (second revision) Method for Rockwell hardness test for metallic material (scales A-B-e-D-E-F-O-H-K ISN, 30N, 4SN, 1ST, 30T and 4ST) (third revision)' Reprography Unit,DIS, New Delhi, India (CED 20) 2 Wood Products Sectional Committee, BDC 20 22 April 1989, after the draft finalized by the Wood Products Sectional Committee had been approved by the ivil Engineering Division Council. FOREWORD This Indian Standard ( Part 1 ) ( First Revision) wag adopted by the Bureau or Indian Standards on Resin treated compressed wood laminates, also known as compregs, are laminates made from thin wood veneers and thermosetting phenol. or cresol formaldehyde resins. They combine within themselves enhanced mechanical properties with the stabilizing and moisture-proof qualities of thermosetting resins; besides, they have good machining properties, electrical insulation, and resistance to corrosive agents and termite attack. Compregs are manufactured in different shapes, such as, sheets, rods and moulded shapes. In the electrical industry, compregs are extensively used for lifting rods and guide plates in HV circuitbreakers; cleats and supports for HV tappings in transformers; insulating stator brackets in turbogenerators; drums and finger boards for traction control gear; stay wire insulators, insulating studs, nuts, bolts, etc. The grading of compregs is based upon the extent and nature of impregnation of the resin-formlng chemicals, and also upon the compression and density as a result of pressure applied for curing and bending whereas the different types in each of the grades Indicate the arrangement of the veneer, and therefore the relative orientation of wood fibre in various directions. The dimensions of cornpreg boards and rounds have not been covered exhaustively as these vary widely depending upon end use. However, for general guidance. certain stock dimensions have been indicated. This standard was first published in 1966. In the present revision, the requirements of various properties of compregs have been revised keeping in view the latest developments in the industry and the feedback from the users. This standard is now published in four parts, namely, Part 1 For electrical purposes Part 2 For chemical purposes Part 3 For general purposes Part 4 Sampling and tests For the purpose of deciding whether a particular requirement of this standard is complied with. the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 19(\0 'Rules for rounding off numerical values ( revised)'. The number of significant places retained in the rounded off value shoulc be the same as that of the specified value in this standard. IS 3513 ( Part 1 ) : 1_ Indian Standard SPECIFICATION FOR RESIN TREATED COMPRESSED WOOD LAMINATES ( COMPREGS ) PART 1 FOR ELECTRICAL PURPOSES ( First Revision) 1 SCOPE (Part I) covers the requirements of resin treated compressed wood laminates (cornpregs) for electrical purposes. 1.1 This standard 1.2 This standard does not cover the ments for solid compressed wood. require- 4.2 Types 4.2.1 The types of compreg shall be as follows depending on grain orientation of individuai veneers in a board: a) Type I - In this type, the grain orientation of the constituent veneers shall be substantially tangential to the periphery of the board or the round. The joints in the adjacent layers of laminae shall be staggered. This type is suited for fabrication of large circular rings. 2 REFERENCES 2.1 The Indian Standards listed in Annex A are necessary adjuncts to th is standard. 3 TERMINOLOGY 3.1 For the purpose of this standard. definitions given in IS 707: 1976 and the following shall apply. 3.2 Comprel b) Type II - In this type, the grain orientation of the constituent veneers shall be more than 75 percent in the direction of the major mechanical stress. Every fourth veneer comprising this type shall have its grain direction at right angle to the grain direction of adjacent three veneers which will have their grains in the same direction. The mechanical properties achieved in this type are generally comparable to Type V but the cross lamination gives improved made from thin wood veneers either impregnated under vacuum and/or pressure with synthetic resins or coated with synthetic resin or interlaid with synthetic impregnated paper and further bonded and densified under heat and pressure. The synthetic resins are usually of phenol or cresol/formal. dehyde type. A wood-based laminated material resistance to splitting. This arrangement is specially suitable for tensile Jinks where the end fixings are in the form of bolts or rivets located close to the end of the com- ponents. c) Type III - In this type, the grain orientation of the constituent veneers shall be approximately equal in all radial directions. This type shall have each successive lamination angularly disposed in relation to the adjacent one. This type is suited for fabrication of gears, chucks and wheels. d) ~J'pe IV -- In this type, the grain orientation of constituent veneers shall be oriented mainly at 45° to the load axis. T~j$ 3.3 Hllh Density Compreg Compreg with specific gravity between 1'25 and ) ·35. 4 TYPES 4.1 ~ompreg for electrical purposes shall be a fully Impregnated. high density material suitable for HV and LV electrical insulation requirements and for certain general mechanical purposes. This grade shail have six types, that js Type I to VI. arrangement is suitable for parts under high voltage stress with limited clearances. IS 3513 ( Part 1 ) : 1989 e) Type V - In this type, the grain orientation of the constituent veneers shall be in the direction of axis of load. This type is suitable for parts subject to tensile stress and is thus suited for fabrication of sticks. flats. rods, turned parts and threading. 5.1.2 In selecting the species for the manufacture of compregs, it is recommended that, as far as possible, a single species of timber be used in a pack and where combination of different species is unavoidable, care shall be taken to prevent incompatibility of various species in the physical and mechanical properties. 5.2 Syntbetic Resins' The synthetic resins used for impregnation and bonding of Veneers shall be of thermosetting phenol or cresol formaldehyde type and shall generalJy conform to IS 848 : 1974. f) Type VI - In this type, the grain orientation of the constituent veneers shall be more or Jess equal in each axis, at right angles to each other. This type is of high compressive strength in the direction of its thickness and is also rigid. It is suited for sheet and block forms. ·5.3 Solvents Denatured spirit conforming to IS 324 : I 59 or any suitable solvent conforming to its Indian Standard Specifications, shall be used for compreg of electrical grade. 4.2.2 Typical sketches illustrating the directions of grains of the veneers in the assembly for various types are indicated in Fig 1. S.4 Varnishes 5 MATERIALS s.i Timber Any non-resinous species of timber be can be used for the manufacture of veneers required for making compreg. Insulating oils and varnishes used for treating compreg boards and the machined components of compreg shaJJ conform to IS 10026 ( Part 3/ Sec 1 to 7 ) : ) 983. Special high-viscosity insulating varnishes may also be used for electrical cornponents if so required by the purchaser. S.l.l The veneers shall be either rotary cut or sliced and maximum variation in grains shall not exceed 1 in 10. They shall be smooth, free from knots, splits, dry rot or any other type o~ rot, and resin pockets. The veneers shall be of uniform thickness with tolerance of ± 5 percent, and dried to a suitable moisture content not exceeding 8 percent. 6 MANUFACTURE 6.1 Compreg of electrical grade shall be manufactured from suitable veneers by impregnating them with a thermosetting phenol or cresol formaldehyde resin dissolved in a suitable solvent like denatured spirit. Vacuum, with or without subsequent pressure, using a suitable impregnation TYPE I TVPE II SHOWN IN PLAN TVPE III TYPE IV NOTE - TYPE V Arrows show direction of grains 111 TYPE VI the Ianuuae. F,G. I TYPES OF COMPRFG SHOWING ARRANGEMEN'T OF LAMIl'!."t 2 IS 3513 ( Part 1 ) : 1_ schedule, shall be applied to ensure that the veneers are uniformly impregnated to such an extent tha t the resin content of the veneers is not Jess than 45 percent on an oven-dry basis. 6.1.1 The impregnated veneers shall be dried in a suitable drier or evaporating chamber at a suitable temperature to drive off the solvent and moisture, care being taken that the resin does not polymerize beyond the desired extent. The irr pregnated veneers shall then be inspected, and assembled into the required grain configuration and pressed in a hydraulic press at a suitable temperature and pressure. The press charge shal~ usually be cooled by cutting off steam and Introducing a cooling medium. 6.2 Compreg for electrical purposes shall be manufactured in such a way that the following conditions are satisfied: Synthetic Impregnation Percent Curing Curing and Resin Method Resin TempePickup rat UTe Bonding Pressure on Oven (Range) Dry (MPa) Basis Natural phenol formaJdehyde in alcohol 6.4 The compreg boards after discharge from the press, shaJJ be kept for a minimum period of one week to normalize internal stresses and then they shall be cut to the required sizes and finished. 6.5 The resins used shall have no fillen or extenders. A suitable modifying agent may be used to impart the required special properties to the board. 6.5.1 When the thickness of the board required exceeds the thickness the press can accommodate, it may be obtained by glueing two or more boards using similar and compatible resin used for impregnation and bonding with the prior approval of the purchaser. 6.6 A purchaser ordering for machined components shall provide the necessary drawings giving details as to the dimensions of the components and tolerances, and the components shall be supplied in accordance with the drawings. 6.7 The edges of all the boards and the surfaces of all the components shall be given a protective coat with suitabJe insulating varnish conforming to relevant Indian Standards [IS JOO26l Part 3/ Sec I to 7 ) : 1983 ]. 7 DIMENSIONS AND TOLERANCES solution Vacuum 45, Min impregnation with or without subsequent pressure 135 7 to to 15UoC 15·5 7.1 Boards The dimensions of platten finished compreg boards shall be quoted in the following order: The first dimension. shall represent the length, that is, the dimension parallel to the grafn of faces, the second, the width, that is the dimensions at right angle to the pins of faces and the third, the thickness. 6.3 The thickness of veneers for the manufacture of compregs shalJ be between 0'7 and 2-0 mm. The thickness of individual veneers shall not vary beyond ± 5 percent of the average thickness. 6.3.1 The veneers required to be edge jointed shall be so done on a tapcless splicer and no staples or tapes shall be used, The adhesive used for splicing should be compatible with phenol or cresol formaldehyde resins to be used later for impregnation and bonding. 6.3.2 Wherein an assembly different species are used, care shall be taken to see that they are not incompatible and that they are balanced around the central axis ( see also 5.1.2 ). 6.3.3 In one pack, usually veneers of the same thickness shall be used except where adjustment is to be made for density but in case different thicknesses are used. these shall be balanced around the centra) axis. 6.3.4 The veneers of one pack shall be cut by the 7.1.1 Size The stock sizes for compreg boards sban generally be the foilowing: mm 2100 2 100 ) 800 1800 1 500 1 SOO 1 500 1 SOO I 500 I 200 I 200 1 200 3 X mm 1 200 900 x x X x I 200 900 1 200 900 x x 600 x x x 300 ISO 1 200 600 same method, that is. either rotary cut or sliced. If cut by different methods, these should be so assembled that these balance around the central axis. x X 300 IS 3513 ( Part 1 ) : 1_ mm J 200 900 900 900 900 600 600 600 mm x x JSO x )( 900 600 300 ISO 600 300 150 x x 7.2.2 The tolerance on diameters of compreg rods shall be as folJows: Rods up to and including 40 mm dia +Omm -0·20mm Rods 50 mm dis and above +Omm -O'2Smm x x 7.1.2 Thlcknel, The preferred thickness of comptea boards shaJJ be 3. 4·5, 6, 8, 12, 16, 20,2S, 32, 40, 50, 60 and 10 mm. 7.1.3 Tolel'tlllcea 7:3 The purchaser ordering compreg cut to special size and shapes, such as, .round discs, rings and sear blanks to any required taper or finished parts. shall provide the necessary drawings specifying materia', dimensions and tolerances, and' the supplies shall be in accordance with the drawing of the purchaser. 7.3.1 Tolerances in finished components or blanks shall be accordina to the drawinp of the purchaser. The following tolerances on the nominal size of the tinished compreg boards sball be permissible: Dlmmsion 8 PHYSIC L PROPER~ AND MECHANICAL Tolerance - Omm a) Leolth b) Widtb + 6mm therein. 8.1 The physical properties of compreg for electrical purposes for aU types shaJJ conform to Table I when tested by the methods specified . + 3mm -Omm ± 10 percent 5 percent 8.2 Electrical Properties c) Thickness Jess than 6mm 6 mm and above 7.2 Rods 'The electrical properties of the electrical purpose compreg of all types shall conform to TabJe 2. 8.2.1 In case of electrical components, the following further test requirements shall be complied with: a) All components shall stand a minimum flashover voltage of 4 kV per cm length between cylindrical electrodes when tested according to IS 3S J3 ( Part 4 ) : J966. b) The varnished components for electrical ± The sizes for round rods of compreg shall generaJly be tbe following: ungth Diameter mm I SOO I 200 mm 8 to SO 3 to SO SO to 80 6 to 40 grades shaJJ have a minimum tracking time of 20 minutes when tested accord ins to IS 3513 ( Part 4 ) : 1966. 8.3 Mechanical Properties The mechanical rroperties of com pre,s for electrical purposes 0 Type V and VI shall conform to Table 3 when tested by the methods specified 900 600 7.2.1 Compreg rods of longer lengths and intermediate or greater diameters may be manufactured according to the requirements of the purchaser. therein. Table J Physical Properties or Compregs ( All Types ) Requirement ( Clause 8. 1 ) 81 No. Property Specific Ifavity Moisture content and volatile matter Water absorption at 27 ± 2°C Sporadic working temperature i) ii) iii) iv) 1·25, Min 4 percent, Max 1-2 percent, Max 90°C. Max Method 01 Test IS 1708 ( Part 2 ) : 1986 IS 1708 ( Part J ) : J986 IS 3513 ( Part 4 ) : 1966 IS 3513 ( Part 4 ) : J966 IS 3513( IWt 1 ) : 1_ T,We 2 Eleetrleal Properties 01 Com..... lor EledrIeaJ P8rpoIe ( AUT". ) ( Cklul. 8.2 ) SINo. j) Test a.........t 10 Megohms, Min M.... ofTeIt Insulation resistance after immersion in water at 27:1:2°C Volume and surface resistivity ohm-em Flatwise electric strenath in oil at 90 ± 2 Edgewise electric strenlth in oil at 90°C Power ractor ( tan 3 ) Comparative tracking index (or varnished components e IS 2259 : J963 IS 3396: 1979 ii) 2-Sxl0' ii i) iv) v) e 4 kV/mm for 6 mm thick specimen IS 1998 : 1962 IS 1998 : 1962 18 1998 : 1M2 IS 2824: 1975 25 tV for 2S mm wide specimen 0·019 at SO cycles at 2()OC (Typical, Dot mandatory ) vi) CTIIOO T.ble 3 Medaaaleal Properties ( Clou,e 8.3 ) SINo. (I) Test ( MetHdofTeit \ Type V (2) Type VI (3) (4) 90 95 (5) J Minimum tensile streDlth ( MPa) 175 195 IS 1734 ( Part 9) : 1983 2 Minimum static bending strength ( MPa ) 3 Minimum compressive strenath ( MPa ) (Specimen 20 mm x 20 mm x 20 mm ) a) Parallel to laminae b) Perpendicular to laminae IS 1998 : ·1962 IS J708 ( Parts 8 and 9 ): 1986 170 120 9S 14 ISS IS 1708 ( Part II ): 1986 20 4 Minimum shear strength ( MPa ) a) Parallel to grain and laminae b) Perpendicular to grain and perpendicular 60 70 to laminae ( flatwise) S Minimum hardness Rockwell M Scale 45 70 IS 15B6 : 1988 IS 1998 : 1962 6 Minimum impact strength ( Izod ) Unnotched sample ( kl.m/m ' ) a) Perpendicular to laminae b) Parallel to laminae O·SO 0·30 9 WORMANSHIP AND FINISH '.1 Wh~n supplied in board form, the face and the back of a board shall be free from checks, splits, blisters, discoloration, overlaps, gaps and open joints and the boards shall be free from warp. 9.2 Compreg boards may be finished, or machine finished. either platten 9.1.1 The machine finished boards shall be liven a protective coat of varnish as required by the purchaser. UsuaJJy the edges of the boards sball be given a coat of protective varnish. 9.1.2 The machined components in case of electrical purpose compreg shall be given a coat of high viscosity varnish. s IS 3S13 ( Part 1 ) : I _ to SAMPLING 10.1 Sampling shaJJ be as specified in IS 3513 ( Part 4 ) : 1966. particulars alon. with such other marks as th~ purchaser may stipulate at the time of placina a contract: a) Type and finish: b) Manufacturer's initials or recognized trademark; c) Year of manufacture; and d) Batch number. 11 TESTING 11.1 Test pieces cut from each of the boards selected shall be tested by the appropriate methods specified in appropriate tables and in IS 3513 ( Part 4) : 1966. 11.2 Tests oa FIalsW Maclaiaed Compooeat. The manufacturer shaH furnish a certificate to the purchaser that the finished component or part is made from compreg conforming to the requirements for the particular type as specified in this standard. If required by the purchaser, sample test pieces shall be tested from the same board, and test results thereon should be supplied. 11.3 Re-tests If any piece fails to fulfil the test requirements specified under 11.1, a further set of duplicate samples on the basis prescribed under 11.1 shall be selected by the purchaser from the same batch for testing in the same manner. Test pieces prepared from these two further samples shall comply with the requirements, otherwise the batch shall be rejected. 13 PACKING AND DELIVERY J3.1 The boards or components shall be delivered in a clean and dry condition and shall be suitably packed. 14 INFORMATION TO BE SlTPPUED BY THE PURCHASER 14.1 The purchaser shall supply tbe foUowing information to the supplier with his order: a) Number of boards or number of components; b) Type of material; c) Size and thickness; d) If components are required, full detailed drawings along with the tolerances and dimensions; e) Whether supply is to be platten finished or machine finished; f) Whether supply is to be oil finished or varnish finished; and g) Any other special requirement. 12 MARKING 12.1 If compreg is supplied in board from, each board, and if supplied in component form, each component, or if components are small, each package of components, shall be legibly and Indelibly marked or stamped with the following ANNEX A ( Clause 2.1 ) LIST OF INDIAN STANDARDS REFERRED IN THE STANDARD IS No. IS 324: 1959 Title Specification for ordinary denatured spirit ( revised) Glossary of terms applicable to timber technology and utilization ( second revision) Specification for synthetic resin adhesives for plywood (phenolic and aminoplassic ) tfirst revision ) Method for Rockwell hardness test for metallic material ( Scales A·B-C~D-E·F-G-H-K) ( second revtston ) IS No. IS 1708 Title Methods of testing of small clear specimens of timber ( second revision) Determination content of IS 707: 1976 Part 1 : J986 Part 2 : 1986 moisture specific IS 848 I 1974 Determination gravity of Part 8 : 1986 Part 9 : 1986 IS 1586 : 1988 Determination of compressive strength parallel to grain Determination of compressive strength perpendicular to Brain 6 IS 3513 ( Put 1 ) : 1989 IS No. Part 1 J : 1986 Title Determination of shear strength parallel to grain Methods of test for plywood ( second revision) IS No. Title solid insulating materials under moist conditions (first revision) IS 3396 : J979 (S 1734 Part 9 : 1983 [8 1998 : 1962 Determination strength of tensile IS 3513 ( Part 4 ) : J966 Methods of test for volume resistivities of solid electrical insulating materials (first revision ) and surface Methods of test for thermosetting synthetic resin bonded laminated sheets IS 2259 : 1963 Methods of test for determination of insulation resistance of solid insulating materials Method for determining comparative tracking index of Specification for high and medium density wood based laminates (compreg): Part 4 Sampling and tests (under revision) [S 2824 : 1975 IS 10026 Specification for insulating ( Part 3/Sec I to 7 ) varnishes containing solvents: Part 3 Specification for individual materials. 7 Bureau of Indian Staadards BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promote harmonious development of the activities of standardization, marking and. quality certification of goods and attending to connected matters in the country. Copyright DIS has the copyright of all its publications. No part of these publications may be reproduced in any form without the pr.ior permission in writing of BIS. This does not preclude the free use, in the course of implementing the standard, of necessary details, sucb as symbols and sizes, type or grade designations. Enquiries relating to copyright be addressed to the Director (Publications), BIS. Review or Indian Standards Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of the latest amendmentsor edition by referring to the latest issue of 'BIS Catalogue' and 'Standards: Monthly Additions'. This Indian Standard has been developed from Doc : No. DDC 20 ( 4266 ) AmeDdmeDts ISlued SlDce PubUcatioD Amend No. Date ofIssue Text Affected BUREAUOF INDIANSTANDARDS Headquarters : Manak. Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110 002 Telephones: 323 01 31,323 33 75, 323 9402 Regional Offices : Central Eastern Northern Southern Telegrams: Manaksanstha (Common to all offices) Telephone 323 76 17 { 323 38 41 : Manak Bhavan, 9 Bahadur Shah Zafar Marg NEW DELHI 110 002 : 1/14C.I.T. Scheme VII M, V. I. P. Road, Kankurgacbi KOLKATA 700 054 : SeQ 335-336, Sector 34-A, CHANDIGARH 160 022 337 8499, 337 85 61 { 337 86 26, 337 91 20 60 38 43 { 60 20 2S : C.I.T. Campus, IV Cross Road, CHENNAI600 113 : Manakalaya, E9 MIDC, Marol, Andheri (East) MUMBAI400 093 254 12 16, 254 1442 { 254 25 19, 254 13 15 { 832 92 95, 832 78 58 Western 832 78 91, 832 7892 Branches AHMEDABAD. BANGALORE. BHOPAL. BHUBANESHWAR. COIMBATORE. FARIDABAD. GHAZIABAD. GUWAHATI. HYDERABAD. JAIPUR. KANPUR. WCKNOW. NAGPUR. NALAGARH. PATNA. PUNE.RAJKOT. THIRUVANANTHAPURAM. Reprography Unit, SIS, New Delbi, Inmr~