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है”ह”ह

IS 11892 (1986): Method of calculation of maximum externaldiameter of cables for indoor installations [LITD 6: Wires,Cables, Waveguides and Accessories]

IS :11892 -1986

Indian Standard METHOD OF CALCULATION OF MAXIMUM

EXTERNAL PIAMETER OF CABLES FOR INDOOR INSTALLATIONS

Wires and Cables for Electronic Equipment Sectional Committee, LTDC 18

Chairman

SHBI J. L. GUPTA

Zuanbu*

Representing

Department of Telecommunications, New Delhi

SHRI K. A. KBISHNAN (Alternate to Shri J. L. Gupta )

SHBI M. K. BAW Hindustan Cables Ltd, Roopnarainpur SEB~ C. D. BEATTACEARYA ( Altarnate )

SHRI K. P. CHHABRA Finolex Cables Ltd, Pune SHBI B. S. REDDIE ( ANeraate )

COL D. K. DESHNANDE Ministry of Defence (DGI), New Delhi LT-COL S. P. MURQAI ( Alternate )

DR JAM MOHAN GARQ Garg Associates Pvt Ltd, Ghaaiabad SHRI SUDHIR MOHAN MITTAL (Alternate )

SERI R. K. GUPTA Delton Cables Ltd, Delhi SHRI P. S. RAMAN (Alternate)

SERI K. GURURA JA Bharat Electronics Ltd, Bangalore Saa~ M. R. RANQACHARI ( Allcraatr )

DR A. K. JAIN Department of Electronics, New Delhi JOINT DIRECTOR STANDARDS Railway Board ( Ministry of Railways )

( S & T)-II DEPUTY DIRECTOR ( S & T )/ES ( AItcraatc )

SHRI B. MUKEOPADHYALY National Test House, Calcutta SHRI D. P. MUKHEBJEE ( AItsrnafc )

Ministry of Defence ( R & D ) National Airports Authority, New Delhi

SHRI G. S. PAI SHRI D. PAL

SHRI R. V. ISRANI ( AItcrnate ) SHRI N. PITAMBARA SHRI K. V. R. RAO

SHRI S. K. DUTTA (Alternate) SHRI P. V. RAO

SHRI H. S. ANANTHANABAYANA RAO ( Alternate )

Hindustan Aeronautics Ltd, Hyderabad Indian Cable Co Ltd, Jamshedpur

Indian Telephone Industries Ltd, Bangalore

( Continued on page 2 )

0 Cojyright 1987

BUREAU OF INDIAN STANDARDS

This publication ir protected under the In&n CoWright AC: ( XIV of 1957 ) and reproduction in whole or in part by any means except with written permission of the publisher shall be deemed to be an infringement of copyright under the said Act.

IS:11892 -1986

Members

DR SHARWAN KUMAB

Reprcsanting

National Physical Laboratory ( CSIR), New Delhi

DR ONKAR NATH ( Alternate ) SERI SUBODH KUMAP. Biren Manufacturing Co ( Cabler ) Pvt Ltd, New

. Delhi Director ( Electronics) Director General, BIS ( Ex-ojicio Member )

Secretary

SHRI HARCHARAN SINQH Joint Director ( Electronics ), BIS

2

IS : 11892 - 1986

Indian Standard METHOD OF CALCULATION OF MAXIMUM

EXTERNAL DIAMETER OF CABLES FOR INDOOR INSTALLATIONS

0. FOREWORD

0.1 This Indian Standard was adopted by the Indian Standards Institution on 21 November 1986, after the draft finalized by the Wires and Cables for Electronic Equipment Sectional Committee had been approved by the Electronics and Telcommunication Division Council.

0.2 Overall diameter of cables is specified in a number of cable specifications. This standard has been prepared to serve as a guide to calculation of external diameter of cables.

0.3 While preparing this standard, assistance is derived from IEC Pub 649 (1979) Calculation of maximum external diameter of cables for indoor installations is issued by the International Electrotechnical Commission (IEC).

0.4 In reporting the result of a test or analyses made in accordance with this standard, if the final value, observed or calculated, is to be rounded off, it shall be done in accordance with IS : 2-1960”.

1. SCOPE

1.1 This standard lays down a method of calculation of maximum external diameter of cables for indoor installation.

2. METHOD OF CALCULATION

2.1 Diampter of Conductor (&) dc = k, x d

where

d = specified nominal diameter of conductor strands

Solid:

Kc = 1

*Rules for rounding off numerical valuer (revised ).

3

IS : 11892 - 1986

Stranded: *

Seven strands I& = 3.

More than seven strands KC = 1’162/&

( n, = number of strands )

The diameter G$ obtained is rounded off to the nearest 0’05 mm.

Examples:

nl d dc

(mm) (mm)

16 0’20 0’95 24 0’20 1’15 32 0’20 1’30 30 0’25 1’60

2.2 Diameter of Insulated Conductor ( di )

di = dc + 2 ei,

where

ei, = average thickness used for calculation (Table 1 ).

TABLE 1 RELATIONSHIP BETWEEN THE SPECIFIED MINIMUM THICKNESS AND THE AVERAGE THICKNESS

OF THE INSULATION

SPECIFIED MINIMUM AVERAGE THICKNESS THICKNESS OF

INSULATION or INSULATION

ci aim

(mm) (-1 o-10 0’15

0’12 0’17 O-15 0.20 0.20 0’275 0’25 0.325 o-30 0.40 0.40 o-50

2.3 Increase of Diameter for Screening Individual Insulated Conductor or Elements -The increase Si of the diameter is as follows:

- taped screen: 3 X n X te;

-lapped wire screen: 2 X t,;

4

IS: 11892 -1986

-braided wire screen: 5 X ts;

- wrapping over or under screen: n x 0’1 mm.

where

ta = thickness of screen tape or diameter of screen wire

n = number of tapes

NOTE - For tapes applied without overlap: 2 x n x ts.

2.4 Diameter of Screened Insulated Conductor (&)

de - dl -?- S,

2.5 Diameter Over Assembly - The diameter over assembly DA is calculated from the following formula:

Da = K,d, (for unscreened insulated conductors).

DA = K,d, ( for individually screened insulated conductors ).

where

K-a = assembly coefficient ( Table 2 ),

dl = insulated conductor diameter, and

d, = screened insulated conductor diameter (see Note 2 of Table 1 ).

2.6 Increase of Diameter for Taping -The increase P of the diameter is as follows:

3 x n x tp

where 9

n = number of tapes, and

tp = thickness of protective tape.

2.7 Increase of Diameter for Collective Screen -The increase Ss of the diameter is as follows:

-taped screen: 3 x n x ts;

-lapped wire screen: 2 X ts;

-braided wire screen: 5 X ta;

- wrapping over screen: n X 0’1 mm.

where n = number of tapes, and

ta = thickness of screen tape or diameter of screen wire.

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IS : 11892 - 1986

TABLE 2 ASSEMBLY COEFFICIENT (K.)

( Clause 2.5 )

NUMBER OR SINoLE PAIRS TRIPLES CABLING CONDUCTORS

QUADS

ELEMENTS (.N) ,

1 1.0 2.0 2.15 2’41 2 2’0 3.4 * *

3 2’15 3.65 4.1 4.9 4 2’41 4.1 4’6 5.5 5 2.7 4’6 5’2 6’2 6 3.0 5.1 6.0 6’9 7 3.0 5.1 6.0 I 6’9 8 3.4 5.5 6’5 7.6 9 3.6 6.0 7.0 8.3

10 4.0 6.4 7.5 8.8

QUINTUPLES

2.7 *

,5.6 6.3 7.0 7.8 7.8 a.7 9.4

10’0

>lO l-20 d\/56i 1.95d”V 2’25 %/x 2*70&? 3*101/s

NOTE 1 -No special coefficient has been proposed for unit cables as it is considered that the 10 percent tolerance on the maximum external diameter (see 2.9) is sufficient to cover the increase in diameter which might result from this type of assembly.

NOTE 2 - For cables assembled from individually screened pairs, triples, quads or quintuples, the thickness of the screen S1 is added, then this diameter is divided by the assembly coefficient of this element ( 2 for pair, 2.15 for triple, etc ).

A diameter ds is so obtained for an imagioary single conductor, this diameter will be multiplied by the assembly factor corresponding to the composition of the cabll,.

r See example in Appendix A.

*Since these types are rarely manufactured, no coefficient is given.

2.8 Sheath Thickness - The minimum value for specified thickness eg is given in the relevant cable specification. The value egm represents the average value to be taken into consideration for calculating the external nominal diameter (see Table 3 ).

2.9 Maximum External Diameter ( &,x ) - To obtain the maximum external diameter Dmgx o f cable, the diameter over the sheath DC is first of all calculated.

Da = DA + P + 2 egm for cables without collective screen

Da = DA + P + S, + 2 egm for cables with collective screen

A tolerance is added to this value: +I0 percent ( with minimum of 0’5 mm ).

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IS : 11892 - 1986

TABLE 3 RELATIONSHIP BETWEEN THE SPECIFIED MINIMUM THICKNESS AND THE AVERAGE THICKNESS OF THE SHEATH

( Clause 2.8 )

SPECIFIED MINIMUM TEIICKNESS OF

SHEATH eg

(mm) 0.4 0’6 0.7 0.8

0.9 1-O 1.15 l-35

1’6

AVERAQETHICKNESS OF SHEATB

egm (mm)

0.6 0.8 0.9 1’05 1.2 l-3 1.5 l-7 2-o

This value is rounded to two decimal places, that is to say xX.xX.

The value is then rounded upwards to the first decimal place if the value is 5 mm or less, for example 4’61 rounded to 4’7.

If the value is greater than 5 mm, it is rounded to the first decimal place and further rounded upwards to the next multiple of 0’5 mm, examples: 25’05 rounded to 25’1 then to 25’5, 25’04 rounded to 25’0 then to 25’0.

3. TABLE OF DESIGNATIONS

3.1 The designations employed in the calculation of external diameter of cables are listed below:

d = diameter of conductor strand

dC = conductor diameter

di = average diameter of insulated conductor

de = average diameter of screened insulated conductor

Da = diameter over assembly

DO = diameter over sheath

D max = maximum external diameter

GiS = minimum specified thickness of sheath

7

IS:11892 -1986

egm = average thickness of sheath ei = minimum specified thickness of insulation

eim = average thickness of insulation K, = assembly coefficient for cabling elements KC = stranding.factor for stranded conductors n, = number of strands of stranded conductors n = number of tapes

jV = number of cabling elements P = diameter increase of protective tap’ing Sr = diameter increase of individual screens S, = diameter increase of collective screens tp = thickness of protective tape ts = thickness of screen tape or diameter of screen wire

APPENDIX A ( Table 2, Note 2 )

EXAMPLE OF CALCULATION OF DIAMETER OVER ASSEMBLY FOR CABLE WITH SCREENED ELEMENTS

A-l. CABLE WITH SEVEN TRIPLES UNDER TAPED SCREEN

- conductor 32 wires 0’20 mm dc = 1’30 mm - specified minimum thickness of

insulation - average thickness of insulation - diameter of insulated conductor

- diameter of triple

- thickness of screen tape - diameter of the screened triple

- diameter of an imaginary single conductor

ei = 0’20 mm

eim = 0’275 mm

di z llztmm2 X 0’275) .

1’85 x 2’15 = 3’98 mm

ts = 0’05 mm 3’98 + ( 0’05 x 3 ) ’

= 4’13 mm 4’13 : 2’15 ds

= 1’92 mm

A-2. DIAMETER OVER ASSEMBLY DA ( SEVEN TRIPLES )

x,=6’0

DA = 1’92 x 6’0 = 11’52 mm

8