BS-6121-5-1993.pdf

BRITISH STANDARD BS 6121-5: 1993 Mechanical cable glands Part 5: Code of practice for selection, installation and inspection of cable glands used in electrical installations Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:26:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6121-5:1993 This British Standard, having been prepared under the direction of the Cables and Insulation Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 January 1993 © BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference CIL/20 Draft for comment 91/33339 DC ISBN 0 580 21260 2 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Cables and Insulation Standards Policy Committee (CIL/-) to Technical Committee CIL/20, upon which the following bodies were represented: Aluminium Federation Association of Consulting Engineers Association of Manufacturers of Domestic Electrical Appliances British Approvals Service for Cables British Cable Makers Confederation British Plastics Federation British Steel Industry British Telecommunications plc Department of the Environment (Property Services Agency) Department of Trade and Industry (Consumer Safety Unit, CA Division) Electricity Association Engineering Equipment and Materials Users Association Institution of Electrical Engineers London Regional Transport The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Association of British Mining Equipment Companies Electrical Installation Equipment Manufacturers Association (BEAMA Ltd.) Gland Manufacturers Technical Committee Amendments issued since publication Amd. No.DateComments Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:26:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6121-5:1993 © BSI 07-1999i Contents Page Committees responsibleInside front cover Forewordii Introduction1 1Scope1 2References1 3Definitions1 4Selection of cable glands1 5Installation2 6Inspection and test3 Annex A (informative) Guidance chart for the selection of BS 6121 cable glands4 Table 1 Non-integral earth connection short circuit ratings2 Table 2 Integral earth connection short circuit ratings2 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:26:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6121-5:1993 ii © BSI 07-1999 Foreword This Part of BS 6121 has been prepared under the direction of the Cables and Insulation Standards Policy Committee. Other Parts of the standard are as follows. BS 6121-1, gives a specification for metallic glands. BS 6121-2, gives a specification for polymeric glands. BS 6121-3, gives a specification for special corrosion resistant glands. BS 6121-4, will give a specification for insulated cable glands1). BS 6121-6, will give a specification for polymeric glands for light industrial and commercial use, with or without mechanical restraint or cable guards1). This Part of BS 6121 is a code of practice and gives recommendations on the selection, installation and inspection of cable glands for use in electrical installations. It is necessary to read this code in conjunction with the other relevant Parts of BS 6121. NOTEThere is a high probability that BS 6121-1:1989, BS 6121-2:1989 and BS 6121-3:1990 will be withdrawn and replaced by European CENELEC standards. BS 6121-4 and BS 6121-6 may be published as European Standards rather than as Parts of the BS 6121 series. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) In preparation. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:26:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6121-5:1993 © BSI 07-19991 Introduction Cable glands used in electrical installations should be selected for the specified duty, and should be installed and inspected in a manner which ensures safe use. This Part of BS 6121 gives recommendations for the selection, installation and inspection of cable glands and should be used in all new, existing or replacement installations, in conjunction with national standards or regulations concerned with electrical installations. This standard is not intended to inhibit innovative techniques in cable installation practice, protective circuit design and earthing circuitry, or consultation with manufacturers of cable glands and/or accessories. 1 Scope This Part of BS 6121 gives recommendations on the selection, installation and inspection of cable glands. This code applies to the basic requirements for the installation of cable glands for industrial applications. For cable glands installed in potentially explosive atmospheres, reference should be made to the relevant Parts of BS 5345. 2 References 2.1 Normative references This Part of BS 6121 incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. Subsequent amendments to, or revisions of, any of these publications apply to this Part of BS 6121 only when incorporated in it by updating or revision. 2.2 Informative references This Part of BS 6121 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. NOTEThe following publication is currently available and should be associated with this standard: IEE Regulations for electrical installations in buildings, (IEE Wiring Regulations), 16th edition 1. 3 Definitions NOTEThe definitions and terms applicable to specific cable glands are included in the other Parts of BS 6121, as relevant. For the purposes of this Part of BS 6121, the following definitions apply. 3.1 non-integral earth connection an accessory which is fitted to the cable gland and which, when installed, will carry the fault current rating in accordance with Table 1 3.2 integral earth connection a connection point which is permanently attached to the gland component part and is in contact with the armour clamping arrangement. It is of sufficient cross-sectional area to carry the maximum fault current and has a means for attaching an earth conductor 3.3 cable support an additional means of supporting cables, used as fixed wiring in such a way that the cable is not exposed to excessive mechanical strain 3.4 locking device an additional means of securing the cable gland into apparatus or equipment 3.5 shroud an elastomeric or plastic shaped moulding which provides a cover over the cable gland assembly and cable oversheath to give additional protection (e.g. taking into account environment conditions and operator safety) 4 Selection of cable glands 4.1 General This code of practice has been prepared to give recommendations for the selection of the correct cable gland. However, the purchaser has responsibility for the selection of the correct size and type of gland and further advice should be sought from the manufacturer where special problems arise. 4.2 Flow chart selector For a flow chart giving guidance for the selection of cable glands, see Annex A. 4.3 Materials Care should be taken when selecting cable glands, to ensure compatibility of materials used to avoid detrimental effects caused by: a) electrolytic action; b) corrosion; c) environment. Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:26:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6121-5:1993 2 © BSI 07-1999 NOTECertain types of cable employ materials which can exhibit significant “cold flow” characteristics which could reduce the effectiveness of seals and have adverse effects on the protection of the apparatus or equipment. The cable supplier should be consulted and, if necessary, a suitable cable entry device should be employed, for example, a cable entry device not employing compression seals. 4.4 IP ratings All cable glands having cable sealing arrangements and conforming to BS 6121 will meet the rating IP66 and are, therefore, suitable for use with equipment having equal or lower degrees of IP rating. The method of connection of the cable gland to the equipment should maintain IP66, or the IP rating of the equipment, whichever is the lower. To achieve this it may be necessary to seal between the cable gland and the equipment (e.g. by using a sealing washer or thread sealant). NOTE 1Higher IP ratings than IP66 may be available. NOTE 2Reference should be made to BS EN 60529:1991. 4.5 Shrouds If additional protection against environmental conditions or operator safety is required, then cable gland shrouds should be specified. 4.6 External earth connections 4.6.1 General The following methods of additional earthing or bonding of cable glands are recognized. 4.6.2 Non-integral earth connection A non-integral earth connection should be used where there is a requirement for attaching an earth connection (e.g. to the cable armour). It is recommended that the short circuit ratings are in accordance with Table 1. NOTEIf interface sealing arrangements are required when using a non-integral earth connection, advice should be sought from the cable gland manufacturer. Table 1 Non-integral earth connection short circuit ratings 4.6.3 Integral earth connection An integral earth connection should be used where the non-integral connection is not suitable. It is recommended that the short circuit ratings are in accordance with Table 2. Table 2 Integral earth connection short circuit ratings 5 Installation 5.1 General Cable glands conforming to BS 6121 should be installed in accordance with this code of practice as well as in accordance with the installation instructions of the manufacturer. 5.2 Torque levels for cable gland components Although cable glands are designed to be installed with a torque of at least 50 % of the proof torque specified in the appropriate Parts of BS 6121, due consideration should be given to the mechanical strength of the equipment to which the gland is attached. NOTEWhere cable gland seals are incorporated, consideration should be given to possible damage of the cable due to excessive torque/compression values, in which case, torque levels may differ from those stated in the relevant Parts of BS 6121. 5.3 Cable supports A cable support should be installed as near as reasonably practicable to the cable gland with due reference to the IEE Regulations for electrical installations in buildings, (IEE Wiring Regulations), 16th edition 1. 5.4 IP rating The method of connection of the cable gland to the equipment should maintain IP66, or the IP rating of the equipment, whichever is the lower. To achieve this it may be necessary to seal between the cable gland and the equipment (e.g. by using a sealing washer or thread sealant). Where the interface between cable gland and equipment is the sole means of earth continuity the thread seal, if any, should not impair the earth path. 5.5 Shrouds Cable gland shrouds should be used where additional protection against environmental conditions is required. Care should be taken to use the correct size of shroud and, where required, it should be trimmed to suit the cable diameter. Gland size mm Short circuit rating for 1 s kA (min.) 16 20 25 32 40 50 63 75 3.06 3.06 4.00 5.40 7.20 10.40 10.40 10.40 NOTEWhere the system short circuit rating is higher than that recommended in Table 1, the non-integral earth connection should be chosen to suit that rating or, if not practical, an integral earth connection is recommended. Gland size mm Short circuit rating for 1 s kA (min.) 16 to 40 50 to 75 26 43 Licensed Copy: sheffieldun sheffieldun, na, Tue Dec 05 05:26:39 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 6121-5:1993 © BSI 07-19993 5.6 Temperature Cable glands should not be installed at a temperature below that recommended by the manufacturer, since the temperature can be critical for the correct function of the cable seal. The minimum temperature can be taken as being below 0 °C. If the minimum temperature for the gland being installed is not shown, the manufacturer should be consulted. After installation, the temperature is not a critical factor. However, glands should not be chosen for installation outside the operating temperature range declared by the manufacturer. 5.7 Earth connections When provision is made for integral or non-integral earth connections, reference should be made to 4.6. 5.8 Locking devices Cable glands fitted into clearance holes should be secured by a locking device, e.g. a locknut, inside the apparatus, which is capable of meeting the gland torque requirements of the relevant Parts of BS 6121. Where such a locking device is the sole means of providing earth continuity to the apparatus, it should be metallic and should not impair the earth path. NOTEIt is recommended that all clearance holes have a diametrical clearance not greater than that of the thread major diameter + 0.7 mm. 6 Inspection and test 6.1 General It is recommended that the inspection and test procedures of 6.2 to 6.4 are carried out on all new, existing or modified installations. 6.2 Visual inspection In a visual inspection, the following procedure applies. a) Check cable gland markings to ensure cable gland type is suitable for the type of cable (see Annex A). b) Visually check that the outer seal is in contact with the sheath of the cable, where applicable. c) Check that any external thread sealing device is in position, where applicable. d) Check for any apparent damage to the cable gland shroud, if fitted. If irreparable damage is observed, refer to the mechanical inspection procedure, detailed in item c) of 6.3. e) Where applicable, check that the cable restraint device is in place and effective. f) Check that external earth connections, where fitted, are effective, making due reference to 4.6. g) Check any cable gland deterioration resulting from environmental conditions (see 4.3). If severe deterioration is apparent, the advice of the cable gland manufacturer should be sought. h) Check the cable gland for any mechanical damage which may impair the construction or performance of the cable gland see item c) of 6.3. 6.3 Mechanical inspection In a mechanical inspection, the following procedure applies. a) Check the tightness of the cable gland entry thread component to the