BS 6121

Cable Glands to BS 6121

In the late 1950's and early 1960's, with the need for urgent response to increasing energy demands, CMP Products quickly developed a role as a specialist solution provider in cable connecting and cable termination. In fact CMP Products were pioneers in this field of industry, breaking new ground with several original design concepts that were adopted and implemented by clients even before the basic idea of a cable gland standard was formulated.

Having been instrumental in establishing the earliest design standards for cable glands (BS4121) the company was also heavily involved in providing cable gland solutions that could be used in hazardous areas, or where flammable atmospheres could exist.

BS 6121 was the British Standard that was originally developed to embrace both Industrial and Hazardous Area cable gland design. Eventually, due to several changes in the standards, and with the emergence of harmonised European Normatives for products and equipment used in potentially flammable atmospheres, the BS 6121 standard concentrated on the Industrial cable gland design only, the essence of which has prevailed for more than 40 years.

Today the BS 6121 requirement, although still called for in many engineering specifications around the world, is slowly being lost and diluted in the process of harmonisation and globalisation. Whilst new EN standards may be brought in to deal with generic subject headings, and are considered to replace existing National Standards, they do not always address the issues and needs of all situations.

CMP Products still bases the majority of it's cable gland designs around the BS 6121 standard. There are however a number of manufacturers who openly claim compliance with BS 6121 on their product literature and / or product, when they clearly do not. Demonstrating the fact that products do not fulfill some of the basic requirements of the standard can be a very straightforward exercise. In particular the areas where some makers do not comply with BS 6121 are the maximum bore dimensions through the cable gland, the wall thicknesses as a result of the bore size discrepancies, and the sealing ranges that differ considerably from the standard.

Ultimately clients and users should be aware that if they require BS 6121 compliance within their specification, there is a distinct possibility that when they purchase products from selected suppliers that are labeled in this way, they may not always be getting what the specification requires.

CMP Products would be happy to discuss with any client the details of how to avoid such misinformation being used to disguise a non-conformity in design.

Below are tables composed from data included in BS 6121 : Part 1 : 1989 :-

Type Definition
A1 For unarmoured cable with an elastomeric or plastic outer sheath, with sealing function between the cable sheath and the sealing ring of the cable gland.
A2 As type A1, but with seal protection degree IP66
A3 As type A1, but with an electrical bond for the metallic inner screen.
Table A: Cable gland type designations for unarmoured cables

Code Definition
B No Seal
C Single Outer Seal
D Single Inner Seal
E Double (Inner & Outer) Seal
suffix '1' = Normal
suffix '2' = Lead Sheathed
Table B: Cable gland type designations for armoured cables

Designation of cable armouring
T Pliable Wire Armour
W Single Wire Armour
X Braid
Y Strip Armour
Z Tape Armour
Table C: Cable type designations

Type Definition
A2 Cable Gland for unarmoured cable with outer seal
BW Cable Gland for SWA cable without seal
CW Single Seal Cable Gland for SWA cable
E1W Double Seal Cable Gland for SWA cable
CX Single Seal Cable Gland for braided cable
E1X Double Seal Cable Gland for braided cable
Table D: Typical Cable Gland type designations derived from tables A to C