BS 7211:2012 pdf download – Electric cables – Thermosetting insulated and thermoplastic sheathed cables for voltages up to and including 450/750 V for electric power and lighting and having low emission of smoke and corrosive gases when affected by fire
7.4 Corrosive and acid gas emission from insulation and tape(s) When tested in accordance with BS EN 50267-2-1, the level of HCl shall be not greater than 0.5%.
8 Identification of cores
8.1 General The cores of all cables shall be identified by colour. Each core shall be identified by its colour as indicated in Table 3 to Table 5. NOTE Other colours may be used by agreement with the manufacturer; in this case the requirements in 12.2 do not apply.
8.2 Core colours The colour shall be applied throughout either the whole insulation or the outer cohesive layer and shall be applied as part of the extrusion process. The insulation of the coloured cores, irrespective of the method of colouring, shall be tested as a complete single layer (see 7.2). The colours of the cores, determined by the number of cores in the cable, and also the sequence of the colours shall be as given in Table 3 to Table 5. Where alternative colours are used (see 8.1, Note), the sequence shall be agreed with the manufacturer. On a core with the bi-colour combination of green-and-yellow, the distribution of these colours shall be such that for every 15 mm length of core, one of the colours shall cover not less than 30% and not more than 70% of the surface of the core, while the other colour shall cover the remainder of the surface. Conformity shall be checked by measurement.
NOTE 1 In cases of dispute regarding the green-and-yellow combination, and where appropriate to the method of colour marking of the insulation, a suitable test method for checking conformity is given in BS EN 50396, 5.2.
NOTE 2 It is understood that the colours green and yellow, when they are combined as specified, are recognized as identifying exclusively the core intended for use as an earth connection or similar protection. The colour blue is for the identification of the core intended to be connected to neutral but, if there is no neutral, blue may be used to identify any core except for the earth or protective conductor. NOTE 3 Depending on where the cables are used, restrictions may apply to the use of certain colours for some applications.
8.3 Clarity and durability The colour used for core identification shall be clearly identifiable and durable such that it cannot be removed when tested in accordance with BS EN 50396, 5.1.
9 Multi-core circular cables
9.1 Assembly and core colour sequence
The cores of 2-core, 3-core, 4-core and 5-core circular cables shall be laid up together. Cores shall be laid up in the sequence of colours as given in Table 4. If alternative core colours to those specified in Table 4 are used, then an alternative sequence shall be agreed with the manufacturer. Conformity shall be checked by visual examination.
The maximum length of lay for circular cables shall be not more than 25 times the diameter of the assembly of laid up cores. Conformity shall be checked in accordance with 16.7. If necessary, a compact and reasonably circular cable shall be formed by one of the following methods:
• the application of synthetic fillers; or
• the application of binder tape(s); or
• a combination of both.
It shall be possible to strip the fillers and/or tape(s) from the cable without damaging the insulation of the cores.
9.2 Corrosive and acid gas emission from binder tape(s) and fillers
When tested in accordance with BS EN 50267-2-1, the level of HCl of any filler or binder tape(s) shall be not greater than 0.5%.
10 Optional extruded inner covering
10.1 General
NOTE 1 The manufacturer has the option to include, or not, an inner covering for cables in Table 4.