50 years of Development in Fireby T.L.Journeaux, Prysmian Cables and Systems
50 years ago, the Thirteenth Edition of the IEE Regulations for the Electrical equipment of Buildings had just been published. The hardback edition cost 8s 6d and the paperback 6s 0d. Reviewing the Index for references to fire finds none relating to the main body of the text, but the Introduction states “Where the fire risks of the premises are of an unusual character, the special requirements of the Fire Office insuring the risk should be ascertained and complied with”. By comparison the Index to the Sixteenth Edition (2001) shows some 25 entries relating to fire.
A contemporary text to the Thirteenth Edition, Choosing Electric Cables by C.C.Barnes published in 1954 at 3s 6d does not discuss fire performance as a parameter in cable choice but concentrates on the differing electrical and mechanical performance of various cable making materials. However the author makes an interesting point in relation to the newly introduced pvc cables (BS2004:1953) stating that “It is also highly resistant to burning and although it can be made to take fire under intense heat, combustion does not continue after the source of heat is removed”. Such performance would later be described as flame retardant and demonstrated by the “Bunsen burner” test described in BS4066-1.
The last 50 years have certainly seen a major change in our attitude to fire in relation to the cables that we use in and around today’s buildings. Now we can take for granted good electrical and mechanical properties from our cable making materials and the choice of cable type is largely driven by performance in the event of fire, either its reaction to fire or its resistance to fire.
Reviewing the product literature archives for the 1950’s does not reveal any cables marketed specifically on their fire performance, but the “Asbestal heat resisting cables” were advertised as with “non-inflammmability”. The design based on asbestos-paper tape insulation and argon-arc welded aluminium sheath would certainly have given interesting fire performance.
Development continued apace in the 1970’s with attention turning to the smoke, corrosive and toxic fumes emitted during burning. Whereas initially such LSOH products were for specialised applications such as metro (the first “low smoke zero halogen” cables were supplied to London Underground in 1975), continued development in the 1980’s led to more cost effective LSOH cables and the eventual introduction of these types into British Standards with the publication of BS6724:1986 and BS7211:1989.
The 1980’s saw work turn towards development of testing methods and protocols that ensured that consideration was given in one test to all reactions to fire parameters (i.e. flame spread, heat release, smoke production, flaming droplets and the emission of fumes), rather than the use of individual tests for each parameter. This approach has led to a proposed European classification “Classes of reaction to fire performance for cables” which has been under discussion within the EC for a number of years, but is likely to provide the framework for development over the next 50 years.
Turning to resistance to fire, the development of new cable types has been equally a feature of the last 50 years. The first International test method “IEC 331 fire-resisting characteristics of electric cables” was published in 1970, but at that time the use of such cables was restricted to specialist applications such as naval ships. Mineral insulated copper sheathed cables or designs based upon an extruded silicone enclosed in glass braid insulation were used.
The 1972 publication of CP1019 “The installation and servicing of electrical fire alarm systems” made no reference to fire resistant requirements for cables and wiring, concentrating on mechanical robustness and protection, although MICS cables to BS6207 were an allowable wiring type. It was not until CP1019 was revised as BS5839-1 in the 1980’s that such requirements were introduced.
The continuing growth in the availability of fire resistant cabling is clearly illustrated by the number of such entries in the LPCB “Red book”. In 1995 there were 13 cable types from 7 manufacturers, whereas by 2005 the list had grown to about 50 types from 19 manufacturers. This possibility for such growth dates back to 1976 and the introduction of the patented Pirelli General FP200 fire resistant cables, the first cost effective, easy to use design based upon an extruded insulation and requiring no special techniques for installation.
Developments continue apace in this sector; new requirements and new test methods under development to reflect the move to Eurpoean Harmonisation (EN50200:2000) and the UK demand for more onerous testing that combines the effects of fire, impact and water on cable. The publication of BS5839-1:2002 for fire alarm and detection and BS8519:2010 for life safety and fire fighting systems have driven our new product development.
Improvements to buildings and building services suggests we develop and extend our fire performance cables for the forseeable future.