WCA September 2011

The effects of the new European regulatory framework for the classification of a cable’s reaction to fire performance will be a major change from the existing voluntary position. Just how the European classification and CE Marking of fire performance under the CPD will affect the cable market is difficult to predict. Implementation is strictly a National matter and whilst it is known that some countries that do not now regulate for the reaction to fire performance of cables have no intention of regulating in the future, other countries have indicated an intention to use the classification in regulation. However, which Euroclass is specified for any particular application is again a national matter. At a European level, it is likely that the cable industry will continue to be required to supply many different levels of performance, although in time we may expect to see users moving towards the higher classes as cost effective cable designs become available. Comparison of prEN50399 tests with results from existing IEC tests is difficult due to the different conditions selected for the tests and the multi-criteria approach of the classification. Experience gained from the CEMAC II project has shown that prEN50399 results are in general greatly influenced by cable size – the smaller the cable, the more onerous the test. Results for larger power cables (conductor sizes greater than 35mm 2 ) can generally be predicted from IEC60332-3-24 (Category C) test results as the mounting in each test is similar but no such relationship exists for smaller cables due mainly to the totally different mounting in each test. Recent work has demonstrated that real time measurement of effluent in a large scale fire test (such as prEN50399) is possible and that such results can be used as input into modelling studies. However, it is clear that further work would be necessary before any standardisation could take place. Through its ongoing and demonstrated ability to invest in research, the cable industry will be in a good position to meet the challenges resulting from any new regulatory or end user demands on the fire performance of its products. 1 Zanelli, C, Philbrick, S, Beretta, G, “Cavi e pericolo di incendio” Cired, London 1973 2 Philbrick, S, McConnell, J, “Cables having improved fire performance” Jicable 84, Versailles 1984 3 Journeaux, T, Beratta, G, Gautier, P, “Development of cables with improved fire performance characteristics” Jicable 87, Versailles 1987 4 Journeaux, T, “The development of new standards for offshore cabling” PRI Conference Polymers for Offshore Cabling Proceedings, London 1987 5 IEC Standard IEC 60332-3-10:2000 + A1:2008 Tests on electric cables under fire conditions – Part 3-10: Test for vertical flame spread of vertically mounted bunched wires or cables – Apparatus 6 IEC Standard IEC 60754-1:1994 Test on gases evolved during combustion of materials from cables – Part 1: Determination of the amount of halogen acid gas 7 IEC Standard IEC 60754-2:1997 Test on gases evolved during combustion of electric cables – Part 2: Determination of degree of acidity of gases evolved during the combustion of materials taken from electric cables by measuring pH and conductivity References

The EXAP rules have been developed through the CEMAC II research project and will be published by CENELEC.

Possible Future Developments It is clear that the European cable industry will be heavily involved with the new integrated reaction to fire test approach of EN50399 and this, together with the other test requirements of the European classification, will require considerable effort in the development of products to meet the various Euroclasses. It is likely that EN50399 will be considered by IEC at the next major review of spread of flame test methods which is due to be conducted 2012 – 2015. Although at present there is an absence of any strong regulatory of user driven impetus, the industry is beginning to give consideration as to suitable product tests that could be used to measure effluent and provide data that could be used in fire safety engineering studies such as escape modelling. The integrated EN50399 test could provide a good basis if further equipped to measure effluent quantity and quality. The development of real time FTIR techniques for measuring effluent has led to some preliminary work being carried out to determine if it is possible to measure effluent quality during the EN50399 test. Papers presented at the Europacable Seminar “Safety during fire” in May 2009 (18,19,20) suggested that it was feasible to measure effluent from the EN50399 test using FTIR techniques, to use such techniques to investigate the smoke effluents and to use the input in a simulation of critical evacuation conditions in order to compare the use of different cable types. Determination of a FED and FEC index according to ISO TS13571 during the test could provide a useful measure. Using such techniques, it was concluded from the simulation study that whereas critical conditions for some of the occupancies were achieved for the design fire when considering standard (PVC sheathed) cables due to the production of irritant gases (HCl, acreolin, formaldehydes) and smoke (reduction of visibility below 10m), critical conditions were not achieved for any occupancy when considering Low Fire Hazard cables. Conclusions By reacting to the requirements of its customers with regards to the reaction to fire performance, the cable industry continues to offer a range of products with different levels of performance consistent with user’s needs for particular applications and installation conditions. The principles established more than 20 years ago of control the burning, control the smoke emission and control the emission of the most important corrosive and irritant gases still remain valid today although refinement and improvement in methodologies have been achieved in the intervening years. The advent of new requirements based on integrated tests involving heat release has been, and will continue to be, a major challenge particularly in Europe.

108

Wire & Cable ASIA – September/October 2007 11