EoW July 2011

technical article

For performance characteristics, the scope covers reaction to fire, resistance to fire and dangerous substances. CENELEC had accepted the Mandate in principle and was expected to submit a detailed response with a work programme within 2009. The first phase of the work was focused on those documents needed to support marking for reaction to fire, but it is unlikely that these will be completed before late 2011. The Harmonised Product standard is the key to CE marking under the CPD but development of such a standard presents a difficult problem as there being many diverse cable types and the CPD only applies to their reaction to fire, resistance to fire and dangerous substances, with other safety parameters are covered under the LVD. A solution of a performance based standard that can be applied to any cable type and specifically covering aspects under the CPD is under consideration. The classification standard is an important administrative document that links test results to a classification and includes information on the tests to be carried out, the number of tests for classification, the assessment of results and the classification criteria. It has been agreed in principle by CEN and CENELEC that cables will be included as an amendment to the existing EN 13501-1 so that all products under the CPD are included in one document. The test method standard (EN 50399) has to ensure that the data necessary for classification can be obtained. The final draft standard is ready for formal vote in CENELEC. As part of the development of the test method, more than 20 laboratories have taken part in a proving round robin and repeatability and reproducibility were found to be comparable with other large scale tests such as the SBI. Considerable experience (more than 200 tests on cables representing generic constructions widely used in Europe) has also been obtained with the test method during the CEMAC II project which has brought together cable manufacturers, research and testing laboratories and research establishments in the implementation process in order to create the technical background. A specific objective of the CEMAC II project was to develop rules and procedures for extended application of test results (EXAP) that define which constructions should be tested in order to obtain classification for a defined family of cable constructions. The final report was expected before the end of 2009.

FEC max = 2.47 at 420 sec FEC = 0.3 at 7.5 sec FED max = 0.23 at 1200sec no FED = 0.3

Time (s)

▲ ▲ Figure 5 : Typical output of toxic gas production in an EN50399 test

Definitive documented rules for extended application (EXAP) are necessary in order to prevent a situation where every individual cable design has to be tested for classification. It is necessary to establish which cables need to be tested to gain approval for a product range through rules which enable tests on defined products within a family to be extrapolated to other similar constructions within the family. The EXAP rules have been developed through the CEMAC II research project and will be published by CENELEC. 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. Possible Future Developments

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

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EuroWire – July 2011