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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.
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.
References
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