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Cables: reaction to fire tests. A new challenge for the industry

30-12-2011 | Electrical tests | news

“The long way to regulation which started with Council Directive 89/106 EEC is about to bear fruit with respect to the classification of the reaction to fire properties of power, control and communication cables.

The Construction Products Regulation (CPR) – Regulation (EU) No 305/2011of the European Parliament and of the Council, of 9 March 2011 laying down harmonised conditions for the marketing of construction products and repealing Council Directive 89/106/EEC, of 21 December 1988, will come into force on 1 July 2013 and contains, as a highly important modification for the manufacturers, the replacement of the EC declaration of conformity with a declaration of compliance based on specific tests.

Cable manufacturers have been testing their products in accordance with the requirements and demands of their clients for over 30 years, developing test methods with which to examine the characteristics and behaviour against fire, in order to limit the risks in the case of fire.

Test for vertical flame propagation for a single insulated wire or cable. Non flame propagating according to Standard UNE-EN-60332-1-2. This feature makes it possible to limit the possibility of the cable acting as a propagator of the flame.

Test for vertical flame spread of vertically-mounted bunched wires or cables. Non fire propagating according to Standard UNE-EN 60332-3. This feature makes it possible to limit the possibility of the cable acting as an element of propagation in the case of a fire.
Measurement of smoke density of cables burning under defined conditions. Verification of the opacity of the fumes emitted during combustion in accordance with Standard UNE-EN 61034. This feature makes it possible in the case of fire to have sufficient time and visibility to enable a complete evacuation of the area.

Determination of the amount of halogen acid gas. In accordance with UNE-EN 50267-2-1. This feature makes it possible to limit the contribution of the cables to the fumes generated in a fire, thus reducing the risks from the inhalation of gases.

Determination of degree of acidity of gases for materials by measuring pH and conductivity. In accordance with Standard UNE-EN 50267-2-2. This feature limits the adverse effects on equipment or electronic or computer circuits from the corrosive effect that the fumes can have on them.

At a regulatory level and in general, the testing methods have been applied in accordance with the International IEC standards and the corresponding equivalent EN European standards and/or related with IEC.

The new materials introduced in the manufacturing of isolations and covers for cables in recent years have led to safer products with regard to complying with all of the requirements stemming from the applicable regulation notwithstanding the electrical and mechanical features. These new materials, commonly defined as “halogen free” have had a rapid introduction into the market and their growth has mainly been motivated by the demand for products with improved behaviour and features in the case of fire.

Once we have reached this situation, in which the application of the different fire testing standards has been generalised and safety against fire is another element to be considered in the election of cables for a specific use, there is a new step forward in search of the way of integrating in a single test the parameters that make it possible to measure: the propagation of the flame, the release of heat, the opacity of the fumes and the emission of gases from combustion.

Standard EN 50399 edited in April 2011 was developed to support the performance of these tests. This standard indicates a testing method based on the use of the testing equipment of Standard UNE EN 60332-3, (the same as the one currently used for the verification test on the non propagation of fire), equipped with different measuring systems that facilitate the collection and analysis of fumes and the measurement of the speed of heat release. To do this, a small piece of conduit is incorporated. It is instrumented to the equipment exhaust system. The piece of conduit contains all of the gas sample probes, the temperature and mass flow probes and has ports for the smoke measurement system.

Piece of conduit with the measurement probes

The tests that are carried out with this testing method must be used to establish a classification (Eclass) of the reaction to fire properties of the construction products as established in the Directive.

The measuring technique was developed as part of the three year project “Fire Performance of Electric Cables” (FIPEC) which was recently completed.

The following table indicates the parameters and definitions of this testing method developed in accordance with what have been defined as “Scenario 2 FIPEC20” and “Scenario 1 FIPEC20

CLASSES OF FIRE PERFORMANCE OF ELECTRICAL CABLES (*)

(*) The prescriptions on the classes of fire performance demanded of the electrical cables, according to the different expected uses, should be established in the corresponding regulation or in the revision of the current regulations.
(1) For the product overall, except the metallic materials, and for any external component (cover) of the product.
(2) s1 = TSP1200 ? 50 m2 and SPR max. ? 0.25 m2/s
s1a = s1 and transmittance in accordance with UNE-EN 61034-2:2005 ? 80 %
s1b = s1 and transmittance in accordance with UNE-EN 61034-2:2005 ? 60 % < 80 % s2 = TSP1200 ? 400 m2 and SPR max. ? 1.5 m2/s
s3 = neither s1 nor s2
(3) For scenarios 1 and 2 FIPEC20: d0 = no fall of drops./ inflamed particles for 1200 s; d1 = no fall of drops./ inflamed particles that last more than 10 s over 1200 s; d2 = neither d0 nor d1.
(4) UNE-EN 50267-2-3: a1 = conductivity < 2,5 ?S/mm and pH > 4,3; a2 = conductivity < 10 ?S/mm and pH > 4,3; a3 = neither a1 nor a2. No declaration = No determination of behaviour
(5) The air inlet flow in the chamber shall be established at 8 000 ± 800 l/min.
Scenario 1 FIPEC20 = prEN 50399-2-1 with assembly and securing as indicated below.
Scenario 2 FIPEC20 = prEN 50399-2-2 with assembly and securing as indicated below.
(6) The class of smoke declared for the class B1ca cables shall derive from the test in scenario 2 FIPEC20.
(7) The class of smoke declared for classes B2ca, C ca y D ca shall derive from the test in scenario 1 FIPEC20.
(8) Measurement of the dangerous property of the gases that are formed in the case of a fire, which hinder the capacities of those who are exposed to them to act efficiently and manage to escape, and not the description of their toxicity.
Origin: Spanish Official Journal (BOE) No 37 of 12 February 2008

From the comparison of the tests, the current one in accordance with Standard EN 60332-3 and the test proposed in accordance with Standard EN 50399, it is concluded that there is no equivalence between the two as test EN 60332-2 is a test of the type that only determines the non propagation of the fire while the method proposed in EN 50399 goes beyond testing defined cable assemblies, evaluating conditions and parameters not determined until now.

At present all of the tests described in the above table can be applied and will be used to comply with the mandatory requirement of the CE Marking in power, control and communication cables, though in order to reach this phase the standard that supports this CE Marking has yet to be developed. This is the reason why it is still not possible to find cables with the CE Marking on fire performance properties on the market.

In order to issue the corresponding certificates of conformity it is also necessary to develop the product standards prh EN 50 – Reaction to fire. This is the standard that will be used to classify the cables according to Eclasses and its progress is being delayed by the difficulty involved in standardising because of the large number of different cable that it will affect.

In this situation the question that all of those who are interested in this matter are asking ourselves is when can the CPR be applied? In order to respond to this question, initially it would be necessary to publish the mentioned prh EN 50 -. Reaction to fire. Regarding certification it is also necessary to publish the certification systems that apply to cables in the Spanish Official Journal (BOE) together with the notified Spanish bodies to act on this product.

On the other hand, the notified body must use a laboratory accredited by ENAC for the tests. On this matter, ceis is taking the actions required to have the equipment and experience that will allow us to satisfy the needs of all of our clients when the CPR is applied.

Another important issue and subject to uncertainty, in light of the different situations that may arise, is the one that affects the obligation of classifying the cables in Eclasses and the incorporation of the CE Marking.

Based on the obligation that the cables to be used in construction work incorporate the CE Marking, there may be several regulatory situations that must be cleared up in the near future with regard to the application of the Directive in Spain. Nevertheless, it is expected in this situation that it will be the user who will define the Eclass for its installations with which he/she shall be demanding compliance with the Directive.

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