On November 4, 2006, the EU commission published the fire-classification in their publication “Official Journal”, see fire classification information linked to the right.
Flame spread test together with heat release’and smoke production measurements according to EN 50399
There are seven classes: Aca, B1ca, B2ca, Cca, Dca, Eca, and Fca. Class Aca is for non-combustible products, e.g. cables with ceramic insulation. Class B1ca is the best class of the combustible products, while B2ca and Cca represent products capable of some degree of spreading a fire. Dca has fire characteristics similar to that of ordinary wood, while Eca consists of products that are difficult to ignite by a small flame but heat and smoke release is not assessed. Fca indicates that no performance class has been determined. Comparing this system with that for surface covering materials, in which Euroclass A is non-combustible while Euroclass D represents wood, it can be seen that the cable classes are parallel to the corresponding classes for surface covering materials. A short summary of the testing standards used for the classification is given below.
EN ISO 1716 Reaction to fire tests for building products – Determination of the heat of combustion
In this method the gross heat of combustion, PCS, is measured in a bomb calorimeter. The heat of combustion is calculated on the basis of the temperature rise. PCS is a French acronym for “Pouvoir Calorifique Supérieure”.
FIPEC Fire performance of Electric Cables
FIPEC was a research programme set up to develop methods for measuring the fire performance of electric cables based on sound engineering principles rather than prescriptive tests. FIPEC20 Scenarios 1 and 2 means a 20 minutes test where the heat output from the burner shall be 21 kW and 30.7 kW, respectively. Also the mounting is different. According to FIPEC20 Scenario 2 a non-combustible calcium silicate board at the back of the ladder shall be mounted to make the test more severe.
EN50399 Common test methods for cables under fire conditions – Heat release and smoke production measurement on cables during flame spread test
This is the most commonly used fire test for cables, developed from the test IEC 60332-3. Reference is made to EN 50266 where the details for the test apparatus are given. Measured quantities are flame spread (FS), heat release rate (HRR), total heat release (THR), Fire Index Growth Rate (FIGRA), smoke production rate (SPR), and total smoke production (TSP). This test set up allows testing cables in one of the most advanced test arrangements available in Europe.
EN 60332-1-2 Tests on electric and optical fibre cables under fire conditions – Test for vertical flame propagation for a single insulated wire or cable
In this test a flame with 1 kW heat output is applied on a single cable. The measured quantity, H, is the combusted or charred length of the cable.
EN 61034-2 Measurement of smoke density of cables burning under defined conditions
Smoke is accumulated in a cubic test box with 3 m sides containing cable sample and a fire from 1 l alcohol. The optical transmittance is measured by a white light system.
EN 50267 Common test methods for cables under fire conditions – Determination of degree of acidity of gases for cables by determination of the weighted average of pH and conductivity
This test is used to measure acidity. Conductivity and pH are analysed after components have been completely consumed by heat in a tube furnace. Test standard IEC 60754 is similar to EN 50267.
IMO Fire Test Procedures
SP offers the complete range of fire test methods not only for the CPR also for the fire test procedures code of IMO, including several tests applicable for cables.
ISO 5660 Reaction-to-fire tests – Heat release, smoke production and mass loss rate
Experience has been gained by SP to use this test method for research, product development, and for quality control purposes. Only 100 mm by 100 mm samples are required in this test. ISO 5660 is an inexpensive small-scale test that gives detailed knowledge of the reaction to fire behaviour of, for example, cables.
Presently SP is heavily engaged in the implementation of a testing and classification system in Europe. SP participated in the management and co-ordination of the FIPEC research program described above. A full scale investigation on how the choice of cable material affects evacuation in fires has been conducted by SP within the project Plastics in a Sustainable Society. The report is published on SP’s web page.
The functional performance of electric cables subjected to elevated surrounding temperatures and to thermal radiation has been investigated experimentally and theoretically.
There are plenty of other research projects involving cable fires performed by SP. Please see our publication web page for a complete listing.