New fire prevention standards in Europe - significance with regard to sandwich elements

General
In the context of European harmonisation it has become a requirement for standards to be unified. For many materials - steel, galvanised and pre-lacquered sheets to name but a few - this has already been done. A more difficult matter, on the other hand, would be a uniform system for building products. The national perceptions and regulations are too varied here to be able to find a quick solution.

In the realm of fire prevention, certain basic European standards have already been established and these have appeared in German speaking areas as a white paper or will appear as such soon. Below we will give a brief picture of their interpretation in terms of sandwich elements with metal cover coatings and polyurethane insulating cores. It is important to state that this concerns the status of the matter as of July 2002. Changes or the introduction of further newer standards or guidelines can take place very rapidly and have a further influence upon the information below.

The flammability of sandwich elements
The flammability of sandwich elements has thus far been assessed in terms of DIN 4102-1.

There was a minimal value of the construction material class B2 (small fire test, see Fig. 7.5.1) and the fire shaft test for the grouping of elements in B1 (see Fig. 7.5.3).

Fig. 7.5.1 Small fire test as per DIN 4102

DIN 4102-1 comprises 5 construction material classes, from A1 through B3 (see Fig. 7.5.2 Table 1, Line 2). The new European standardisation will comprise 7 construction material tests A1 - F (see Fig. 7.5.2 Table 1, Line 3).

Fig. 7.5.2 Table 1: Euro classes of flammability

The Euro class E was tested according to DIN EN ISO 11 925-2 and this test is virtually equal in terms of coverage to the B2 test as per DIN 4102-1.

The criteria are: flame spread within 20 seconds less than 150 mm. As additional requirement, for the Euro class E burning drops/flakes of burning parts (d2) are included.

Euro class A1 will certainly not affect original sandwich elements. The non-flammability thus far will also be demonstrated with this material. The standards are virtually identical to the former ones.

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SBI Test (single burning item test)

For classes A2 through D, the SBI test has been added. This replaces the former fire shaft test as per DIN 4102-1. In this test, in a corner a fire source is placed that roughly corresponds to a burning wastebasket in the corner of a room. The diagram for this test is shown in Fig. 7.5.4, the test item illustration in Fig. 7.5.6.

Here too, three tries are carried out for each system of a particular thickness. A new point is that not every attempt need yield the desired result. The results are added together and the mean value obtained.

If the client of the tests feels that this result is not good enough, it is possible for two further tests to be carried out.

From the five results then available, the best and the worst are discarded. The mean value of the remaining three tests is used for the final classification.

Thus far it was standard practice that none of the three fire shafts as per DIN 4102-1 could be worse than the required value (here the residual length).

Another new point is that in the SBI test the theoretical test body thickness can be up to 200 mm. For sandwich elements the thickness is, however, limited to a maximum of 150 mm (as per EN 14509), with the greater thicknesses thereby being covered.

Fig. 7.5.3 Fire shaft test as per DIN 4102

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In total in each instance three tests with the smallest and largest element thickness to be evaluated (max. 150 mm) are to be carried out. Different joint constructions must be evaluated separately.

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The following are measured in the SBI test:

• energy release (THR)
• flame spreading (LFS)
• speed of fire spread (FIGRA)
• smoke development (SMOGRA)
• burning pieces and/or drops falling

Valuation and grouping
The valuation of the results is not very simple and may be read about by the interested reader in DIN EN 13823, SBI Test. We will therefore not describe the valuation in this document.

Depending upon the results of the SBI tests, grouping is done in the Classes A2 through D. Indeed the SBI test is not sufficient on its own in order to facilitate a grouping in a Euro class.

Further tests are required and these are summarised in Fig. 7.5.11, Table: Composition of Euro classes, Standards.

Execution of the test layout

In the SBI test the corner is put together either as per Fig. 7.5.6 or according to the actual situation. Length, width, and height of the elements as well as the joint organisation are not changed.

The test is set up or built up on a cart, the so-called test support cart, in the test room. For the manufacturer it is recommended that the test bodies be pre-assembled in the plant. Depending on the test location the long side may be at a different point, which plays no role with respect to symmetrical test bodies, however this must be borne in mind with regard to asymmetrical bodies.

Fig. 7.5.5 SBI Test - Test support cart

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Fig. 7.5.6 SBI Test - Test set-up

Illustrations 7.5.7 through 7.5.9 show the course of an SBI test for the technical fire prevention classification of sandwich elements (B1 - hard foam B2) of 4 February 2000 at the MFPA Leipzig. The sandwich elements do not contribute to the fire. After the removal of the source of the fire, the fire goes out. The diagram in Fig. 7.5.10 shows the course of an SBI test in terms of time.

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Abb. 7.5.7

Abb. 7.5.8

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Abb. 7.5.9

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Fig. 7.5.10 Diagram: Course of an SBI test in terms of time.

Fig. 7.5.11 Table 2: Composition of the Euro classes, standards (continuation of table see Page 7.5.6).

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For the sake of completeness:

Fig. 7.5.11 Table 2: Composition of the Euro classes, Standards (first part of the table see Page 7.5.5).

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Classification as per European standards

After the Council of the European Community had accepted the construction products directive in 1988, construction products legislation also anchored this directive in law after a period of time. The European classification concept for the realm of fire prevention that has been developed over the last few years has meanwhile been completed. European test standards are available that to a great extent have already been published - in German speaking areas as a white paper.

These standards represent a clear change from the German standards that existed in the past.

As per DIN 4102, construction components are tested and grouped in flammability classes. The European standards are sub-classified in test standards and classification standards.

The European test standards contain very precise descriptions of the testing equipment, test layout, test execution and if applicable the destination of the measurement results (SBI test). However they do not contain any specifications as to how the measurement values should be assessed or evaluated. For this purpose there are classification standards such as those for sandwich elements and other products, for example DIN EN 13 501-1.

In order to view the different safety and protection levels of the individual member states there are classes of requirements and performance levels that should suffice for classifying building products. Between these classes and performance levels the member states can choose their building products as required.

Which classes and performance levels are necessary in order to guarantee adherence to German safety standards have been decided upon by the committees of the German construction industry authorities. Industrial representatives were not involved/accepted. The commission’s decisions as to which criteria apply to the individual classes are summarised in Fig. 7.5.12 Table 3.

Fig. 7.5.12 Table 3: Flammability.

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German safety level
It should be possible to find the obligatory allocation of classes for flammability in terms of the currently applicable construction supervision standards in Appendix 0.2 to the Construction Regulation List A, Sub-publication 2002/1 (appeared in July of 2002, was not yet available when this document was prepared).

Table 4 in Fig. 7.5.13 below nonetheless shows clearly how the construction supervisory authorities guarantee the German safety levels. And this will amaze the interested reader. Not every building substance that is categorised with A fulfils the German standards for non-flammable substances. The classes of smoke development and burning drops/pieces are decisive, depending upon standards, with respect to the construction authority requirements.

It is debatable how planners and construction and certification authorities will deal with this situation. In any case the property owner will not accept this without question. The fear even arises that the unclear definitions contained herein will lead to anti-competitive situations.

Fig. 7.5.13 Table 4: Classification of the flammability of construction materials

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Uniform test not guaranteed in various member states
A further danger lies in the fact that a large number of European harmonised product standards come onto the market without a suitable confirmation of test specifications. For example for the SBI test it is not specified how test bodies of various materials are confirmed and/or adhered to during testing (exception: sandwich elements: this regulation applies here, Fig. 7.5.6). Therefore there is no guarantee of a uniform test for all member states.

German testing agencies also confirm that differences in valuation of results and/or in the execution of tests exist. It is up to the customer to determine which agency can “optimally” test his product, they say.

Therefore it is possible that the highest construction supervision authorities may demand a general construction supervision certification to determine building materials classes A1 through D for unregulated and harmonised building products with which we once again arrive at the end of the second chapter. At present much is still up in the air.

Table 5 in Illustration 7.5.15 once again shows the European classes of flammability of construction products with a specification of their testing processes, classification criteria and additional classifications.

Recommendations and hints
With the appearance of a harmonised European standard, delineated in German speaking areas as the “white paper”, the standard acquires validity and can be applied. It should be noted that there are both harmonised and non-harmonised European standards. This might for example be compared to DIN standards that have been established both inside and outside construction legislation. A harmonised European standard is generally recognised by its bearing the appendix ZA.

German standards continue to be valid for a specific period of time, generally speaking 12 months. Thereafter they are revoked. According to current practice, test certificates for the classification of construction products in the construction material classes as per DIN 4102 remain valid without limitation.

The classification of construction products according to European standards, however, can only take place if these have appeared as harmonised standards. These standards can already be used for certification before they are harmonised.

The test results can then be classified after the introduction of this standard. For sandwich elements a classification in terms of flammability can already take place as per DIN EN 13501-1. Fire resistance as per European classification can be determined as of the end of 2002.

For manufacturers of sandwich elements, it is recommended that fire testing now be carried out not only according to German standards but also according to European standards, even if these have not all yet appeared as harmonised standards.

After that it is a case of “wait and see” regarding which further changes or updates will confront the manufacturers of sandwich elements and their customers and planners.

Fig. 7.5.14 Testing room for SBI test

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Fig. 7.5.15 table 5: Classes of flammability of construction products

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Photo sources :
7.5.1, 7.5.3, 7.5.7, 7.5.8 und 7.5.9: Koschade, R.: Die Sandwichbauweise, Verlag Ernst & Sohn, Berlin 2000;
7.5.4, 7.5.5, 7.5.10, 7.5.14: BRUFMA: Briggs paper SBI only; 23.4.02
7.5.6: Autor

Author
Dr. Ing. Siegfried Burkhardt

Hoesch Siegerlandwerke GmbH
Public Expert (IHK Siegen) Light Construction - Sandwich Elements, trapeze profile