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No, we do not forge “magic rings” for elves in the “fire” of ift Rosenheim. Furthermore, 20 burner with a performance of each 600 kWh spark of a “standard fire” with up to 1,200 °C, which complies exactly with the temperature-time curve according to EN 1363-1.
The fire resistance of doors, gates, walls, glazings and other bulding elements can be tested in order to ensure the resistance in case of a fire for 90 minutes and more. If the fire safety elements fail in case of emergency and people will be injured, usually the judiciary springs into action to investigate the causes. Then, everything is turned upside down and it will be investigated if the used fire safety elements were working, the necessary test certificates are available and if they comply with the regulations. Therefore, ift Rosenheim has invested a lot and built a furnace with 8 m width and 5 m height in the new ift technology center. In Juli 2017, another furnace with the dimensions 5 m x 5 m will be moved to Rosenheim from the ift Centre for Fire Testing in Nuremberg. For many years now, the competent ift fire protection team led by Dr. Gerhard Wackerbauer and Anyke Aguirre Cano tests the fire resistance and the fire behaviour of building elements and building materials. Above all, the exact control of the fire resistance test according to normative specifications with corresponding tolerances is important. The following publication shows how this is made.
Large and still burning according to standard – is this also possible with large furnaces?
For a long time, the fire resistance tests could only be made in “small” furnaces with an opening of 3 m x 3 m. At the same time, building components in fire protection are getting larger, so that the testing bodies had to extrapolate the tests. However, practice shows that reliable statements for fire resistance could only be given when testing large test elements. So even larger furnaces were built that have demonstrated the deficiencies and limits of some extrapolation rule. Therefore, a close eye on and in the furnaces is interesting in order to understand how a “standard fire” is controlled and the complete building element is exposed to the normative defined loads. Besides, there are rather generous tolerances for the furnace. The temperature distribution can deviate by ± 100 °C from the determined temperature value (generally the standard temperature-time curve). If one considers that with an excess of 1 °C of the limit of the temperature on the surface of the test specimen the reached class is already influenced, it becomes apparent that an even temperature distribution in the furnace is essential.
If you monitor fire resistance tests at thermal insulated glasses closely, you will realize that the intumescence of the insulating layers starts in small areas and then spreads very quickly. As the reaction of the intumescent material starts at a certain temperature, the spatial and temporal temperature distribution in the furnace can easily be observed. The burner for the generation of the temperature in the furnace are generally arrange at the sides with flames parallel to the surface. The exhaust gases are mostly be extracted centrally via some openings in the centre of the back of the furnace. This will result in a higher temperature in the center of the furnace. In order to load the test specimen evenly, the furnaces can be built so large that the cooler areas are located outside of the test opening. At ift Rosenheim, the “old” furnace with 3 m x 3 m was designed according to this principle, i.e. the test opening was 3 m and the chamber was 4 m wide. In addition, there are six exhaust ports instead of one, so that a even loading of the test specimen with the temperature-time curve was achieved. This principle was transferred to the large wall test furnace in the new ift technology center. The furnace has a maximum size of 8 m width and a height of 5 m, which can be completely used for the tests. The exhaust gases are exhausted via a variable number of openings, so that an ideal and very homogeneous temperature distribution arises during tests at a size of 5 m x 5 m.
What happens with tests of XXL building elements that needs the complete furnace size of 8 m width? For optimal test conditions, the known problem of the clear temperature drop at the edges and the higher temperatures in the centre has to be avoided. Therefore, the engineers at ift Rosenheim developed innovative solutions with the furnace manufacturer of ift MessTec (a subsidiary of ift Rosenheim). When using the complete furnace opening of 8 m width and 5 m height, an ideal, even temperature distribution is created by installing “temperature distributer” in the furnace chamber, so that neither the edges are underloaded nor the centre is overloaded and therefore preventing the risk of premature failure of the test specimen by stress cracks. Hence, a furnace with excellent temperature and pressure distribution is available for manufacturer of fire resistant building components. The furnace maintains the normative permitted tolerances optimally and that with the sizes 5 m x 5 m and 8 m x 5 m.
Oil or Gas – no question of technology!
As long as there are fire resistance tests, the correct fuel will be discussed. Wood was used as fuel in old DIN standards, which was replaced by oil. Since the introduction of the European fire classification standards gas may also be used. To start with - the temperature is high with all fuels. While older oil burner were hard to control as they could only be used in “on” or “off” mode, the modern oil burner in the technology center can be controlled “sensitively” like gas burner. In addition, the yellow lighting “torches” of old oil burner and the related excessive air heating, thermal radiation and soot formation are things of the past. The flames of modern oil burner are compact and the exhaust gases as hot as the exhaust gases of gas burner. The furnace chamber will be heated that the heat reaches the test specimen as thermal radiation, so that there are no differences to gas burner during loading. However, the violent pressure shock which occurred while ignitition of the oil burner and damaged the test specimen is not present in this form in modern burner.
The pressure distribution in the furnace affects the distribution of hot gases that takes a significant amount of heat in the joints of the test specimen due to leaks. Therefore, the pressure distribution is also part of the verification of the furnace according to EN V 1363-3. Considering the large amounts of fuel and the accompanying combustion air and exhaust gases, it is astonishing that an even pressure gradient is set. This is only possible if the adjustment between furnace size and exhaust ports is right. Therefore, years of experience and competence in construction and operation of furnaces are necessary, of which the experts at ift Rosenheim, ift MessTec and Peiner Ofenbau have, so that the approval and calibration of the new furnace in the technology center was passed withouth any problems. The normative necessary pressure value was reached earlier than requested (see image 3, dashed line), already after 1-2 minutes, and stuck to it with high precision for the remaining time of the test. Also with pressure-sensitive fire curtains, a standard deviation of only σ = 1 Pa was reached. For comparison: The wind force 1 (“light air”) correspond after Beaufort 10 Pa, wind force 3 (“gentle breeze”) is already 70 – 180 Pa.
At the ift technology center, both furnaces (8 x 5 m and 5 x 5 m) with the latest burner and exhaust technology guarantee the manufacturer of fire resistant components standard-compliant, reliable and reproducible test conditions. The service includes also rapid and prompt processing of the test order and the expert advice of clients by the experienced ift-experts in Nuremberg and Rosenheim. In Nuremberg, the experts of the “notified product certification body” plan and coordinate the test specimen and the tests according to the motto “as many tests as necessary and as little as possible”. In 2018, further furnaces will be added in Rosenheim in order to offer manufacturer the most efficient test combinations.
- EN 1363-1 – Fire resistance tests - Part 1: General requirements
- V ENV 1363-3 – Fire resistance tests - Part 3: Verification of furnace performance
- EN 16034 – Pedestrian doorsets, industrial, commercial, garage doors and openable windows - Product standard, performance characteristics – Fire resistance and/or smoke control characteristics
- EN 1634-1 – Fire resistance and smoke control tests for door and shutter assemblies, openable windows and elements of building hardware - Part 1: Fire resistance test for door and shutter assemblies and openable windows
Standards and excerpts from the standard are published with the knowledge of DIN Deutsches Institut für Normnung e.V. (German Institute for Standardization). The version with the most resent issue date is relevant for the use of DIN standards, which can be bought at Beuth Verlag GmbH, Burggrafenstr. 6, 10787 Berlin, Germany.
Dr. Gerhard Wackerbauer
Dr. Gerhard Wackerbauer, a doctor of physics, has been working at ift Rosenheim since May 1996. Initially, he worked in the area of acoustic insulation as well as protection against moisture and heat. In November 2004, he moved to the Centre for Fire Testing in Nuremberg and was Head of Testing Department in the area of fire safety until its relocation in 2016. He then moved to the notified product certification body Fire in Nuremberg, a department of the ift certification body, and has been the person responsible there since October 2016. Furthermore, he is also active in construction supervision approvals in the area of safety in case of fire.
In addition, he has represented ift Rosenheim in the European Sector Group of Notified Bodies SH02 in the field of safety in case of fire since the end of 2013, is a member of the German mirror committee NA 005-52-05 AA and represents it in the European Standardization Committee TC127-WG3.
Anyke Aguirre Cano
Dipl.-Ing. (FH) Anyke Aguirre Cano has been working as a test engineer in the field of safety in case of fire for building components at ift Rosenheim since July 2010. Following the relocation of the Centre for Fire Testing from Nuremberg to Rosenheim, she took over the position of test center manager in the area of fire protection for building components at the Technology Center in December 2016. Since March 2019, she has been the test center manager for fire and smoke protection at the ift Technology Centre Rosenheim.
In addition, she has represented ift Rosenheim in the EGOLF (European Group of Organisations for Fire Testing, Inspection and Certification) since the end of 2018. Since December 2020, she has been a member of the expert committee of the DIBt. Furthermore, she has been registered in the committee NA 005-52-02 Fire behaviour of building components since April 2021.