One of the Government’s main responses to the shock of the Grenfell fire catastrophe is to emphasize that products claiming resistance against fire must be properly tested. Composite fire doors from Grenfell (i.e. those with significant plastic content) failed to meet the most basic of requirements when test checked. That led to more testing of composite doors from several suppliers. Again, there were prominent failures, including doors with glazing cassettes.
How should testing for fire resistance be carried out? And what type of performance is expected?
All products and assemblies intended for fire-resistance must be tested to show that they meet minimum requirements. That means installing the complete element (e.g. a door set assembly or a glazed partition) in the front wall of a standard test furnace, fired by a bank of gas or oil burners to follow a standardised temperature-time heating curve, for a standard exposure time (usually 30 minutes, but also 60, 90, 120 , 180 and 240 minutes depending on the product class).
The test curve was first derived from typical temperatures in building fires. It is intended to represent a post-flashover condition, when all combustible materials in a compartment are burning. Standard temperatures reach around 740oC at 15 minutes, 842oC at 30 minutes, 945oC at 60 minutes and 1,006oC at 90 minutes, rising only slightly further to 1,010oC at 3 hours.
Exposure time is only one aspect. Two levels of performance are used to pigeonhole products. The most basic is “integrity”, which requires the test element to stay in one piece forming a physical barrier against fire, without gaps that allow penetration by flame or hot fumes. “Insulation” is a much higher level of performance. It requires integrity with an ability to limit heat transfer from the fire by conduction, convection and radiation. Insulation performance requires surface temperatures on the non-fire side of the test elements to be below prescribed limits, measured by contact thermocouples (a maximum rise of 140oC overall, with no single reading above a rise of 180oC).
The element must be assembled in the test as it is to be used. That should include, for example, the frame, all components, and fixings to the surrounding structure. Since fire penetration around the frame into the structure is a risk, the installed system should also include tested sealing measures to fill and protect the gap around the frame. If the door or glazed element is different from one side to the other, in a way that could affect fire performance depending on the side exposed to fire, then the performance in both orientations needs to be established from test information.
The expectation is that products when tested will perform exactly as claimed - not just once, but consistently and reliably whenever necessary. That means continuous and repetitive testing with continual R&D in developing the scope of product application.
The first development work for Pyrostop was carried out almost 50 years’ ago. Early approvals were in timber doors; the first major glazing of this type during 1978 in an Aachen clinic, Germany (steel framed panels, for 90 minutes insulation). When glazing from that project was taken out and tested more than 20 years’ later it showed exceptional performance, significantly more than the designated 90 minutes insulation.
Pilkington Pyrostop and Pyrodur now have a tremendous track record of success in furnace testing, in hundreds of tests. They have been used worldwide in many different framing conditions for many different applications, in several major projects including airports, hotels, office and residential blocks, medical centres, commercial buildings, care homes and schools. They have even been used in iconic Government buildings such as Sir Norman Foster’s Reichstag in Berlin, where special innovative ceiling applications and massive panel glazing around the central chamber had to be proven in special tests before authorities would endorse use of the products.#.
T A Anders Limited is a longstanding Licensed Supplier of Pilkington Pyrostop and Pilkington Pyrodur fire-resistant glass. We stock the entire range at our modern processing facility in Trafford Park, Manchester, and can process, distribute, install in proprietary frames and provide fire safety and product guidance if required. For further information, please contact T A Anders Limited on 0161 736 2487 or email@example.com or visit www.andersglass.co.uk for product specification and test evidence.
These opinions are offered in good faith but it is the responsibility of the reader to satisfy themselves as to their veracity and form their conclusions