EN 1363 and the Plate Thermocouple
Why do we need it?
Until recently, manufacturers of products with fire resistance properties had to test to a different national standards when selling their products across Europe. This was costly, and also meant that some products needed to be slightly modified for each market. In order to remove such barriers to trade, pan-European tests had to be developed and agreed, so that one standard could apply across the EC. This has finally happened, and the result is EN 1363. This will soon be adopted as a British Standard. BS 476 and BS EN 1634 tests will be accepted in parallel for some time in the UK - the changeover time-scale has yet to be agreed - but most new testing will be to the BS EN. During the changeover period, specifiers and contractors will need to take care that items intended for use together have all been tested to the same standard. It will not be possible to mix and match BS 476 and BS EN 1363 tested products.
How do EN 1363 tests differ from BS 476?
There are two major differences.
Temperature in the furnace will be measured using plate thermo-couples.
The neutral axis for air pressure will be reduced to 500 mm above threshold.
Plate thermocouples
Fire test furnaces across the EC come in many shapes and sizes, and burn a variety of fuels. This leads to different results, even when the same test is being used. A way had to be found to give consistent results, no matter which furnace was used, in order to have acceptable test data.
The change to plate thermocouples has made it much easier to harmonise test results on the wide variety of furnaces in use in European countries. A plate thermocouple with a large surface area exposed to the furnace, but insulated from the test specimen, gives a more representative measurement of heat received by the specimen, especially in the early stages of a test. It is less affected by convected heat, or other factors connected with the furnace construction. During the last ten years, the use of the plate thermometer has spread across Scandinavia, and a large bank of data has been built up. Together with further testing done in a variety of furnace types in Europe, this has provided firm evidence that the plate thermocouple can harmonise the test regime in these furnaces.
Neutral pressure zone moves down
In the BS 476 tests, furnaces are managed to give positive air pressure at the top, and negative pressure at the bottom. The neutral axis (changeover point) is at 1 metre from the threshold. In EN 1363, the neutral axis is positioned lower down, at 500 mm from the threshold. The pressure at the top of the test specimen is not greater than before, but there is positive pressure over more of the surface area. It was agreed that this represented more accurately the situation in a real fire.
How do these changes affect our products?
There is still much to learn about the effects the new tests will have on UK products, and a research project has just received approval. Warrington Fire Research and a number industry partners have been successful in bidding for funding under the DETR Partners in Innovation Scheme. The PiI project involves testing a variety of products and constructions to both the existing British Standards (BS) and the new European (BS EN) methods . The aim is to determine the magnitude of any changes in severity and performance and hence the impact on the construction industry. The results of the test programme will be analysed and recommendations made to the DETR on the periods of fire resistance / levels of reaction to fire performance specified in the AD B.
The aim of the project is to accommodate the changes to the test methods and the classification system without imposing a major added burden on industry, as it is felt that any increase in the required performance of products resulting from changes in the test methods cannot be justified on life safety grounds.
By Niall Rowan
niall.rowan@wfrc.co.uk
http://www.warringtonfire.net/
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