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AD 299: The Use of Intumescent Coatings for the Fire Protection of Beams with Circular Web Openings

In December 2003, SCI issued a report, RT983, Interim guidance on the use of intumescent coatings for the fire protection of beams with web openings and an Advisory Desk Note, AD269. The report described an approach for determining the thickness of intumescent coating required for composite beams with web openings. AD269 contained a simplified form of the RT983 guidance. Following work by an industry group consisting of SCI, ASFP, warringtonfire and BRE, a new protocol for testing and assessing the fire protection requirements of cellular beams has been developed. The protocol comprises a detailed test program, a thermal assessment and a structural assessment.

During the development of the new protocol, which is based on a detailed analysis of test results, it has become apparent that a more complex relationship exists between bottom flange temperature and coating thickness than that used in AD269 and RT983. Therefore, SCI have recently issued RT1085, Guidance on the use of intumescent coatings for the fire protection of beams with web openings¹. This is a modified version of RT983 and contains a more realistic relationship between bottom flange temperature and coating thickness. It has therefore been decided to withdraw the quantified guidance contained in AD269 and, instead, point designers to RT1085. Like RT983, RT1085 contains generic guidance applicable to any intumescent product. The guidance in RT1085 applies to both composite and non-composite beams.

A small number of intumescent coating manufacturers have already carried out tests in accordance with the new protocol, and their results will allow a reduced thickness of these specific products to be used on most cellular beams, and is likely to encourage other manufacturers to test their products.

During 2006, SCI will be issuing reports on product specific assessments, similar to the generic RT1085, to manufacturers who have completed the new assessment procedure on their products. This product-specific guidance will be less conservative than that contained in generic RT1085 and should be used where possible.

RT1085 may be withdrawn towards the end of 2007 by which time most manufacturers will have completed the new assessment procedure and the generic guidance will not be required.

1 RT1085 is available on SteelBiz at Paper copies may be purchased for £30 through the SCI Publications Department.

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