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Why Is AD-HOC Testing Valid and Valuable?

There maybe a misunderstanding of the terminology “AD-HOC” in the construction industry particularly when it comes to testing and in this case fire testing to structural steel.

For many years solid rods in tension have been able to rely on BS476 Part 20&21 for the qualifying material thickness for fire protection. This was based on the equivalent Hp/A (or more commonly used A/V) of circular hollow section (CHS) fire test results. In 2008 it was discovered that tension rods did not perform as well as CHS using the same criteria. 

The ASFP and member intumescent paint manufacturers, have now enhanced the thickness requirement to cater for this anomaly and published a new set of tables. Be sure to secure the correct set of tables as these were only published recently (circa 27 January 2020). For an example of a full document, click the following button…

In July 2020 a new standard, BS EN 13381-10, was published which is specific to rods in tension and suspension. However, the industry is still trying to catch up with the requirement to actually test in tension. Facility upgrades are in progress.

In the meantime, BS476 – 20&21 is still a valid test (BSI, UKAS, ASFP) for CHS profiles and until such time as the grace period expires (our information is that it will be 2024 at the earliest) the basic principles of BS476 can be used for the testing of solid rods. BS476 does not require testing while the test piece is in tension. The problem with BS476 is, “it cannot be used verbatim” because this test regime does not cover the nuances of positioning of thermocouples or testing in compression which is not appropriate as the tension rods behave differently.

Adopting data for BS EN 13381-8 for thermocouple positions would then seem a reasonable way to remedy this issue. However, this is not BS 476 and all test documents must therefore state this as “Ad-Hoc” to any certification. Unfortunately, “Ad-Hoc” has worrying implications and may deter the client from agreeing its use, i.e. a product which meets the design criteria of the architect but worries the engineer, particularly since the Grenfell Tower incident.

The ASFP supports third party product certification as the most appropriate way of demonstrating the performance of passive fire protection products in the market. See Indicative or Ad-Hoc Testing (courtesy of ASFP).

In summary: There should be no fear of using Ad-Hoc test data, providing it stipulates the reason for this type of test. In the case of solid rods in tension and suspension, it is an excellent solution until such time as BS EN 13381-10 and can fully replace BS476. Before that, the test houses need to tool up and the ASFP, we have no doubt, will redouble their efforts in supporting both BS476 -20&21 and BS EN 13385-10 when the time is right.

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Tony Tiernan

Tony Tiernan

Materials Specialist: Epoxy fire protection Castings

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