RISCAuthority insight
Dr Jim Glockling discusses a possible alternative method for evaluating fire performance of future cladding systems, based on a technique used in historic insurer sandwich panel research
use, and nowhere is this more apparent than in discussions pertaining to combustible and non combustible materials in cladding systems (and let’s not forget limited combustibility while we are about it). Complications can start at an early stage beginning with whether the terms are to be ascribed to individual materials or built up systems. In built up system testing, a non combusting result can be achieved by construction detailing that does not allow involvement of potentially combustible materials in a fire, and/or via the individual fire properties of the component parts. Individual materials under test show their
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properties unaided by design detailing, but even that may not be straightforward to explain and demonstrate through testing because materials can respond in very different ways to different fire challenges – a combustible material could appear non combustible under certain stimuli. For example, there are materials that: •
ignite easily and sustain burning thereafter (obvious)
•
ignite only after a sometimes sizeable ignition source is applied and sustain burning thereafter (less obvious)
• do not sustain burning but contribute to increasing the heat release rate of a fire whilst a fire from another source is acting upon it (not obvious without specific measurement equipment)
• do not ignite, or contribute to increasing the heat release rate of an impacting fire (obvious)
Knowledge of these different participation (performance) types is essential to forming a good understanding of how products and systems will perform in end use, and will go some way to improving the understanding of
16 JUNE 2018
www.frmjournal.com
OMETIMES THE most simple things are difficult to describe with a rigour that prevents misinterpretation or abuse in
combustible/limited combustibility/non combustible materials – actually what is needed is to understand material ‘participation’. This approach has been undertaken before
in historic insurer funded research on sandwich panel systems using calorimetry techniques. Using a computer controlled fire source, the applied fire challenge is ramped up at intervals, and the response of the sandwich panel system to the challenge directly measured by way of its contribution to the net measured heat output. The advantage of such an approach is that the
output data is not subjective, is directly comparable between materials and system geometries, and lends itself to the inclusion of toxicity measurement since all gaseous byproducts are collected and metered. In this study a computer controlled gas fire acted as the fire source, and the response of a corner rig constructed of many different sandwich panel products compared.
Figure 1 – Test fire source On a polystyrene based panel the response is as
expected both visually and in terms of contribution to overall heat release rate, although it is useful and informative to see that in this configuration, involvement of the combustible components does not start until the fire source is above 100kW in size – below that, the system appears non combustible.
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