Small-scale test protocol for firefighting foams def(AUST)5706: Effect of bubble size distribution and expansion ratio
Laundess, A.J., Rayson, M.S., Dlugogorski, B.Z. and Kennedy, E.M. (2011) Small-scale test protocol for firefighting foams def(AUST)5706: Effect of bubble size distribution and expansion ratio. Fire Technology, 47 (1). pp. 149-162.
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The experimental program described in this paper sought to assess the suitability of the small scale DEF(AUST)5706 standard for measuring the suppression and burnback performance of Class B foams on pool fires. DEF(AUST)5706 is an Australian Defence standard mandatory for use by the Australian Navy, Army and Air Force. The test protocol required the measurement of the 3/4 control, extinguishment and 1/3 burnback times for a circular pan of aviation gasoline (AVGAS 100/130), 0.28 m2 in surface area. The test program involved compressed-air foams (CAF) and aspirated foams of two expansion ratios, and employed two AFFF formulations: a 6% telomer concentrate and, to obtain base-line measurements, 3% PFOS FC-600 concentrate which was manufactured by the 3 M company prior to the PFOS phase out. At lower expansion (7:1), the aspirated and compressed-air foams demonstrated similar fire control performance, whilst more expanded (9:1) CAF was generally more efficient at extinguishing, but less efficient in controlling the fire. CAF formed a better seal over the fuel surface and at the hot pan walls, and these foams performed noticeably better than aspirated foam against fuel re-ignition. The paper links these observations with the underlying distributions of bubble sizes, which were measured and fitted to modified Rosin/Rammler cumulative volume distribution functions. We propose that a modified version of DEF(AUST)5706 be adopted as a universal small-scale test protocol.
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