Fire service measures
another supplier may be as effective, as would walls constructed of concrete or other fire resistant material. The blocks were arranged into three bays.
Bay 3 was sealed using a proprietary own brand intumescent mastic sealer purchased from a builder’s merchant; and Bays 1 and 2 were left unsealed. The constructions were subject to the tests outlined in the table on previous page (see also Figures 10, 11 and 12). The pre crushed wood fire was used to
demonstrate the test method and to evaluate the effectiveness of video heat and smoke detection technologies. Both technologies proved very effective with this type of material, and detected the thermal lance before the pile had been involved. The resulting deep seated fire took a further four hours to breach the surface (see Figure 13 below). The configuration of the bay acts like a
room and, as a result, the flame is stretched up the ‘overboard’ by air being entrained (see Figure 12 on previous page). This is a well documented phenomenon in fire dynamics. In practical terms, it is unlikely that the overboard could be raised high enough to overcome this problem, although theoretically it may be possible. This is discussed in An Introduction to Fire Dynamics3
, by Dougal Drysdale. It is more likely, however, that fire crews would
have to consider this effect and position covering jets to the material either side of the bay that is on fire (see Figures 14, 15 and 16 below). Although the Legioblock walls had been exposed to temperatures in excess of 900°C
for 20 hours and then rapidly cooled with firefighting jets, the spalling was relatively minor at around 10 to 15mm maximum. This bay was subjected to a further intense plastics fire for two hours at around 1,100°C, and again rapidly cooled with water jets. The block work did not display any signs of instability or failure.
Baled plastic fire tests
Recycled mixed plastic bales were piled three bales high and three bales in each other direction, forming a stack of 27 bales. Plastic was selected due to the intense heat release rate observed in earlier tests. All the fires were piloted by the application of a naked flame at the base of the gaps between the stacks on the upwind elevation. All the fires behaved in a similar way. Fire spread in the virgin material was quick:
from point of ignition to full involvement within four minutes. The test beds were built 6m from the previous fire to establish the effectiveness of the separation distances suggested in the Environment Agency Fire Prevention Plan (FPP) guidance document. In Figure 17, which was the water with wetting agent test, all three test beds were fully involved in under 12 minutes of the pilot flame being applied to the first stack. In all, baled plastic stacks have been
the subject of nine fire tests using various plastic compositions. In these tests, it was noted that the plastic did not enter the liquid phase, but rather appeared to enter the vapour phase and combust almost instantaneously. The heat output
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