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of the firewater runoff to prevent environmental harm. The most effective solution to this problem is to use the site emergency response plan to contain the firewater inside the affected building using a combination of sandbags, Floodsax, Quick Dam and HydroSnakes after the fire is extinguished. This is an issue that the Environment Agency (EA) and the waste industry continue to grapple with as the EA’s Fire Prevention Plan (FPP) requirements begin to bite.

Deluge water mist systems Deluge water mist systems will always be installed with a dedicated water supply arrangement using relatively low volume fire pumps and low volume water tanks. As a misting product, the quantity of water discharged is much less than traditional sprinkler systems. This has real benefits from the viewpoint of cost, system footprint, water usage, clean up difficulty and environmental containment or runoff. Typical density of delivery from water mist

systems for waste piles needs to be around 3mm/ min equivalent, and droplets need to be mixed in size from very small to medium. This is to ensure that the water mist that is delivered onto the fire can achieve suppression through saturation of the exposed surfaces, and penetration to the seat of the fire. Most often triggered by flame detectors,

the water mist is discharged simultaneously from all misting nozzles onto the growing fire below. Provided the density of water and mixed droplet size is sufficient, water mist is an excellent fire suppression medium for small sized waste bunkers. Discharge periods are typically only a few minutes (vs 60 to 120 minutes for deluge waterspray systems), so it is important to have additional water capacity for a second discharge, whether manually or automatically activated. The main concern with water mist systems

has always been effects of natural and forced airflows through a building. In large open waste sheds, as it is not uncommon for there to be significant horizontal and vertical air movements, discharging water mist into such open spaces is unlikely to be successful, as it will get blown or sucked away. Focusing the water mist into relatively small, high walled bunkers will help to contain the discharge and protect it from passing airflows. Also, mixing medium sized ‘spray’ droplets with true ‘mist’ droplets gives the discharge strong downward momentum. In practice, for water mist systems, only full scale fire testing on realistic waste piles can prove their efficacy. VID Fire-Kill is a good example of a water mist system that has received relevant approvals through


full scale fire testing on realistic waste piles, and it is being installed by several installers, such as Fire Shield Systems Ltd and Helios Systems Ltd.

Monitor nozzles/water cannons

Monitor nozzles, or water cannons as they are often called, can deliver a significant amount of firewater onto a fire at high velocity and intense density. Provided the cannons are pointing at the fire, they can be very effective. Limitations include not necessarily pointing at the fire; not reaching the fire with sufficient density; the risk of spreading burning materials; being impeded by abandoned mobile plant; needing to be manned physically or remotely; and substantial volumes of firewater runoff. Despite these issues, their success when

deployed in energy recovery facilities (ERFs) [power generation stations] has led to them being installed at other waste handling sites more and more often. Whether or not a site has roof sprinklers or waste bunker deluge protection, having high capacity water cannons in the arsenal can be a real bonus when rapid response and knock down of a fire is required.

Manually operated monitor nozzles These require a supervisor to attend and direct the nozzle onto the fire, and are not commonly seen in materials recovery facilities (MRFs) or transfer stations. They are sometimes installed on high level gantries with easy access DECEMBER 2018/JANUARY 2019 47

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