foam systems
Proportional response Water-driven positive pressure foam proportioning systems are growing in popularity. David Owen from Hawkes Fire explains the practical, environmental, and financial benefits of a proportional response to foam attack.
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Foam proportioners from Firedos are made up of two main elements: the water-powered motor and the mixer pump. No other power source is required other than the water supply.
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t is often said that the fire suppression industry operates on an ‘evolution not revolution’ approach. Game-changing new developments rarely come out of nowhere to shake up the industry. Instead, technology is refined and redesigned to keep pace with modern materials and techniques and changes in operational practices. David Owen from Hawkes Fire believes that the increased use of wind-turbine proportioning for fixed extinguishing systems and mobile fire service units is an example of this evolution. Hawkes Fire is a distributor of Firedos, one of the manufacturers of such systems. Owen explains the Firedos targets those areas of fire suppression it believes can be improved on, and focuses on two main product areas: foam proportioning and water/foam monitors. Foam proportioners from Firedos are made up of two main elements: the water-powered motor and the mixer pump. No other power source is required other than the water supply. There is a proportional relationship between volumetric flow rate and the rev speed of the motor. Changes in the volumetric flow rate have a direct effect on the speed of rotation of the motor drive shaft, and the water-powered motor drives the mixing pump. ‘One of the key benefits of these systems is the flexibility to deal with different flow rates,’ Owen explains. ‘Units can accommodate flow rates from as low as 100lpm up to 22,000lpm and each unit has a turndown ratio of 10:1, providing a range of options in each size. The systems also offer flexibility on the fireground because they can be mounted at various
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points in the supply chain.’ Owen explains that the units can usually be mounted far enough away from the fire that it won’t pose an unacceptable risk to firefighters. 'The run-out of hose or fixed pipework is only limited by the pressure and flow available to mount the foam attack. In addition, because the piston pump is a positivedisplacement pump, it has none of the problems associated with inductors. Nor does it require specialised discharge devices other than those in common use by both municipal and industrial fire and rescue services.' Owen also argues that the flexibility in flow rates means that not all hazards need to be dealt with using large volume firefighting techniques. ‘These techniques certainly have their place, but it is also important to remember that numerous hazards can be dealt with using mid-range flow rates. This kind of situation can be accommodated by using Firedos units of typically around 6,000lpm in conjunction with monitors or fixed pourers.’ Foam proportioning can also be beneficial for environmental reasons as these systems can provide more accurate and less wasteful foam proportioning alongside testing that doesn’t discharge to ground. ‘Accurate mixing can minimise both wasteful rich mixtures and make the best use of modern 1% concentrates,’ Owen explains. ‘With a directly proportional system, stepless variable adjustment is possible so that injection can range from 0.1% to 1%, 0.3% to 3% and 0.6% to 6% and is not subject to the back pressures that affect inductors.’
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