High Expansion Foam generator consists of a fan, driven directly by the shaft of a water turbine, which blows air to a nylon net. The net is wetted by foam water solution from spray nozzles which are supplied from the discharge if the water turbine, the foam concentrated being drawn into the water stream by means of a built-in induction system.
Its special feature is the by-pass system which allows the generator to operate against a high back pressure due to use of long lengths of ducting or when forcing the foam to a height.
With the by-pass shut, all the water passing through the generator us used for driving the turbine and for foam production, thereby producing reduced expansion foam. In order to overcome high back pressure, which long of tubing, the by-pass is opened and some water is diverted to pass through the turbine to waste, leaving less for foam production. This results in a higher expansion foam and also increases the water flow to the turbine, speeding up the fan and consequently the air flow. The generator can also be used as a smoke extractor, in which case the valve controlling the foam solution supply to the spray nozzles is closed.