The fish-friendly foam is only used when oil is present in the water or when the fireboats must quickly smother a fire, such as when a fiberglass boat catches fire and produces black smoke.
A fire-retardant foam is mixed with water drawn up from the surrounding river and pumped into the dispensing system; all controlled by an onboard PLC. Depending on the volume of water being pumped, foam is directed through a 3-way selector valve offering different pipe sizes to accurately mix a ratio between 3% and 5% per volume. When the PLC requires a foam flow rate less than 9 gallons per minute, it is directed through the 1⁄2” line, and when more than 9 GPM is needed, foam is routed to the 2” pipe.
This fireboat manufacturer fitted 2 different size turbine meters on the foam lines and a mag meter on the large line. The job of the turbine flow meters is to provide feedback to the PLC of actual flow rate volumes. This is done by AW-Lake’s RT-30 Flow Transmitters attached to the turbine meters. The RT-30 Transmitter accepts the Turbine’s pulse input, then displays readings locally and provides a scalable 4- 20mA output signal to the PLC to control the opening and closing of the valves for the desired ratio.
Turbine meters were chosen due to the restricted mounting space available below deck to accommodate the flow meters. AW-Lake’s TRG Turbine meters were ideal for this project due to their rugged stainless-steel body construction, material compatibility with the low viscosity fluid, and most importantly their compact size and small face-to-face dimension.
Once the river water and foam are mixed, that mixture is routed to two high-pressure spray nozzles positioned at the front of the boats. The flow rate is controlled at 500-600 GPM to achieve the desired spray height of approximately 500 feet for effective fire extinguishing.