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Foam 105.2 - Foam Proportining

            The key to delivering the finished Foam to its target is the proper proportioning within the hose-line in the form of Foam solution. This occurs “after” the Foam concentrate has been “educted” from its container into the delivery hose-line or standpipe system. The percentage becomes critical in obtaining maximum results to best deploy the finished Foam allowing its particular characteristics to shine. By having the correct “eduction” percentage drawn into the Foam solution maximum suppression and vapor suppression is achieved. When the incorrect setting is used, Foam wastage occurs and your resources are drained at a faster rate thus limiting a positive outcome. This feature in the “system” operation is a critical one balancing resources, cost, successful outcome of your incident all at the same time.

          As NFPA 11 dictates the need for correct proportioning, it does not mention any reference other than to refer to the Foam manufacturer recommendations. This is purposeful as the manufacturer “designs” the Foam Concentrate to be “educted” at specific percentages for its exact purpose. This is critical to the Foams performance and needs to be included into the SOP documents of your Department. When changing from Foam concentrates this feature may be overlooked and cause poor performance. Always be sure that eduction is set for the correct percentage or your attack results may be rendered useless.

          While line eductors are the first choice for suppression operations due to their portability and ability to be used from “Engine-to-Engine” one device for large scale fires should be more closely looked at. These are the “around-the-pump-proportioners”.

          This device functions by using the discharge of a fire pump to create the venture affect, drawing Foam Concentrate into your Fire Service Pump. The benefit of this technique is that “ANY” discharge device on your vehicle or relayed to another device can produce Finished Foam. This has wide reaching capabilities. Finished Foam can be delivered to your target through any large scale master stream device you wish. This is especially useful on large scale tanker truck fires. Facilities that store or contain are volume of Flammables or toxics can also be suppressed using this device. The downside is Foam solution is now contained inside the entire pumping circuit system. This means that EXTENSIVE flushing of ALL intake and discharge pathways will need to be completed before Fire Service Apparatus is returned to normal emergency service. This is sometimes ignored due to exhausted crews after the fire, and disastrous results have occurred. When Foam solution or concentrate is not properly flushed out of your system it can crystalize and block discharges, drain valves, block nozzles, and generally cause future fire suppression pumping actions to fail. Always flush your systems pump and discharge after using this tool to avoid these problems.

          The versatility of the around-the-pump proportioner far exceeds the tedious exercise in proper flushing. One technique that is successful is to drain the pumper after flushing. This will eliminate any crusty issues from forming preventing future operations. Follow this procedure at a minimum;

1] Flow water through all discharges and intake until clear of Foam solution

2] Fill all intakes, discharges, and tanks with clear water

3] Drain the above until empty and no longer dripping (this takes time)

          You may want to add to this procedure to enhance your safety, this is fine, just allow enough time for all the above operations to be done properly to prevent any future clogging issue.

                                 Haz Mat Mike

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