Firefighting foam cannot be pre-mixed, stored or transported to the fire scene in finished form. Adding concentrate to the fire stream is a challenge that’s been addressed in several different ways over the years. As with most things, the best systems turn out to be the most expensive ones.
To produce a foam firefighting stream you need five things—water, a fire pump, foam concentrate, a metering system to control concentrate amounts added to the with water, and a method of mixing air with the finished foam solution to produce bubbles.
The most simple system is batch mixing, but wastes expensive concentrate and delivers inconsisten results. A more accurate method uses an eductor to pick up and proportion the foam, but has many limitations. The most accurate systems are those which inject concentrate into the discharge flow under pressure.
Batch mixing, which is achieved by simply pouring foam concentrate into the apparatus tank or a porta-tank, can result in pump cavitation and washing the lubricant out of pump shaft seals and valves. Class A foam is a highly effective detergent. In addition, when pumping directly from a porta-tank, maintaining a precise foam-to-water ratio quickly becomes impossible.
Foam eductors which use high pressure water flow through a venturi to draw concentrate into a proportioning valve is simple in design but requires close operator attention to maintain accuracy. A basic apparatus mounted eductor requires 200 psi inlet pressure which often means manually gating back all other discharges being used for handlines.
Pressurized streams of metered amounts of foam produce the most accurate results and can be used for foams formulated for both Class A (ordinary combustibles) and Class B (hydrocarbon liquid) fires.
Most proportioners directly inject the desired ratio of foam into the discharge side of the pump, often into a manifold which permits only certain designated valves to deliver either foam or plain water. The “around the pump” systems utilize part of the water flowing through the pump to create a negative pressure in an eductor which then draws foam concentrate from its tank and sends it into the foam-designated discharge valves.
In the simplest terms, proportioners ration foam concentrate into fire streams, mixing water and concentrate at a prescribed ratio. Most foams are designed to be mixed with 94 to 99.9 percent water, depending on the fire fuel and type and class of foam. For instance, to make 100 gallons of foam using a three-percent ratio, a proportioner would measure out three gallons of foam to 97 gallons of water.
Most proportioners operate with balanced – or positive – pressure and directly inject the appropriate amount of foam into the discharge side of fire pumps. However, some inject on the intake side for around-the-pump foam capabilities.
There are more than a half dozen foam proportioner manufacturers. Darley, FoamPro, Hale, Waterous, Robwen are some of the more prominent ones. Pierce Manufacturing has its own proprietary Husky proportioning system, while Ansul, National Foam and William Fire & Hazard Control make larger units often used in the petrochemical industry.
Most foam proportioners have similar features and delivery methods, but there are some nuances and features that make each system just a little different.
Robwen Bladder System
Robwen Inc., headquartered in Los Angeles, Calif., was one of the first foam injection system manufacturers to make products available to the fire service.
Dennis Langley, sales manager for Robwen, said the company started producing foam proportioners in 1988 and has continued with the same basic design, making one improvement in 1996 by switching from aluminum components to brass.
Langley said the simple design has withstood the test of time because it uses no external power to operate, relying solely on the flow of water and a differential pressure valve. Foam in a bladder within a tank is squeezed by the water pressure to inject foam into the fire stream, he explained. A seven-pound differential puts pressure on the bladder, and as it collapses, the foam is injected. When the bladder is empty, it can be refilled and the process is started again.
The Robwen system is very popular with wildland firefighters, and the company has developed an apparatus fixed system that can be found from coast to coast.
Langley said the cost of ownership is slightly less than other competitive products and the cost of maintenance over the life of the product is significantly less. There’s no calibration necessary, he said, as a machined metering valve is the primary controller for the system with no adjustments or electronics that need attention.
“If water flows, foam will flow,” he said. “Our system will work every single time it’s used.”
One of the biggest names in foam proportioning is FoamPro, a company based in New Brighton, Minn., that has been around nearly as long as Robwen, entering the direct injection foam system market in 1989.
One of the strongest features of FoamPro injection systems are the motors. FoamPro is part of Pentair, a world-wide company involved in filtration, flow technologies and the pool and spa business, and it has a wide variety of motors available for foam solution injection. Marketing Manager Mike Dupay said the company selected two and three plunger pumps for injecting foam solutions.
Accuracy Saves Foam
“We had the advantage to pick the foam pump we wanted, and we picked the one we thought would work the best for our applications,” he said.
FoamPro makes systems capable of handling Class A and Class B foam concentrates in percentages from .1 to 10 percent with electric and pto-driven motors, according to Dupay.
Because the system measures water flow as well as the flow of foam with a micro-processing computer, the injection of concentrate into the fire stream is very accurate, he said. “When foam costs $20 to $30 per gallon, being accurate is very important,” he said.
Features of the FoamPro system include continuous operation by refilling the foam cell either manually from buckets or with a proprietary electric refilling system. Bladder systems, on the other hand, must shut down for refilling, he said.
FoamPro makes a multiple point foam injection system that allows for different foam percentages to be flowed from different discharges, as well as proportioners that will flow Class A and Class B foams through the same system. The system flushes with clear water for at least eight seconds prior to switching classes of foam, Dupay said, because mixing foams will gum up most systems and create maintenance nightmares.
“We’ve chosen the most efficient and most accurate components available,” he said.
W.S. Darley & Company, through its Odin Foam division, headquartered in Toledo, Ore., makes an affordable direct injection foam system with two models – Fast Foam 50 and Fast Foam 250 which deliver one percent of foam at 50 gpm and one percent at 250 gpm.
“We offer an economical direct injection system compared to some of the other systems available,” said Jim Guse, Odin’s foam division manager.
He said the Darley/Odin system is balanced pressure system that doesn’t use a bladder like the Robwen system. “Instead, we use an auto balance valve, the same one we use for our CAF system,” Guse said.
Darley Fast Foam
The system, he said, uses a signal that measures water pressure and a diaphragm to balance the water and foam pressure. The greater the pressure differential, the more foam gets injected.
“You get the benefit of a direct injection system without the high cost of printed circuit boards and paddle wheels,” he said. “We offer good accuracy at an affordable price.”
Darley’s Fast Foam systems are popular on wildland brush trucks, Guse said, and the 250-gpm models can be used for limited structural firefighting attacks.
Hale Products, a division of IDEX, based in Conshohocken, Pa., has been in the foam business since 1999 when it acquired Foam Master Electronics. The company’s foam products have improved greatly since then, especially with Hale’s acquisition of Class 1, an electronics control business based in Ocala, Fla.
Hale makes a flow-based direct inject proportioner line called FoamLogix. “Our system works over a wide range of flows and pressures,” said Dominic Colletti, the company’s global foam systems product manager.
Hale uses electronic microprocessors to measure flow rates and accurately dispense foam for “cost effective” foam applications, he said.
As ethanol becomes more prevalent as an alternative fuel, Colletti said he’s getting e-mails and calls from fire departments looking for equipment to confront the threat. He believes the FoamLogix 5.0 model is the answer, as it’s capable of flowing high volumes of foam, including alcohol resistant and Class B foams, which are thicker.
Hale uses rotary gear pumps for its proportioner systems rated at 3.3 gpm and 5 gpm, both of which are patented. A lower cost 2.2 model, which uses a piston pump to inject foam into the discharge, is also available.
With Class 1 as part of the company, Colletti said Hale’s foam proportioners benefit from electronic accuracy and digital read outs that measure and display total water and foam consumption. He said Hale takes detailed measurements of foam output in real time to ensure accuracy.
“We have great electronic capacities in this company as well as very high mechanical pump expertise,” Colletti said.
In 2006, Waterous introduced probably the most sophisticated foam system of all, called the Advantus. The company doesn’t even call it a proportioner.
“We call it a foam management system,” said Geary Roberts, president of Waterous Arizona operations in Peoria, Ariz. He said Waterous uses conductivity to measure foam content in the fire stream – before the injector and after the solution has been added – and compensates according to the operators’ preferences for an extremely accurate foam delivery system.
Waterous Hydra-Cell Pump
The Advantus uses a Hydra-Cell pump from Wanner Engineering to inject the solution, according to Roberts, who said it is the best pump available for foam management. Two-year warranties, double those of its competitors, back all of Waterous’ foam systems, Roberts said.
Waterous also makes a more traditional and affordable foam proportioning system called the Aquis, which uses a plunger pump for injection. Two models are available – one rated at up to 1.5 gpm and the other at 2.5 gpm – and can be set up for dual tank operations.
Roberts is passionate about firefighting foam. He was a career firefighter, engineer and captain in Glendale, Ariz., who founded Pneumax, which was sold to Waterous in 2000 and became it’s foam division.
“There are some fire departments that still do not have foam, and I don’t get it,” he said. “I don’t care whose system you have, everyone should have foam.”