By Paul Shapiro
When we respond to a fire, we are expected to be able to extinguish it in a quick and efficient manner.
1 This 1985 American La France with a 1,250-gpm pump is capable of 3,000 gpm through its four-inch Stang gun. (Photos courtesy of author.)
For the most part, I think the fire service has this down. Of course, nothing is perfect. Every once in a while, we experience unexpected problems that challenge us. One such challenge is a large-water-demanding fire that requires us to not only get enough water from water supplies to overwhelm the British thermal units (Btus) but also deliver or discharge the water onto the fire to get the knockdown as quickly as possible. This is where a lot of fires go bad.
We have all seen the big “super pumpers” that are used in refineries across the nation and all over the globe. These pumpers are designed to flow thousands of gallons per minute (gpm) to protect property (the oil) worth billions of dollars. These facilities are set up with water delivery systems that can support the flows that super pumpers are capable of. We are generally talking about flows in excess of 5,000 gpm. In fact, one available unit can flow 10,000 gpm when using a pressurized water delivery system.
2 The stack tips on this four-inch gun start at 13⁄8 inches and go up to 2¾ inches.
3 Note the gated Siamese valve on the discharge side of the evolution in the background and the short section of LDH. This creates too much turbulence that causes pressure loss. The Siamese valve connected directly to the inlet of the gun works better.
There are also units with pumps rated at up to 3,000 gpm that can produce flows reaching close to the 5,000-gpm mark when used in the appropriate pressurized water delivery evolutions. Remember that pumps are rated at draft at 150 pounds per square inch (psi) net pressure. When a pressurized incoming water supply is used, it subtracts its incoming pressure from the overall pressure, thus allowing the pump to produce higher than rated flows. F
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