by Alan Robidas
Over the past several decades, technological advances have helped to improve much of our firefighting equipment. However, one critical piece of equipment has been neglected for far too long: the solid stream nozzle tip.
Since the introduction of the steam engine or maybe as far back as leather riveted hoses, tip sizes have generally remained the same. Tips available commercially have consistently been sized in increments of eighths or sixteenths of an inch, with some sizes not available at all.
At the 1912 National Fire Protection Association (NFPA) Annual Meeting in Chicago, Charles H. Fox of Ahrens-Fox proposed changing solid tip nozzles to be measured in caliber. His argument was that the 1/8-inch increments were arbitrary and bore no relationship to the job the nozzles were expected to do. The records show his remarks were received with great enthusiasm and with every intention of official action; however, for some unexplained reason, nothing further was done with this. (Kimball 1966, 11)
Although it may seem that these sizes must remain constant because of formula or nozzle/hose theory constraints, this is simply not true. Major technological advances in hose construction have improved efficiency and increased flow capacities. But while flow capacities have increased, the most important piece of the solid tipped hoseline equation—the tip—has largely been ignored. If we aren’t maximizing the flow rates on our hoselines, why not use smaller hoses? You wouldn’t put a 7/8-inch tip on a 2½-inch hoseline, so why use a 1-inch tip on a 2-inch line? Why leave unused water in the hose? Tip sizes should correlate with the maximum efficient flow rate that a hose has to offer.
The solid tip selection needs an overhaul. In a profession in which we are continuously asked to “do more with less,” we need more than ever to strive for efficiency. One way to do this is with solid tip nozzles that are measured in flow rate, as opposed to inches of diameter. Obviously, each flow rate would have a correlating orifice size, but why not a 0.974-inch diameter tip that flows 200 gallons per minute (gpm) at 50 psi to maximize the matching flow capacity of 1¾-inch hose? Or a 1.089” diameter tip to maximize the 250 gpm flow capacity offered by 2-inch hose? It would make sense to keep the 1¼-inch tip approximately the same for use on 2½-inch handlines (not because the flow capacity is reached as 2½-inch hose can flow far more than required by a handline, but more because flow rates higher than 325 gpm become difficult to handle). This nozzle tip revolution would also align us with how we do business on the fireground. When was the last time you heard someone on the radio state that their nozzle flow rate was at 266 gpm? We don’t hear it because, as pump operators, the odd numbers become trivial. Doesn’t 200, 250, or 330 gpm make more sense when calculating friction losses?
In the meantime, we will continue to just come as close as we can to efficient flow rates on our solid tip lines: 15/16 of an inch for 1¾-inch hose, 1 1/16 inches for 2-inch hose (yes, this tip is available from one of the major manufacturers and produces a nice stream), and 1¼ inches for 2½-inch hose. Unfortunately, the previously noted nozzle/hose combinations represent the most efficient options commercially available. The reality is that many fire departments are not even matching these flow rates from their lines. The charts shown highlight some of the more common tip choices and what these combinations bring to the table. The charts also indicate the efficiency of these combinations, keeping in mind that 100 percent efficiency is optimal.
Though this article has been limited to handline tips, the same theory can be applied to all solid tips, and, even to some degree, all hose/nozzle combinations. Even when we employ fog streams, it rarely makes sense to flow lower rates through larger hoses. This would be the equivalent of a marathon runner carrying a gallon of water that he is not allowed to drink throughout a race. Play with the ideas and think outside the box. If you want a certain flow rate, figure out the orifice size using the Freeman Formula, (Iseman 1984, 266), then take a nozzle tip to a local machine shop to get rebored. Another idea is to tap resources like high schools or vocational technology programs specializing in machining. These students would love the opportunity to work on practical pieces of equipment, and there would probably be little to no associated costs. Just because something isn’t available or hasn’t changed in a century shouldn’t mean that we are stuck with a “close is good enough” attitude. Don’t leave water in the hose--put it where it belongs.
Kimball, Warren Y. Fire Stream Fundamentals. Boston: National Fire Protection Association, 1966.
Iseman, Warren E. Fire Service Pump Operator’s Handbook. New York: PennWell, 1984.
Alan Robidas is a lieutenant with Concord (NH) Fire Department and is currently assigned to Tower 1 on Battalion 3. He started his career with Somersworth (NH) Fire Department in 2000. He has an associate’s degree in fire science and is a certified New Hampshire Instructor as well as a Level II Firefighter.