Newer combination nozzles
Reference is made to “Building a Case for Smooth Bore Nozzles” (Todd Connors, February 2006) and other articles of late that do not address the newer available nozzles. Connors’ information on the background of nozzles is complete and accurate. But, it seems that he is comparing the old 100-psi combination nozzles to smooth bores. Many firefighters are still unaware of the newer low-pressure combination nozzles and their capability. Comparing 100-psi fogs to smooth bores is unfair and old school. These old nozzles were of an inferior design that required more pressure to achieve their desired results.
Connors mentions that his men were impressed with the knockdown ability and steam conversion of the smooth bore over the fog nozzle. If they had been comparing the low-pressure combination at an equal flow (apples to apples), they would have seen absolutely no difference in stream quality, reach, nozzle reaction, or knockdown ability. In fact, when operating these streams side by side, they are identical. Even the newest edition of the Firefighters Handbook by Delmar states on page 285 that the new combination nozzles have a solid stream with great reach and penetration abilities and, in fact, some are better than solid stream nozzles.
You can overpump or underpump a nozzle, and it will perform just fine. The manufacturer-specified nozzle operating pressures are just guidelines. If you pump the same nozzles at 50-psi tip pressure, you will get approximately 160 gpm from both. Both streams look identical, and physics tell us that they are.
At 50 psi, both nozzles produce 2.7 gallons per second (mass) and exit the nozzle at 58.5 mph (velocity). Mass × velocity equals force. Both nozzles have a nozzle reaction of about 58 pounds. Both have a reach of more than 100 feet, and the combination had a slightly better reach (much more than the 20 feet we require indoors).
These new combination nozzles do not have more nozzle reaction at equal flows. When we are comparing the larger nozzles, a 1 1/8-inch tip produces 250 gpm @ 50 psi, whereas the low-pressure combination nozzle also produces 250 gpm @ 50 psi. You can also increase both to 75 psi for even greater flow and reach. The combination nozzle does have slightly less nozzle reaction at these higher flows (89 pounds vs. 95 pounds for the smooth bore when both are at 50 psi). I won’t go into the reasons for this here.
With regard to kinking issues, as we decrease pressure to the 50 psi that a smooth bore requires, the result is a softer line that will be more prone to kinks. Firefighters are going to have to be more diligent in their line management when using 50 psi at the tip.
It used to be said that the fog nozzle had a hollow stream when operating in a straight stream position. This is true only for the first few feet and is actually an advantage, as the negative pressure draws the stream into a tight pattern. When one drop of water touches another, the molecules combine. They cannot stay separate, and a pitot tube reading at four feet out will give you the same reading as on a smooth bore.
As far as steam production is concerned, a fog pattern converts much more quickly and should be used only in certain circumstances; however, either stream when overapplied will upset the thermal balance.
The bottom line is that the new low-pressure combination nozzles produce a stream equal to or better than the smooth bores, and they are equally as effective in fire situations. Maybe the Clearwater firefighters were resisting the change to smooth bores, realizing that the right combination nozzle could do everything a smooth bore can do while offering more versatility!
Ron Eilken
Lieutenant
Des Plaines (IL) Fire Department
Todd Connors responds: I agree with Lt. Eilken’s comments on the low-pressure fog nozzles to a point. We currently use 100-psi automatic fog nozzles that flow between 60 and 200 gpm. I prefer the 50-psi fog nozzles at 150 gpm, with which, as Eilken states, you can flow more gpm. The lower-pressure fog nozzle produces a lower nozzle reaction similar to that of a smooth bore nozzle. This is a key issue with the limited personnel situation in most fire departments.
As far as reach is concerned, Eilken is correct that the smooth bore and low-pressure fog nozzles have similar reach. I disagree with the issue of penetration. A fog nozzle produces droplets of water; that is the way the nozzle is designed. A smooth bore produces a solid mass of water.
Yes, a smooth bore has water droplets that drop off the solid mass of the stream; however, there is still a mass of solid water. A fog nozzle, regardless of high or low pressure, produces a mass of droplets. The larger the mass of water, the more Btus it will absorb. The more Btus the water can withstand, the farther the water can enter into the fire-heated area. The farther the water can travel, the greater the ability to reach the heated material emitting the gases. The greater the ability to reach the heated material emitting the gases, the faster the heated material is cooled. The faster the heated material is cooled, the lower the amount of steam produced. The lower steam production is good not only for the firefighters but also for any victims we must assume are inside the structure. Life is our primary goal.
Having said that, I still believe there is a time and a place for both a smooth bore and a fog nozzle. I strongly believe low-pressure fog nozzles are beneficial over the high-pressure fog nozzles. As Eilken states, the lower nozzle reaction is key between the old and new fog nozzles. However, a smooth bore must be the weapon of choice in an aggressive interior attack because of the greater penetration and knockdown abilities.
Katrina article “challenges governments to plan for large-scale events”
I just finished reading Editor in Chief Bobby Halton’s “Katrina: Size, Scope, and Significance” (May 2006). A job well done. He has given the nation’s fire service leaders some strong encouragement to continue to challenge their governments and to become involved in larger-scale event planning and preparation. I applaud him for this.
His use of strong words like “incompetent,” “failure,” “poorly trained,” “dysfunction,” and “inexcusable” should become a gateway that leads to more fire chiefs’ standing up to the lack of concern and laissez-faire attitude of city managers and other governmental officials.
His identification of new and existing management teams and groups will act as a “guidepost” to fire chiefs who want to get involved and to know more about what they need to do.
One suggestion: In a future issue, it would be very helpful if an organizational flowchart showing the federal and state organizations, some key names, and some contact points fire chiefs need to know about were included.
Jim Murtagh
Deputy Chief (Ret.)
Fire Department of New York
Congratulations: “extremely great issue!”
The May issue of Fire Engineering is simply fantastic! Having been there, I know how much work is involved in putting together a “Special Dedicated Issue.” The staff did a superior job with the Katrina disaster coverage. It should go a long way toward assisting emergency management organizations in their preparedness to handle similar disasters. In fact, it should become a handbook for every Emergency Management Committee (EMC) staff and board member.
I am going to recommend to our county EMC that it purchase enough copies for everyone involved and also will try to filter the same message up to the Provincial level.
Steve Cooke
Chief
Central Huron Fire Area
Clinton, Ontario, Canada
