BY JIM REGAN AND ANDREW A. FREDERICKS
Surprisingly, very little research has been conducted into the development of effective solid fire streams. With fire departments returning to the use of solid stream nozzles in large numbers, we thought it was important to explore various factors that affect the quality of the solid streams produced by handline nozzles and master stream appliances. Although solid stream nozzles are simple to operate and maintain, the importance of producing streams of superior quality should not be taken for granted and will result in safer, more effective performance on the fireground.
According to the Fire Protection Handbook, Thirteenth Edition: “Much of the fundamental data now employed in hydraulic work in fire protection was developed in a series of extensive investigations conducted by John R. Freeman in 1888 and 1889.”1 Freeman compared streams from more than 40 different nozzles, and the data collected from these tests resulted in the design of the “Underwriter’s Playpipe,” still widely used in flow testing of all kinds. Freeman also defined what he felt constituted a “good” fire stream, and these factors have remained undisputed for more than 110 years. He defined a “good” fire stream as one that
- had not lost continuity by breaking into showers of spray;
- appeared to shoot 90 percent of the volume of water inside a 15-inch-diameter circle and 75 percent of the water inside a 10-inch-diameter circle as nearly as could be judged by the eye;
- would probably be stiff enough to attain height or distance in fair condition, even if a fresh breeze were blowing; and
- with no wind blowing, would enter a room through a window opening and strike the ceiling with force enough to spatter well.2
What factors must you consider to obtain a “good” fire stream from a solid stream nozzle? Some are obvious and apply to nozzles of all types, but each is vitally important in attaining a stream of the highest quality, which in turn translates into improved performance and a higher degree of operational safety.
Triple stacked tips (1 1/2-inch outer tip) and 10.5-inch vane type stream straightener. Well-designed stacked tips should act like a single, long nozzle tip. (Remaining photos by Jim Regan unless otherwise noted.)
The first factor is the nozzle pressure. Most handline solid stream nozzles are designed to operate at 50 psi, master stream nozzles at 80 psi. Too high a pressure will cause the stream to break up prematurely; too low a pressure, and the stream will falter.
Nine-inch tip (1 1/2-inch orifice) with 10.5-inch vane type stream straightener and short “honeycomb” stream straightener.
The second factor concerns the nozzle tip size. The tip selected should be properly sized for the required flow. Although some leeway exists with tip size, trying to squeeze more volume through an undersized tip will result in premature stream disintegration. Too large a tip, and the sheer weight of the water being discharged will produce a nozzle reaction force that may be difficult to control.
Stang Aeroglas Shaper Tip(R) with 10.5-inch vane type stream straightener and short “honeycomb” stream straightener.
A third factor is the condition of the nozzle. Burrs or other imperfections in the waterway (tip and shutoff assembly) will harm the stream. A nozzle tip “out-of-round” will significantly compromise stream quality.
A fourth factor concerns the hose layout (length, size, deployment). Hose supplying the handline and master solid stream nozzles should be of sufficient size to provide the required flow and deployed so as to minimize turbulence. Turbulence caused by kinks in a handline, particularly when they are close to the nozzle, will wreak havoc with solid stream quality.
The fifth and final factor is the design of the nozzle or the appliance to which it is attached. This includes the length of the nozzle tip(s) and the use of a stream straightener (also called a stream shaper or discharge pipe) to reduce turbulence.
The next section will examine and compare various master stream nozzle configurations in an effort to produce the highest quality solid stream.
In August 1999, with the assistance of Captain Kenneth Wojtecki and the members of Chicago Fire Department Engine Company 47, a series of subjective tests were conducted utilizing various tips and stream straighteners attached to a portable multiversal nozzle. Three types of master stream nozzle configurations were evaluated:
- 1½-inch tip (triple stacked tips) with long (10.5-inch) stream straightener;
- 1½-inch interchangeable tip (nine inches long) with both long stream straightener and short “honeycomb” stream straightener; and
- 1½-inch Stang Aeroglas Shaper Tip® with both long streamstraightener and short “honeycomb” stream straightener.
The portable multiversal nozzle was fed by a four-inch supply line looped around the front of the appliance for stability. The nozzle pressure was measured at 80 psi for each series of tests. Stream quality was evaluated by those present for conformance to Freeman’s definition of a “good” fire stream.
Since smoother or more laminar flow into and through a nozzle and tip assembly produces a better fire stream, reducing turbulence is essential to achieving “good” stream quality. As can be seen in photos 5-7, the stream quality produced by the first and third tip configurations were essentially identical (photo 5-triple stacked tips with long stream straightener; photo 7-Stang Aeroglas Shaper Tip with both stream straighteners). The second tip configuration (photo 6), even with the addition of the “honeycomb” stream straightener, produced a demonstrably inferior stream. Based on these limited evaluations, it appears that the length of the tip is at least as important as the length and type of stream straightener in producing high-quality solid master streams.
Stream produced by the tip configuration in photo 2 (80-psi nozzle pressure).
One of the major concerns expressed by firefighters using solid stream nozzles is that, as a result of the lower nozzle pressure, the handline has an increased tendency to kink. Kinks can severely restrict the flow and will have a decidedly negative impact on stream quality, particularly when the kink occurs close to the nozzle. It has been said that the first five to 10 feet of hose behind the nozzle should be considered part of the nozzle and must be kept as straight as possible to ensure a stream of “good” quality. Under fireground conditions, this is often very difficult to achieve. Even relatively small bends in the hose can have an adverse effect on the stream.
Stream produced by the tip configuration in photo 3 (80-psi nozzle pressure). Even with two stream straighteners, the stream appears less cohesive, breaks up earlier, and is noticeably inferior to the stream in the photo directly above.
We wanted to evaluate the effect that a small “honeycomb” stream straightener would have on handline stream quality. We utilized the Chicago Fire Department’s standard “shutoff pipe” (2½-inch solid stream nozzle fitted with a 1¼-inch tip) for the tests. As can be seen in photos 9 and 10, the addition of the stream straightener between the controlling handle (shutoff) and the tip results in a smoother, higher quality stream. The use of a stream straightener causes the turbulent flow entering the nozzle tip to “recover” some of its laminar characteristics, even when a bend in the handline is formed in close proximity to the nozzle. Stream straighteners are now available specifically for handline applications and are rapidly attracting a loyal following.
Keep in mind two cautions when using a handline stream straightener. First, one of the advantages of solid stream nozzles is that they do not clog readily. Although a stream straightener can have a very beneficial effect on stream quality, it introduces both a clog point and an increased potential for ice formation in the waterway. Second, care must be exercised in the placement of the stream straightener. If it is placed between the hose and nozzle, the line would have to be shut down or clamped and the nozzle unthreaded from the hose should it become clogged with debris. It must be placed between the controlling handle (shutoff) and the tip. If it becomes clogged in this position, the nozzle can be closed and the tip and stream straightener easily removed to clear the obstruction.
Another potential means of improving the quality of handline solid streams is to lengthen the nozzle tip. We compared the streams produced by the standard handline nozzle used by the Fire Department of New York (FDNY) and an identical shutoff equipped with a longer tip. The nozzles were attached to portable master stream devices to maintain identical 35-degree discharge angles and to keep turbulence to an absolute minimum. The FDNY nozzle used with 1¾-inch hose consists of a 15/16-inch tip and a 1½-inch shutoff (13/8-inch clear waterway). The tip is 3.75 inches in length. The manufacturer of the standard FDNY nozzle supplied us with three six-inch-long prototype tips (15/16-, one-, and 11/8-inch) for testing. In a series of side-by-side comparisons to evaluate effective stream reach and overall stream quality, the six-inch-long, one-inch-diameter tip produced the smoothest stream with the longest reach. In addition, flow volume increased by approximately 40 gallons per minute over the standard 15/16-inch tip.
This is the Chicago Fire Department’s 2 1/2-inch “shutoff pipe.” It is fitted with a 1 1/2-inch nozzle tip.
These test results subjectively confirm what many busy FDNY engine company officers and firefighters have believed for years: Longer, larger tips “kill” fire much more effectively than smaller, more compact solid stream tips. Obviously, a larger tip means more flow volume at the same pressure, but it is felt that a longer tip maintains better stream performance (effective reach, compactness) as the handline is turned and bent while advancing through the narrow hallways and crowded rooms of New York’s brownstones, tenements, and apartment houses.
Stream produced by the Chicago “shutoff pipe” at 50-psi nozzle pressure.
Another interesting fact concerning nozzle tip length affects those fire departments that have adopted “breakapart” nozzle systems incorporating solid stream “slug” tips. We assumed that the stream from such a short tip would be rather sloppy; but, in fact, with proper nozzle pressure it is quite good. The reason, we have learned, is that the shutoff itself acts like an extension of the nozzle tip, creating, in essence, a longer tip and a “cleaner” solid stream.
Stream produced by the Chicago “shutoff pipe” at 50-psi nozzle pressure with a short, “honeycomb” stream straightener inserted between the shutoff and tip. There is a noticeable improvement in stream quality.
Finally, when discussing the quality of solid streams produced by handline nozzles, one additional point bears mentioning: It is vital that the ball valve be fully open during fire attack operations. Otherwise, the projection into the waterway caused by the partially closed valve will disrupt the stream and greatly diminish its characteristics.
This solid stream handline nozzle incorporates a small, 1 1/2-inch stream straightener.
It is irrelevant to discuss the quality of the solid stream produced by a handline nozzle if the nozzle reaction burden makes the line unmanageable. A major benefit of solid stream nozzles is that at equal flows, a solid stream nozzle will produce approximately one-third less reaction force than a 100-psi fog nozzle set to straight stream position. But many times, solid stream nozzles are still difficult to control, and to discover the reason for this requires that we explore the concept of nozzle reaction a little more completely. Elementary Newtonian physics teaches us that when a force is applied to an object, the object (in this case the water being discharged from the nozzle) exerts an equal but opposite force (in this case known as nozzle reaction). Nozzle reaction, sometimes termed “backpressure,” is a force (measured in pounds) exerted in the opposite direction of stream discharge. If this force is too great, the nozzleman will have to fight the tendency of the nozzle to slide backward through his hands, rapidly fatiguing his arm muscles and reducing fire extinguishing effectiveness in the process.
Small stream straighteners can have a very beneficial effect on the quality of solid streams produced by handline nozzles. (Photos by Andrew A. Fredericks.)
Nozzle reaction is a factor of both the nozzle pressure and the weight of the water being discharged. Since higher flows mean more water weight, nozzle reaction increases as tip size increases. Studies have shown that a nozzle reaction force exceeding approximately 70 pounds is too difficult for a single firefighter to handle safely. While ideally a firefighter will never be left alone at the nozzle, in reality, the backup firefighter (if present) is often several feet behind the nozzleman pulling hose around corners and struggling to keep the line moving. How, then, do we reduce nozzle reaction without sacrificing the flow volume that is critical for expeditious fire control and firefighter safety? The solution is twofold: First, we must decide on a minimum safe fire flow for both residential and commercial fires. Second, we match the appropriate tip size capable of producing this minimum flow to the size of the nozzle crew and their average level of training and experience.
For some reason, many firefighters believe that the FDNY standard 15/16-inch nozzle tip is the only tip size that can be effectively used with 1¾-inch handlines. This is simply not true. At 50-psi nozzle pressure, a 15/16-inch tip will flow 182 gpm and produce a nozzle reaction of approximately 66 pounds. While this is within the safe range for handling by a single firefighter, in reality, it can be very difficult to control and advance a line flowing 182 gpm unless the nozzleman is well experienced. In addition, if the nozzle pressure exceeds 50 psi (a common problem among pump operators accustomed to supplying 100-psi fog nozzles), the reaction burden may quickly become excessive. Although the 15/16-inch tip works well in New York City, many fire departments lack the staffing to use such a large tip successfully. For these departments, the 7/8-inch nozzle tip may very well be the answer.
Given the nature of the contemporary fire environment, it is our contention that residential fire flows less than 150 gpm are unsafe and do not provide efficient use of 13/4-inch hose. At 50 psi, a 7/8-inch tip will flow approximately 160 gpm with a nozzle reaction burden of only 57 pounds. In the sidebar “The Retooling of the One-Inch Smooth Bore Tip” on page 62, the St. Petersburg (FL) Fire Department found the 7/8-inch tip ideal. The authors point out that with a 15/16-inch tip, any overpressurization causes excessive nozzle reaction. If the nozzle is underpressurized, there is an increased tendency for kinks to form. Unless the line can be maintained straight behind the nozzle (unlikely, unless a backup firefighter is always behind the nozzleman), kinks that form near the nozzle can be very dangerous. When the line kinks, the flow is drastically reduced. As soon as the kink is straightened, the sudden release of energy results in a pressure surge at the tip that can cause the nozzleman to lose control of the line. The experience of the St. Petersburg Fire Department indicates that problems with kinks and line control are far less severe when a 7/8-inch nozzle tip is used.
Of course, if a sufficient number of experienced personnel are available, tips larger than 7/8-inch can be used with great success. A favorite among busy FDNY engine companies is the one-inch solid bore tip. It produces a reaction force of about 75 pounds at 50-psi tip pressure while flowing more than 200 gpm. FDNY engine companies can use this line effectively because their staffing always provides for a nozzleman and backup man (under an officer’s supervision) to work together as a team. This eases the reaction burden and permits effective handling of the nozzle. Regardless of the tip size or nozzle type, safe and effective use of any handline nozzle requires constant practice and a mastery of proper nozzle mechanics.
As far as a minimum required flow for commercial building fires is concerned, 2½-inch hose and flows of at least 250 gpm are strongly recommended. Suffice it to say that the safe and effective use of 2½-inch handlines involves several additional considerations that will not be addressed here. For more information on the need for and proper use of 2½-inch handlines, see the articles “1¾-Inch Hose: The Booster Line of the ’90s?” by James J. Regan (Fire Engineering, September 1993) and “The 2½-Inch Handline” by Andrew A. Fredericks (Fire Engineering, September 1996).
You must adhere to the basics of proper fire stream development regardless of the type of nozzle you use. An adequate water supply, proper nozzle pressure, proper tip size, the correct hose layout, and equipment in satisfactory condition are essential to the development of a “good” fire stream. Our limited subjective analysis reveals that the type of stream straightener, the length of the nozzle tip, and the elimination of kinks in the handline will produce streams that are much more likely to meet the criteria established by Freeman more than 100 years ago and will keep firefighters safe as they rise to meet the challenges posed by today’s fireground.
- Fire Protection Handbook, Thirteenth Edition, (Boston: National Fire Protection Association, 1969), 12-31.
- Ibid, 12-33-35.
JIM REGAN is the senior vice president of Star Technical Risks Agency Inc. and a member of the Western Springs (IL) Fire Department. He graduated as a fire protection engineer from the Illinois Institute of Technology and has been a registered professional engineer in Illinois since 1973.
ANDREW A. FREDERICKS, a 20-year veteran of the fire service, is a firefighter with Squad 18 in the Fire Department of New York (FDNY). He is a New York state-certified fire instructor at the Rockland County Fire Training Center in Pomona, New York, and an adjunct instructor at the New York State Academy of Fire Science. He has two bachelor’s degrees, one in political science and one in public safety, with a specialization in fire science, and a master’s degree in fire protection management from John Jay College of Criminal Justice. He developed the Fire Engineering “Bread and Butter” Operations videos Advancing the Initial Attack Handline (1997), Stretching the Initial Attack Handline (1998), and Methods of Structure Fire Attack (1999).