"I'm happy with what I have, so why confuse me with another hose size?" While there have been hundreds of thousands of discussions throughout the fire service on, for example, the flow merits of one nozzle or the penetration qualities of another, it must be understood that the most important...
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"I'm happy with what I have, so why confuse me with another hose size?"
While there have been hundreds of thousands of discussions throughout the fire service on, for example, the flow merits of one nozzle or the penetration qualities of another, it must be understood that the most important element of attack line operation is gallons per minute (gpm). Just when fire departments are realizing the need to flow more water on more intense fires, however, many are being forced to operate with fewer members. This shortage becomes critical during first-arriving-company operations, when relatively few on-scene firefighters have to simultaneously perform command, size-up, rescue and fire suppression operational tasks.
Photo by David P. Fornell
Looks can be deceiving. Two-inch hose generates only about half the friction loss of 1 3/4-inch hose but when they are laid side by side, it is hard to tell them apart. One way to identify the larger line is to compare the size of the coupling bowls, in this case, making the two-inch orange hose easy to spot.
Common sense tells us that fire service planners need to address the problem of increasing the gpm flow rate per line to better cope with larger fires but must also keep in mind that for that flow rate to be effective, the line has to be capable of being maneuvered inside a fire building by as few as two firefighters. For years, the only practical hoseline size that could flow over 200 gpm was 2 1/2 inches. But 2 1/2-inch line, while it can be easily stretched before it is charged, becomes almost impossible to operate offensively (moved rapidly) inside a building by a crew with limited staffing.
In a search for an answer, it's been described how 1 3/4-inch line could be designed to address the problem of the high-flow handline. This has led many departments to believe manufacturers' claims that the 1 3/4-inch line could flow up to 300 gpm on the fireground; however, the high engine pressures (above 300 psi) needed to generate this flow rate makes the line extremely stiff and hard to handle. Coupled with extremely high nozzle reaction forces, this makes flowing more than about 180 gpm through a 1 3/4-inch line impractical and, at times, downright dangerous on the fireground.
Facing the paradox: 2 1/2-inch line is too heavy and 1 3/4-inch line is too difficult to handle.
It's a matter of physics that to accomplish extinguishment, you must put enough water on the fire to overcome the heat being produced. That law deals with energy exchange during the physical reaction called combustion and cannot be changed. Simply put, if you don't flow enough water, the fire will not go out and the interior operating crew will remain in increasing danger until withdrawn.
If you want to flow more water with a limited staff, a good place to begin is to design a line that provides a relatively easy-to-handle conduit (hose size) coupled to a nozzle that flows a lot of water but doesn't generate unmanageable nozzle reaction force. Let's first discuss the merits of hoseline size.
While many departments are satisfied with their present handlines and attack strategy when there are enough personnel on the scene to enable the quick deployment of 2 1/2-inch initial or backup lines, a number of progressive fire officers are now investigating the addition of a "day line" one that provides for high flow rates yet can be easily and quickly deployed by the first-arriving firefighters when relatively few people are available, such as during daytime hours.
Because of its ability to provide easily attainable flow rates up to about 250 gpm, many of these officers are evaluating two-inch hoselines coupled to low-pressure or smooth-bore nozzles as an effective alternative to 1 3/4-inch and 2 1/2-inch hoselines when staffing is limited. Two-inch hose is a relatively common size in the marine industry and has been available for years. Standard practice on ships has been to equip the hose with two-inch threaded couplings; in some areas of New England, the use of two-inch hose equipped with one-third-turn Storz couplings is relatively common.
Probably the most practical method of utilizing two-inch hose without having to inventory a number of adapters is to equip it with couplings having common 1 1/2-inch hose threads. Until a few years ago, this could have been accomplished only by using complicated and expensive five-part couplings. These couplings cost about $50 to $60 per set, which made the per-foot cost of two-inch hose as expensive as 2 1/2-inch line. Sensing a need in the market, one coupling company developed an expansion ring drawbar that allowed the installation of inexpensive three-piece couplings on two-inch hose. This had the effect of materially reducing the per-foot cost of two-inch line to little more than 1 3/4-inch hose.
Photo by David P. Fornell
Engine 9 of the Danbury, CT, Fire Department replaced its 2 1/2-inch pre-connect with a 300-foot line of two-inch hose equipped with a 1 1/8-inch smooth bore. This combination gives the engine company an easily deployed and easily handled line that flows 240 gpm and which can be quickly stretched into the commercial structures or to the rear of the large homes or apartment buildings prevalent in its congested response district.
Photo by David P. Fornell
When considering the use of two-inch line, it is important to evaluate nozzle equipment that generates high flows at low nozzle operating pressures. At left is a smooth-bore nozzle with a 1 1/8-inch tip that provides 250 gpm at 45 psi nozzle pressure. At right is a Boston combination tip that provides 250 gpm at 50 psi nozzle pressure.
|Flow Rate||Midrange Automatic||200 gpm at 75 psi||250 gpm at 75 psi||Smooth-Bore (tip size)|
|230||116||117||77||72 (1 1/8")|
|240||121||126||81||78 (1 1/8")|
|250||126||135||85||89 (1 1/8")|
Advantages & Disadvantages
Two-inch line offers a number of advantages:
- It is not much larger in flat width than 1 3/4-inch hose. Often, the same amount of two-inch hose will fit in the hose bed space as the smaller line.
- It will deliver the same flow as 1 3/4-inch line at about half the engine pressure, or almost double the volume at the same engine pressure.
- It has the same 1 1/2-inch thread size couplings as other attack lines and is as easily deployed by as few personnel.
Two-inch line also has some disadvantages:
- It is somewhat heavier than 1 3/4-inch hose when filled with water, approximately 65 pounds per 50-foot length vs. 54 pounds for 1 3/4-inch line, but not nearly as heavy as 2 1/2-inch hose, which weighs approximately 120 pounds.
- While the charged two-inch hoseline looks and handles like 1 3/4-inch hose, its high-flow characteristics will allow the rapid generation of high nozzle reaction forces, similar to those experienced when operating 2 1/2-inch lines.
Before deciding to add two-inch hose to a firefighting toolbox, departments must understand that it creates the enigma of being able to more easily deliver high flow rates to the nozzle yet creates the problem of whether the nozzle operator can safely and effectively use these flows during attack operations. Proper nozzle selection becomes extremely important if it is desired to exploit the two-inch line's full potential. If it is decided to utilize a 100-psi combination nozzle on the business end, it makes more sense to utilize 2 1/2-inch hose because that line's increased weight can help the nozzle operators to better cope with relatively high nozzle reaction forces.
Designing Attack Lines
It's been noted that two-inch hose can usually be packed in the same beds as the present attack lines, can be easily moved into a fire building when charged and has the potential of supplying in-creased flow rates. The only part of the equation missing at this point is selection of a nozzle that can provide relatively high flow rates at manageable nozzle reaction forces.
While standard pressure combination nozzles can function well from a flow standpoint, the combination of a high flow rate exiting the nozzle at 100 psi generates nozzle reaction forces that could cause handling problems when they are operated by one or two firefighters. To lower the nozzle reaction force, it may be wise to investigate the advantages of low-pressure combination or smooth-bore nozzles.
Many fire departments that feel uncomfortable operating with smooth-bore nozzles are opting for combination nozzles that are designed to operate at pressures as low as 50 psi. Many large cities such as Boston, Miami, Chicago, Los Angeles, Phoenix and Memphis, TN, have switched to low pressure nozzles for offensive attack operations. A review of the reaction forces of various nozzles that can be effectively paired with two-inch attack lines, shows why.
|200 gpm at 75 psi Nozzle|
|Hose Length||170 gpm||240 gpm|
|150 feet||75 psi||140 psi|
|200 feet||80 psi||152 psi|
|250 feet||85 psi||165 psi|
|300 feet||90 psi||180 psi|
|250 gpm at 50 psi Nozzle|
|Hose Length||210 gpm||250 gpm|
|150 feet||80 psi||110 psi|
|200 feet||95 psi||125 psi|
|250 feet||110 psi||150 psi|
|300 feet||125 psi||170 psi|
|Hose Length||1" tip (200 gpm)||1 1/8" tip (250 gpm)|
|150 feet||90 psi||105 psi|
|200 feet||105 psi||125 psi|
|250 feet||120 psi||145 psi|
|300 feet||135 psi||165 psi|
Let's assume for general attack operations it is desired to flow about 160 gpm. It can be seen by the chart on page 135 that a low-pressure nozzle rated 200 at 75 psi can deliver this flow while generating a relatively easily handled reaction force of only 64 pounds/force reaction. If 160 gpm is the only flow desired, the 15/16-inch tip can provide acceptable streams up to about 180 gpm, it must be kept in mind that since the main reason for changing to two-inch hose in the first place is to provide flows that parallel those obtained from 2 1/2-inch lines, attempting to flow more water through the 1 5/16-inch tip will not be successful because streams from smooth-bores begin losing their reach and generating high nozzle reaction forces at nozzle pressures over 65 psi.
One advantage to operating with a low-pressure combination nozzle is that the stream quality in flow ranges from 150 to 250 gpm is extremely good, even though nozzle pressures may vary. This means that with a little planning, a beginning pump pressure can be sent that provides, for example, a flow rate of 170 gpm. This insures that the interior crew can easily maneuver and safely operate the line yet still flow enough water to handle about three to four rooms of fire. If more water is needed, the supervisor can radio the pump operator to provide more pressure that will allow the interior crew to flow more water without having to stop the attack to change nozzle tips.
Photo by David P. Fornell
More and more fire departments that protect rural areas are taking advantage of the two-inch line's compactness and "user friendliness" when flowing big water. Wyocena, WI, equipped its new tanker/pumper with a 200-foot "heavy hit line" designed to flow 250 gpm through a 250-gpm at 50-psi low-pressure combination nozzle.
Operating pressures can be determined beforehand and the needed engine pressures marked on individual line pressure gauges with 1/8-inch automotive pin-striping tape available at any auto parts store. For example, the Memphis Fire Department marks its gauges in two increments. One line, in red, gives the operator the pressure needed to flow 170 gpm on pre-connected attack lines. A second line, in blue, indicates the pump pressure needed to flow 240 gpm on the same line. During an attack operation, if the officer feels that more flow is needed, he or she will radio the pump operator to increase the pressure to "blue-two." Since the pressure will not be increased until called for, the officer has time to prepare the crew to handle the increase in nozzle reaction, which is approximately equal to that of a 100-psi nozzle flowing the same amount of water on a 2 1/2-inch line.
This procedure has the decided advantage of having the increased flow rate immediately available on the line working the fire without the time-delay of having to stretch a second line. Since the day-to-day flow of 170 gpm is used most often, it is provided at only 64 pounds/force reaction, whereas under the old system the nozzle generated a hard-to-handle 84 pounds/force reaction.
This system has proven to be extremely flexible and, with a little training, extremely effective since it allows a single, easily stretched handline to be operated at relatively low pressures for the majority of fires but, has enough cushion built in that enables a first-in crew to flow 21/2-inch-size streams when necessary.
When replacing 2 1/2-inch pre-connects with two-inch line, many departments find that smooth-bores work quite well. One eastern fire department replaced its 2 1/2-inch pre-connects with a two-inch, 300-foot line that operates with a 1 1/8-inch tip. The pump pressure is set to supply 38 psi at the tip, which generates 230 gpm at 72 pounds/force reaction. The stream reaches about 70 feet and, despite the high flow, can be handled quite easily by a trained operator. If more punch is needed, the officer can call for 15 pounds more pressure, which provides an offensive flow rate at 250 gpm.
Another approach would be to utilize the two top tips (one-inch and 1 1/8-inch) from a 2 1/2-inch stacked tip assembly at the end of a shutoff, which can give the nozzle crew some flexibility in fitting the flow rate to the job at hand, utilizing the one-inch tip when maneuverability is a factor and the 11/8-inch tip when a heavier stream is needed.
Some Final Thoughts
With the widespread use of lightweight building components, there is a more pressing need than ever for a quickly deployed line that can realistically and safely flow at least 200 gpm into a heavily involved, heavily insulated interior space. The National Institute of Standards and Technology (the former National Bureau of Standards) has documented the fact that fires are becoming more intense due to increased use of synthetic building and furnishing materials.
Combatting fires in occupancies of the 1990s requires more water to combat more intense fires. What may have worked in the past may no longer prove effective. Consider the fact that to continue to send firefighters inside a structure to combat fires of ever-increasing intensity, with lines that flow a marginal amount of water, is simply increasing the possibility of firefighter injury and death, without having any appreciable positive outcome on limiting fire damage.
Not long ago, police officials realized that the .38-caliber revolver was not effective as it used to be, given the increased intensity of criminal activity and firepower. To help even the odds, most police departments have converted to heavier automatic weapons. So too should fire departments investigate and implement better, more effective tactics and methods of combating more intense fires. Increasing the caliber of initial attack lines to two inches could be the hardware we've been looking for to help increase our combat firepower.
Captain David P. Fornell recently retired as commander of Beckerle & Company, Hose Company, Engine 9 of the Danbury, CT, Fire Department. He is the author of Fire Stream Management Handbook as well as the producer of a number of fire service training videos. Fornell teaches around the country and is a field instructor for the Illinois Fire Service Training Institute.