Larger Attack Lines May be the Answer To Manpower Reductions
STRATEGY AND TACTICS
If you’ve stopped hamstringing your pumpers with 2-inch and 3-inch supply lines, and if the auxiliary suction is no longer the primary suction used in your department (see FIRE ENGINEERING, June 1983), then perhaps you’d like to explore the benefits of large-diameter attack lines. With the odds mounting against fire fighters, you don’t just want to meet the fire on equal terms, you need to overwhelm it! Modern nozzles and hose are a first step.
Today’s fire fighter and fire administrator are faced with the same problem-fire attack with less manpower. In our attempt to provide equivalent protection with a shortage of personnel, we’re turning to new, improved technology where possible.
One of the most dramatic examples of this new technology is hose size. Large-diameter supply hose (3½ to 6inch) is accepted by progressive administrators as the norm, not the exception. But large-diameter hose should not stop with supply lines. Fire attack lines need the same thinking. Presently 1½ and 2 1/2-inch hose is the norm and 1¾, 2,3,3½ and 4-inch hose is the exception. We need to turn that around! However, just changing hose size is not enough. Nozzles, plumbing, advancement techniques, hydraulics, pump operations, and many other factors need to be considered before a hose change is made.
The best way to explain what size hose to use is to talk flow. Chart A is based on the average flow you can expect from the five most common hose sizes at various engine pressures. The chart shows flows up to 400 gpm. To my knowledge, only one handline nozzle manufacturer makes a nozzle above that flow that can be controlled by one or two fire fighters. Depending on the type of hose, in our flow studies, we noticed a variation in flow of 19 percent more or 14 percent less than what the chart says. The friction loss can be as much as 26 percent less or 33 percent more. In other words, the type of hose and its manufacturer do make a difference. With a 1 3/4-inch hose, for example, we’re talking about 70 gpm, depending on whose hose you buy. We also noticed that the two hose lines with this 70-gpm flow difference exhibited totally different handling characteristics. The hose flowing 70 gpm of water less was impossible for two fire fighters to control. The higher flowing hose was controllable with one hand.
According to the International Society of Fire Service Instructors, 100 gpm is the minimum water flow for fire attack. That being the case, at normal pressures, l’/2-inch hose should not exceed 250 feet, 1 3/4-inch should not exceed 700 feet. All other sizes do allow well over 2000-foot lays. If your department uses long lines, l 1/2-inch probably isn’t the right size hose. By using 1 3/4-inch, your pump pressure will be lower and your flow higher.
What about cost? Chart B, based on a 200-foot line at 200 psi, is a cost benefit chart to assist you in selecting the best hose size. Chart B, like Chart A, is based on a 400-gpm maximum handline flow. Column 1 shows the various hose sizes; column 2 shows the flow you can expect as an average; column 3 is a cost per gallon comparison, with 2½inch hose being the cheapest and 1½inch being the most expensive. Column 4 is a ranking of hose cost, with 1½-inch being the least expensive and 3-inch being the most expensive; column 5 is the number of fire fighters required to effectively advance a hose of that size; column 6 is the percent increase in flow over the next smaller size; column 7 is a percent increase in cost to get the flow increase in column 6. Column 8 is the percent flow increase over l 1/2-inch hose; column 9 is the weight of 50 feet of charged hose; column 10 is the square foot fire knockdown capability of the line (10-foot ceiling height).
Chart B can give you an idea of the most cost-effective hose. For example, 1 3/4-inch hose flows up to 68 percent more than 1½-inch hose with essentially the same crew. The 68 percent increase in fire attack capability will cost 13 percent more than l 1/2-inch hose. Depending on the manufacturer, that’s as little as $30 on a 200-foot line! That may be the best $30 your department ever spent.
Conventional 2½-inch hose flowing the standard 250 gpm, when compared to 1 3/4-inch hose at 210 gpm, requires only two fire fighters instead of four on the 2½-inch. The 1¾-inch hose allows your manning to go further. Using two 1¾-inch lines, a flow of 420 gpm can be attained using the same crew required to flow 250 gpm with 2½-inch hose. That’s flexibility—and a good increase in flow per fire fighter.
All things considered, 2-inch hose is the ideal. It exhibits the highest flow per fire fighter (120 gpm); and it allows for longer hose lengths (up to 400 feet) and still flows more than 250 gpm. Two-inch hose is also one of the cheapest, based on cost per gallon.
All in all, 1 3/4-inch or 2-inch attack lines are the way of the future. Both can be purchased with 1½-inch threads to keep everything standard on the fireground. Hose is your first step in improving your fire attack.
It is important to mention that any change in hose size must be used with a high flow nozzle to attain that increase in flow potential.
Conventional nozzles have fixed flows, 20, 60, 95, 125, 250 gpm, etc. Some conventional nozzles have several flow settings. The flow settings assume that “x” gpm are reaching the nozzle at 100-psi nozzle pressure. However, if more or less than “x” gpm arrives, a poor stream results. Using conventional nozzles, the pump operator is the key to achieving a usable flow. In practice, we don’t always see picture-perfect streams. Hopefully, conventional nozzles are on the way out.
What makes a nozzle automatic? An automatic nozzle is simply a nozzle with a spring built into it. An automatic nozzle balances pressure at or near 100 psi against a high-quality spring. If more than 100 psi reaches the spring, the spring opens to allow more water to flow through the nozzle and still maintain 100-psi nozzle pressure. If less than 100 psi reaches the spring, the nozzle will flow less water but still flow it at 100 psi. The end result is no matter how much water reaches the nozzle, the automatic will give you the best possible stream and maintain a fairly constant nozzle pressure.
An automatic nozzle is supposed to give constant nozzle pressure at variable flow. However, this is not the case. The nozzle pressure may vary as much as 65 psi, depending on the type of nozzle. Some of the better automatics maintain 95 to 100 psi over the most common flow ranges (150 to 250 gpm).
The flow ranges of all automatic nozzles are: 60 to 400 gpm; 50 to 350 gpm; and 50 to 342 gpm. An automatic nozzle will provide a good stream throughout its flow range. Don’t let advertised flow ranges fool you. In reality, any flow over 350 gpm will cause the stream to break up. You won’t be able to control the pattern or the shape of the stream. What you end up with is a narrow fog with little reach. So realistically, 50 to 350 gpm is the range of all handline automatic nozzles.
Automatic nozzles simplify pump operations. Instead of calculating a different engine pressure for all of the various hose layouts, you just pump one preset pressure. The pump pressure is determined by what’s known as the “water triangle.” The three sides of the water triangle are:
- maximum engine pressure (250 psi or whatever your standard operating procedure dictates),
- compound gage (suction) reading of 0 to 5 psi minimum,
- maximum engine rpm.
The pump operator simply advances the throttle until one of the sides of the water triangle is reached. After the pump pressure is achieved, the governor or relief valve is set to maintain the pressure. Automatic nozzles free the pump operator from “by the book” hydraulics. Irregardless of the size of the hose or length of the line—no more hydraulics!
The control of volume is left in the hands of the nozzle operator, where it’s needed most. The fire fighter at the nozzle throttles the flow with the nozzle shut off as the need dictates.
The concept behind the automatic nozzle is one nozzle for all handline hose sizes (1 1/2, 1¾, 2,2½, and 3-inch). Instead of owning 1½ and 2½-inch nozzles, you own several automatics that will work on any size hose.
The NFPA recommends two 1 1/2 and two 2 1/2-inch spray nozzles minimum per pumper. The total flow from this recommendation for conventional nozzles is 750 gpm [(125 X 2) + (250 X 2)]. If all four nozzles were automatics, the flow would be 1400 gpm (4 X 350)! That is a bargain no matter how you look at it.
Automatic nozzles “think,” allowing the nozzle to open and close to meet the water supply. This is really essential when operating master streams. Automatic master streams (150 to 1000 gpm) “grow with the flow” automatically. As additional water supply becomes available on the fireground, the nozzle automatically adjusts the flow. It sure beats changing tips or switching back and forth between too high a flow setting and too low a flow setting on a conventional nozzle. The automatic nozzle is the answer to many of our fire stream problems.
Some nozzles, both automatic and conventional have flow settings of 30, 60, 95,125 gpm, etc. Is this an advantage? According to sales folks, it’s a good idea. Why? They say one fire fighter can’t handle the full flow alone. So by simply turning the flow down instead of gating back on the nozzle shutoff, the operator is safer. It sounds reasonable. It’s not the case though.
Why can’t a fire fighter hold a hose at high pressure? Because there is too much nozzle reaction. Let’s say you have 200 feet of 1 3/4-inch hose flowing 200 gpm with a pump pressure of 190 psi. The nozzle reaction is 101 pounds. If you set the nozzle flow on the 150gpm setting, you’ll actually be flowing 168 gpm and your nozzle reaction will be 94 pounds. With a standard automatic nozzle without flow settings, the nozzle reaction at 168 gpm is only 85 pounds—that’s 11 percent less than with nozzle flow settings.
If the flow setting on the nozzle is reduced to 100 gpm, the actual flow would be 123 pounds and the nozzle reaction would be 76 pounds. On a nozzle flowing 100 gpm without flow settings, the reaction would be 62 pounds—23 percent less than with nozzle flow settings.
Are flow settings an advantage? You decide. Many fire fighters see flow settings as a worthless gimmick. Adding flow settings to an automatic nozzle limits its flow potential and it’s no longer an automatic nozzle. If you’re concerned about the fire fighter operating the nozzle being hurt by a wild hose line, your problem is not the nozzle, pump pressure or flow. Your problem is training. The first rule a fire fighter should learn is open any nozzle only to the point where you can safely control it. If your people are slamming the nozzle open and shut (a common fire fighter birth defect), it is going to be out of control. paratus arrives or is refitted, hydraulically test lines to see if they flow to your specifications.
If you change hose and flow, you should change your methods of hose control. High flow nozzles on 1 1/2, 1¾, and 2-inch hose makes the use of pistol grips essential.
What about the everyday fire that 1 1/2 and 2 1/2-inch hose handle just fine? One and three-quarter-inch and 2-inch attack lines will handle it better! Let’s say, for example, you have a room requiring 60 gpm to extinguish fire in a room 30 X 20 X 10 feet. A pair of booster lines at 30 gpm or a 1½-inch line at 60 gpm would extinguish the fire in 60 seconds and use 60 gallons of water. However, this is the 1980s, and we’re told any stream less than 100 gpm does not provide crew protection. We’re also told that a fire will not remain static. Can you guarantee that while you’re spraying, the fire is not getting larger?
Okay, let’s take the same fire and use a 120-gpm nozzle this time. In 30 seconds, it will spray 60 gallons and knock the fire down. Which attack was more efficient? Use a 1¾ or 2-inch attack line with an automatic nozzle on the same fire and it would take 10 to 17 seconds to bring the fire to its knees and we would still use only 60 gallons.
Efficiency is related to flow rate.
Many fire departments in this country have been taught to conserve water. Apparently, we don’t trust the nozzle operator. Why do 1 say this? Because we arm this fire fighter with our most expensive (dollar to gallon) hose line—the booster line with its outstanding 10 to 30-gpm flow potential.
There isn’t any way to waste water. Conserving water is hitting the fire as hard as you possibly can and if it runs you out of the building, you can be proud knowing you gave it your best shot! If yours is a progressive fire department (the one that starts with the booster reel and progresses through the hose sizes on every fire), you can go home knowing you haven’t accomplished a thing, except to save water. The way I see it, that’s not our job. Our job is saving lives and property!
What do you do about water damage? Water damage is based on the person with the nozzle shutoff. If you haven’t trained this person in application, then you can expect water damage, no matter what size hose you use.
There is a method of nozzle operator control called the 10 to 30-second rule. Four simple, commonsense steps to apply:
- Get as close to the fire as safely possible. Open the nozzle 10 to 30 seconds. If the fire is not knocked down with that blast, it’s time for the next step.
- Reposition the line and reapply as many times as necessary to reach all the fire. At no time is the nozzle opened more than 10 to 30 seconds without repositioning. If you know you’re hitting the fire and your efforts aren’t accomplishing anything, it’s time for one of the next two steps.
- • Do you have the correct agent (foam, dry chemical, dry powder, etc.)? If not, get it and reapply for 10 to 30 seconds. If you know you have the correct agent and are not achieving knockdown, it’s time for the final step.
- Do you have enough of the correct extinguishing agent? If not, get a second line or a larger diameter stream.
The 10 to 30-second rule offers the person in charge the security of knowing that the hose crews are evaluating and reevaluating their actions.
Attack line backups
The ability to place a large flow of water in a short period of time is essential to accomplish our goals on the fireground. What do you back a 1 ¾ or a 2-inch attack line up with? I suggest a bomb line (see Chart C), a lightweight master stream device with an automatic nozzle attached, supplied by a preconnected, single 2½-inch to 4-inch hose line that is 100 to 300 feet long. In other words, a preconnected line that can flow the capacity of the pumper, or at least twice what the standard attack line will flow. What do you do when you want a master stream behind, inside, or beside a building? If it makes sense to preconnect 1½, 1¾, 2 and 2 ⅛-inch lines, then why not a bomb line? Sure a fixed gun has its place on every pumper, so does the preconnected heavy-caliber stream. How can you guarantee the flows you want from a discharge? Specify performance, not pipe. Use the above pipe sizes only as a minimum. Demand “x” gpm and account for no more than “x” friction loss. When the ap-
Recently, I watched an engine company with three fire fighters place two bomb lines 200 feet apart, flowing a total of 1600 gpm in 60 seconds. Can you do it? Why not?
A preconnected gun and a bomb line allow you to control all four sides of most buildings. Simply place two streams on opposite corners of the structure.
Better equipment specifications
In order to achieve the proper flows from your preconnects, it’s essential to make sure your piping and valves are adequate. One and three-quarter-inch attack lines should not be connected to a pump with less than 2-inch plumbing. Two-inch lines should have at least 2½-inch piping.
How can you guarantee the flows you want from a discharge? Specify performance, not pipe. Use the above pipe sizes only as a minimum. Demand “x” gpm and account for no more than “x” friction loss. When the paratus arrives or is refitted, hydraulically test lines to see if they flow to your specifications.
What type of hose is best? Plastic, synthetic rubber, or double-jacketed hose? It all depends on whether you want your hose to last. If you enjoy washing hose, investing in hose washers and dryers, spending $40,000 for drying towers built into your station, having spare loads of hose and mildew, continue to buy standard double-jacketed hose. It doesn’t really make sense to have three or four times more money in hose maintenance than in hose. A good set of hose specifications and a little research can eliminate all of these traditional problems in addition to improving abrasion resistance, kink resistance, subzero characteristics, and even reducing the weight of your hose.
The future success or failure of the fire service will be based on our ability to get away from obsolete tradition. We need to improve our performance on the fireground.
It doesn’t make a bit of sense to have booster lines (10 to 30 gpm, maybe?), 1½ (30 to 125 gpm), and 2 1/2-inch (120 to 328 gpm) hose, and a monitor (100 to 1250 gpm) on the same pumper. Does a police officer carry four guns for each size bad guy that he may run up against? Why do we? We certainly can decide on one highly mobile large flow attack line that can be advanced by a few well-trained aggressive fire fighters. The large-diameter line will replace the three inferior hose sizes. This line should be backed up by a preconnected ultrahigh-flow bomb line, and these lines should be equipped with the best automatic nozzles made. With today’s force multipliers, we can do more with less.
Are you ready for the challenge?