BY JAY COMELLA
The Oakland (CA) Fire Department (OFD) convened a Board of Inquiry to investigate the line-of-duty-death of Firefighter Tracy Toomey, who died on January 10, 1999. The fire building at 3052 Broadway was a two-story, balloon-frame building of mixed occupancy, with a residential area over the commercial premises. It was not an unusual building for Oakland.
On arrival, the first-alarm companies encountered a heavy fire condition on the first floor with extension up the stairway. They made an aggressive interior attack using multiple 11/2-inch handlines. Fire was not extinguished in time to prevent the loss of structural integrity. The resulting collapse of the second floor into the first floor killed one OFD member and left two others with career-ending injuries. One of the three direct causes the Board of Inquiry report cited for the line-of-duty death was the inability of 11/2-inch hose to flow sufficient water to extinguish the heavy volume of fire encountered.
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| (1) Left to right: automatic nozzle (50-350 gpm), adjustable-gallonage nozzle (30-60-90-125 gpm @ 100 psi), constant-gallonage nozzle (150 gpm @ 50 psi), and 15/16-inch smooth-bore nozzle (180 gpm @ 50 psi). (Photos by Daryl Liggins.) |
The report further recommended using 13/4-inch hose to remedy insufficient fire flow volume of the 11/2-inch hose. By simply upgrading from 11/2-inch to 13/4-inch hose, the OFD could eliminate fully one- third of the direct causes cited by the Board of Inquiry. The Board of Inquiry report included findings, recommendations, and OFD res-ponses. It was published in September 2000.
The Board of Inquiry's findings were based on the assumption that the departmental target flow rate of 125 gallons per minute (gpm) through 11/2-inch hose was met. This, however, is unlikely for the following reasons:
1. Age, condition, and kinds of nozzles
2. Age and condition of hose.
3. Inaccurate pump chart that states friction loss (FL) to be 15 pounds per square inch (psi) per 100 feet to flow 125 gpm through 11/2-inch hose. This underestimates friction loss by 23 psi per 100 feet. Actual FL in 100 feet of 11/2-inch hose while flowing 125 gpm is 38 psi.
4. The pump chart underestimates accurate nozzle pressure (NP) by 20 psi. The only combination (fog) nozzles that the OFD currently employs are designed to operate at 100 psi NP. The pump chart states nozzle pressure to be 80 psi.
5. Theoretical flow at 15 psi FL per 100 feet of 11/2-inch hose is 79 gpm.
6. Recent flow tests performed with various engine companies showed flows ranging from 60 to 105 gpm. The average was about 85 gpm.
The Board of Inquiry report raises grave concerns about inadequate fire flow volumes. The fact that the actual flows were even less than the assumed 125 gpm compounds these concerns.
Today's fireground is a much more volatile environment than that of the past. The flow rate of 125 gpm was deemed to be adequate at a time when fuel loads were lighter and comprised of so-called ordinary combustibles, such as wood, paper, and cloth (cellulosic materials). Most likely, the OFD's current target flow rate was based on 1918 testing that established the standard fire time/temperature curve.
Fuel loads today are heavier and largely hydrocarbon-based (plastics). Plastics are petrochemical products that behave like solid gasoline and generate large quantities of thermal energy. One pound of cellulosic materials gives off 8,000 British thermal units (Btus) when burned, whereas plastics generate 16,000 Btus per pound of fuel. Not only do plastics produce twice the Btus, but they do so at a heat-release rate that is much faster than that of traditional fuels. Couple these factors with tighter and better insulated buildings that inhibit fire from self-venting (tight building syndrome), and the millennium engine company most definitely faces a much more dangerous enemy than it had in the past.
Since the enemy has become much more dangerous, the weapon used to combat the enemy must be upgraded accordingly. Akin to the police evolving from the 38-caliber revolver to the 40-caliber automatic, the fire department also must make a more intelligent weapon selection. The hose and nozzle system is the engine company's weapon for attacking the fire. The vast majority of the American fire service considers 150 gpm to be the minimum acceptable flow rate for interior structural fire attack. Many fire departments use a target flow rate of 180 gpm to ensure an added margin of safety.
In his brilliant treatise on the art and science of applying water on fire ("Little Drops of Water: 50 Years Later," Parts 1 and 2, Fire Engineering, February and March 2000), Andrew Fredericks, the foremost expert on engine company operations, further states that in addition to 150 gpm being the minimum acceptable flow for residential fires, 250 gpm is the minimum acceptable handline flow for operations in commercial occupancies. OFD's target flow rate of 125 gpm is well below the nationally accepted fire service standard, and its actual flow rate of 85 gpm simply is inadequate for modern fire conditions.
The outcome of fireground operations depends on the outcome of the battle between the water the engine company delivers (gpm) and the heat (Btus) the fire generates. The flow at which the engine company can win the battle and kill the fire is defined as the critical flow rate. If the critical flow rate is not met, the battle will be lost. This dictates that the single most important characteristic of a hose and nozzle system is water flow capability. The water the engine company delivers must be sufficient to expediently kill the fire. Maneuverability of the hose and nozzle are important factors, but to sacrifice flow for ease of use has proved to be suicidal.
Although an adequate flow rate cannot be sacrificed for ease of use, handling characteristics cannot be completely overlooked either. The amount of effort required from the nozzle operator is that which is necessary to resist the nozzle reaction. Nozzle reaction is measured in pounds of force and is a function of two factors—flow rate and nozzle pressure. An increase in one or both of these factors will result in an increase in nozzle reaction force (RF). The higher the nozzle RF, the more difficult the nozzle is to control. Since adequate flow rate is the ultimate goal of a well-conceived hose and nozzle system, the logical way to keep nozzle RF within the manageable range is to keep nozzle pressures low and avoid sacrificing flow. More than 75 pounds RF is considered to be too much reaction force for a handline. However, RF less than 45 pounds is considered to be a sign of an ineffective stream.
Hoseline handling characteristics are a function of the following factors:
1. Flow rate.
2. Hose size.
3. Friction loss.
4. Pump discharge pressure.
Handline maneuverability is determined by the pressure at which a given size line must be pumped to attain a desired flow rate. If hose size remains constant and flow is increased, pump discharge pressure must be increased to account for greater friction loss. This reduces maneuverability as the line approaches the stiffness of a pipe. Conversely, if hose size increases while flow remains constant, pump discharge pressure may be reduced due to lower friction loss requirements. This results in improved maneuverability because the line becomes more bendable.
The aforementioned parameters lead to certain conclusions about what constitutes a well-planned hose and nozzle system for residential fires. The hose should be capable of flowing between 150 and 180 gpm with relatively low friction loss. The nozzle should have similar flow capability at a nozzle pressure that will maintain reaction force in the range of between 45 and 75 pounds.
Because of the pressures required to account for friction loss, the practical flow limit for 11/2-inch hose is 125 gpm, whereas the practical flow limit for 13/4-inch hose is 200 gpm (see Figure 1).
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The tool at the very heart of the entire fireground operation is the nozzle. It is the weapon with which members enter into close-quarter combat with the enemy. If the nozzle malfunctions or is not used properly, all other tools and tactics on the fireground are likely to become quite limited in their effectiveness in saving life and protecting property. All kinds of nozzles perform their all-important mission by providing some rather simple, uncomplicated, albeit incredibly necessary, functions. They control flow, create shape, and provide reach. Since the functional requirements for a nozzle are relatively simple and yet immensely important, intuitively it makes sense to select the kind of nozzle with the least complicated design and the fewest moving parts. The low-tech choice in nozzle selection ensures the greatest degree of durability and reliability. Simple, durable, and low-tech are all qualities that contribute to low initial and long-term costs. More importantly, these qualities lead to reliability, which, in turn, leads to increased safety. There is an inverse relationship between nozzle cost and suitability for interior structural firefighting. Unlike so many things in modern-day, high-tech society, the best kind of nozzle actually costs substantially less than the other kinds.
The kinds of nozzles available today, in descending order of simplicity and durability, are smooth-bore, constant-gallonage (single gallonage) fog, adjustable gallonage fog, and constant pressure (automatic) fog.
Smooth-Bore Nozzle. The smooth bore is the most low-tech of all nozzle designs. It consists of a ball valve shutoff device onto which is threaded the smooth-bore tip, which is basically a piece of tapered pipe. Together, the shutoff and tip present a very compact (73/4-inch) and lightweight (21/2 lbs.) package. Genius lies in the simplicity of its design. It has only one moving part—the ball valve.
To emphasize how difficult it is to clog a smooth-bore nozzle, Fredericks held a 15/16-inch tip up to his eye and, looking through it, he exclaimed to his lecture audience, "This is all the water sees on its way to the fire." It is the most durable and reliable of all nozzles. It requires the least maintenance of any nozzle type and has the longest service life.
Smooth-bore nozzles are by far the least expensive kind to purchase and maintain. Of all nozzles, the smooth-bore requires the least amount of training for pump and nozzle operators to become proficient. The incredible reliability of the smooth-bore nozzle is a significant safety feature. Since you can produce only a solid stream with the smooth-bore nozzle, its use ensures that members and victims will not be exposed to the potentially debilitating or lethal effects associated with introducing a fog stream into the fire area.
Emphasizing the need for durability, reliability, and low maintenance in nozzles, OFD Captain Ted Aff in Fire Stream Management Handbook by David P. Fornell (Fire Engineering, 1991) says, "If you give a fireman a 2-inch stainless steel ball bearing and put him in a bare, windowless room for an hour, when you open the door and ask about the ball bearing, he will have either bent it, broken it, or lost it." The smooth-bore nozzle is the safest and most efficient weapon for combating interior structural fires. Therefore, it is the only kind of nozzle that should be taken into the most hostile work environment on the face of the earth—the interior of a burning building. Fog nozzles should be kept in the inventory for other uses, such as flammable-liquid fires.
Constant-Gallonage Fog Nozzle, The constant-gallonage nozzle is the simplest, most reliable, least maintenance-intensive and, hence, safest member of the fog nozzle family. Of all fog nozzles, this type requires the least training. It does, however, require somewhat more training than the smooth-bore nozzle. Constant gallonage or single gallonage indicates that this nozzle is designed to flow a specific gallonage when operated at the specific pressure for which it is designed, such as 150 gpm at 100 psi NP.
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| (2) Oakland (CA) Fire Department (OFD) members operate a 21/2-inch hoseline with a 11/8-inch smooth-bore nozzle (266 gpm @ 50 psi) during testing and evaluation. |
In addition to the 100-psi model, constant-gallonage nozzles also come in 75-psi and 50-psi models. The nozzle is 121/4 inches long and weighs 6.1 pounds. As the name suggests, there is the distinct possibility of a fog stream being introduced into the fire area. This has the potential to, in short order, turn a still-tenable environment into one that is untenable. As with all fog nozzles, when the water flows from the hose—through the shutoff, into the tip, to be broken into a spray stream—a clog point exists. The constant-gallonage nozzle is the only kind of fog nozzle that should be in an engine company's inventory.
Adjustable-Gallonage Fog Nozzle. The adjustable gallonage takes fog nozzle technology to the next level of complexity. It has more moving parts and is more maintenance-intensive than the constant-gallonage nozzle and, hence, has an increased potential for nozzle failure or malfunction. Using a flow-selection ring, the nozzle operator can choose a desired flow. This operation requires an increased level of training for nozzle and pump operators. If the nozzle operator changes the flow setting, the pump operator must be informed so he can adjust pump discharge pressure to the appropriate level for the selected flow. It is possible to put the flow-selection ring on the wrong setting, resulting in the nozzle's flowing less than the desired amount of water. So, in addition to the possibility of introducing a dangerous fog stream into the fire environment, there is a great potential to produce a flow that is less than the acceptable minimum. The adjustable-gallonage nozzle is 121/4 inches long and weighs 5.6 pounds. The adjust-able-gallonage nozzle should not be part of an engine company's nozzle inventory.
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| (3) The 13/4-inch hose allows significantly higher flow than the 11/2-inch line, yet size and weight differences are nominal. |
Automatic Fog Nozzle. Automatic nozzles originally were de-signed in the late 1960s by Chief Clyde McMillan of the Gary Fire Task Force, an auxiliary unit of the Gary (IN) Fire Department. One of the roles of the task force was to respond to large fires and put master streams into operation. Often, initial water supply was inadequate when transitioning to defensive operations. McMillan set about de-signing a master stream appliance nozzle that would produce a stream with good reach, even at the low flows available during the transitional phases of operations. He also wanted that same nozzle to be appropriate for the high flows achievable after augmentation of the water supply.
The automatic nozzle is also called the constant-pressure nozzle. Constant pressure refers to the fact that the nozzle produces a stream of reach and appearance consistent with 100-psi tip pressure regardless of the pressure actually coming into the base of the nozzle. This is accomplished by a baffle and spring arrangement. As a given amount of water enters the nozzle base, it puts the spring under a given amount of tension. This, in turn, moves a baffle that changes the nozzle's orifice size. As the amount of water flow fluctuates, so does the orifice size. The orifice is maintained at a size that, for the given amount of water, provides approximately 100 psi NP. This creates a visually attractive stream with good reach over an extremely wide range of flows. This has prompted nozzle sales representatives to state, "The automatic nozzle will produce an effective stream no matter what the flow." Though stream quality and reach are important, stream effectiveness is determined by whether it meets the critical flow rate. Often, the stream produced by the automatic nozzle is good-looking but doesn't have much water in it.
The automatic fog nozzle is bulky (length—133/4 inches, weight— 6.5 pounds) and costly. It is at the high-tech end of the spectrum of fire service nozzles. To be used properly, it requires more training for both nozzle and pump operators than any other nozzle type. It has the most complicated design of any nozzle and the most moving parts. It is the most maintenance-intensive and the most susceptible to failure.
To use a suitable military analogy, the automatic nozzle is to the smooth bore as the early M-16 was to the AK-47. The simple, low-tech, battle-proved AK-47 with its simple design and loose operating tolerances could handle an incredible amount of abuse in the field and still remain a very functional and effective weapon. On the other hand, the early model M-16, with its complex design, superior machining, and fine tolerances, was very susceptible to malfunction in the harsh environment of the battlefield.
Because of its design intricacy, the automatic nozzle has a high susceptibility to malfunction. It also has a propensity to mask insufficient flow by presenting an attractive stream over a wide range of flows.
The first step in planning a hose and nozzle system is to establish the needed flow for the occupancy type in question. The flow requirement is derived by determining the flow at which the engine company most often will overwhelm the heat generated by the encountered fuel load. To deliver the desired volume of water, parameters for hose selection are based on flow and friction loss characteristics. Parameters for selecting a nozzle to couple to the business end of that hose are based on flow and reaction force characteristics. This holds true for residential occupancies and for fires in commercial buildings.
As mentioned earlier, when paraphrasing Fredericks, the minimum acceptable handline flow for operations in commercial occupancies is 250 gpm. For this type of flow, 21/2-inch hose is the line of choice. Friction loss at 250 gpm is 12 psi per 100 feet of 21/2-inch line. For the same flow in two-inch hose, the friction loss is 50 psi per 100 feet. Though a 21/2-inch line is a very substantial piece of equipment, it is not too heavy to aggressively advance as a handline, as would be the case with three-inch hose.
The key to using a 21/2-inch line efficiently is proper nozzle selection. The 100-psi combination nozzle effectively has removed the 21/2-inch line from the department's arsenal of offensive weaponry because of the astronomical nozzle reaction force of 126 pounds while flowing 250 gpm at 100-psi nozzle pressure. When pumped according to the department pump chart at 80-psi tip pressure, flow drops to 220 gpm with a still relatively high reaction force of 113 pounds. Low-pressure nozzles (50-psi tip pressure) that impart significantly less reaction force will return the venerable 21/2-inch line to its former status as a very aggressive, very offensive weapon.
Many departments successfully employ a 11/4-inch tip. Its 324-gpm flow technically classes it as a large-caliber stream, making this size tip possibly better suited for use with master stream devices. A far greater number of departments use the 11/8-inch tip. With a flow of 266 gpm at 50-psi nozzle pressure, it has a reaction force of 95 pounds. Although it is still very important to keep nozzle reaction force low, it would be impractical to try to apply the previously cited 75-pound cap to flows from large-caliber handlines.
Paired together, the 21/2-inch line and the 11/8-inch tip create a user-friendly, offensive, large-caliber weapon. As Fredericks states in his article "The 21/2-Inch Handline" (Fire Engineering, December 1996), "No combination of smaller handlines can duplicate the volume, reach, and pure knockdown power of a single, well-placed 21/2-inch line. In addition to its high-volume flows (between 250 and 320 gpm) and long stream reach, 21/2-inch hose provides the following benefits when used with a 11/8-inch solid stream tip:
- low friction loss per 50-foot length (only about six to eight psi at 262 gpm),
- exceptional penetrating power due to hydraulic force of the stream,
- little premature water vaporization in highly heated fire areas,
- easy reduction to smaller handline(s) after knockdown, and
- much better maneuverability than three-inch hose (sometimes used as a handline) or portable master-stream devices."
Using a 21/2-inch line is indicated in situations in which fire conditions are likely to overwhelm smaller handlines. Fredericks cites the oft-used mnemonic device "ADULTS," which refers to scenarios requiring the use of 21/2-inch line:
Advanced fire on arrival
Defensive operations
Unable to determine extent (size) of fire area
Large, uncompartmented areas
Tons of water
Standpipe system operations
The ADULTS acronym is reminiscent of an anecdote related by retired Chicago (IL) Fire Department Battalion Chief Ray Hoff regarding proper handline selection. On seeing an engine company stretching a 13/4-inch line toward a commercial occupancy exhibiting a heavy fire condition, Hoff requested, "Would you please put that down and bring me an adult-size line?"
When the engine company encounters advanced fire on arrival, the high flow available from 21/2-inch hose is needed for rapid control. Even a private dwelling may exhibit a fire condition heavy enough to warrant the quick knockdown power of the 21/2-inch line. This is especially true of extensive involvement of the first floor or front porch.
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| (5) OFD members comparing a 13/4-inch hose with a 15/16-inch smooth-bore nozzle flowing 180 gpm vs. a 11/2-inch hose with 125 gpm @ 100 psi adjustable-gallonage nozzle flowing 79 gpm (pump discharge pressure as per OFD SOPs). |
Although using master stream appliances is not recommended for occupied residential buildings, the same cannot be said of 21/2-inch hose. The 21/2-inch line with 11/8-inch smooth-bore nozzle is a large-caliber weapon that is aggressive, mobile, and offensive. It can rapidly darken down a very heavy fire condition to allow an interior attack. This permits three tactical options: The 21/2-inch handline can be advanced into and through the structure; the attack can transition to the use of a smaller line with the big line left where it is; or the 21/2-inch line can be reduced down to a smaller line to press the interior attack for final extinguisment.
Whether operations are defensive initially or transition from offensive to defensive, smaller-caliber handlines should not be used. The 21/2-inch line is a much safer and more efficient alternative. The reach afforded by the larger lin
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