By Paul Shapiro

I think it is pretty accurate to say that the majority of municipal fire departments are using either four- or five-inch large-diameter hose (LDH) for their water supply lines.

There are many statistics that departments need to consider when deciding what size LDH to purchase. Some of the more common stats involve nonperformance facts such as the weight and the cost of the hose. These are important, but if a department makes a decision based totally on the weight and cost of the hose, it could be limiting its water delivery capabilities.

The most important factor for a fire department to look at when making this decision should be water delivery capabilities. Many factors go into analyzing the hose's water delivery capabilities, including water supply demands, hydrant performance and spacing, the amount of pumping apparatus available for water delivery operations, and water delivery operation tactics.

Here are some simple facts about four-and five-inch LDH:

1. There are two types of LDH: supply hose and attack hose. Supply hose has a maximum operating pressure of 185 pounds per square inch (psi). Attack hose has a maximum operating pressure of 275 psi.
2. Five-inch hose (100 feet) weighs approximately 105 pounds empty. Four-inch hose weighs approximately 80 pounds. Some manufacturers offer lightweight versions for four- and five-inch LDH that weigh several pounds less.
3. LDH can be used for either supply lines or discharge lines.
4. Five-inch hose flows twice as much as four-inch hose.

Before comparing four- and five-inch hose in specific supply line evolutions, users need to understand the fire hydrant system itself and how it supports a supply line evolution. A fire hydrant is supported by water mains filled with water under pressure. The system has two basic pressure ratings. The first is called the static pressure. It measures the water pressure at rest, or water that is not flowing. Many people think the static pressure is the number to look at when determining how good a fire hydrant is. This is misleading because it is measuring the water at rest. Residual pressure is the measurement of the water at the hydrant while water is flowing. It is the residual pressure that determines how well the supply hose can deliver the required flow. Finally, the volume of water has to be available whether the pressures are high or low.

1 LDH can be used for either supply lines or discharge lines. (Photos by author.)

Supply Line Evolution

Let's take a look at the most common supply line evolution deployed by fire departments: a house fire scenario where a department lays a single supply line from a hydrant. In most cases, the flow will be 500 gallons per minute (gpm) or less. The hydrant being used in this example has a 60-psi static pressure. After flowing 500 gpm, the residual pressure is down to 40 psi. This is the pressure that will move the water through the supply hose to the pumper at the fireground. The friction loss in four-inch hose flowing 500 gpm is approximately five psi. Dividing 40 psi by five psi equals eight. This means that this hydrant will flow 500 gpm for 800 feet using four-inch supply hose.

Now let's see what five-inch hose will do with the same hydrant. The friction loss for five-inch line flowing 500 gpm is roughly two psi. In reality, this would not show up on a discharge gauge, but the number will serve for this comparison. Divide 40 psi by two psi and the result is 20. This means that five-inch hose will move 500 gpm with the 40 psi residual hydrant pressure 2,000 feet. This is a little bit more than twice the distance of the four-inch hose.

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1 The Holmatro HCT 3120 hand-operated combi tool. (Photo courtesy of Holmatro.)

It's helpful to understand the basics behind high-pressure hydraulic technology. Oil is almost incompressible and can transfer very high pressures. A pump generates the oil flow and needed pressure as it pumps oil into a cylinder with a piston. The resulting pressure is transferred to the tool, where it generates an applied force. Whether it is a cylinder like a push-pull ram, a cutter, or a heavy-duty spreader, the force generated is proportional to the pressure of the oil and the surface area of the piston. With high pressures of up to 10,443 pounds per square inch (psi), the surface area of the piston can be very small and still generate tremendous force.

Hand-Operated Tools

2 The HCT 4120 is Holmatro's latest hand-operated spreader unit. It has a maximum spreading force of 49,458 lbf and a maximum cutting force of 55,528 lbf. For fire departments on limited budgets, this is an excellent tool to start with on every engine company so they have the ability to perform auto extrications without carrying the entire Holmatro arsenal and power unit. (Photo courtesy of Holmatro.)

Not every extrication requires firefighters to use large hydraulic rescue tools to cut patients out of twisted steel. Sometimes it requires a more precise application, like using a scalpel instead of a hacksaw. The Holmatro HCT 3120, a hand-operated, hydraulic combination tool, is such a unit. This tool is the smallest combi tool in the Holmatro arsenal, but don't let its size fool you. It is a compact, powerful tool. Certain rescue scenes may not accommodate larger cutters and spreaders with hoses and power units. Some fire departments may not have the money to outfit every apparatus with a complete hydraulic rescue system. If you have to start from the bottom and work your way up, the HCT 3120 combi tool is a good place to start. With proper training, you can accomplish a wide variety of auto and rescue extrications.

This hand-operated combi tool weighs 32.1 pounds and measures 27.5 x 8.1 x 6.4 inches. It has a maximum working pressure of 10,443 psi with a 2:1 safety factor. That means the cylinder will withstand 20,886 psi before it fails. When the tips of the blades are in the closed position, the initial minimum spreading force is 5,845 pound force (lbf). As a user opens the blades and the angle increases, the maximum spreading force is 11,690 lbf. When the blades are wide open, the spreading distance is 10.6 inches with a pulling distance of 7.1 inches. When the blades are closing, cutting, or squeezing, the maximum cutting force at the apex of the blades is 49,008 psi Mid-blade, the cutting force is substantially reduced to 18,659 psi, but that is still a tremendous amount of force. The maximum squeezing force at the tips before t

Neal E. Brooks

"In the beginning" could refer to a biblical verse or a handful of new fire recruits gathered around an older, experienced firefighter explaining the virtues of "now vs. then." And, so is the story about the evolution of control systems in the fire service and how it has affected both apparatus builders and end users. I recently visited a small volunteer fire department in rural Seneca, Illinois, and viewed its fully restored 1911 Waterous hand-drawn pumper.

It was the first new fire truck the village of 1,000 purchased, and it arrived via box car on the railroad. I marveled at the simplicity of design but also questioned the quality of gasoline available at the time or how many fingers, wrists, or arms were broken starting the motor with the infamous Model-T-type crank start. There were exposed gears in the pump assembly and rudimentary operating gauges that gave the operator only better than a guess for what the pump pressure was. If the fire stream hit the target, then it must be the correct pressure, right? Yes, the good old days.

Well, to paraphrase my mother, who was raised during the depression, "The good old days are now!" So it is within the rank and file of the modern day fire service and those fire apparatus builders that strive year after year to make operating what has become a complex piece of machinery safer and simpler. Merely three decades ago, a phenomenon known as the Internet was just getting started. Who would have guessed how it would affect the global community or those in their own fire service? The information network, in my humble opinion, affected many changes in our own private fire society in a shorter timeframe than what may have transpired in the good old days. Manufacturers and end users were now able to compile useful information to make the dangerous job of firefighting increasingly more controllable from a safety standpoint. The improvements in training methods, personal protective equipment, thermal imaging, and tools of the trade have evolved into a continuum of progress toward the goal of being safer and smarter. Apparatus manufacturers were quickly on board to take full advantage of this newfound computer age to develop safer, smarter fire apparatus.

Not lost in that desire to improve fireground safety was the fact that the manufacturing industry had to do its part to improve product reliability and safety. National Fire Protection Association (NFPA) 1911, Standard for the Inspection, Maintenance, Testing, and Retirement of In-Service Automotive Fire Apparatus, and NFPA 1901, Standard for Automotive Fire Apparatus, probably bear the brunt of that platform and road map for developing, maintaining, and designing safer fire apparatus. One thing, for sure, is that apparatus operations today are light years ahead of where they were just 10 to 15 years ago. There may be a few of us left who can remember fire trucks with standard transmissions. We arrived on scene, shifted the PTO into gear (many times outside the cab of the truck), placed the transmission shift rod into pump gear, and "locked" it in with the pin or hook that caught the latch on the shift rod. This sounds pretty safe if it is what you had back in the 1950s and 1960s-and decidedly so, because, for many, that was the only option.

The Modern Evolution

With the advent of higher horsepower engines, stronger automatic transmissions, and increasing demand from end users for "bigger pumps" came what I deem the modern evolution of fire apparatus. Manufacturers had the capability to meet all of those demands, but where did safety play into the mix? I can recall far too many stories of apparatus "launching" from their blocks while in pump gear and other tragic fire apparatus accidents. Looking forward, the apparatus industry investigated methods to isolate fire pump control at th

By Bill Adams

Apparatus specifications (specs) published by fire departments, manufacturers, vendors, and consultants regularly refer to National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus, as they should. Some refer to a Class A pumper (Class A), which they shouldn't.

A few refer to the Insurance Services Office (ISO), which could result in a longer lasting financial impact on a community than using NFPA 1901 and Class A. Spec writers should understand the significance using each term may or may not have. There should be justifiable reasoning when references are included in a spec.

The intent of this article is not to split hairs over specification verbiage. The objective is to make purchasers aware that referencing the ISO and NFPA 1901 can have financial implications as well as operational consequences. Class A, on the other hand, is an ambiguous traditional term that has no formal definition. Its historical meaning is subject to multiple interpretations. Consequently, it doesn't belong in a specification.

The ISO's requirements have changed (for those jurisdictions that subscribe to them), and NFPA 1901's are about to. Spec writers should be cognizant of those changes.

ISO

According to the ISO's Web site, "ISO evaluates municipal fire-protection efforts in communities throughout the United States." It analyzes efforts, grades them, and assigns a rating to them, which underwriters use to set insurance rates. The ISO states it is an "advisory organization" and "insurers may use our information, modify it, or not use it as they see fit." Compliance is voluntary. Noncompliance may detrimentally affect a community's rating and ultimately the cost of insurance within it.

One ISO tool used to grade fire protection is the Fire Suppression Rating Schedule (FSRS). It evaluates three major criteria: fire department, emergency communications, and water supply. There are substantial changes to the 2012 FSRS, including a new section designated "Community Risk Reduction." Fire departments should understand the grading system, what is expected of them, and how they will be evaluated. I only address ISO changes to ancillary equipment carried on apparatus herein. It is a very small part of the grading process.

NFPA 1901

NFPA 1901 is a minimum standard for fire apparatus. I describe it as an unenforceable nationally recognized safety standard. The fear of legal action resulting from noncompliance influences voluntary adherence by manufacturers and end users. NFPA 1901's newest revision is due in 2016. It is unlikely a manufacturer will deliver a noncompliant rig unless it receives a sign-off from the purchaser per NFPA 1901 Sentence 4.4.1.2. Whether fire departments actually equip and operate apparatus per NFPA 1901 after delivery is questionable. I pass no judgment on that important local decision. Refer to NFPA 1901 Section 4.21 regarding responsibility. Be mindful-the definition of responsibility can encompass accountability and liability.

The authority having jurisdiction (AHJ) or a political subdivision at a local or state level may have legislation mandating NFPA 1901 and ISO compliance. The fire department, or even a professional association representing department members, may have contractual agreements requiring similar compliance. Understanding ISO and NFPA criteria and concurrent changes will benefit all parties. Exercise caution. Changes in NFPA 1901 and ISO requirements may place a financial burden on a community. There are no NFPA or ISO police, but there are tort lawyers.

Class A Pumpers

There is no formal description for Class A pumpers. NFPA 1901 does not address them nor does the ISO. But, purchasing specifications reference them on a daily basis. What do purchasers expect when they specify one? Most manufactu

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