Richard Marinucci

Since the beginning of time, almost, water has been the choice for extinguishing fire. Even with the advent of foam, most departments have not deviated too far from the most basic extinguishing agent.

Even though the use of foam has demonstrated improved extinguishing power, it has not yet established itself as a "must-have" tool to put in the toolbox. Still, fire departments must continue to evaluate foam's benefits compared with the cost of adding another option for fire attack.

Foam Usage

There are many types of foam to choose from, but they essentially break down into use on either Class A or B fires or both. I believe a majority of departments have access to Class B foams for use on flammable liquid fires. They may have only a minimal amount or perhaps enough for a more significant fire. There seems to be a need for at least some basic capabilities to address flammable liquid fires regardless of where a fire department is. Fires involving liquids are possible wherever you are, so most departments anticipate the need and opt for this resource.

In a bit of a contrast, many departments have not chosen to adopt Class A foam as a component of their extinguishing capabilities. This could be for various reasons, including cost issues, adequate water supply such that a department does not feel compelled to add foam, or an organization does not fully understand what foam adds to its capabilities. Regardless, it is prudent to regularly evaluate an organization's needs and make a conscious decision regarding the cost/benefit appraisal of whether the time is right to add foam to the repertoire.

Justifying Enhancement

There is no doubt that using foam can enhance a department's capabilities. This does not always justify the costs and additional training and maintenance required. Departments must make their own decisions but should do so based on the latest information and their own specific circumstances. Like so many things, foam products and technology are changing rapidly. As such, departments should visit this issue frequently and make an informed decision.

Research into foam and its capabilities is essential. There are many types of foam, and they have different uses. A quick review of even the most basic information available will reveal many options. Internet searches will provide much information. There is also much to be learned from trade magazines and also from manufacturers and suppliers. Although much information is available, some misinformation exists. Learning as much as possible allows departments and end users to make informed decisions. This may be a topic to assign a suppression officer who can continually monitor the available information.

Departments must know the various options for foam available to them. Obviously there are foams for Class A and B fires. Foam can be low-, mid-, or high-expansion. Compressed air foam systems (CAFS) are an option. There are protein foams, fluoroprotein concentrates, film forming and aqueous film forming, alcohol-resistant, and synthetic detergent foams. Each has a purpose, benefit, and some features that are not as good for certain fires. There are physical characteristics to consider such as flow and knockdown speed, heat, fuel, and alcohol resistance, along with vapor suppression. The more an organization knows about its choices the more likely it will make the best choice for the department.

Equipment Considerations

Using foam requires additional equipment including a proportioner-either an inline eductor or an around-the-pump system. Departments will need to make that decisi

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