June 2007

Nozzle Selection Depends On Philosophy And Components

By David A. Smith

Firefighting requires a range of key components – among them pumps, hose and nozzles – to deliver water to a fire.

Just as pumps and hoses have evolved through the years, so have nozzles, to the point where seemingly countless options exist. Nozzle selection can be a daunting task that depends on the other components as well as an individual department’s firefighting philosophy.

“Fundamentally, the nozzle must put the fire out. That goes without saying,” says Jay Johnson, director of product marketing at Akron Brass Co., the Ohio-based maker of nozzles, valves, hand tools and other firefighting accessories. “The reality is, there’s a lot of differences of opinions across the country and around the world as to what is the best approach.”

At the basic level, nozzles break down into a handful of main categories. The solid stream, or smoothbore nozzles, deliver a solid stream of water. Combination nozzles deliver both straight and so-called “fog” streams. There are also broken stream nozzles, which break the water stream into smaller droplets and are of particular use in certain applications, such as in piercing nozzles or cellar nozzles.

Further, combination nozzles can be additionally broken down to include “fixed-gallonage” – also called constant gallonage – which deliver water at a fixed rate; “selectable” – also called adjustable – which allow the nozzle operator to adjust the rate of gallons distributed; and “automatic,” which mechanically adjust flow to maintain pressure. And not to be forgotten, there are also high-pressure and low-pressure nozzles.

So which is the right one to use? That depends, say industry experts, and the debate over smoothbore versus combination, or adjustable versus automatic, can be as intense as the fire service debates over pump sizes or using water or CAFS (compressed air foam systems) or any number of other long-debated topics.

Comfort Level
“Any nozzle, whether it’s a fixed or selectable or automatic, really does one thing: It creates backpressure in the line, and that creates velocity,” says Rod Carringer, vice president of sales and marketing for Task Force Tips Inc., the Valparaiso, Ind.-based company manufactures nozzles, hand tools for rescue use and other firefighting equipment.

One of the more innovative nozzles in the fire service is the SaberJet, manufactured by Akron Brass Co. It is a combination nozzle, capable of offering a solid bore and fog stream as well as a combination stream – simultaneous solid and fog streams.    (Akron Brass Photo)

Mid-Force nozzles are part of Task Force Tips’ automatic dual-pressure nozzle line. The nozzles are adjustable from a straight stream to a dense fog pattern and are among the most popular products offered by TFT.

As for nozzle selection, he says, “A lot of it is tradition, how departments pump and the types of hose they use.”
Johnson agrees.

“The fundamental starting point is at the fire department level, in terms of how they approach firefighting within their organization,” he says. “There’s not a right or a wrong way. It’s just the comfort level.”

As the name would indicate, solid stream nozzles project a solid – or unbroken – stream of water through a nozzle equipped with a straight, smooth bore. Its design is among the most basic, with fewer moving parts requiring less maintenance, and the nozzle is noted for its ability to deliver a compact stream, with significant reach and maximum penetration.

Solid stream proponents cite the nozzle’s greater penetration and less disturbance to the thermal balance, in which hotter fire gases are found higher levels, while cooler gases are found at the lower levels. Disruption to that thermal balance can cause burns or injuries to firefighters or victims inside the burning structure.

Because solid streams are less likely to disrupt that thermal balance, they can offer firefighters better visibility, proponents say. They can also deliver a higher volume of water at lower pressures.
However, the nozzle does have some limitations. For one, it does not allow for a choice of patterns depending on a given fire fighting situation. It also provides for less heat absorption than fog streams, which maximize heat absorption by breaking up the water into smaller droplets with greater overall surface area.

Conversely, combination nozzles deliver a variety of flows, from a straight stream to a narrow fog pattern of 15 to 45 degrees to a wider fog pattern – wide-angle fog – beyond 45 degrees. It should be noted that there is a difference between solid and straight streams, as the solid stream produces a solid column of water and the straight stream is similar in shape to a solid stream, but with a hollow core.

Typically, combination nozzles are good for dissipating heat because their streams consist of thousands of water droplets and an accompanying large surface area. They also offer firefighters flexibility when it comes to selecting a pattern and can aid in ventilation, as fog patterns can move a great deal of air.

On the other hand, combination nozzles can offer less penetration and reach, as the stream is more affected by gravity, wind and other factors than solid streams. Combination nozzles can also cause heat inversion and may contribute to fire spread if used incorrectly, because of the volume of air they move.

Combination nozzles further break down into a variety of types. Those types include fixed-gallonage, manually-adjusted and automatic nozzles.

Fixed-gallonage nozzles deliver water at a predetermined flow. When nozzle pressure varies, for any number of reasons, so does the water flow. Manually-adjustable nozzles allow the nozzle operator to change the flow. Automatic nozzles, mechanically adjust and maintain pressure as the flow changes.
Each offers advantages and disadvantages.

Like A One-Speed Bike
Similar to smoothbore nozzles, fixed-gallonage nozzles operate at an optimum flow and pressure, Carringer says. A difference, he explains, is the smoothbore does not use “teeth” that break up the water stream, as happens with the combination nozzle.
“If you need more flow, you pull a second line or you over-pressurize the nozzle, which is not ideal,” he said. “It’s kind of like a one-speed bike, in that there’s an optimal range there.”

Selectable, or adjustable nozzles, meanwhile, offer the ability to change the nozzle setting.

“If a firefighter gets into a situation where more or less is desired, the firefighter can make that decision,” Carringer says. However, that flexibility comes with a caveat.

“There’s more flexibility, but it also requires a level of communication that goes along with that,” he says. “You need communication between the pump operator and the nozzle operator.”

Automatics, on the other hand, automatically adjust the flow to maintain a desired pressure. As the nozzle operator adjusts the shutoff valve, the nozzle makes the mechanical adjustment.

“The [advantage] is it is much more forgiving in a pumping operation,” Carringer says. That means the nozzle can be “gated ,” or adjusted by opening or closing, but stream quality remains optimal.

On the other hand, the nozzle is more complex, having more parts than a smoothbore.

Ultimately, the decision can boil down to department preference, says Johnson. For example, some departments want their firefighters to have control of what’s happening at the nozzle, and they opt for adjustable nozzles.

“That allows the firefighter to make the decision,” he says. “One of the things that has to be taken into account is to what degree does the fire department want to put that responsibility to the firefighter.”

That’s a decision to be made by each individual department.

Other factors to consider include the use of CAFS, which generally performs optimally with smoothbore nozzles

“That may have a bearing on your nozzle selection,” Johnson said. “You have to look at your fire fighting philosophy.”

And a lot goes into that discussion, Carringer says.

“We have hundreds and hundreds of choices,” he says. “To have a real discussion on nozzles, it needs to include hose. It needs to include pumps. It needs to include flow. Then it comes down to choices. Do you like fixed? Do you like selectable? Do you like automatic? And there’s features and benefits for each of them."