By Homer Robertson
Published Sunday, April 1, 2012
| From the April 2012 Issue of FireRescue
The deck gun is our version of the military’s heavy artillery. The fire service has used deck guns mounted to the top of apparatus as far back as the days of horse-drawn fire trucks.
Why mount a master-stream device to the top of an apparatus? High-flow streams with lots of reach and penetration also produce lots of nozzle reaction. The deck gun provides a fixed, stable platform to absorb that reaction and operate the device in a safe manner. The deck gun has also found a home on top of many new trucks due to the weight and size of some of the old portable master-stream devices. Although they produced good flows on the fireground, they were heavy and slow to deploy and took up a great deal of compartment space.
Some deck guns can be used on top of the truck or removed and used in a ground set configuration. While versatile, these units are harder to use and require firefighters to train substantially prior to an incident to ensure a safe operation. You may also see standard two- or three-inlet ground set monitors that have been retrofitted to the tops of older apparatus; these monitors are rigged with short sections of 2½" or 3" hose that can be connected to a pump discharge and used from the top of the truck. Again, training and practice are the keys to success when using deck guns in this set-up.
Let’s take a look at some specific training points for deck guns.
Positioning Is Key
The key to using your deck gun effectively: apparatus positioning. Using your master stream will show you just how important proper positioning is.
There are a lot of factors to consider when choosing where to spot the truck, the most critical being the design and capabilities of the apparatus. Try to choose a spot that allows you to use the apparatus to its fullest extent. For example, if you’re coming to a building that’s fully involved and you know that the deck gun is the best weapon to use, you must determine a good spot from which to hit the fire or cut off extension.
Remember that in most cases, where you initially position the truck is where it will stay for the remainder of the incident, because as the supply lines are attached, it becomes difficult to reposition.
When practicing apparatus placement, always consider other factors that can obstruct your attack stream, such as phone poles and trees. Try to avoid these and still take full advantage of your stream by making a direct hit on the fire.
Height can also be a problem. As our apparatus have gotten bigger and bigger through the years, our deck guns have gotten taller; many are 9–11 feet tall and some are even taller. This becomes a problem when we try to bring a stream to bear on a one-story building, or when we have elevation differences between the structure and the apparatus. It’s hard for us to produce a good stream from the deck gun inside a first-floor window or door opening if it’s high up on the truck.
Also remember that little thing called gravity that your stream is fighting. Pay close attention to how far inside the building the stream reaches. If it only goes a few feet inside, it may not be reaching the seat of the fire.
Water Is a Must
I’ve seen many departments use their deck guns to quickly knock down a large volume of fire or to cut off extension by giving the fire a short burst from the deck gun for 30 seconds or so, using tank water. Sometimes this works; sometimes it doesn’t.
If you use this tactic, remember that your on-board tank size will limit the time you have to do it—so make the shot count. Point the gun at the desired target, then throttle up to your normal pump discharge pressure for that outlet. Then open the deck gun discharge. You don’t have much time so you must be on target. If you try to throttle up or position the gun after opening the valve, you’ll waste a lot of your tank water trying to get a stream before ever hitting fire.
Also, remind your pump operators about the limiting factor of the tank-to-pump valve. This is the valve and piping that allow water to enter the pump from the on-board water tank. Most are limited to 500 gpm or less.
To take full advantage of your deck gun, you’ll need a continuous water supply as soon as possible. Whatever method your department chooses —forward- or reverse-laid supply lines or tanker shuttles—just make sure that everyone knows that high-flow operations are planned so that ample water can be supplied.
Train to Be Safe
Deck guns bring a lot of firepower when delivering high-flow streams, but they come with some dangers. One of the most obvious is the fall hazard of being on top of the apparatus, along with getting up there to operate it and getting down afterward. Make sure that you take time to do it safely.
If the deck gun is removable, take extra precautions to make sure that it’s locked in place before opening the discharge. Also, never stand over the deck gun when pressure is applied. If you’re operating a deck gun from a fixed position on an apparatus in a fireground operation that has gone from offensive to defensive, make sure that all interior crews have been safely removed before applying the stream.
The bottom line: Don’t assume that the deck gun is easy to use just because you see it up there on top of the truck every day. Take time to go out and flow some water and learn your device’s characteristics.
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