Fire truck mounted monitors explained
Better understanding what mounted deck guns are and when and how to use them enhances your fire attack capabilities
By Robert Avsec
Thomas Herman, a retired Richmond, Va. firefighter and antique fire apparatus restorer shared a bit of history mounted deck guns.
"Deck pipes were used in the horse-drawn fire apparatus era. They technically were used as far back as the hand pumper era, as the larger hand pumpers had pre-connected nozzles mounted on the top, some of which could throw a stream to almost 200 feet."
Though initially constructed using brass, today's monitors are made with brass, pyrolite or stainless steel. In addition to these lighter-weight materials — which aid in reducing the overall vehicle weight — today's monitors have a much lower profile and smaller footprint because of re-engineering of the water flow path through the nozzle.
Monitor nozzles can be found on practically any type of firefighting apparatus. The top-mounted monitors on pumpers can also be specified as a hybrid — that is, small and easily detachable so as to be used on the pumper or deployed as a portable monitor.
Adding weight to an aerial device is an important design consideration. Monitors are fed by pre-piped telescoping waterways with typical flow rates of 1,000 gpm to 2,000 gpm.
Pump requirements to provide adequate pressure at the end of a long aerial are demanding, therefore the internal efficiency or friction loss of the monitor should be carefully considered.
In days of old, ladder-mounted monitors were controlled from the ground using rope halyards. Modern monitors are available with electronic controls enabling the operator to control the fire stream's direction from the apparatus turntable.
Taking that one step further, wireless controls are now available that give the operator the ability to control the monitor's directional flow from anywhere around the apparatus. Multiple travel stops and the ability to stow to a preset position are other common features of aerial monitors.
Pumper-mounted monitors provide the capability to deliver a high-flow fire stream for a quick knockdown or as a master stream in defensive fire control. The typical flow rates of these monitors are from 500 gpm to 2,000 gpm. Both water stream and foam stream capabilities should be specified with foam being supplied by an internal vehicle proportioning system.
An increasingly popular monitor component is a device that extends the height of the gun above vehicle obstructions and gives the operator 360 degrees of operating range. While traditionally hand extended, electronic extenders are now available that raise the gun at the push of a button. These devices can also be controlled using a wireless remote control set.
Bumper or turret monitors are typically operated from within the vehicle, often by the vehicle's operator. These monitors are normally electric controlled by either joysticks or toggle switches with a manual override. Bumper monitors have typical flows of 15 gpm to 500 gpm depending upon the type of apparatus they are mounted on.
Electric turret-mounted monitors found on ARFF vehicles typically have flow rates of 350 gpm to 2,000 gpm. The vehicle operator can control both the fire stream's direction and pattern from within the vehicle.
Boots on the ground
A hybrid monitor is one part deck gun and one part portable monitor. This versatile device functions as a deck gun when mounted to the apparatus, yet it can be detached and deployed as a portable ground monitor.
These monitors can be manually controlled or controlled electronically using a wireless remote control unit. Flow rates vary from 350 gpm to 1,250 gpm.
Both hard-wired and wireless electric controls for monitor nozzles provide a significant safety advantage. Typically, the control point for an electrically operated monitor is at the pump panel or aerial turntable. For monitors mounted atop pumping apparatus, employing electric controls prevents a firefighter from having to climb atop the apparatus to operate the monitor.
NFPA 1901: Standard for Automotive Fire Apparatus, in its guidelines for apparatus construction, recommends the use of remotely operated monitors, without the need for a person to climb to the top of the apparatus.
Wireless electric controls offer all the advantages of hard-wired electric controls and enable operator control from multiple locations around or on the apparatus. This allows a firefighter to better sight the monitor stream, remain in a safer and less congested area and perform other supportive tasks.
Because they typically use more advanced controls over hard-wired devices, wireless-controlled monitors provide automatic stow, programmable stops, multiple travel speeds and programmable oscillation. Another big advantage over hard-wired systems is just like your personal computer or wireless device, system upgrades are a simple download away.
Placing the rig
The key to using the deck gun effectively is apparatus positioning. Using the 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, where you initially position the truck is where it will stay for the remainder of the incident; once the supply lines are attached it becomes difficult to reposition.
Consider other factors that can obstruct your attack stream, such as utilities poles and lines and trees. Likewise, take into account the structure's collapse zone.
As our apparatus has gotten bigger and bigger through the years, our deck guns have gotten taller. Many are 9 to 11 feet tall, 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 to produce a good stream from the deck gun inside a first-floor window or door opening if it's high on the truck.
A blitz attack using a monitor to quickly knock down a large volume of fire or to cut off extension using tank water can be an effective tactical operation. Keep in mind that tank size will limit the time you have to do it — so make the shot count.
Does your monitor have a control valve on the monitor itself? The time to find out should not be at a working fire; at best you may only have about 30 seconds worth of fire flow.
For a monitor without its own control valve, point the gun at the desired target, and then throttle up to your normal pump discharge pressure for that outlet.
Finally, open the deck gun discharge. 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.
And be mindful that the tank-to-pump valve — the valve and piping that allow water to enter the pump from the on-board water tank — limits the amount of water available for the monitor. Most tank-to-pump valves are limited to 500 gpm or less.
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. When operating a deck gun from a fixed position on an apparatus at a fire that has gone from offensive to defensive, make sure that all interior crews have been safely removed before applying the stream.
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.