|V-Tech installed a rear-mount pump on a Metz aerial creating a very unique apparatus.|
|Aerials with pumps are far more common these days than in years goneby. (Fire Apparatus Photo)|
|Aerials and towers are installed on apparatus with many combinations of sizes and locations.|
There was a time when there were only straight aerials, water towers with no escape ladder, and city service apparatus with only ground ladders. Rarely did we see any fire pumps on these apparatus. They were normally supplied by a pumper or directly from a hydrant when a master stream was required. These straight aerials had no fixed waterway. Instead, they had a clamp-on portable monitor mounted on the base section fed by hoses.
Aerials and city service apparatus were commonly equipped for rescue and salvage operations. This lead to some apparatus being equipped with small pto-driven pumps, and many times they were high-pressure, gear-type pumps, used for auto fires and mop-ups.
Eventually, the city service trucks evolved into quads – Class A pumpers with full aerial complements of ground ladders.
The suburbs essentially did not exist, so city service and water towers rarely showed up outside the largest cities and aerials would not be found outside moderately sized towns.
There have always been exceptions, like the Sutphen Tower, which dates back to the late ’50s, but in general, the very big master stream flows seen today did not exist. City water systems were often limited to low flows. Water was delivered in 2.5-inch hose. Interior fires were fought with three quarter-inch booster reel to save water.
In the 1970s, major pumps started to show up on aerials and the trend continues today. The big change came with the rapid acceptance and advanced technology that the aerial towers, heavy-duty aerials with waterways and telesquirts brought to the market.
New products do not just appear without there first being a potential market. What were the social and environmental shifts that caused this change in product availability? There was a revolution in the US fire service in the ’70s, when it was recognized that water put out fires, not pressure.
The realization that big water is the best way to stop big fires led to a shift from 500- to 1,000-gallon water tanks on most pumpers; from .75-inch to 1.75-inch hose to attack a fire; from 2.5-inch to 5-inch water supply hose; and from a 750 gpm pump to 1,250 gpm pump, being the most common.
The second change came with high-powered diesel engines propelling large, heavy apparatus and driving big pumps.
Add to this the changes to building styles and location, coupled with the suburban growth. The mass development of large housing and office buildings set back from roads, and shopping malls gave the fire service the need for a long horizontal reach and a large master stream flow.
Those factors were the genesis of the quint tower apparatus seen today.
The other contributing factor was the federal funding of upgrades to municipal water systems in the ’60s. With water systems, there was sufficient water to operate the bigger master streams.
The ’70s also brought extrication rescue tools and a boom in rescue truck sales. This trend helped shift the rescue and overhaul work away from aerials and city service apparatus.
The late ’80s added the rescue pumper, which only encouraged this trend. This shift to specific rescue apparatus coincided with more cars, more accidents, and more rescue calls.
City Service Trucks
These newer apparatus eliminated the need for the city service truck. With the exception of a small number of ladder tenders used in Phoenix, Ariz., and a few other cities, the city service truck is gone. This also helped kill the demand for small pto pumps on aerials.
Lastly, in the ’60s, the old industrial cities of the Midwest and Northeast saw declining neighborhoods full of row homes, mostly made of wood that were usually poorly maintained.
Fires were common and complete city blocks were in jeopardy. The 55-foot Telesquirt on a pumper gave these departments a powerful weapon that was maneuverable enough for these narrow streets.
Over time, 75-foot aerial pumpers replaced the Telesquirts. The availability of bigger single rear axles and high-strength, lower-weight ladder designs made the 75-foot aerial pumper possible.
Starting in the ’80s, many departments had fewer personnel, so a “one-truck-does-all” with fewer people fit just fine.
That kind of apparatus could pump 30 gpm at a trash fire, or feed an aerial at 2,000 gpm at 220 psi. A full complement of crosslays, jump line, 2.5-inch and LDH discharges fulfill the normal pumper role while the aerial feed discharge handles the aerial device.
Since the bigger, heavy rescue and salvage equipment is now on a big rescue truck, the compartment space can be used for fittings, adapters and tools used on a pumper. This has also reduced ground ladder complements required by NFPA, and led to the almost total demise of the quad-type apparatus.
Nobody has the manpower to put up all these ground ladders. Setting up a 50-foot Bangor ladder takes more than two people.
The ’80s saw bigger waterways and better base swivels permitting even bigger performance. Today, 1,500 to 2,000 gpm are now common elevated waterway performances.
But what does it take to get that much water up 100 feet? Well, given the modern waterway design is about 220 psi, it is common to see waterways with a base section of 4 or even 5-inch piping.
Pumping From Draft
A 1,500 gpm pump with a 2.28 ratio and a 430 hp, could pump 1,500 gpm at 220 psi from draft with two sets of suction hose.
That same truck, given 40 psi at 2,000 gpm hydrant feed, will do the 2,000 gpm aerial performance. In both cases the engine speed will only be about 1,700 RPM. As you can see, the hydrant does enhance the amount of water delivered to the top of the aerial device.
The pump will out flow its ratings when connected to a positive water source and the additional pressure supplied to the pump is added to the pressure the pump produces.
These factors allow you to use the available engine power to produce the added performance. The good news is very few aerial operations happen with out a positive water source and the engine power needed to move an aerial down the road is significant.
So, you do not need a two-stage pump or a high-pressure, booster stage and have to live with the lower flows that accompany these higher operating pressure pump systems. Most aerial device waterways are not designed to operate at more than about 225 psi. That said, why would you want a two-stage or high pressurepump system that produces 600 to 700 psi?
Today, aerials and towers are installed on apparatus with many combinations of pump sizes and pump locations.
There are aerial apparatus with 3,000 gpm midship pumps, which can be fed by very high performance hydrants, which will allow for 4,000 gpm flows at the top of 100-foot or higher waterways.
Installing a major pump on an aerial device is very common today. Approximately 85 percent of all aerial apparatus have a major pump.
Even the Europeans are starting to get pumps on their aerial devices – they call them CARP, which stands for Combined Aerial Rescue Platform.
Here in the states, there are even some aerials with rear-mounted pumps as small as 1,000 gpm. Los Angeles County even buys tractor-drawn tillers will full midship pumps.
It’s becoming more common to add compressed air foam systems to aerials as well. In fact, foam systems on aerials are almost routine.
As you can see, there’s a wide variety of options and configurations for pumps on aerials. Thoughtful planning will help you decide what’s best for your department.