Fire Service Hydraulics and Water Supply

Fire Service Hydraulics and Water Supply

Question 1

A fire apparatus, fire engine, fire truck, or fire appliance is a vehicle designed to assist in fighting fires by transporting firefighters to the scene and providing them with access to the fire, along with water or other equipment. In some areas, the terms fire engine and fire truck represent different types of firefighting apparatus[1].

A modern fire engine is usually a multi-purpose vehicle carrying paid firefighters or volunteers and equipment for a wide range of firefighting and rescue tasks. Therefore, most fire engines carry equipment such as ladders, pike poles, axes and cutting equipment, halligan bars, fire extinguishers, ventilating equipment, floodlights, hose ramps, self-contained breathing apparatus (SCBA), and general tools. Many fire appliances are based on standard truck or lorry models with heavy duty suspensions, brakes, tires, alternator, transmission and cooling systems; audible and visual warnings such as sirens, horns, and flashing lights; and a two-way radio[2].

The fire engine may have several methods of pumping water onto the fire, such as passing water obtained from a fire hydrant through hoses or using a pumping "cannon" (also known as a monitor or deck gun); some trucks have an onboard water reservoir. Some fire engines may carry ladders to gain access to fires occurring in high-rise buildings and remove casualties, or hooks used to pull walls away to expose hidden fire or break windows. In some regions, a rescue unit is an EMS truck with tools to carry out technical rescues of people from traffic collisions or structural collapses.

Question 2

Up until the late 1940's, structure fires were fought directly using solid streams. Although significant experimentation with fog streams had been underway for some time, their role was limited to fires involving oils and other combustible liquids. Then the late Chief Lloyd Layman introduced his “indirect method of attack” as a means of efficiently controlling fires in structures using the cooling and smothering effects of expanding steam. This launched a revolution, and within a short time the fire service was divided into two camps. One continued to advocate the use of solid streams; the other embraced the use of fog and spray streams.

Those who argued for the use of fog streams were further buoyed by the introduction of the so-called “combination attack” in the late 1950's. Developed by Keith Royer and the late Floyd W. “Bill” Nelson of Iowa State University's Fire Service Extension, combination attack theory did not necessarily mandate the use of fog streams. Royer and Nelson's main concerns were the rate of flow in gallons per minute and the efficiency of water distribution within the involved area. The form of the applied water was secondary, but fog stream proponents largely ignored this point [3].

The 1950's also saw nozzle manufacturers begin to tout the advantages of their new (and more expensive) fog nozzles. Scanning the pages of Fire Engineeringand Firemen magazines from the 1950's and 1960's, one gets the impression that to use anything other than water fog would brand you a tactical ...