5-Inch Hose Boosts Pumper Capability
Improvements in the materials used in large-diameter hose and couplings have made handling, deployment and use relatively easy. Departments which use large-diameter hose can improve the deployment capability of each pumper committed to a fire fighting operation while minimizing the time, equipment and effort required to deliver the potential volume of the pumper.
Friction loss charts and water flow tests show that one 5-inch hose delivers a volume approximately equivalent to six 2 ½-inch lines or four 3-inch lines at a given pressure and distance. Friction loss has a minimal effect on the delivery of up to 1000 gpm in a 5 or 6-inch hose lay as long as 600 feet. Where deliveries must exceed 1000 gpm or must be moved longer distances, as in rural areas, large-diameter hose provides the most efficient means of minimizing friction losses and developing the full potential of pumpers and water supplies.
Communities with water systems that meet insurance grading standards will have hydrants spaced 300 to 500 feet apart. Where hydrant spacing, volumes, and pressures are adequate, a pumper with 700 feet or more of largediameter hose will be able to use a single hvdrant-to-fire hose lay as a standard operating procedure and have adequate water flows for its pumping capacity.
Using the forward lay for in-line pumping with large-diameter hose eliminates the time and additional equipment required to lay multiple supply lines. Where hydrant pressures are adequate, an additional pumper need not be committed to the hydrant to overcome the friction loss problems of 2½ or 3-inch hose. Pumpers are placed at the fire, where equipment is readily available and attack lines can be more easily deployed for maximum effectiveness.
Where hydrants are unavailable or hydrant pressures are inadequate, a single fire-to-hydrant lay with 5 or 6inch hose provides a rapid and efficient system for delivering maximum available water to the fireground from a drafting location. Where the distances between the fire and a water supply are excessively long, relay pumping through large-diameter hose will establish adequate water supplies with minimal time and effort.
Triple combination pumpers with large-diameter hose can be rapidly deployed by two or three fire fighters. Using a single forward lay, well-trained, properly equipped teams can pump up to 500 gpm or more immediately upon arrival at a fire and can be operating on a hydrant supply and flowing water to the capacity of the pumper within one minute of arrival.
Laying supply line
In making a forward lay, one hydrant man is dropped off at the closest hydrant with the appropriate tools and adapters as the pumper arrives at the fire. When the pumper is spotted, one fire fighter can speed the supply system evolution by assisting the engineer in completing the large-diameter hose connections to the pump inlet while the engineer initiates pumping operations off the tank supply. A gate valve on the pump suction inlet will allow preconnected lines to be charged with tank water until the hydrant supply is available.
When the hydrant supply line is charged, the engineer should bleed off excessive air by using an air bleeder valve and then use the gate valve to control the change to the hydrant supply system. Once the pump is fully operational on the hydrant supply and the inlet gage shows a positive pressure, the engineer can refill his tank and maintain it as a reserve in the event of a water supply interruption.
In situations where a fire-to-water supply hose lay is required, the use of a gated manifold, or portable hydrant, at the fire will speed the completion of the evolution and provide outlets for the operation of pumpers or multiple hose lines.
Pumper design important
Pumpers carrying large-diameter hose should be designed for maximum safety and efficiency. Pump capacity should be compatible with the water system and the fire flow requirements of the community. The use of larger pumps (1250 to 1750 gpm) gives each pumper greater fire control capabilities.
Tank capacity should be as large as possible, considering road conditions and apparatus bay limitations. A modern pumper chassis can carry up to 1000 gallons of water and associated equipment safely if roads are capable of handling the additional size and weight of the apparatus. Larger tank volumes provide additional water for initial attack operations while giving the engineer a better margin of time and safety in maintaining a water supply to hose lines.
Tank-to-pump plumbing should be designed for the delivery of a minimum of 500 gpm to the pump without cavitation, whirlpooling or excessive friction losses. This provision will allow at least two 2½ -inch lines or four 1 ½ – inch lines to be operated from the tank supply for initial attack and containment operations. The plumbing should include a tank-fill valve so the tank can be used as an automatic reservoir once the hydrant supply is in operation.
When operating off the tank, a means should be provided for alerting fire fighters to an impending water supply interruption. A water level indicator connected to a solenoid switch to automatically blow the truck horn when the water level drops below 1/4 tank level, is an excellent alerting system. The horn alerts fire fighters and allows them sufficient time to back out of a hazardous situation.
Hose bed design
The hose bed should be designed to carry a minimum of 700 feet of largediameter hose and 1000 feet of 2 ½ or 3-inch hose. The 1000 feet or more of 2 ½ or 3-inch hose gives flexibility for the placement of multiple attack lines and provides sufficient additional hose for situations where smaller supply lines can be used. Many commercially designed hose beds can be modified to handle this additional hose by extending the height of the sides and dividers.
Sufficient preconnected hose lines should be provided for a rapid, flexible attack as soon as the pumper is spotted at the fireground. A minimum of two 1 ½ or 1 3/4-inch lines and one 2 ½ or 3inch line, in lengths of at least 150 feet each, should be preconnected on each pumper. Supplementing this with two additional 1 3/4-inch lines of at least 200 feet provides greater flexibility for attack. A preconnected deluge gun with an automatic nozzle extends control capabilities in attacking large fires.
Adequate compartment space must be provided to store large-diameter hose appliances and adapters as well as standard pumper equipment. Pumpers carrying 100-foot lengths of large-diameter hose in the hose bed should carry one 50-foot and one 25-foot length of the same hose for completing connections of 50 feet or less. A clappered Siamese adapter with 15 to 20-foot sections of 2 ½ or 3-inch hose attached should be carried on each pumper to adapt to hydrants without steamer outlets and for pumping into a large-diameter hose lay from 2 ½-inch pump outlets. Space should also be provided for a gated manifold, or portable hydrant, used in reverse lays and water distribution evolutions.
The tactical efficiency of a ppmper equipped as described was demonstrated in McCloud, Calif., on April 17, 1977. A dust explosion ripped through a sawdust processing plant, engulfing the 80 x 32 x 45-foot structure in fire. The fire department arrived three minutes after the explosion and found fire showing at all entrances, extending through holes blown in the roof and showering the surrounding structures with burning embers.
One 1250-gpm pumper with a 750gallon booster tank laid 300 feet of 5inch hose from the nearest hydrant to the fire. As soon as the pumper was spotted, four 1 1/2-inch lines and one 2 1/2-inch line, fed from the tank, were stretched to surround and attack the fire. Slightly more than half the tank water had been used by the attack lines when hydrant water was received.
Once the hydrant supply was on line, a master stream supplied by two 2 1/2inch lines supplemented the attack lines. An additional 2 ½-inch line was then stretched to supply two additional 1 ½-inch lines.
The fire was controlled about five minutes after the companies arrived at the scene. Damage was limited to the destruction caused by the explosion and moderate heat damage to the interior and the electrical distribution system.