"I'm happy with what I have, so why confuse me with another hose size?" While there have been hundreds of thousands of discussions throughout the fire service on, for example, the flow merits of one nozzle or the penetration qualities of another, it must be understood that the most important...
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Probably the most practical method of utilizing two-inch hose without having to inventory a number of adapters is to equip it with couplings having common 1 1/2-inch hose threads. Until a few years ago, this could have been accomplished only by using complicated and expensive five-part couplings. These couplings cost about $50 to $60 per set, which made the per-foot cost of two-inch hose as expensive as 2 1/2-inch line. Sensing a need in the market, one coupling company developed an expansion ring drawbar that allowed the installation of inexpensive three-piece couplings on two-inch hose. This had the effect of materially reducing the per-foot cost of two-inch line to little more than 1 3/4-inch hose.
Photo by David P. Fornell
Engine 9 of the Danbury, CT, Fire Department replaced its 2 1/2-inch pre-connect with a 300-foot line of two-inch hose equipped with a 1 1/8-inch smooth bore. This combination gives the engine company an easily deployed and easily handled line that flows 240 gpm and which can be quickly stretched into the commercial structures or to the rear of the large homes or apartment buildings prevalent in its congested response district.
Photo by David P. Fornell
When considering the use of two-inch line, it is important to evaluate nozzle equipment that generates high flows at low nozzle operating pressures. At left is a smooth-bore nozzle with a 1 1/8-inch tip that provides 250 gpm at 45 psi nozzle pressure. At right is a Boston combination tip that provides 250 gpm at 50 psi nozzle pressure.
|Flow Rate||Midrange Automatic||200 gpm at 75 psi||250 gpm at 75 psi||Smooth-Bore (tip size)|
|230||116||117||77||72 (1 1/8")|
|240||121||126||81||78 (1 1/8")|
|250||126||135||85||89 (1 1/8")|
Advantages & Disadvantages
Two-inch line offers a number of advantages:
- It is not much larger in flat width than 1 3/4-inch hose. Often, the same amount of two-inch hose will fit in the hose bed space as the smaller line.
- It will deliver the same flow as 1 3/4-inch line at about half the engine pressure, or almost double the volume at the same engine pressure.
- It has the same 1 1/2-inch thread size couplings as other attack lines and is as easily deployed by as few personnel.
Two-inch line also has some disadvantages:
- It is somewhat heavier than 1 3/4-inch hose when filled with water, approximately 65 pounds per 50-foot length vs. 54 pounds for 1 3/4-inch line, but not nearly as heavy as 2 1/2-inch hose, which weighs approximately 120 pounds.
- While the charged two-inch hoseline looks and handles like 1 3/4-inch hose, its high-flow characteristics will allow the rapid generation of high nozzle reaction forces, similar to those experienced when operating 2 1/2-inch lines.
Before deciding to add two-inch hose to a firefighting toolbox, departments must understand that it creates the enigma of being able to more easily deliver high flow rates to the nozzle yet creates the problem of whether the nozzle operator can safely and effectively use these flows during attack operations. Proper nozzle selection becomes extremely important if it is desired to exploit the two-inch line's full potential. If it is decided to utilize a 100-psi combination nozzle on the business end, it makes more sense to utilize 2 1/2-inch hose because that line's increased weight can help the nozzle operators to better cope with relatively high nozzle reaction forces.
Designing Attack Lines
It's been noted that two-inch hose can usually be packed in the same beds as the present attack lines, can be easily moved into a fire building when charged and has the potential of supplying in-creased flow rates. The only part of the equation missing at this point is selection of a nozzle that can provide relatively high flow rates at manageable nozzle reaction forces.
While standard pressure combination nozzles can function well from a flow standpoint, the combination of a high flow rate exiting the nozzle at 100 psi generates nozzle reaction forces that could cause handling problems when they are operated by one or two firefighters. To lower the nozzle reaction force, it may be wise to investigate the advantages of low-pressure combination or smooth-bore nozzles.