Fighting Fires in Buildings Equipped with Standpipes
The Volunteers Corner
As high buildings become more common in suburban—and even rural —areas, you should expect to find standpipe systems going right along with them.
The existence of a standpipe system in a community calls for folded or rolled hose to be carried on pumpers for use with standpipes. Whether you carry 1 1/2 or 2 1/2-inch hose for this purpose depends on the size hose the standpipe systems in your area are designed to supply. In some cases, one size hose will suffice, while in communities that have both large and small standpipe systems, both sizes of hose should be carried folded or rolled for standpipe work.
It is convenient to fold each 50foot length of hose in about 8-foot folds. The folds are often held together with leather or webbing straps. Another method is to pass sail twine four or five times around the folded hose about 2 feet from each end and tie it. (It is,easy to break one strand and release the hose for use.) The folded hose can be tossed over your shoulder and carried into a building without any of the folds dropping off. Hose that is rolled should be in donut rolls for easy stretching in cramped stairwells.
Hose in the standpipe rack should be disconnected from the standpipe valve and fire department hose should be connected to it. Never trust the building hose. You have no control over its quality or current condition.
Supplying standpipes: Like sprinkler systems, standpipe systems should be supplied by a fire department pumper to ensure an adequate flow of water with the proper pressure. Two supply lines should be run from the pumper to the standpipe Siamese. If one line should burst, the other will usually keep the standpipe system supplied while the length that failed is replaced. Although 2 1/2-inch hose is frequently used to supply standpipes, 3-inch hose is preferrable. It has a lower friction loss and can supply a greater volume of water. When only one hose line is used, only one supply line need be charged.
If the building has both sprinkler and standpipe systems, both systems should be supplied by pumpers at hydrants. The first system to be supplied should be the standpipe system and this should be done by the firstin engine company. The second-in engine should then hook up to the sprinkler system.
The reason for this, which sometimes stirs debate, is that your own men are on hose lines off standpipes and depend on a reliable water supply for their own safety as well as for extinguishing the fire. There must be no interruption in this water supply. If the water supply for the sprinkler system should fail, the chances are that no life is endangered as long as the line, or lines, off the standpipe remain in operation.
For their maximum protection, fire fighters should always connect the first line to the standpipe connection on the floor below the fire. They then advance the line up the stairs to the door on the fire floor. The excess hose can be taken up the stairs above the fire floor so that when the line is charged and the men enter the fire floor, it will be easier for them to advance the line as gravity helps move the hose down the stairs.
Engine pressures: To supply adequate pressure on the nozzle, the pump operator must consider several things in determining his engine pressure. First, he should figure a 25-psi allowance for friction losses in the standpipe system. This applies to any standpipe system in any building. Then he should consider the back pressure, nozzle pressure and friction losses in both the working hose line and the supply lines.
Calculate back pressure at 5 psi per floor. Fighting a fire on the seventh floor would result in a back pressure of 7 X 5 or 35 psi back pressure. Nozzle pressures for initial attack inside a high-rise building should be defined in a department’s operating rules and procedures. For fog tips, 100 psi on 1 1/2-inch lines and 70 psi on 2 1/2-inch lines will provide good operating streams with optimum mobility for the lines. The friction losses in the hose line and supply lines will, of course, depend on the volume of water flowing.
Let’s look at how a pump operator determines his engine pressure for a fire on the seventh floor. A 2 1/2-inch line has a fog nozzle flowing 200 gpm at 70 psi nozzle pressure and one of the two 3-inch, 200-foot supply lines is charged.
The operator would pump at 115 psi.