Page:Fires and Fire-fighters (1913).djvu/406

 floors of buildings on fire, let it be assumed that there is an outbreak on the sixteenth floor of a 20-story building. The companies arrive and connect to the stand-pipe, and as the fire is a threatening one four lines are led to the Siamese. Hook and ladder and engine company men proceed to the floor directly beneath the fire, by order of the Chief, using the elevator for this purpose. The ordinance requires that night and day elevator service must be pro- vided in all buildings over 150 feet in height. Each com- pany has its instructions, and a Battalion Chief, in com- mand on the inside accompanies them. As soon as con- nections have been made to the Siamese, the chief officer must determine the pressure necessary to furnish effective fire streams on the sixteenth floor, or an approximate height of 170 feet. The formula, for this procedure is to multiply the height of the building by .434, but here there is no time for pad and pencil. The best method is to allow 5 pounds for each floor of elevation, and at the height above mentioned it can be readily grasped that the result is 80 lbs.—7 lbs. more than the exact formula but which will be needed as the stand-pipe goes from the sidewalk to the basement and perhaps to the sub-basement. This gives the column additional length and as the stand-pipe often makes a right angled turn at the basement level there is an additional loss of pressure at that point. Also there is a nominal friction loss in the pipe itself. The writer's purpose is not to weary the reader with technical details, but it is necessary to explain this procedure for the benefit of commanding officers at fires, at greater length than many other subjects with which firemen are more familiar. Therefore, 5 lbs. will be allowed to each story for weight, about 4 lbs. friction loss for each 50- foot length of 3-inch hose, 5 lbs. loss at Siamese connections and 10 lbs. for entry head at the valve outlet on the upper floors.

It will be assumed that there are two lengths of 3-inch hose in each line, giving 8 lbs., 5 lbs. for Siamese, 80 for weight of water column and 10 for entry head; making 103 lbs. in all. Add to this the force necessary to