FIRE STREAMS FROM SMALL HOSE AND NOZZLES

The importance of adequate fire protection has become so well recognized that most buildings even of moderate size are equipped with some sort of fire apparatus for immediate service in case of fire in the interior of the building, until the city fire department arrives. The ordinary water buckets and portable chemical fire extinguishers have in a large measure been supplemented with small fire hose. Very little data is available concerning the hydraulics of small fire streams. Many inquiries about the discharge from small nozzles and the loss of head in small hose lead to the tests which are herein described. The tests were undertaken with the object of acquiring data and putting it into such workable form that an owner or builder might be able to compute the quantity of water delivered by a nozzle of the size ordinarily used in the fire protection of the interior of the buildings, or the pressure necessary in the mains to give an effective fire stream with such nozzles, and also to throw some light upon the quantity of water which would be considered sufficient for temporary protection. The tests were conducted at the University of Illinois under the direction of the writer by A. O. Korsmo and A. B. Neininger, of the class of 1911, as thesis work. Much credit is due them for the care and thought given the problem and the thoroughness with which they did their work.

In 1888 John K Freeman conducted an extensive series of tests upon 2 1/2-inch fire hose and nozzles. The results of these tests are reported in an article, “Experiments Relating to the Hydraulics of Eire Streams,” in the Transactions of the American Society of Civil Engineers, 1889, vol. xxi, page 304. Deductions from these tests are given in Turneaure and Russell’s “Public Water Supplies,” page 250. In general, Mr. Freeman arrived at the following conclusions: Smooth control nozzles give co-efficients of discharge as high as any other form of nozzle, the iets reach further and no streams remain solid for greater distances than for any other form of nozzle of the same size of opening and with the same pressure at the base of the nozzle. For smooth conical nozzles 1 1/8 or 1 ¼ inches in diameter, a co-efficient of discharge of 0.977 may be taken with great confidence that this will not be more than one-half of 1 per cent, in error. The co-efficient will be slightly larger for smaller nozzles. The nozzle makes a very convenient method of measuring water. The friction is hut slightly more in smooth rubber-lined hose than in clean iron pipe of the same diameter. The friction in unlined linen hose is about two and one-third times as much as in smooth rubberlined hose. A hose elongates from 2 to 5 per cent, with a pressure of 50 pounds per square inch. This elongation produces a sinuosity which increases the loss of head about ti per cent. Care should be exercised that there is no abrupt change of section in the hose couplings and that no washers or gaskets are so left as to impede the flow of water. It is frequently recommended that a 250-gallon per minute fire stream be used in business districts, while a 175 or a 200-gallon stream may be used in a residential district. These discharges correspond to a nozzle pressure of 40 to 50 pounds per square inch and a hydrant pressure of NO to 110 pounds per square inch.

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