In an automatie-sprinkler system the sprinkler-heads are attached to tees in pipes against the ceiling: the arrangement being such that there shall be at least a sprinkler to every 100 ft. of floor, some places requiring a still larger ninnber of sprinklers. There should be two sources of water-supply, with cheek-valves in the pipes leading into the sprinkler system, giving it the benefit of the greater pressure without the intervention of any personal act. If one of these supplies is furnished by an elevated tank, the minimum head from the bottom of the tank to the highest sprinkler should be not less than 12 ft. The inability to withstand freezing temperatures is a defect in automatic-sprinkler systems which has not been fully remedied by invention. There are many so-ealled dry-pipe systems, in which the water is kept from the system until fire occurs, when the heat which releases the sprinkler is presumed to actuate devices which open the main valves, admitting vat er to the syst em. Such apparatus is always corn pl lent ed. These systems have sometimes proved to be inoperative at fires, and have been frequently dis covered to be out of order when examined. The attempts at making a solution of low-freezing point, which should be non-combustible, and under the conditions of its use should also be do not appear to have been successful. Water is sometimes removed from au tom-tie-sprinkler systems during cold weather by pumping in air to a pressure sufficient to displace the water. This method demands a great deal of attention : and in case of a fire it requires even longer to discharge the compressed air from the pipes and throw water on the fire than would be the ease with the usual dry-pipe system.
The only resource for automatic sprinklers in rooms liable to temperatures below the freez ing-point appears to he to stint the supply-valve and slowly draw the water from the pipes late in the autumn and to admit the water in the spring. The valves should be in a place accessible at time of fire. and all persons liable to have any duties in the matter should be made acquainted with the necessity of opening such valves in time rof fire. The discharge of automatic brass sprinklers. including the resistance of the pipe-fittings may be represented by Q=6 V/7, in which Q equals the discharge in eu. ft. per min., and p the pressure in lbs. per sq. in.
The following standard of sizes for pipes for automatic-sprinkler installations is based upon the principle of using the nearest commercial sizes permitting a uniform frictional loss through the system : When automatic sprinklers were first introduced there were many apprehensions that leak age and also excessive water discharged upon small fires would be sources of damage. In Eng land this opinion found expression in increased insurance rates in buildings where automatic sprinklers were installed. Many automatic sprinklers have been made in such a inannor as to impose unusual stress upon the fusible solder, which is a weak alloy, possessing but little re silience, and therefore ill-adapted to withstand the forces due to water-pressure. water-ham mer, and what is sometires greater than either, the initial tension in setting up the sprinkler to make it tight. iI is not surprising that such sprinklers break or leak : het among the score or more automatic. sprinklers on sale it is easy to select several varieties, any one of whiell would impose but little risk of leakage from water-pressure. The logic of figurt'S shows that this liability to damage is merely nominal in the ease of well-vet:strut:tett sprinklers. 1u rsalpinIinn of underwriters who have given eareftil attention to the subject obtained the [acts that out of 514,071 automat le sprinklers which had been in actual service on the average for five years, under a water-pressure reaching in some instances Is0 lbs. to the sq. in., hut averaging 09.111s. le Ile- sq. in., there had been only iestanees of sprinklers leaking from water-pressimra. and :117 instanees of leakage frame other pauses than tire. generally by acci
dents to the maphinery er by earelessness of t he employils, the average damage from all these causes being $2.56 per plant per annum. Although automatic sprinklers have proved to be so reliable and etteetive, yet, in order to provide for all possible row ingeneies, their introduc tion should not displace other forms of lirc-apparatus. particularly stand-pipes mu the stair way-towers with hydrants at each story. The hose at these hydrants should be festooned on a row of pins, or doubled on some of the reels made especially for such purposes. Stand pipes are not recommended to be placed in rooms or on fire-escapes; and inside hydrants should not be attached to the vertical pipes supplying automatic sprinklers. One pound of burning wood produces sufficient heat to evaporate 01 lbs. of water, and owing to the waste, a much larger proportion of water to fuel is necessary to quench a fire.
Fire-pumps are generally too small for the work required of them, 500 gals. per min. being: the minimum capacity recommended. For a five-story mill there should be an allowance of 250 gals. per min, for an effective fire-stream through a If in. nozzle, and for lower buildings the estimate should rarely be less than 200 gals. for each stream. Contrary to the general assumption, a ring nozzle is not so efficient as a smooth nozzle, the relative amount of dis charge of ring and smooth nozzles of the same diameter being as three is to four. For stand pipes fin. nozzles are recommended. but for yard-hydrant service the diameter should never be less than 1 in., and 1* in. generally fulfills the conditions of the best service. It is impor tant that the couplings on the hose and hydrants should fit those of the public fire department. The best diameter of hose is 21 in., the loss by friction under equal deliveries of water being only one third in a 21-in. hose of what it is in a hose 2 in. in diameter. Fire-pumps should be equipped with a relief-valve and also a pressure-gauge, and placed where they will be ac cessible under all circumstances, and so connected that they can be started at least once a week.
The best location for fire-pumps is a matter differing with the conditions of each mill, but they should be situated as near to the source of supply as practicable, with full-size suction pipe, easy of inspection and not containing any avoidable bends. In a steam-mill it is some times preferable to draft the water from a point below where the water of condensation is discharged into the stream, as there is less freezing there. In mills driven by water-wheels it is a convenience in time of repairs for steam tire-pumps to draft water from the wheel-pit. Rotary fire-pumps should have a short draft, but not placed below the level of the supply. Water-mains about a mill-yard should be of ample capacity not to cause an excessive loss by friction, their diameter being based upon a limit of velocity of 10 ft. per sec. for the maxi mum delivery. The yard hydrants should he placed at a distance of 50 ft. from buildings, and covered with a house which should also contain hose, nozzles, axes, bars, and spanners. Hydrant-houses are made in a great variety of forms, but it is important that the doors should be high enough to avoid ice, or that the house should be placed upon slight mounds. An economical hydrant-house may be built 6 ft. square with two adjacent sides hung on hinges, so that the doors can be swung around to the other side and be held by catches. The pins on which the hose is hung should be 2 in. in diameter, and placed diagonally and stag gered in two rows. If there is no hose-cart, the reserve hose can be placed on shelves. Stop valves in the mains should be covered by boxes 4 ft. in height, and the direction of opening clearly marked on the hand-wheel of the gate. (The foregoing is taken from Methods of Re ducing Fire Loss, by Mr. C. J. If. Woodbury, Trans. A. S. 31. E., vol. if. p. 271.)