设置和照顾FIRE HYDRANTS

设置和照顾FIRE HYDRANTS

In general, there are two types of hydrants, "post” hydrants and "flush” hydrants. The first named is the more commonly used; the latter being employed only in large cities. “Post” hydrants project above the street level about two and one half or three feet, "Flush” hydrants, as the name suggests are flush with the street. In other words, they are placed in a chamber usually constructed of brick with a metal cover which is removed when the hydrant is to be used. In practically every case the main valve consists of leather discs held in place by metal washers and nuts, although in a few instances water is admitted by metal faced valves which move in a vertical plane. The first named type is known as “compression” hydrant while the latter, "gate” hydrant. Radical differences in the various designs of hydrants are shown in the illustrations herewith. Waste pipe or drip is pro vided hydrants as a rule to drain out the water in the chamber after the valve has been closed. No hydrant should be allowed to freeze up for an occasional inspection of tbe drip will insure perfect drainage. Hydrants should all open by turning in the same direction. When ordered from different makers, care should be taken that top and nozzle nuts and threads per inch on couplings are the same from each. If possible, have the couplings standard with adjacent cities for co-operation at large fires. In the selection of fire hydrants the following points should be carefully weighed: Durability, simplicity, accessibility of working parts, frost-proofness, waterway area and possible friction loss, liability of water-hammer and case of making repairs. Never use less than a six-inch connection for two and three-way hydrants. In operating hydrants, they should be opened and closed slowly. A good rule to follow is to employ as many seconds in opening or closing the hydrant as there are pounds static head of water.

Spacing of Hydrants.