DOUBLE EXTRA STRONG PIPE: This pipe is approximately twice as heavy as extra strong, and is made from to 8 inches, in both iron and steel._ It is difficult, however, to find any quantity in "Strictly Wrought-Iron," and the stock carried is usually soft steel. This pipe is shipped with plain ends, without couplings, unless ordered to thread and couple, for which there is an extra charge.
Fittings. For low-pressure heating systems, standard weight Cast-iron screwed fittings are used on pipes up to 7 inches or 8 inches diameter. On larger pipes it is customary to use standard flanged tings. Flange unions should be placed at vals in the pipes when screwed fittings are used, to provide for readily disconnecting them in case of alterations or repairs.
Pipe grease or various compounds are used in "mak ing up" the joints. This ma terial should be applied to the male threads only. When the threads of the fittings are coated with it, as is commonly done, the compound is pushed into the fitting when the pipe is screwed in, and, becoming disen gaged, is likely to cause trouble later by clogging pipes, etc. For flange fittings it is she practice with many fit ters to use inside gaskets, so called, cut to come just inside the bolts.
To describe a tee, al ways give the dimensions of the "run" first and the outlet last; for example, a tee 6 inches at one end, 5 inches at the other, with an outlet at the side 31 inches, would be known as a 6 by 5 by 31 tee. _ A tee with the outlet larger than the openings on the run, is known as a bullhead tee. Tees with all three openings of the same size are known as straight tees.
It is far better to use reducing sockets or reducing elbows and tees, in place of straight tees with bushings.
Hangers. Pipes up to 4 inches diameter inclusive are commonly suspended by malleable-iron hang ers, one type of which is shown in Fig. 44, with a gimlet point on the rod, a beam clamp being substituted when I-beams are used in place of floor timbers. One form of
adjustable hanger for large pipes is shown in Fig. 45.
Sleeves, etc. Where pipes pass through floors and parti Lions, they are encased in tubes with plates at floor and ceiling or at walls, as the case may be. One type of these sleeves is shown in Fig. 46.
Where branches from risers pass through partitions, it is often necessary to use sleeves of elliptical shape to provide for the expansion of the risers. Sleeves for mains passing through basement walls are generally made of pieces of wrought-iron pipe of the proper length, the diameter of the sleeves to be not less than inch greater than the pipe diameter if covering is omitted in walls, and 21 inches greater if covering is continuous along the pipe.
When sleeves are placed in plastered walls, they should project a slight distance beyond the face of the plaster. When ceiling plates are made fast to risers, they should be placed at least inch down from the ceilings, so that, when the riser expands, the ceil ing plate will not be forced into the plaster.
Valves. Valves for base ment piping are commonly globe or gate pattern, with rough bodies and plain iron wheels (Figs. 47 and 48). Brass or composition body valves, with screwed tops, are generally used up to 2-inch size inclusive; and iron body valves, with bolted tops, above that size (see Figs. 48 and 49). Both are made with renewable discs or seats.
It is largely a matter of pref erence which type of valve shall be used, though of course the straightway gate valves interpose the least resistance to the flow of steam or water.
When the radiators are but little above the water line in the boiler, gate valves are frequently used on the returns to insure an easy flow of the water.
It seems hardly necessary to point out that a globe valve should be connected in the pipe with its stem horizontal, to avoid the water pocket which occurs when the stem is vertical; nevertheless fitters frequently overlook this point.