Document 3N1GRp7nODKN6nMVBDQV9veqD

HEATING VENTILATING AIR CONDITIONING CUIDE 1942 prevent excessive load on the bottom support when expansion takes place, or the bottom support should be designed to withstand the entire load. TYPES OF FITTINGS Fittings for joining the separate lengths of pipe together are made in a variety of forms, and are either screwed or flanged, the former being generally used for the smaller sizes of pipe up to and including 334 in., and the latter for the larger sizes, 4 in. and above. Screwed fittings of large size as well as flanged fittings of small size are also made and are used for certain classes of work at the proper pressure. The material used for fittings is generally cast-iron, but in addition to this, malleable-iron, steel and steel alloys are also used, as well as various grades of brass or bronze. The material to be used depends on the character of the service and the pressure. As in the case of pipe, there are several weights of fittings manufactured. Recognized American Standards for the various weights are as follows: Cast-iron pipe flanges and flanged fittings for 25 lb (sizes 4 in. and larger), 125 lb, and 250 lb maximum saturated steam pressure. Malleable iron screwed fittings for 150 lb maximum saturated steam pressure. Cast-iron screwed fittings for 125 and 250 lb maximum saturated steam pressure. Steel flanged fittings for 150 and 300 lb maximum steam service pressure. The allowable cold water working pressures for these standards vary from 43 lb for the 25 lb standard to 500 lb for the 300 lb steel standard. Screwed fittings include: nipples or short pieces of pipe of varying lengths; couplings, usually of wrought-iron only; elbows for turning angles of either 45 deg or 90 deg; return bends, which may be of either the close or open pattern, and may be cast with either a back or side outlet; tees;, crosses; laterals or Y branches; and a variety of plugs, bushings, caps, lock-nuts, flanges and reducing fittings. Reducing fittings as well as bushings, both of which are used in changing from one pipe size to another, may have the smaller connection tapped eccentrically to permit free drain age of the water of condensation in steam lines or free escape of air in water lines. Fittings for copper tubing are available in the soldered, flared, or com pression types. Illustrations of each of these types are shown in Fig. 2. Fittings for copper pipe of IPS dimensions are available in screwed or soldered types of connection. American Standard A40.3-I941 has been prepared to cover certain dimensions of soldered-joint fittings for copper water tube including (1) detailed dimensions of the bore, (2) minimum specifications for materials, (3) minimum inside diameter of the fittings, (4) metal thickness for both wrought-metal and cast-brass fittings, and (5) general dimensions for cast-brass fittings including center-to-shoulder dimensions for both straight and reducing, cast fittings. Table 6 from A.S.A. Standard A40. 3-1941 contains dimensions for soldered joint elbows, tees, crosses, and 45 deg elbows. The compression type fitting is generally limited to smaller size tubing while the flared and soldered types are used in both large and small sizes. 350 CHAPTER 18. PIPE, FITTINGS, WELDING An American Standard, A.S.A. A40.2-1936 has been prepared to stand ardize dimensions for brass fittings for flared copper water tubes. Flared tube fittings are widely used in refrigerating work where S.A.E. dimen sions and a 45-deg flare render most fittings interchangeable, although for refrigeration'use, thread fits and tolerances on thread gages must be maintained within dose limits. Brass fittings with S.A.E. dimensions are not interchangeable with the American Standard fittings for water tubes. Ammonia pipe fittings made of cast-iron were,formerly used extensively in handling refrigerants in large installations. Replacement of ammonia by other refrigerants operating at lower pressures has seriously curtailed -- _ REFRIGERATOR TYPE FlARED-TUBING fittings CAE COMPRESSION TUBING nnwos FLAftED-TUfUNG FITTINGS. Fig. 2. Copper or Brass Tubing Fittings the market for these fittings. For this reason formulation of an American Standard for these fittings was abandoned by the A.S.A. in 1936. ThTrehardeaCdosnnuescetdionfosr fittings are the same American Standard taper pipe threads as those used for pipe, and unless otherwise ordered, right-hand threads are used. To facilitate drainage, some elbows have the thread tapped at an angle to provide a pitch of the connecting pipe of 34 in- to the foot. These elbows are known to the trade as pitched elbows and are commercially available. Malleable iron fittings, like brass fittings, are cast with a round instead of a flat band or bead, or with no bead at all. Fittings are designated as male or female, depending on whether the threads are on the outside or inside, respectively. Flanged fittings are generally used in the best practice for connecting all piping above 4 in. in diameter. While screwed fittings may be used for the larger sizes and are satisfactory under the proper working con ditions, it will be found difficult either to make or to break the joints in these large sizes. 351 j j \ I :