Document x1nDkm45ek17Yk4jmyvr20E5J

$12 Chapter 16 1945 Guide _ t _____. i ' _ . ______ ______ ___ so"as to secure srtighfjoiriC The number of threads peTinch'varies witlf "the pipe size. Threads for fittings are the same, except that it is regular practice to furnish straight tapped couplings for Schedule 40 pipe 2 in. and smaller. For steam pressures in excess of 25 psi, it is recommended that taper-tapped couplings be used to obtain a tight-joint. These may be secured by ordering line pipe3 which is used for oil piping, the couplings of which are provided with taper-tapped threads and may be used with regular miil-threaded standard weight pipe. Thread lengths should be in accordance with A.S.A. B2.1. Right-hand threads are used unless otherwise-ordered. To facilitate drainage, some elbows have the thread tapped at an angle to provide a pitch of the connecting pipe of in. to the foot. These elbows are known to. the trade as pitch elbows and are SOLDER-TVFC FmtHG FUTCD-TUB1NG FITTINGS Fig. 2. Copper or Brass Tubing. Fittings commercially available. All threaded pipe joints should be made up with a thread paste suitable for the service for which the pipe is to be used. 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 3% 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, 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 of inside, respectively. Screwed galvanized fittings are made according to the 150 lb American Standard. . *See API Specification 5L for Line Pipe. American Petroleum Institute. Pipe, Fittings, Welding 313 As in the case of pipe, several weights of fittings are 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 2501b maximum saturated steam pressure, A.S.A. B16b2, B16a, and B16b respectively. ' Malleable iron screwed fittings for 150 lb maximum saturated steam pressure, A.S.A. B16c. Cast-iron screwed fittings for 125 and 250 lb maximum saturated steam pressure, A.S.A. BIGd. Steel flanged fittings for 150 a!nd 300 lb maximum steam service pressure, A.S.A. B16e. 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. War standard ratings in effect for the duration of. the emergency now permit higher. ratings for certain sizes of the 125 lb cast-ir-on flanged fitting standard, and for 300 lb steel flanges and flanged fittings than are shown in the regular American Standards mentioned previously. Screwed fittings include: nipples or short pieces of pipe of varying lengths; couplings of steel or wrought-iron; 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. Table 5 from A.S.A. Standard A40.3-1941 contain 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. An American'Standard, A.S.A. A40.2-I936 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 5.A.. dimen sions and a 45-deg flare render most fittings interchangeable, although for refrigeration use, thread fits and tolerances oh thread gages must be maintained within close 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 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. FLANGE FACINGS AND GASKETS A number of different flange facings in common use are plain face, raised face, tongue and groove, and male and female. Cast-iron fittings below are normally furnished with a plain face, while the cast-irn fittings are supplied with a Jd6-in. raised face. The s . facing for steel flanged fittings for 150 and 300 psi is a. J^-in. raised face although these fittings are obtainable with a variety of lacings. The gasket surface of the raised face may be finished smooth