Document x1JprJzBoKO9ygzbam3JONK5Q

610 CHAPTER 27 1953` Guide with a.taper of 1 in 16 measured on the diameter of the pipe.so as to secure a tight joint. The number of threads per inch varies with 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 order ing line pipe2 which is used for oil piping, the couplings of which are provided with taper-tapped threads and may be used with regular mill-threaded standard weight pipe. Thread lengths should be in accordance with ASA 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 pipe. Fittings, Welding 611 S. American Standard Dimensions op Elbows^ Tees (Rosses, and 45 SOtDOHTPt FirmG BEFRlGERATOfi TYPE FIARED-TUBWG FITTW6S SAE COMPRESSION TUBING FITTINGS flARED*TUBMG FITTINGS Fio. 2. Copper or Brass Tubing Fittings known to the trade as pitch elbows and are 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 char acter 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 or inside, respectively. Screwed galvanized fittings are made according to the 150 lb American Standard. All dimensions given in inches. * This size is the nominal bore of the tube. k These dimensions may be used for wrought-metal fittings as well as for cast-brass fittings at manufac turer 8 option. This dimension is the same as the inside diameter Class L tubing (American Standard Specifications for Copper Water Tube, ASA H23.1-1939 (A.S.T.M. B88). ** Patterns shall be designed to produce body thicknesses given in the table. Metal thickness at no point shall be less than 90 percent of the' thicknesses given in the table, * This dimension has the same thicknesses as Type L tubing. {These dimensions are minimum, but in every case the thickness of wrought fittings should be at least as heavy as the tubing with which it is to be used. Note 1:--Wrought fittings, as well as cast fittings, must be provided with a shoulder or stop at the bottom end of socket. Note 2:--Street fittings with male ends are for use in connection with other fittings illustrated. 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 250 lb maximum saturated steam pressure, ASA B16b2, B16a, and B16b, re spectively. Malleable iron screwed fittings for 150 lb maximum saturated steam pressure, ASA B16c. Cast-iron screwed fittings for 125 and 250 lb maximum saturated steam pressure ASA B16d. Steel flanged fittings for 150 and 300 lb maximum steam service pressure, ASA Bl6e. 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 per mitted higher ratings for certain sizes of the 125 lb cast-iron flanged