Piping

Standard pipe is made in a discrete number of sizes that are designated by nominal diameters in inches, as “inches IPS (iron pipe size).” Table A5 lists some of these sizes with dimensions in inches. Depending on the size, up to 14 different wall thicknesses are made With the same outside diameter. They are identified by schedule numbers, of which the most common is Schedule 40. Approximately,


Schedule number = 1000 PIS,



where:
P = internal pressure, psig
S = allowable working stress in psi.



Tubing for hecat exchangers, refrigeration, and general service is made with odside diameters measured in increments of 1/16 or 1/$ in. Standard size pipe is made of various metals, ceramics, glass,  and plastics.
Dimensional standards, materials of construction, and pressure ratings of pipiing for chemical plants and petroleum refineries are covered by ANSI Piping Code B31.3 which is published by the ASME, latest issue 1980. Many details also are given in such sources as C~ocker and King, Piping Handbook (McGraw-Hill,
New York, 19\67) Pery’s Chemical Engineers Handbook (1984), and Marks Standard Handbook for Mechanical Engineers (1987). In sizes 2in. and less screwed fittings may be used. Larger joints commonly are welded. Connections to equipment and in lines whenever need for disassembly is anticipated utilize flanges. Steel flanges, flanged fittings, and valves are made in pressure ratings of 150, 300, 600, 900, 1500, and 2500 psig. Valves also are made in 125 and 25Opsig cast iron. Pressure and temperature ratings of this equipment in various materials of construction are specified in the piping code, and are shown in Chem. Eng. Handbook 1984, pp. 6.75-6.78.