(steel and wrought iron pipe)
In sizes from 1/8-inch thru 12-inch, pipe is known by its nominal inside diameter, which differs somewhat from the actual inside diameter. Early pipe manufacturers made the walls in the smaller sizes much too thick, and in correcting this error in design they took the excess from the inside to avoid changing the sizes of the companion fittings. To distinguish pipe sizes from actual measured diameters the terms iron pipe size (IPS) or nominal pipe size (NPS) are usually used. For sizes larger than 12-inch, pipe is known by its actual outside diameter. In all pipe sizes the outside diameter (OD) remains relatively constant; variations in wall thickness affect only the inside diameter (I.D.).
To distinguish different weights of pipe, three long standing traditional designations are used: standard wall (Std., extra strong wall (XS) and double extra strong wall (XXS). These last two designations are sometimes referred to as extra heavy wall (XH) and double extra heavy wall (XXH), respectively.
For the purpose of standardizing pipe dimensions, the American Standards Association (ASA), sponsored by the American Society for Testing Materials (ASTM) and the American Society of Mechanical Engineers (ASME), published ASA. B36.10. To broaden the range of wall thicknesses, schedule numbers from schedule 10 (S.10) thru schedule 160 (S.160) were adopted for steel pipe. These schedule numbers indicate approximate values for 1000 times the pressure-stress ratios. Later, stainless steel schedule numbers from schedule 5S through schedule 80S were published in ASA B36.19 for sizes thru 12-inch. The addition of the letter S after the schedule number identifies it as pertaining to stainless steel.
Certain relationships exist among the traditional designations of Std, XS, XXS, the ASA schedule numbers and the actual wall thicknesses. Std and S.40 are the same in sizes thru 10-inch; in sizes above 10-inch, Std has a wall of 3/8-inch. XS and S.80 are the same in sizes thru 8-inch; in sizes 10-inch and above, XS has a wall of 1/2-inch. XXS has no corresponding schedule number, but in sizes thru 6-inch, XXS has a wall twice as thick as XS. Stainless steel schedules 40S and 80S are identical with carbon steel designations Std and XS, respectively, thru 12-inch.
Weights for carbon steel pipe are based on a density of 0.2833 pounds per cubic inch; for wrought iron pipe the density is 0.2777 pounds per cubic inch. Since wrought iron pipe is made to steel outside diameters and steel weights per foot, the wall thicknesses of wrought iron pipe are necessarily slightly greater than steel pipe to compensate for this difference in densities. Wrought iron pipe is referred to as Std, XS, and XXS and not by schedule numbers.
Unless otherwise designated, references to pipe wall and thickness always mean the nominal, or average, wall thickness. Most ASTM tolerances on regular pipe products specify that the wall thickness of pipe at any point is to be no more that 12-1/2% under the nominal wall thickness specified. This means that a minimum wall of 0.875 times the nominal wall could apply for regular mill rolled pipe.
Unless ordered to cut lengths, at a higher price, pipe is supplied in random lengths (RL). This is due to the method on manufacture where damaged ends of each length are cut away during the finishing operations. For Std pipe a single random length usually falls in the range of 16 to 22 feet.
Threaded and coupled (T&C) pipe has threads that taper 3.4-inch per foot on the diameter for all sizes. Threads conform with the ASA B1.20.1. End to end measurements of T&C pipe include the attached coupling.
Unless otherwise specified: standard wall steel is furnished black; with threads and couplings; in random lengths; butt-weld in sizes 3-inch and smaller.
Random Lengths are considered to be 16 to 22 feet. We reserve the privilege, however, of supplying not more than 5% of the total number of lengths as "joiners" (two pieces coupled together) and, when ordered with plain ends, of supplying not over 5% of the total order in lengths 12 to 16 feet.
Cut Lengths carry an extra charge over random lengths.
Ends are available in plain (square cut) in all sizes and beveled in sizes 1-1/4 inch and larger.
Threads have a taper for all sizes of 3/4-inch per foot measured on the diameter.
Weights and dimensions are nominal. Permissible variation in weight is approximately 5% above and 5% below those shown. Weight per foot of pipe with threads and couplings is based on a length of 20 feet including coupling. Minimum wall thickness at any point shall not be more that 12.5% under nominal wall.
Extra Strong Wall
Unless otherwise specified: extra strong wall steel pipe is furnished black; with plain ends; in random lengths; butt-weld in sized 3-inch and smaller.
Please see above Standard Wall specifications for lengths, ends, and weight notes.
Double Extra Strong Wall
Unless otherwise specified: double extra strong wall steel pipe is furnished black; with plain ends; in random lengths.
Random Lengths are considered to be 12 to 22 feet. We reserve the privilege, however, of supplying not over 5% of the total order in lengths 6 to 12 feet.
Ends furnished with threads and couplings at an extra charge over plain ends.