All pipe should be of wrought iron or soft steel. Pipe at present is made in "standard", "extra strong"[76] and "double extra strong" weights. Until recently, a fourth weight approximately 10 per cent lighter than standard and known as "Merchants" was built but the use of this pipe has largely gone out of practice. Pipe sizes, unless otherwise stated, are given in terms of nominal internal diameter. Table 62 gives the dimensions and some general data on standard and extra strong wrought-iron pipe. TABLE 62 DIMENSIONS OF STANDARD AND EXTRA STRONG[76] WROUGHT-IRON AND STEEL PIPE _______________________________________________________________ | | | | | | Diameter | Circumference | | |__________________________|__________________________| | | | | | | | |External| Internal |External| Internal | | |Standard|_________________|Standard|_________________| | | and | | | and | | | | Nominal | Extra |Standard| Extra | Extra |Standard| Extra | | Size | Strong | | Strong | Strong | | Strong | |_________|________|________|________|________|________|________| | | | | | | | | | 1/8 | .405 | .269 | .215 | 1.272 | .848 | .675 | | 1/4 | .540 | .364 | .302 | 1.696 | 1.144 | .949 | | 3/8 | .675 | .493 | .423 | 2.121 | 1.552 | 1.329 | | 1/2 | .840 | .622 | .546 | 2.639 | 1.957 | 1.715 | | 3/4 | 1.050 | .824 | .742 | 3.299 | 2.589 | 2.331 | | 1 | 1.315 | 1.049 | .957 | 4.131 | 3.292 | 3.007 | | 1-1/4 | 1.660 | 1.380 | 1.278 | 5.215 | 4.335 | 4.015 | | 1-1/2 | 1.900 | 1.610 | 1.500 | 5.969 | 5.061 | 4.712 | | 2 | 2.375 | 2.067 | 1.939 | 7.461 | 6.494 | 6.092 | | 2-1/2 | 2.875 | 2.469 | 2.323 | 9.032 | 7.753 | 7.298 | | 3 | 3.500 | 3.068 | 2.900 | 10.996 | 9.636 | 9.111 | | 3-1/2 | 4.000 | 3.548 | 3.364 | 12.566 | 11.146 | 10.568 | | 4 | 4.500 | 4.026 | 3.826 | 14.137 | 12.648 | 12.020 | | 4-1/2 | 5.000 | 4.506 | 4.290 | 15.708 | 14.162 | 13.477 | | 5 | 5.563 | 5.047 | 4.813 | 17.477 | 15.849 | 15.121 | | 6 | 6.625 | 6.065 | 5.761 | 20.813 | 19.054 | 18.099 | | 7 | 7.625 | 7.023 | 6.625 | 23.955 | 22.063 | 20.813 | | 8 | 8.625 | 7.981 | 7.625 | 27.096 | 25.076 | 23.955 | | 9 | 9.625 | 8.941 | 8.625 | 30.238 | 28.089 | 27.096 | | 10 | 10.750 | 10.020 | 9.750 | 33.772 | 31.477 | 30.631 | | 11 | 11.750 | 11.000 | 10.750 | 36.914 | 34.558 | 33.772 | | 12 | 12.750 | 12.000 | 11.750 | 40.055 | 37.700 | 36.914 | |_________|________|________|________|________|________|________|