CHROME MOLLY - It has been used for temperature upto 593oC. In the small diameter, the material is usually available in the seamless construction because of the inability of seamless mills to fabricate large dia and heavy wall pipe. It may be necessary to resort for a high temperature piping system & should be selected after a careful review of technical and economic considerations. For temperature upto 510oC, 1/2 carbon, 1/2 molly, A-335. Grade P-2 is used. For temperature 510-538oC, 1 Cr, 1/2 Molly steel. A-335 grade p-12 is used. For temperature 538oC to 566oC, 1 1/4Cr, 1/2 molly A-335 P-11 may be used. For temperature 566oC to 593oC, 2 1/4 Cr, 1 Molly A-335 Grade P-22 is frequently used. When there is a combination of high temp and erosive action 5 Cr 1/2 molly , A-335 Grade has been desirable. 

STAINLESS STEEL - It is available in a variety of compositions, most popular of which are ASTM-A-213, Grade TD-321. (16% Cr, 8%N stabilized with titanium) and ASTM-A-213 Grade TD-347 (18% Cr, 8% Ni) stabilized with columbium. Either of these two may be used upt to 649oC. Care must be given to choice of welding rold to avoid brittleness in the welds. 

SEAMLESS - A heated billet is brought into contact with tapered revolving rolls in such a way that the billed is pulled into the space allowed between the rolls. The mandrel is placed in the space. The soft centre of the billet makes it possible for the rolls to draw the billet over the mandrel, producing a hollow shell. When the billet has entirely passed over the mandrel, it is in the form of a thick walled seamless tube. The heavy walled tube is then passed to a rolling mill which reduces the tube to piping of proper outside diamter and wall thickness. Depending upon the process condition (temperature), seamless tube/pipes is termed as Hot Finish Seamless or cold drawn seamless as the term implies. 

Apart from above tubes and pipes can be formed by other processes, like forged, tunned, bored, etc depending upon the requirement.

Outside  Diameter/ Thickness in. 1/8  5/32  3/16  7/32  1/4  9/32  0.125 0.156 0.188 0.219 0.250 0.281 in. mm 3.175 3.969 4.763 5.556 6.350 7.144 1 7/16  36.51 0.796 0.970 1.140 1.295 1.440 1.557 1 1/2  38.10 0.834 1.017 1.196 1.361 1.516 1.661 1 5/8  41.28 0.909 1.111 1.310 1.493 1.667 1.838 1 11/16  42.86 0.948 1.159 1.368 1.560 1.744 1.918 1 3/4  44.45 0.985 1.206 1.424 1.626 1.819 2.002 1 7/8  47.63 1.061 1.301 1.538 1.759 1.970 2.172 1 29/32  48.42 1.080 1.324 1.566 1.792 2.008 2.215 2 50.80 1.137 1.395 1.652 1.892 2.122 2.343 2 1/8  53.98 1.213 1.490 1.766 2.024 2.273 2.513 2 5/32  54.77 1.231 1.508 1.794 2.057 2.311 2.555 2 1/4  57.15 1.288 1.584 1.880 2.157 2.425 2.683 2 3/8  60.33 1.364 1.679 1.994 2.290 2.577 2.854 2 1/2  63.50 1.440 1.773 2.108 2.423 2.728 3.024 2 5/8  66.68 1.516 1.868 2.222 2.556 2.880 3.165 2 3/4  69.85 1.591 1.693 2.336 2.688 3.031 3.365 2 7/8  73.03 1.667 2.057 2.450 2.821 3.183 3.538 3 76.20 1.743 2.152 2.564 2.954 3.334 3.706 3 1/4  82.55 1.895 2.341 3.792 3.219 3.638 4.046 3 1/2  88.90 2.046 2.530 3.020 3.485 3.941 4.387 3 3/4  95.25 2.198 2.719 3.248 3.750 4.244 4.728 4 101.60 2.349 2.908 3.476 4.016 4.547 5.068 4 1/4  107.95 2.501 3.098 3.704 4.282 4.850 5.409 4 1/2  114.30 2.652 3.287 3.932 4.547 5.158 5.750 4 3/4  120.65 2.804 3.476 4.160 4.813 5.456 6.091 5 127.00 2.955 3.665 4.388 5.078 5.759 6.431 5 3/32  129.38 3.012 3.736 4.473 5.178 5.873 6.559 5 1/4  133.35 3.107 3.854 4.616 5.344 6.063 6.772 5 3/8  136.53 3.183 3.949 4.730 5.476 6.214 6.942 5 1/2  139.70 3.259 4.043 4.843 5.609 6.366 7.113 5 9/16  141.28 3.297 4.091 4.901 5.676 6.442 7.199 5 3/4  146.05 3.410 4.232 5.071 5.875 6.669 7.453 6 152.40 3.562 4.422 5.299 6.140 6.972 7.794

Outside  Diameter / Thickness in. 5/16  11/32  3/8 13/32 7/16 15/32 1/2 0.313 0.344 0.375 0.406 0.438 0.469 0.5 in. mm 7.938 8.732 9.525 10.319 11.113 11.907 12.700 1 7/16  36.51 1.708 1.825 1.933 2.032 2.124 2.204 2.275 1 1/2  38.10 1.802 1.929 2.046 2.354 2.256 2.345 2.425 1 5/8  41.28 1.992 2.137 2.273 2.400 2.522 2.629 2.728 1 11/16  42.86 2.087 2.242 2.388 2.524 2.655 2.773 2.881 1 3/4  44.45 2.181 2.346 2.501 2.646 2.787 2.914 3.031 1 7/8  47.63 2.371 2.554 2.728 2.863 3.053 3.198 3.334 1 29/32  48.42 2.418 2.606 2.785 2.954 3.118 3.269 3.410 2 50.80 2.561 2.763 2.955 3.139 3.318 3.482 3.638 2 1/8  53.98 2.751 2.971 3.183 3.385 3.584 3.767 3.941 2 5/32  54.77 2.798 3.023 3.239 3.446 3.650 3.837 4.016 2 1/4  57.15 2.940 3.180 3.410 3.631 3.849 4.051 4.244 2 3/8  60.33 3.130 3.389 3.638 3.877 4.115 4.335 4.547 2 1/2  63.50 3.320 3.597 3.865 4.123 4.380 4.620 4.850 2 5/8  66.68 3.510 3.806 4.092 4.369 4.649 4.904 5.153 2 3/4  69.85 3.699 4.014 4.320 4.616 4.911 5.188 5.456 2 7/8  73.03 3.889 4.223 4.547 4.862 5.177 5.453 5.759 3 76.20 4.079 4.431 4.774 5.108 5.442 5.757 6.063 3 1/4  82.55 4.459 4.848 5.229 5.600 5.974 6.326 6.669 3 1/2  88.90 4.838 5.265 5.684 6.192 6.505 6.894 7.275 3 3/4  95.25 5.218 5.683 6.138 6.585 7.036 7.463 7.881 4 101.60 5.597 6.100 6.593 7.077 7.597 8.032 8.488 4 1/4  107.95 5.977 6.517 7.048 7.569 8.098 8.600 9.094 4 1/2  114.30 6.356 6.934 7.520 8.061 8.629 9.169 9.700 4 3/4  120.65 6.736 7.351 7.957 8.554 9.160 9.738 10.306 5 127.00 7.115 7.768 8.412 9.046 9.691 10.306 10.913 5 3/32  129.38 7.258 7.925 8.583 9.231 9.891 10.520 11.140 5 1/4  133.35 7.495 8.185 8.866 9.538 10.222 10.875 11.519 5 3/8  136.53 7.684 8.394 9.094 9.784 10.488 11.159 11.822 5 1/2  139.70 7.874 8.602 9.321 10.031 10.753 11.444 12.125 5 9/16  141.28 2.970 8.707 9.436 10.155 10.887 11.587 12.278 5 3/4  146.05 8.254 9.019 9.776 10.523 11.284 12.012 12.731 6 152.40 8.633 9.436 10.230 11.015 11.815 12.581 13.338

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