Attachment 4 Subject: Part 2, Supplement 2, S2.10.4 – Average
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Attachment 4 Subject: Part 2, Supplement 2, S2.10.4 – Average Staybolt Pitch File Number: NB12-1201 Proposal: Update text in S2.10.4, S2.10.6 to include provisions and mathematics for rectangular staybolt patterns found on many historical boilers. Current text: Reword as follows: S2.10.4 STAYED SURFACES The maximum allowable working pressure for stayed flat plates and those parts which, by these rules, require staying as flat plates with stays or staybolts of uniform diameter, uniformly spaced, shall be calculated using the following formula or Table S2.10.4. ð= ðĄ2 × ð × ðķ ð2 When pitches of stays or staybolts of uniform diameter are symmetrical and form a rectangle, the equation may be replaced with the following equation: ð= 2 × ðĄ2 × ð × ðķ ð2 + ðĪ 2 See definitions of nomenclature in S2.10.6. […] S2.10.6 NOMENCLATURE […] ï· ï· ï· ï· ï· p = maximum pitch measured between straight lines passing through the centers of the staybolts in the different rows, which lines may be horizontal, vertical, or inclined, inches or mm l = the pitch of stays in one row, passing through the centers of the staybolts, which line may be horizontal, vertical, or inclined, inches or mm w = the distance between two rows of staybolts, inches or mm h = the hypotenuse of a square or rectangle, defined as either √2ð2 or √ð 2 + ðĪ 2 , inches or mm d = minimum diameter of corroded staybolt, inches or mm […] p Thickness of Stayed Surface, in. 0.19 0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.4 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 Staybolt Spacing (Square Pitch), in. (p) 3.500 85 95 104 115 125 136 148 160 172 185 199 213 227 242 258 273 290 307 324 342 360 379 398 417 437 480 502 524 547 571 3.625 80 88 97 107 117 127 138 149 161 173 185 198 212 226 240 255 270 286 302 318 335 353 371 389 408 447 468 489 510 532 3.750 74 82 91 100 109 119 129 139 150 162 173 185 198 211 224 238 252 267 282 298 313 330 346 364 381 418 437 457 477 497 3.875 70 77 85 93 102 111 121 130 141 151 162 174 185 198 210 223 236 250 264 279 294 309 324 340 357 391 409 428 447 466 TS = Tensile Strength, 55,000 psi S = 13,800 psi t = Thickness of Stayed Surface, in. p = staybolt spacing, in. 4.000 65 72 80 88 96 104 113 122 132 142 152 163 174 185 197 209 222 235 248 262 275 290 304 320 335 367 384 402 419 437 4.125 61 68 75 82 90 98 106 115 124 134 143 153 164 174 185 197 209 221 233 246 259 273 286 300 315 345 361 378 394 411 4.250 58 64 71 78 85 92 100 108 117 126 135 144 154 164 175 185 197 208 220 232 244 257 270 283 297 325 340 356 371 387 4.375 55 61 67 73 80 87 95 102 110 119 127 136 146 155 165 175 185 196 207 219 230 242 255 267 280 307 321 336 350 365 4.500 52 57 63 69 76 82 89 97 104 112 120 129 138 147 156 165 175 185 196 207 218 229 241 252 265 290 304 317 331 345 4.625 49 54 60 66 72 78 85 92 99 106 114 122 130 139 148 157 166 176 185 196 206 217 228 239 251 275 287 300 314 327 ð= 4.750 46 51 57 62 68 74 80 87 94 101 108 116 123 132 140 148 157 166 176 185 195 206 216 227 237 261 272 285 297 310 ðĄ2 × ð × ðķ ð2 4.875 44 49 54 59 65 70 76 82 89 96 103 110 117 125 133 141 149 158 167 176 185 195 205 215 225 247 259 270 282 294 5.000 42 46 51 56 61 67 72 78 85 91 97 104 111 119 126 134 142 150 159 167 176 185 195 204 214 235 246 257 268 280 5.125 40 44 49 53 58 64 69 75 80 87 93 99 106 113 120 128 135 143 151 159 168 177 185 195 204 224 234 245 255 266 5.250 38 42 46 51 56 61 66 71 77 82 88 95 101 108 115 122 129 136 144 152 160 168 177 185 194 213 223 233 243 254 5.375 36 40 44 49 53 58 63 68 73 79 84 90 96 103 109 116 123 130 137 145 153 160 169 177 185 203 213 222 232 242 5.500 35 38 42 46 51 55 60 65 70 75 81 86 92 98 104 111 117 124 131 138 146 153 161 169 177 194 203 212 222 231 5.625 33 37 40 44 48 53 57 62 67 72 77 82 88 94 100 106 112 119 125 132 139 147 154 162 169 186 194 203 212 221 5.750 32 35 39 42 46 50 55 59 64 69 74 79 84 90 95 101 107 114 120 127 133 140 147 155 162 178 186 194 203 212 5.875 30 34 37 41 44 48 52 57 61 66 71 76 81 86 91 97 103 109 115 121 128 134 141 148 155 170 178 186 194 203 6.000 29 32 36 39 43 46 50 54 59 63 68 72 77 82 88 93 99 104 110 116 122 129 135 142 149 163 171 178 186 194 For thicknesses 0.4375” and less, C = 2.1 For thicknesses larger than 0.4375”, C = 2.2 P = MAWP, psi Table S2.10.4 [US Customary Units] Maximum Allowable Working Pressure for Square Stayed Surfaces, Formula per ASME Section 1, PG-46.1 p Thickness of Stayed Surface, mm 5 5.25 5.5 5.75 6 6.25 6.5 6.75 7 7.25 7.5 7.75 8 8.25 8.5 8.75 9 9.25 9.5 9.75 10 10.25 10.5 10.75 11 11.25 11.5 11.75 12 12.25 Staybolt Spacing (Square Pitch), mm (p) 89 630 694 762 833 907 984 1064 1148 1234 1324 1417 1513 1612 1714 1820 1928 2040 2155 2273 2394 2519 2646 2777 2911 3048 3339 3489 3643 3800 3959 92 589 650 713 779 849 921 996 1074 1155 1239 1326 1416 1509 1604 1703 1805 1909 2017 2127 2241 2357 2476 2599 2724 2852 3125 3266 3409 3556 3705 95 553 609 669 731 796 863 934 1007 1083 1162 1243 1328 1415 1505 1597 1692 1791 1891 1995 2101 2211 2322 2437 2555 2675 2931 3063 3197 3335 3475 98 519 573 628 687 748 811 878 946 1018 1092 1168 1248 1329 1414 1501 1590 1683 1777 1875 1975 2077 2182 2290 2401 2513 2754 2878 3004 3134 3266 TS = Tensile Strength, 380,000 kPa S = 95,000 kPa t = Thickness of Stayed Surface, mm p = staybolt spacing, mm 101 489 539 592 647 704 764 826 891 958 1028 1100 1175 1252 1331 1413 1497 1584 1673 1765 1859 1956 2055 2156 2260 2366 2593 2710 2829 2950 3075 104 461 508 558 610 664 721 779 840 904 970 1038 1108 1180 1255 1333 1412 1494 1578 1665 1753 1844 1938 2034 2132 2232 2446 2555 2668 2783 2900 107 436 480 527 576 627 681 736 794 854 916 980 1047 1115 1186 1259 1334 1411 1491 1573 1656 1743 1831 1921 2014 2108 2310 2414 2520 2629 2739 110 412 454 499 545 594 644 697 751 808 867 927 990 1055 1122 1191 1262 1335 1411 1488 1567 1649 1732 1818 1905 1995 2186 2284 2385 2487 2592 113 391 431 473 517 562 610 660 712 766 821 879 938 1000 1063 1129 1196 1266 1337 1410 1485 1562 1641 1723 1806 1890 2072 2165 2260 2357 2456 116 371 409 448 490 534 579 626 676 726 779 834 890 949 1009 1071 1135 1201 1269 1338 1409 1483 1558 1635 1713 1794 1966 2054 2144 2237 2331 ð= 119 352 388 426 466 507 550 595 642 690 740 792 846 902 959 1018 1079 1141 1205 1271 1339 1409 1480 1553 1628 1705 1868 1952 2038 2125 2215 ðĄ2 × ð × ðķ ð2 122 335 369 405 443 483 524 566 611 657 705 754 805 858 912 968 1026 1086 1147 1210 1274 1340 1408 1478 1549 1622 1777 1857 1939 2022 2107 125 319 352 386 422 460 499 539 582 626 671 718 767 817 869 922 978 1034 1092 1152 1214 1277 1341 1408 1476 1545 1693 1769 1847 1926 2007 128 304 336 368 403 438 476 514 555 597 640 685 731 779 829 880 932 986 1042 1099 1158 1218 1279 1342 1407 1473 1614 1687 1761 1837 1914 131 291 320 352 384 419 454 491 530 570 611 654 698 744 791 840 890 942 995 1049 1105 1163 1221 1282 1343 1407 1541 1611 1681 1754 1828 134 278 306 336 367 400 434 469 506 544 584 625 667 711 756 803 851 900 951 1003 1056 1111 1167 1225 1284 1344 1473 1539 1607 1676 1747 137 266 293 322 351 383 415 449 484 521 559 598 638 680 723 768 814 861 909 959 1010 1063 1117 1172 1228 1286 1409 1473 1537 1603 1671 140 254 281 308 337 366 398 430 464 499 535 573 611 651 693 735 779 824 871 919 968 1018 1069 1122 1176 1232 1350 1410 1472 1536 1600 143 244 269 295 323 351 381 412 445 478 513 549 586 624 664 705 747 790 835 880 927 976 1025 1076 1127 1180 1294 1352 1411 1472 1534 146 234 258 283 309 337 366 395 426 459 492 526 562 599 637 676 717 758 801 845 890 936 983 1032 1082 1132 1241 1297 1354 1412 1471 149 225 248 272 297 323 351 380 409 440 472 505 540 575 612 649 688 728 769 811 854 899 944 991 1038 1087 1191 1245 1300 1356 1413 For thicknesses 11mm and less, C = 2.1 For thicknesses larger than 11mm, C = 2.2 P = MAWP, kPa Table S2.10.4 [Metric Units] Maximum Allowable Working Pressure for Square Stayed Surfaces, Formula per ASME Section 1, PG-46.1 152 216 238 261 285 311 337 365 393 423 454 486 519 553 588 624 661 699 739 779 821 863 907 952 998 1045 1145 1196 1249 1303 1357 l h Thickness of Stayed Surface, in. 0.19 0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.4 0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 w Staybolt Spacing (Rectangular Pitch), in. (h) 5.000 84 93 102 112 123 134 145 157 169 182 195 209 223 237 252 268 284 300 317 335 353 371 390 409 429 470 492 514 537 560 5.125 80 88 97 107 117 127 138 149 161 173 186 199 212 226 240 255 270 286 302 319 336 353 371 389 408 448 468 489 511 533 5.250 76 84 93 102 111 121 131 142 153 165 177 189 202 215 229 243 258 273 288 304 320 336 353 371 389 426 446 466 487 508 5.375 72 80 88 97 106 116 125 136 146 157 169 181 193 205 218 232 246 260 275 290 305 321 337 354 371 407 426 445 464 484 TS = Tensile Strength, 55,000 psi S = 13,800 psi t = Thickness of Stayed Surface, in. h = Hypothenusal staybolt spacing, in. 5.500 69 77 84 93 101 110 120 130 140 150 161 172 184 196 209 221 235 248 262 277 291 307 322 338 354 389 406 425 443 462 5.625 66 73 81 89 97 106 114 124 134 144 154 165 176 188 199 212 224 237 251 265 279 293 308 323 339 372 389 406 424 442 5.750 63 70 77 85 93 101 110 119 128 137 147 158 168 180 191 203 215 227 240 253 267 280 295 309 324 356 372 389 406 423 5.875 61 67 74 81 89 97 105 114 122 132 141 151 161 172 183 194 206 218 230 242 255 269 282 296 310 341 356 372 389 405 6.000 58 64 71 78 85 93 101 109 117 126 135 145 155 165 175 186 197 209 220 232 245 258 271 284 298 327 342 357 373 389 6.125 56 62 68 75 82 89 97 104 113 121 130 139 148 158 168 179 189 200 212 223 235 247 260 273 286 313 328 342 358 373 ð= 6.250 54 59 65 72 78 85 93 100 108 116 125 134 143 152 162 172 182 192 203 214 226 237 249 262 274 301 315 329 343 358 6.375 51 57 63 69 75 82 89 96 104 112 120 128 137 146 155 165 175 185 195 206 217 228 240 252 264 289 303 316 330 344 2 × ðĄ2 × ð × ðķ â2 6.500 50 55 60 66 73 79 86 93 100 108 115 123 132 140 149 159 168 178 188 198 209 219 231 242 254 278 291 304 317 331 6.625 48 53 58 64 70 76 83 89 96 104 111 119 127 135 144 153 162 171 181 191 201 211 222 233 244 268 280 293 306 319 6.750 46 51 56 62 67 73 80 86 93 100 107 114 122 130 139 147 156 165 174 184 193 204 214 224 235 258 270 282 294 307 6.875 44 49 54 59 65 71 77 83 89 96 103 110 118 126 134 142 150 159 168 177 187 196 206 216 227 249 260 272 284 296 7.000 43 47 52 57 63 68 74 80 86 93 99 106 114 121 129 137 145 153 162 171 180 189 199 209 219 240 251 262 274 286 7.125 41 46 50 55 60 66 71 77 83 90 96 103 110 117 124 132 140 148 156 165 174 183 192 201 211 232 242 253 264 276 7.250 40 44 49 53 58 64 69 75 80 86 93 99 106 113 120 127 135 143 151 159 168 176 185 195 204 224 234 244 255 266 7.375 38 43 47 52 56 61 67 72 78 84 90 96 102 109 116 123 131 138 146 154 162 170 179 188 197 216 226 236 247 257 7.500 37 41 45 50 55 59 64 70 75 81 87 93 99 106 112 119 126 134 141 149 157 165 173 182 191 209 219 228 238 249 For thicknesses 0.4375” and less, C = 2.1 For thicknesses larger than 0.4375”, C = 2.2 P = MAWP, psi Table S2.10.4.a [US Customary Units] Maximum Allowable Working Pressure for Rectangular Stayed Surfaces l h Thickness of Stayed Surface, mm 5 5.25 5.5 5.75 6 6.25 6.5 6.75 7 7.25 7.5 7.75 8 8.25 8.5 8.75 9 9.25 9.5 9.75 10 10.25 10.5 10.75 11 11.25 11.5 11.75 12 12.25 w Staybolt Spacing (Rectangular Pitch), mm (h) 125 638 704 772 844 919 998 1079 1163 1251 1342 1436 1534 1634 1738 1845 1955 2068 2185 2305 2428 2554 2683 2815 2951 3090 3386 3538 3693 3852 4014 130 590 651 714 781 850 922 998 1076 1157 1241 1328 1418 1511 1607 1706 1808 1912 2020 2131 2244 2361 2480 2603 2728 2857 3130 3271 3415 3562 3712 135 547 603 662 724 788 855 925 998 1073 1151 1231 1315 1401 1490 1582 1676 1773 1873 1976 2081 2189 2300 2414 2530 2649 2903 3033 3167 3303 3442 140 509 561 616 673 733 795 860 928 998 1070 1145 1223 1303 1386 1471 1559 1649 1742 1837 1935 2036 2139 2244 2353 2463 2699 2820 2944 3071 3200 145 474 523 574 627 683 741 802 865 930 998 1067 1140 1215 1292 1371 1453 1537 1624 1713 1804 1898 1994 2092 2193 2296 2516 2629 2745 2863 2983 TS = Tensile Strength, 380,000 kPa S = 95,000 kPa t = Thickness of Stayed Surface, mm h = Hypothenusal staybolt spacing, mm 150 443 489 536 586 638 693 749 808 869 932 998 1065 1135 1207 1281 1358 1436 1517 1600 1686 1773 1863 1955 2049 2146 2351 2457 2565 2675 2788 155 415 458 502 549 598 649 702 757 814 873 934 998 1063 1130 1200 1272 1345 1421 1499 1579 1661 1745 1831 1919 2010 2202 2301 2402 2505 2611 160 390 430 471 515 561 609 659 710 764 819 877 936 998 1061 1126 1193 1262 1334 1407 1482 1559 1637 1718 1801 1886 2067 2159 2254 2351 2450 165 366 404 443 485 528 572 619 668 718 770 824 880 938 998 1059 1122 1187 1254 1323 1393 1466 1540 1616 1694 1773 1943 2031 2120 2211 2304 170 345 381 418 456 497 539 583 629 677 726 777 829 884 940 998 1057 1118 1181 1246 1312 1381 1451 1522 1595 1671 1831 1913 1997 2083 2170 ð= 175 326 359 394 431 469 509 550 594 638 685 733 783 834 887 941 998 1055 1115 1176 1239 1303 1369 1436 1506 1576 1727 1805 1884 1965 2048 180 308 339 373 407 443 481 520 561 603 647 693 740 788 838 890 943 998 1054 1111 1171 1231 1294 1358 1423 1490 1633 1706 1781 1858 1936 185 291 321 353 385 420 455 493 531 571 613 656 700 746 793 842 893 944 998 1052 1108 1166 1225 1285 1347 1411 1546 1615 1686 1759 1833 190 276 305 334 365 398 432 467 504 542 581 622 664 707 752 799 846 895 946 998 1051 1105 1161 1219 1277 1337 1465 1531 1599 1667 1738 195 262 289 317 347 378 410 443 478 514 552 590 630 672 714 758 803 850 898 947 998 1049 1102 1157 1213 1270 1391 1454 1518 1583 1650 200 249 275 302 330 359 390 421 454 489 524 561 599 638 679 721 764 808 853 900 948 998 1048 1100 1153 1207 1323 1382 1443 1505 1568 2 × ðĄ2 × ð × ðķ â2 Table S2.10.4.a [Metric Units] Maximum Allowable Working Pressure for Rectangular Stayed Surfaces 205 237 262 287 314 342 371 401 433 465 499 534 570 608 646 686 727 769 812 857 903 949 998 1047 1097 1149 1259 1315 1373 1432 1493 210 226 249 274 299 326 353 382 412 443 476 509 543 579 616 654 693 733 774 817 860 905 951 998 1046 1095 1200 1254 1309 1365 1422 215 216 238 261 285 311 337 365 393 423 454 486 518 552 587 624 661 699 739 779 821 863 907 952 998 1044 1144 1196 1248 1302 1357 220 206 227 249 273 297 322 348 376 404 433 464 495 528 561 596 631 668 705 744 784 824 866 909 953 998 1093 1142 1192 1244 1296 225 197 217 238 261 284 308 333 359 386 414 443 473 504 536 569 603 638 674 711 749 788 828 869 911 954 1045 1092 1140 1189 1239 For thicknesses 11mm and less, C = 2.1 For thicknesses larger than 11mm, C = 2.2 P = MAWP, kPa 230 189 208 228 249 272 295 319 344 370 396 424 453 483 513 545 577 611 645 681 717 754 792 832 872 913 1000 1045 1091 1138 1186 Explanation: All known course materials and interpretations of all editions of ASME interpret PG-46.1 (STAYED SURFACES) to require application of the largest dimension of the rectangular pattern as the dimension of ‘p’ in the familiar equation: ð= ðĄ2 × ð × ðķ ð2 (also used in S2.10.4). This wording and interpretation is duplicated in ASME Section VIII UG-47. However, ASME 1971 PFT-27.1 and ASME 2002 PFT26.1 both use similar wording stating “The full pitch dimensions of the stays shall be employed in determining the area to be supported by a stay…”. We interpret this wording to mean true dimensions of a rectangle. All editions of the Canadian Interprovincial Standard (1910-1938) provide a variation for the same equation for flat stayed surfaces. Specifically, the dimensions of a theoretical square with the same hypotenuse as that of the rectangle, is used. It is believed that, in this respect, the ASME code and the historic Canadian code share underlying theories. Additionally, traction engine blueprints and registration documents have shown that many historical boilers were built to this Canadian standard. For these reasons, this proposal is based on this precedent. As shown in the following diagram, the red rectangle and the blue square share the same hypotenuse (black), although the blue square actually covers more surface area. The origins of this theory appear to be based in consideration for unsupported area and distance between stays, not supported area of each stay. When the staybolt pattern is square, both equations yield the same results. Most staybolt patterns are very close to being square. Furthermore, the current Swedish, Dutch (“AD-Merkblatt” by Verband der Technischen Uberwachuns-Vereine e.V.) and German (“Drutscher DampfkesselausschuB (DDA)” by Vereinigung der Technischen Uberwachungsvereine e.V. Essen) boiler codes provide equations that replace a rectangle with a circle. Here, the (brown) circle’s diameter is equivalent to the hypotenuse of both the original rectangle and of the theoretical square. Dutch code German Code Of note, that the approach to using a theoretical square or a theoretical circle is equal. The same results can be obtained by applying a linear scale from the square’s area to the circle’s area. Hence, we believe that all of these boiler codes apply the same underlying geometric theories, but apply different criteria and limitations to these theories. Since the European equations would require an additional scale factor and the historic Canadian equations do not, the proposal uses the Canadian equations only for clarity of presentation. Example: Representative boiler dimensions and thicknesses: dimensions retrieved from a historical boiler blueprints, stated thickness deteriorated to 0.300 inches, staybolt pitch of 4.375x4.07. l = 4.375 w = 4.07 t = 0.300 Currently: Pï― t2 ïī S ïīC p2 Pï― 0.300 2 ïī 13750 x 2.1 4.375 2 P ï― 135.8 psi 2 ïī 0.300 2 ïī 13750 x 2.1 4.375 2 ïŦ 4.07 2 P ï― 145.6 psi Rectangular equations: Pï― 2ïīt2 ïī S ïīC l 2 ïŦ w2 Pï― In this real-world example, the historical boiler MAWP has increased approximately 10psi, or about 7%.
