A335 P91 Pipe MAWP Calculator ASTM A335 -P91 Alloy Steel Pipe SMLS <=3" thk, 9Cr-1Mo-V
Material Properties Description
ASTM A335 -P91 Alloy Steel Pipe SMLS <=3" thk, 9Cr-1Mo-V
Min Design Temperature
-20 °F
Y Coefficient
Ref 3 — Ferritic steels
Maximum Allowable Working Pressure (psig) Sch STD Sch XS Sch 160
NPS OD (in) 100 °F 200 °F 300 °F 400 °F 500 °F 600 °F 700 °F 800 °F 1/8 0.405 9,423 9,423 9,423 9,389 9,356 9,223 8,890 8,291 1/4 0.54 9,110 9,110 9,110 9,078 9,046 8,917 8,595 8,015 3/8 0.675 7,372 7,372 7,372 7,346 7,320 7,216 6,956 6,487 1/2 0.84 7,069 7,069 7,069 7,044 7,019 6,919 6,669 6,219 3/4 1.05 5,764 5,764 5,764 5,744 5,723 5,642 5,438 5,072 1 1.315 5,391 5,391 5,391 5,372 5,353 5,276 5,086 4,743 1 1/4 1.66 4,439 4,439 4,439 4,423 4,407 4,345 4,188 3,906 1 1/2 1.9 3,993 3,993 3,993 3,979 3,965 3,908 3,767 3,513 2 2.375 3,364 3,364 3,364 3,352 3,340 3,293 3,174 2,960 2 1/2 2.875 3,679 3,679 3,679 3,666 3,653 3,601 3,471 3,237 3 3.5 3,194 3,194 3,194 3,183 3,172 3,127 3,014 2,811 3.5 4 2,913 2,913 2,913 2,903 2,893 2,852 2,749 2,563 4 4.5 2,708 2,708 2,708 2,699 2,689 2,651 2,555 2,383 5 5.563 2,374 2,374 2,374 2,366 2,357 2,324 2,240 2,089 6 6.625 2,157 2,157 2,157 2,149 2,142 2,111 2,035 1,898 7 7.625 2,011 2,011 2,011 2,003 1,996 1,968 1,897 1,769 8 8.625 1,899 1,899 1,899 1,892 1,885 1,858 1,791 1,670 9 9.625 1,805 1,805 1,805 1,798 1,792 1,766 1,703 1,588 10 10.75 1,722 1,722 1,722 1,716 1,710 1,686 1,625 1,516 12 12.75 1,487 1,487 1,487 1,482 1,477 1,456 1,403 1,309 14 14 1,352 1,352 1,352 1,347 1,342 1,323 1,275 1,189 16 16 1,180 1,180 1,180 1,176 1,172 1,155 1,113 1,038 18 18 1,047 1,047 1,047 1,043 1,040 1,025 988 921 20 20 941 941 941 938 934 921 888 828 22 22 854 854 854 851 848 836 806 752 24 24 782 782 782 780 777 766 738 688 26 26 722 722 722 719 716 706 681 635 28 28 670 670 670 667 665 655 632 589 30 30 625 625 625 622 620 611 589 549 36 36 520 520 520 518 516 509 490 457 42 42 445 445 445 443 442 436 420 392 44 44 425 425 425 423 422 416 401 374 46 46 406 406 406 405 403 397 383 357 48 48 389 389 389 388 386 381 367 342
Allowable Stress vs Temperature 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 1000 1100 1200 Temperature (°F) 0 8 16 24 32 Allowable Stress (ksi) Disclaimer: This calculator is for guidance only. Results are based on ASME B31.3-2024 allowable stresses for seamless pipe (Ej=1.0, W=1.0). Always verify against the current edition of the standard. The engineer of record is responsible for all design decisions.
References ASME B31.3-2024 — Process Piping, Table A-1 ASME B36.10M — Welded and Seamless Wrought Steel Pipe ASME B16.5-2020 — Pipe Flanges and Flanged Fittings 
