Pressure ratings are for annealed steel tubing “hydraulic grade” having a tensile strength of 55,000 PSI (the kind most often used for plumbing hydraulic systems). See notes on back for adjustment to other steels. Pressure ratings are shown for S.F. (safety factors) from 2 to 6. A factor of 4 is recommended for general service. On shockless systems a smaller factor is sometimes used.

GPM ratings are shown for flow velocities from 10 through 30 f/s (feet per second). A general guideline is to use 10 f/s on systems operating at a maximum pressure of 1,000 PSI; 15 f/s on systems having maximum pressures from 1,000 to 2,000 PSI; 20 f/s if system pressure is in the range of 2,000 to 3,500 PSI; and a velocity of 30 f/s on systems designed for pressures higher than 3,500 PSI.

 Wall, Inches 0.025 0.032 0.035 0.042 0.049 0.058 0.065 0.072 0.083 0.095 0.109 3/8˝O.D.TUBING 55,000PSITensile Inside Area 0.0830 0.0760 0.0731 0.0665 0.0603 0.0527 0.0471 0.0419 0.0343 0.0269 0.0194 PSI @ S.F. = 6 1,220 1,560 1,710 2,050 2,400 2,840 3,180 3,520 4,060 4,640 5,330 PSI @ S.F. = 5 1,470 1,880 2,050 2,460 2,880 3,400 3,800 4,220 4,870 5,570 6,390 PSI @ S.F. = 4 1,830 2,350 2,570 3,080 3,590 4,250 4,770 5,280 7,300 6,970 7,990 PSI @ S.F. = 3 2,440 3,150 3,420 4,100 4,790 5,670 6,350 7,040 8,120 9,290 10,650 PSI @ S.F. = 2 3,670 4,690 5,130 6,160 7,190 8,500 9,530 10,550 12,150 13,900 16,000 GPM @ 10 f/s 2.59 2.37 2.28 2.07 1.88 1.64 1.47 1.31 1.07 0.84 0.61 GPM @ 15 f/s 3.88 3.55 3.42 3.11 2.82 2.46 2.20 1.96 1.60 1.26 0.91 GPM @ 20 f/s 5.17 4.74 4.56 4.15 3.76 3.29 2.94 2.61 2.14 1.68 1.21 GPM @ 30 f/s 7.76 7.11 6.84 6.22 5.64 4.93 4.40 3.92 3.21 2.52 1.81 1/2˝O.D.TUBING 55,000PSITensile Inside Area 0.1590 0.1493 0.1452 0.1359 0.1269 0.1158 0.1075 0.0995 0.0876 0.0754 0.0625 PSI @ S.F. = 6 920 1,170 1,280 1,540 1,800 2,130 2,380 2,640 3,040 3,480 4,000 PSI @ S.F. = 5 1,100 1,400 1,540 1,850 2,150 2,550 2,860 3,170 3,650 4,180 4,800 PSI @ S.F. = 4 1,380 1,760 1,920 2,310 2,700 3,190 3,580 3,960 4,560 5,220 6,000 PSI @ S.F. = 3 1,830 2,350 2,570 3,080 3,590 4,250 4,770 5,280 6,090 6,970 8,000 PSI @ S.F. = 2 2,750 3,520 3,850 4,620 5,390 6,380 7,150 7,920 9,130 10,450 12,000 GPM @ 10 f/s 4.96 4.65 4.53 4.24 3.96 3.61 3.35 3.10 2.73 2.35 1.95 GPM @ 15 f/s 7.43 6.98 6.79 6.35 5.93 5.41 5.03 4.65 4.10 3.53 2.92 GPM @ 20 f/s 9.91 9.31 9.05 8.47 7.91 7.22 6.70 6.20 5.46 4.70 3.90 GPM @ 30 f/s 14.9 14.0 13.6 12.7 11.9 10.8 10.1 9.30 8.19 7.05 5.84 5/8˝O.D.TUBING 55,000PSITensile Inside Area 0.2597 0.2472 0.2419 0.2299 0.2181 0.2035 0.1924 0.1817 0.1655 0.1486 0.1301 PSI @ S.F. = 6 730 940 1,030 1,230 1,440 1,700 1,910 2,110 2,430 2,790 3,200 PSI @ S.F. = 5 880 1,130 1,230 1,480 1,720 2,040 2,290 2,530 2,920 3,340 3,840 PSI @ S.F. = 4 1,100 1,400 1,540 1,850 2,160 2,550 2,860 3,170 3,650 4,180 4,800 PSI @ S.F. = 3 1,470 1,880 2,050 2,460 2,870 3,400 3,810 4,220 4,870 5,570 6,390 PSI @ S.F. = 2 2,200 2,800 3,080 3,700 4,320 5,100 5,720 6,340 7,300 4,360 9,600 GPM @ 10 f/s 8.10 7.71 7.54 7.17 6.80 6.34 6.00 5.66 5.16 4.63 4.06 GPM @ 15 f/s 12.1 11.6 11.3 10.7 10.2 9.52 9.00 8.50 7.38 6.95 6.08 GPM @ 20 f/s 16.2 15.4 15.1 14.3 13.6 12.7 12.0 11.3 10.3 9.26 8.11 GPM @ 30 f/s 24.3 23.1 22.6 21.5 20.4 19.0 18.0 17.0 15.5 13.9 12.2 3/4˝O.D.TUBING 55,000PSITensile Inside Area 0.3848 0.3632 0.3632 0.3484 0.3339 0.3157 0.3019 0.2884 0.2679 0.2463 0.2223 PSI @ S.F. = 6 610 860 860 1,030 1,200 1,420 1,590 1,760 2,030 2,320 2,660 PSI @ S.F. = 5 730 1,030 1,030 1,230 1,440 1,700 1,900 2,110 2,430 2,790 3,200 PSI @ S.F. = 4 920 1,280 1,280 1,540 1,800 2,130 2,380 2,640 3,040 3,480 4,000 PSI @ S.F. = 3 1,220 1,710 1,710 2,050 2,400 2,840 3,180 3,520 4,060 4,640 5,330 PSI @ S.F. = 2 1,840 2,560 2,560 3,080 3,600 4,260 4,760 5,280 6,080 6,960 8,000 GPM @ 10 f/s 12.0 11.3 11.3 10.9 10.4 9.84 9.41 8.99 8.35 7.68 6.93 GPM @ 15 f/s 18.0 17.0 17.0 16.3 15.6 14.8 14.1 13.5 12.5 11.5 10.4 GPM @ 20 f/s 24.0 22.6 22.6 21.7 20.8 19.7 18.8 18.0 16.7 15.4 13.9 GPM @ 30 f/s 36.0 34.0 34.0 32.6 31.6 29.5 28.2 27.0 25.1 23.0 20.8 7/8˝ O.D. TUBING 55,000 PSI Tensile Inside Area 0.5346 0.5166 0.5090 0.4914 0.4742 0.4525 0.4359 0.4197 0.3948 0.3685 0.3390 PSI @ S.F. = 6 520 670 730 880 1,030 1,210 1,360 1,500 1,740 1,990 2,280 PSI @ S.F. = 5 630 800 880 1,060 1,230 1,460 1,630 1,810 2,090 2,390 2,740 PSI @ S.F. = 4 790 1,000 1,100 1,320 1,540 1,820 2,040 2,260 2,600 2,990 3,420 PSI @ S.F. = 3 1,050 1,340 1,470 1,760 2,050 2,430 2,720 3,020 3,480 3,980 4,570 PSI @ S.F. = 2 1,580 2,000 2,200 2,640 3,080 3,640 4,080 4,520 5,200 5,980 6,840 GPM @ 10 f/s 16.7 16.1 15.9 15.3 14.8 14.1 13.6 13.1 12.3 11.5 10.6 GPM @ 15 f/s 25.0 24.2 23.8 23.0 22.2 21.2 20.4 19.6 18.5 17.2 15.9 GPM @ 20 f/s 33.3 32.2 31.7 30.6 29.6 28.2 27.2 26.2 24.6 23.0 21.1 GPM @ 30 f/s 50.0 48.3 47.6 46.0 44.3 42.3 40.8 39.2 36.9 34.5 31.7 1˝O.D.TUBING 55,000PSITensile Inside Area 0.7088 0.6881 0.6793 0.6590 0.6390 0.6138 0.5945 0.5755 0.5463 0.5153 0.4803 PSI @ S.F. = 6 460 590 640 770 900 1,060 1,190 1,320 1,520 1,740 2,000 PSI @ S.F. = 5 550 700 770 920 1,080 1,280 1,430 1,580 1,830 2,090 2,400 PSI @ S.F. = 4 690 880 960 1,150 1,350 1,590 1,790 4,980 2,280 2,610 3,000 PSI @ S.F. = 3 920 1,170 1,280 1,540 1,800 2,130 2,380 2,640 3,040 3,480 4,000 PSI @ S.F. = 2 1,380 1,760 1,920 2,300 2,700 3,180 3,580 3,960 4,560 5,220 6,000 GPM @ 10 f/s 22.1 21.4 21.2 20.5 19.9 19.1 18.5 17.9 17.0 16.1 15.0 GPM @ 15 f/s 33.1 32.2 31.8 30.8 29.9 28.7 27.8 26.9 25.5 24.1 22.5 GPM @ 20 f/s 44.2 42.9 42.4 41.1 39.8 38.3 37.1 35.9 34.1 32.1 29.9 GPM @ 30 f/s 66.3 64.3 63.5 61.6 59.8 57.4 55.6 53.8 51.1 48.2 44.9 1¼˝O.D.TUBING 55,000PSITensile Inside Area 1.131 1.105 1.094 1.068 1.042 1.010 0.9852 0.9607 0.9229 0.8825 0.8365 PSI @ S.F. = 6 365 470 515 615 720 850 950 1,060 1,220 1,390 1,600 PSI @ S.F. = 5 440 560 610 740 860 1,020 1,140 1,270 1,460 1,670 1,920 PSI @ S.F. = 4 550 700 770 920 1,080 1,280 1,430 1,580 1,820 2,090 2,400 PSI @ S.F. = 3 730 940 1,030 1,230 1,440 1,700 1,900 2,110 2,430 2,790 3,200 PSI @ S.F. = 2 1,100 1,400 1,540 1,840 2,160 2,560 2,860 3,160 3,640 4,180 4,800 GPM @ 10 f/s 35.3 34.4 34.1 33.3 32.5 31.5 30.7 29.9 28.8 27.5 26.1 GPM @ 15 f/s 52.9 51.7 51.2 49.9 48.7 47.2 46.1 44.9 43.2 41.3 39.1 GPM @ 20 f/s 70.5 68.9 68.2 66.6 65.0 63.0 61.4 59.9 57.5 55.0 52.2 GPM @ 30 f/s 106 103 102 100 97.4 94.5 92.1 89.8 86.3 85.5 78.1 1½˝O.D.TUBING 55,000PSITensile Inside Area 1.651 1.612 1.606 1.575 1.544 1.504 1.474 1.444 1.398 1.348 1.291 PSI @ S.F. = 6 305 390 430 515 600 710 795 880 1,014 1,161 1,332 PSI @ S.F. = 5 370 470 510 610 720 850 950 1,050 1,210 1,390 1,600 PSI @ S.F. = 4 460 590 640 770 900 1,060 1,190 1,320 1,520 1,740 2,000 PSI @ S.F. = 3 610 780 850 1,030 1,200 1,420 1,590 1,760 2,030 2,320 2,660 PSI @ S.F. = 2 920 1,180 1,280 1,540 1,800 2,120 2,380 2,640 3,040 3,480 4,000 GPM @ 10 f/s 51.5 50.2 50.1 49.1 48.1 46.9 45.9 45.0 43.6 42.0 40.2 GPM @ 15 f/s 77.2 75.4 75.1 73.6 72.2 70.3 68.9 67.5 65.4 63.0 60.4 GPM @ 20 f/s 103 101 100 98.2 96.3 93.8 91.9 90.0 87.2 84.0 80.5 GPM @ 30 f/s 154 151 150 147 144 141 138 135 131 126 121 2˝O.D.TUBING 55,000PSITensile Inside Area 2.986 2.944 2.926 2.883 2.841 2.788 2.746 2.705 2.642 2.573 2.490 PSI @ S.F. = 6 230 295 320 385 450 530 595 660 760 870 1,000 PSI @ S.F. = 5 270 350 390 460 540 640 710 790 910 1,040 1,200 PSI @ S.F. = 4 340 440 480 580 670 800 890 990 1,140 1,300 1,500 PSI @ S.F. = 3 460 590 640 770 900 1,060 1,190 1,320 1,520 1,740 2,000 PSI @ S.F. = 2 680 880 960 1,160 1,340 1,600 1,780 1,980 2,280 2,600 3,000 GPM @ 10 f/s 93.1 91.8 91.2 89.4 88.6 86.9 85.6 84.3 82.4 80.2 77.6 GPM @ 15 f/s 139 138 137 135 133 130 128 126 123 120 116 GPM @ 20 f/s 186 184 182 180 177 174 171 169 165 160 233 GPM @ 30 f/s 279 275 274 270 266 261 257 253 247 241 233

For steels with tensile strength other than 55,000 PSI, pressure ratings are proportional to tensile strength. Barlow’s Formula was used for pressure calculations.

P = 2t × S ÷ 0

P = burst pressure, PSI;
t = wall thickness in inches;
S = tensile strength in PSI;
0 = outside diameter in inches.

The following formula was used for calculating flow capacity.

GPM = V × A ÷ 0.3208

V = velocity in feet per second;
A = inside area in square inches.

© 1990 by Womack Machine Supply Co. This company assumes no liability for errors in data nor in safe and/or satisfactory operation of equipment designed from this information.