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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

55,000
PSI
Tensile

 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

55,000
PSI
Tensile

 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

55,000
PSI
Tensile

 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

55,000
PSI
Tensile

 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

55,000
PSI
Tensile 

 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

55,000
PSI
Tensile

 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

55,000
PSI
Tensile

 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

55,000
PSI
Tensile

 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.

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