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Technical Library > FLANGES > FLANGES DIMENSIONS AND WEIGHTS > Flanges Pressure Rating
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FLANGES PRESSURE RATING


In this article, we explain what pressure rating means and show the rating charts for carbon, alloy, stainless steel and nickel alloy flanges. 


WHAT IS PRESSURE RATING?

The pressure rating defines the maximum pressure that a flange of a given class can withstand at given temperatures (such pressure can be expressed either in “psi” or “bars”).

As the temperature increases, the maximum pressure that a flange (of a given class) can withstand decreases according to a specific curve which depends on the material grade of the flange (in the table below, for instance, it’s shown that an ASME / ANSI flange class 150 withstands up to 285 psi when the temperature is below 100 F°, 200 psi for temperatures at 400 F°, and maximum 20 psi at very high temperatures as 1.000 F°).

Flanges with a higher rating can withstand higher pressures than flanges with lower ratings at the same temperature, as they are manufactured using more metal (and are therefore heavier and more robust): in the same example given below, a class 300 carbon steel flange has a rating of 740 psi (instead of 285)at temperatures below 100 F° and of 635 psi at temperatures around 400 F° (instead of 200 psi).

According to ASME / ANSI, flanges are manufactured in seven standard pressure ratings (alternatively defined “pressure classes“): 150, 300, 400, 600, 900, 1500 and 2500. These values, which represent pressure ratings, are given in pounds.

This image shows how thicker and heavier a flange of a given diameter becomes for increasing ratings (from 150# to 2500#). In other words, a flange of a certain size is heavier and heavier as the class rating increases, making the same flange more resistant to pressures at increasing temperatures (whereas the inner diameter and the raised surface are the same regardless the rating). Flanges of the same size, but different rating, require also a different number and diameter of stud bolts (such differences are shown in the flange bolting chart here).

Flanges pressure rating

The dimensions and sizes of key flanges specifications are available here.

To calculate online the flanges pressure rating–> click here

 


PRESSURE RATING CHARTS BY MATERIAL GRADE

Carbon Steel | Alloy Steel | Stainless Steel | Nickel Alloy

Carbon steel WN flange     Stainless Steel WN flangeFlanges of different materials have different pressure ratings: the stronger the material (example stainless steel flange vs. carbon steel flange or Inconel flange vs. stainless steel flange) the higher the max pressure that the flange can withstand at a given, increasing, temperatures. Flanges pressure rating charts are organized by material Group, the most common are 2.1.1 (high-temperature and low-temperature carbon steel) and 2.2.3 (stainless steel flanges).

Other common material grades for flanges are available here.


RATING CARBON STEEL FLANGES (ASME GROUP 1-1.1: A105, A350 LF2, A350 LF6 Cl.1)

FLANGE RATING IN PSI

Temperature (in F°) 150# 300# 400# 600# 900# 1500# 2500#
< 100 285 740 985 1480 2220 3705 6170
200 260 680 905 1360 2035 3395 5655
300 230 655 870 1310 1965 3270 5450
400 200 635 845 1265 1900 3170 5280
500 170 605 805 1205 1810 3015 5025
600 140 570 755 1135 1705 2840 4730
650 125 550 730 1100 1650 2745 4575
700 110 530 710 1060 1590 2655 4425
750 95 505 675 1015 1520 2535 4230
800 80 410 550 825 1235 2055 3430
850 65 320 425 640 955 1595 2655
900 50 230 305 460 690 1150 1915
950 35 135 185 275 410 685 1145
1000 20 85 115 170 255 430 715
Hydrostatic Test Pressure (in Psig) 450 1125 1500 2225 3350 5575 9275

FLANGE RATING IN BARS

TEMP C° 150# 300# 400# 600# 900# 1500# 2500#
   -29 / 38 19.6 51.1 68.1 102.1 153.2 255.3 425.5
50 19.2 50.1 66.8 100.2 150.4 250.6 417.7
100 17.7 46.6 62.1 93.2 139.8 233 388.3
150 15.8 45.1 60.1 90.2 135.2 225.4 375.6
200 13.8 43.8 58.4 87.6 131.4 219 365
250 12.1 41.9 55.9 83.9 125.8 209.7 349.5
300 10.2 39.8 53.1 79.6 119.5 199.1 331.8
325 9.3 38.7 51.6 77.4 116.1 193.6 322.6
350 8.4 37.6 50.1 75.1 112.7 187.8 313
375 7.4 36.4 48.5 72.7 109.1 181.8 303.1
400 6.5 34.7 46.3 69.4 104.2 173.6 289.3
425 5.5 28.8 38.4 57.5 86.3 143.8 239.7
450 4.6 23 30.7 46 69 115 191.7
475 3.7 17.4 23.2 34.9 52.3 87.2 145.3
500 2.8 11.8 15.7 23.5 35.3 58.8 97.9
538 1.4 5.9 7.9 11.8 17.7 29.5 49.2

Notes:

  • ASTM A105: An extended exposure to temperatures above 425°C, converts the carbide phase of steel to graphite (therefore this material is not recommended for constant temperatures above this value.
  • ASTM A350 LF6: shall not be used for temperatures above 260 C°

RATING CARBON STEEL FLANGES (ASME GROUP 1-1.2: A350 LF3, A350 LF6, Cl.2)

FLANGE RATING IN PSI

Temp. °F 150 300 400 600 900 1500 2500
-20 to 100 290 750 1000 1500 2250 3750 6250
200 260 750 1000 1500 2250 3750 6250
300 230 730 970 1455 2185 3640 6070
400 200 705 940 1410 2115 3530 5880
500 170 665 885 1330 1995 3325 5540
600 140 605 805 1210 1815 3025 5040
650 125 590 785 1175 1765 2940 4905
700 110 570 755 1135 1705 2840 4730
750 95 505 670 1010 1510 2520 4200
800 80 410 550 825 1235 2060 3430
850 65 270 355 535 805 1340 2230
900 50 170 230 345 515 860 1430
950 35 105 140 205 310 515 860
1000 20 50 70 105 155 260 430


RATING CARBON STEEL FLANGES (ASME GROUP 1-1.4: A350 LF1)

FLANGE RATING IN PSI

Temp. °F 150 300 400 600 900 1500 2500
-20 to 100 235 620 825 1235 1850 3085 1545
200 215 560 750 1125 1685 2810 4680
300 210 550 730 1095 1640 2735 4560
400 200 530 705 1060 1585 2645 4405
500 170 500 665 995 1495 2490 4150
600 140 455 610 915 1370 2285 3805
650 125 450 600 895 1345 2245 3740
700 110 450 600 895 1345 2245 3740
750 95 445 590 885 1325 2210 3685
800 80 370 495 740 1110 1850 3085
850 65 270 355 535 805 1340 2230
900 50 170 230 345 515 860 1430
950 35 105 140 205 310 515 860
1000 20 50 70 105 155 260 430


RATING ALLOY STEEL FLANGES (ASME GROUP 1-1.5: A182 Gr. F1)

FLANGE RATING IN PSI

Temp. °F 150 300 400 600 900 1500 2500
-20 to 100 265 695 925 1390 2085 3470 5785
200 260 680 905 1360 2035 3395 5660
300 230 655 870 1305 1955 3260 5435
400 200 640 855 1280 1920 3200 5330
500 170 620 830 1245 1865 3105 5180
600 140 605 805 1210 1815 3025 5040
650 125 590 785 1175 1765 2940 4905
700 110 570 755 1135 1705 2840 4730
750 95 530 710 1065 1595 2660 4430
800 80 510 675 1015 1525 2540 4230
850 65 485 650 975 1460 2435 4060
900 50 450 600 900 1350 2245 3745
950 35 280 375 560 845 1405 2345
1000 20 165 220 330 495 825 1370


RATING STAINLESS STEEL FLANGES (ASME GROUP 2-2.1: A182 Gr. F304/304L)

FLANGE RATING IN PSI

Temp. °F 150 300 400 600 900 1500 2500
-20 to 100 275 720 960 1440 2160 3600 6000
200 230 600 800 1200 1800 3000 5000
300 205 540 720 1080 1620 2700 4500
400 190 495 660 995 1490 2485 4140
500 170 465 620 930 1395 2330 3880
600 140 435 580 875 1310 2185 3640
650 125 430 575 860 1290 2150 3580
700 110 425 565 850 1275 2125 3540
750 95 415 555 830 1245 2075 3460
800 80 405 540 805 1210 2015 3360
850 65 395 530 790 1190 1980 3300
900 50 390 520 780 1165 1945 3240
950 35 380 510 765 1145 1910 3180
1000 20 320 430 640 965 1605 2675
1050 20 310 410 615 925 1545 2570
1100 20 255 345 515 770 1285 2145
1150 20 200 265 400 595 995 1655
1200 20 155 205 310 465 770 1285
1250 20 115 150 225 340 565 945
1300 20 85 115 170 255 430 715
1350 20 60 80 125 185 310 515
1400 20 50 65 95 145 240 400
1450 15 35 45 70 105 170 285
1500 10 25 35 55 80 135 230

 


RATING STAINLESS STEEL FLANGES (ASME GROUP 2-2.2: A182 Gr. F316/316L)

FLANGE RATING IN PSI

Temp. °F 150 300 400 600 900 1500 2500
-20 to 100 275 720 960 1440 2160 3600 6000
200 235 620 825 1240 1860 3095 5160
300 215 560 745 1120 1680 2795 4660
400 195 515 685 1025 1540 2570 4280
500 170 480 635 955 1435 2390 3980
600 140 450 600 900 1355 2255 3760
650 125 445 590 890 1330 2220 3700
700 110 430 580 870 1305 2170 3620
750 95 425 570 855 1280 2135 3560
800 80 420 565 845 1265 2110 3520
850 65 420 555 835 1255 2090 3480
900 50 415 555 830 1245 2075 3460
950 35 385 515 775 1160 1930 3220
1000 20 350 465 700 1050 1750 2915
1050 20 345 460 685 1030 1720 2865
1100 20 305 405 610 915 1525 2545
1150 20 235 315 475 710 1185 1970
1200 20 185 245 370 555 925 1545
1250 20 145 195 295 440 735 1230
1300 20 115 155 235 350 585 970
1350 20 95 130 190 290 480 800
1400 20 75 100 150 225 380 630
1450 20 60 80 115 175 290 485
1500 20 40 55 85 125 205 345

RATING NICKEL-ALLOYS STEEL FLANGES (ASME GROUP 3)

Refer to this page.

 


SELECTION OF FLANGE PRESSURE RATING

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