How Does the Flange Rating Work?
ANSI FLANGE PRESSURE RATING EXPLAINED
Now think about what this means for the rating of pressure:
At 600 degrees F, the class 150 flange can only handle 140 pounds per square inch (psi) (as per the rating chart below)
The class 300 flange, which is bigger and stronger but has the same size hole, can handle 570 psi at 600 degrees F°.
Lastly, a class 2500 flange of the same size can withstand 4730 psi at 600 F°, which is 34 times more pressure than a class 150 flange of the same size.
Scroll down to see the table for your flange’s rating (this depends on the material of the flange, as flanges with different material grades have different pressure ratings)
Find out the highest temperature that your piping system can handle (i.e. select one line in the table)
Choose a rating based on the highest pressure you expect to see at that temperature (i.e. select one column in that line)
You now have the rating you needed!
Here are charts from ASME B16.34 that show how much pressure can be put on the most common flange materials (carbon, alloy, stainless).
Pressure rating is the most pressure a flange can handle as the temperature rises. The ANSI/ASME B16.5 standard says that flanges can handle pressures of 150, 300, 400, 600, 900, 1500, and 2500.
When it comes to how a flange manages pressure and temperature, the phrases “pressure rating,” “class,” “#,” “Lb,” and “Lbs” all signify the same thing (and other equipment like valves, fittings, etc).
Let’s look at an example to explain:
If two flanges have the same bore size, say 6 inches, and the same material, say A105, but different pressure ratings, say class 150 and class 300, the class 150 flange will be smaller, lighter, and less strong than the class 300 flange (class 300). What the picture shows is this:
The Flange Rating System and How It Works
Flange rating is often hard to understand for people who are new to the pipe industry. Before we go any further, let’s talk about what a flange is and what it does in the plumbing world.
What is a flange, and how does it do what it does?
A flange is a piece of equipment that connects pipes, pumps, valves, and other piping parts to make a pipeline system. The flange is a key part of the piping system because it makes cleaning, checking, and making changes easier. There are many different kinds of flanges, such as Weld Neck Flange, Slip-on Flange, Socket Weld Flanges, Lap Joint Flange, Threaded Flange, Blind Flange, Orifice Flanges, Reducing Flanges, and Blind Flanges.
How does the flange rating work, and what is it?
In the oil, gas, and petrochemical industries, it’s important to make sure that the flanges can handle the pressures and temperatures they’re put through. The size of the flanges is important, but the rating is also important. So, choosing a flange with the right rating makes sure it can handle the stresses of working at different temperatures.
The class of the flange tells how much pressure a flange can handle when the temperature is high or rising. Flanges with a higher flange rating or flange class are thought to be stronger because they can handle more pressure at higher temperatures.
The industry standard for flanges is the ASME B16.5 standard, which is used for both flanged fittings and pipe flanges. This has flanges with diameters between 12′′ NPS and 24′′ NPS.
So, when the temperature goes up, the maximum pressure goes down. Flange rating is easy to explain with the help of the following example.
A Class 300 flange can handle more pressure than a Class 150 flange because it is made of more metal and can handle more pressure. But there are many things that can change how much pressure a flange can handle.
A Class 300 flange can handle more pressure than a Class 150 flange because it is made of more metal and can handle more pressure. On the other hand, different things affect how much pressure a flange can handle.
CARBON STEEL FLANGE RATING CHART
Carbon steel flange pressure-temperature rating ASME
ANSI FLANGE ASTM A105, A350 Gr. LF2/LF6 Class 1
The maximum pressure for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures (Celsius or Fahrenheit) – in PSI – is shown in the flange rating table.
ANSI/ASME B16.34 | ANSI PRESSURE RATING | ||||||
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 |
Notes
The maximum pressure for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures (Celsius or Fahrenheit) – in bars – is shown in the flange rating table.
ANSI/ASME B16.34 | ANSI PRESSURE RATING | ||||||
Temperature in 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 |
Notes:
ASTM A105 says that when steel is heated above 425°C for a long time, its carbide phase changes into graphite (this material is not recommended for consistent temperatures above this number).
According to the ASTM A350 LF6 standard, it shouldn’t be used at temperatures higher than 260 degrees Celsius.
ANSI FLANGE ASTM A350 Gr. LF3, A350 LF6, Class 2
The flange rating chart shows the maximum pressure (in PSI) for flanges of classes 150/300/400/600/900/1500/2500 at different temperatures (in degrees Celsius or Fahrenheit).
ANSI/ASME B16.34 | ANSI PRESSURE RATING | ||||||
Temperature in °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 |
ANSI FLANGE ASTM A350 Gr. LF1
The flange rating table shows the maximum pressure (in PSI) for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures (in Celsius or Fahrenheit).
ANSI/ASME B16.34 | ANSI PRESSURE RATING | ||||||
Temperature °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 |
ALLOY STEEL FLANGE RATING CHART
Alloy steel flange pressure-temperature rating ASME
ANSI FLANGE ASTM A182 Gr. F1 (Chrome Moly)
The flange rating table shows the maximum pressure (in PSI) for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures (in Celsius or Fahrenheit).
ANSI/ASME B16.34 | ANSI PRESSURE RATING | ||||||
Temperature °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 |
STAINLESS STEEL FLANGE RATING CHART
ANSI FLANGE ASTM A182 Gr. F304, 304L
The maximum pressure for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures (Celsius or Fahrenheit) – in PSI – is shown in the flange rating table.
ANSI/ASME B16.34 | ANSI PRESSURE RATING | ||||||
Temperature °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 |
The maximum pressure for flanges of classes 150/300/400/600/900/1500/2500 at increasing temperatures (Celsius or Fahrenheit) – in PSI – is shown in the flange rating table.
ANSI/ASME B16.34 | ANSI PRESSURE RATING | ||||||
Temperature °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 |
Read More :
Understanding how stainless steel pipes can be used in different fields: Because welded pipes are so versatile, they can be used in almost any kind of business. Because of this, though, they do better at resisting corrosion and less well at resisting pressure than they do at resisting rust. Welded pipes are a lot easier to work with than most other types of pipes.