ASME B16.5 Flange Pressure Ratings and Classes

 

 

Now, ASME B16.5 covers pipe flanges and flanged fittings from 1/2 inch through 24 inch in Class 150, 300, 400, 600, 900, 1500, and 2500. It lays out your pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing, I tell you what. If you want dimensions by size, y'all start with our ASME B16.5 Class 150 flange dimensions.

Dem rating tables below give y'all the maximum allowable working pressure for each material group at temperature. Fixin' to go bigger than 24 inch? Take a look at ASME B16.47 Series A and Series B.

Dem standards and codes help y'all figure out pressure integrity and make the design rules a whole lot simpler.

Knowin' the difference between codes and standards is mighty handy for designers workin' with detailed flange specifications and designs for dem components. Here's the rules and standards y'all run into most often:

1. Minimum wall flange thickness

2. Materials y'all're allowed to build with

3. Allowable work stresses

 

How the structure behaves comes from thermal expansion, live loads, seismic loads, deadweight, internal pressure, and whatever other loads get put on it, inside or out.

Now, the piping codes ain't got no design rules for standard in-line components like standard valves and flange fittings. Y'all design dem kinds of parts by goin' to the industry standards.

 

1. Pressure-integrity standards: Dem standards give everybody the same minimum-performance criteria. When parts get designed and built to the same standards, they'll work the same way, I reckon.

Now, keep in mind pressure integrity ain't exactly the same thing as leakage integrity, friend.

Durin' operation and test, pressure integrity is one guarantee of a leak-tight joint, but it don't cover the whole risk picture for the structural stability of the pressure boundary or any added stresses.

 

2. Dimensional standards: Dem standards set down the configurations and parameters for piping components, so parts from different manufacturers fit together just fine. That consistency is mighty important for keepin' everything compatible across your systems.

 Now, just 'cause a flange meets ASME dimensional standards don't mean it'll perform the same as every other one. Several ASME standards also carry pressure-temperature ratings, which help y'all decide if a part's right for the job.

 

ASME B16.5-2025 puts ever' listed material in a numbered material group, and ever' material in a group shares one pressure-temperature rating table. Y'all can find the complete material list and ever' rating table in ASME B16.5-2025, Pipe Flanges and Flanged Fittings.

Flanges made of any material in the same group can carry the same pressure class of ASME flange and got the same pressure-temperature rating for just about any single material group.

ASME B16.5 gives y'all 7 pressure classes for flanges. Dem are 2500, 1500, 900, 600, 400 (less common these days), 300 and 150. Class 75 also shows up in ASME B16.47 Series B large diameter. Our Class 300 dimensions and weights table covers the next class up, yessir.

Ever' material group got its own pressure-temperature rating table in ASME B16.5-2025. Y'all'll find the full list of Group 1 and Group 2 materials below, then rating tables for the three groups behind most forged flange orders: Group 1.1 (carbon steel, A105 and A350 LF2), Group 2.1 (F304 and F304H) and Group 2.2 (F316, F316H and F317).

Dem tables below are laid out by pressure class across the top, and down the left-hand edge y'all'll find the maximum working temperatures.

In practice, usin' ASME B16.5 to figure the rating of the flange is mighty easy. Here's the three-step way we recommend:

a. Figure out the maximum temperature and operating pressure your flange needs to handle.

b. Find your flange material in the material-group table below and write down its group. Ever' rating table also repeats the materials it covers, with numbered notes, 'cause several materials carry a maximum service temperature that can change what y'all pick.

c. Head on over to that group's rating table and start at the first listed temperature at or above your maximum operating temperature.

Start with the Class 150 column and work your way right until you hit a pressure rating for your temperature that's equal to or higher than the operating pressure you need.

Now, the column that can satisfy the requirements is the one that tells y'all the pressure class you need and your flange's actual pressure-temperature rating.

Now, ASTM A182 Gr. F316 is a Material Group 2.2 forging, I tell you what.

Look in the Group 2.2 rating table below and y'all'll see a Class 600 flange is rated 885 psig at 650°F. Check our Class 600 dimensions and weights for dat flange.

Which rating table fits your material

Ever' material listed in ASME B16.5 belongs to a numbered material group, and ever' material in a group shares one pressure-temperature rating table. Find your specification below, note the group, then go read that group's rating table.

Material Group 1.1: carbon steel (A105, A350 LF2, A216 WCB)

Want dimensions and weights for the classes in dese tables? Here y'all go: ASME B16.5 Class 150 flange dimensions, Class 300 dimensions and weights, Class 600 dimensions and weights, and the flange bolt chart for every class.

Material Group 2.1: 18Cr–8Ni austenitic stainless (F304, F304H)

Material Group 2.2: 16Cr–12Ni–2Mo austenitic stainless (F316, F316H, F317)

Now, dese ratings are for flanges and flanged fittings built to ASME B16.5 and they apply to the flange itself, not to the bolting or the gasket. Your joint is only rated as good as the weakest of the three, I tell you what. We put Class 400 in here 'cause it's part of the standard, even though it's rarely stocked. To find the table that fits a material, look it up in the material-group table above each rating table: A105 and A350 LF2 are Group 1.1, F304 and F304H are Group 2.1, F316, F316H and F317 are Group 2.2.

For bolt count, bolt diameter and stud length in ever' class above, y'all go on and see our flange bolt chart for every class.

If y'all still got questions 'bout pickin' flanges, holler at us in the comment section or give us a call today!