Flange Pressure-Temperature Rating (ASME B16.5)
The maximum allowable working pressure of a flange CLASS at a service temperature.
Example
You enter
- Flange class (pound) 150
- Service temperature (°F) 400
You get
- Max allowable working pressure 200
Checked against published worked examples from: Texas Flange (reproducing ASME B16.5).
Details, formula, and sources
ScopeRead from the ASME B16.5 table with linear interpolation: a Class 150 carbon-steel flange is 285 psig cold but 200 psig at 400 F, and a Class 300 follows its own higher curve (635 psig at 400 F). Bundled ratings are Material Group 1.1 (carbon steel, e.g. A105); other material groups have their own tables. The value is the flange's rating; the weakest component (gasket, bolting, the mating pipe) can still govern the joint. The AHJ and the engineer of record govern.
Formula or tablemawp = interpolate(B16.5 Group 1.1 table[flange_class], temp_f), linear between the table temperatures (100, 200, 300, 400, 500, 600, 650 F). Class 150: 285, 260, 230, 200, 170, 140, 125; Class 300: 740, 680, 655, 635, 605, 570, 550; Class 600: 1480, 1360, 1310, 1265, 1205, 1135, 1100 psig; Class 900: 2220, 2035, 1965, 1900, 1810, 1705, 1650; Class 1500: 3705, 3395, 3270, 3170, 3015, 2840, 2745; Class 2500: 6170, 5655, 5450, 5280, 5025, 4730, 4575 psig (read from the table, not scaled).
Source and editionASME B16.5 Pipe Flanges and Flanged Fittings pressure-temperature ratings, Material Group 1.1 (carbon steel, e.g. A105), by name. The ratings are read from the standard's table with linear interpolation.
Free accessThe pressure-temperature rating is a fixed published table lookup; the Group 1.1 ratings are the standard's carbon-steel values, widely republished.
What governsEstimate. AHJ and licensed professional govern.
API field namesflange_class, temp_f, mawp_psig
- Material group bundled ratings are B16.5 Material Group 1.1 (carbon steel, e.g. A105); other groups have their own tablesASME B16.5
- Interpolation linear between the table temperatures (100 to 650 F)ASME B16.5
- Weakest component the flange rating is not the joint rating; gasket, bolting, and the mating pipe can governASME B16.5