Group 2.1 Pressure-Temperature Ratings

Type 304 austenitic stainless steel. It starts lower than carbon steel at ambient but holds its rating far better above 800 °F.

Standard: ASME B16.5
Group: Group 2.1
Materials: A182 F304, A182 F304H, A351 CF3, A351 CF8, A240 304, A240 304H
Class 150 at 100 °F: 275 psig (19.0 bar)
Class 150 at 600 °F: 140 psig (9.7 bar)

ASME B16.5 pressure-temperature ratings for Group 2.1 materials, in psig.
Class	100 °F	200 °F	300 °F	400 °F	500 °F	600 °F	650 °F	700 °F	750 °F	800 °F	850 °F	900 °F	950 °F	1000 °F
Class 150	275	230	205	190	170	140	125	110	95	80	65	50	35	20
Class 300	720	600	540	495	465	440	430	420	415	405	395	390	380	355
Class 400	960	800	715	660	620	590	575	565	550	540	530	520	510	470
Class 600	1440	1200	1075	995	930	885	865	845	825	810	790	780	765	710
Class 900	2160	1800	1615	1490	1395	1325	1295	1265	1240	1215	1190	1165	1145	1065
Class 1500	3600	3000	2690	2485	2330	2210	2160	2110	2065	2030	1980	1945	1910	1770
Class 2500	6000	5000	4480	4140	3880	3680	3600	3520	3440	3380	3300	3240	3180	2950

Interpolation between listed temperatures is permitted; extrapolation is not.

What Group 2.1 is used for

This is Type 304, the most widely used austenitic stainless steel. It is chosen for corrosion resistance, for cleanliness, for very low temperatures, and for temperatures beyond the useful range of carbon steel.

Reading the ratings

A Class 300 flange in Group 2.1 is rated 720 psig at 100 °F, 440 psig at 600 °F and 355 psig at 1000 °F, which is 49% of its cold rating. Every other class in the group follows the same curve, scaled by the class. Group 1.1 carbon steel is rated 740 psig at 100 °F, so this group starts lower. It passes carbon steel at 850 °F, where it is rated 395 psig against 320 psig.

Each figure is the highest gauge pressure the flange may see at that metal temperature. To use the table, fix the material group and the design temperature first, read down to find the lowest class whose rating is at or above the design pressure, and interpolate between columns if the temperature falls between them. The rating of the flange is often what limits a line, since the pipe wall is usually good for more.

Guides and comparisons for this page

Pressure-temperature deratingReading a P-T table and interpolating between temperatures.Hydrostatic test pressureWhat a line is tested at, and what its flanges allow.Pipe material selectionA53, A106, A312 and A335: which grade suits which duty.304 vs 316 stainless steel pipeWhat the molybdenum in 316 buys.Class 150 vs Class 300Dimensions, bolting and ratings of the two commonest classes.

Common questions

Which materials are in ASME B16.5 Group 2.1?

A182 F304, A182 F304H, A351 CF3, A351 CF8, A240 304, A240 304H.

What is a Class 300 Group 2.1 flange rated at 600 °F?

440 psig (30.3 bar). At 100 °F the same flange is rated 720 psig (49.6 bar).

Other material groups

Group 1.1 Group 1.2 Group 2.2 Group 2.3 Group 1.9 Group 1.10 Group 1.15