Group 1.1 Pressure-Temperature Ratings

The standard carbon steel group and by far the most common material in B16.5 flanges. A105 forged carbon steel sits here.

Standard: ASME B16.5
Group: Group 1.1
Materials: A105, A350 LF2, A350 LF6 Cl. 1, A350 LF3, A216 WCB, A515 Gr. 70, A516 Gr. 70, A537 Cl. 1
Class 150 at 100 °F: 285 psig (19.7 bar)
Class 150 at 600 °F: 140 psig (9.7 bar)

ASME B16.5 pressure-temperature ratings for Group 1.1 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	285	260	230	200	170	140	125	110	95	80	65	50	35	20
Class 300	740	680	655	635	605	570	550	530	505	410	320	230	135	85
Class 400	985	905	870	845	805	755	730	710	675	550	425	305	185	115
Class 600	1480	1360	1310	1265	1205	1135	1100	1060	1015	825	640	460	275	170
Class 900	2220	2035	1965	1900	1810	1705	1650	1590	1520	1235	955	690	410	255
Class 1500	3705	3395	3270	3170	3015	2840	2745	2655	2535	2055	1595	1150	685	430
Class 2500	6170	5655	5450	5280	5025	4730	4575	4425	4230	3430	2655	1915	1145	715

Interpolation between listed temperatures is permitted; extrapolation is not.

What Group 1.1 is used for

This is the ordinary carbon steel group, and the table most flange ratings are quoted from. It suits water, steam, air and hydrocarbon service at moderate temperature. Carbon steel is not normally used for long periods above about 800 °F, where the carbide in the steel can slowly turn to graphite and the metal loses strength.

Reading the ratings

A Class 300 flange in Group 1.1 is rated 740 psig at 100 °F, 570 psig at 600 °F and 85 psig at 1000 °F, which is 11% of its cold rating. Every other class in the group follows the same curve, scaled by the class.

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.Carbon steel vs stainless steel pipeStrength, temperature and corrosion trade-offs.Class 150 vs Class 300Dimensions, bolting and ratings of the two commonest classes.

Common questions

Which materials are in ASME B16.5 Group 1.1?

A105, A350 LF2, A350 LF6 Cl. 1, A350 LF3, A216 WCB, A515 Gr. 70, A516 Gr. 70, A537 Cl. 1.

What is a Class 300 Group 1.1 flange rated at 600 °F?

570 psig (39.3 bar). At 100 °F the same flange is rated 740 psig (51.0 bar).

Other material groups

Group 1.2 Group 2.1 Group 2.2 Group 2.3 Group 1.9 Group 1.10 Group 1.15