Group 1.2 Pressure-Temperature Ratings

Carbon, carbon-manganese and nickel steels, most of them cast or impact-tested grades chosen for low-temperature service. The group is rated slightly above Group 1.1 up to 700 °F.

Standard: ASME B16.5
Group: Group 1.2
Materials: A350 LF6 Cl. 2, A216 WCC, A352 LCC, A352 LC2, A352 LC3, A203 Gr. B, A203 Gr. E
Class 150 at 100 °F: 290 psig (20.0 bar)
Class 150 at 600 °F: 140 psig (9.7 bar)

ASME B16.5 pressure-temperature ratings for Group 1.2 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	290	260	230	200	170	140	125	110	95	80	65	50	35	20
Class 300	750	750	730	705	665	605	590	555	505	410	320	225	135	85
Class 400	1000	1000	970	940	885	805	785	740	675	550	425	295	185	115
Class 600	1500	1500	1455	1405	1330	1210	1175	1110	1015	825	640	445	275	170
Class 900	2250	2250	2185	2110	1995	1815	1765	1665	1520	1235	955	670	410	255
Class 1500	3750	3750	3640	3520	3325	3025	2940	2775	2535	2055	1595	1115	685	430
Class 2500	6250	6250	6070	5865	5540	5040	4905	4630	4230	3430	2655	1855	1145	715

Interpolation between listed temperatures is permitted; extrapolation is not.

How far this table has been checked. The Class 400 row and the columns from 850 °F to 1000 °F rest on a single secondary source. The other values agree in two independent sources. None of the values on this site has been checked against the standard itself; see how the figures are checked.

What Group 1.2 is used for

These are carbon, carbon-manganese and nickel steels, most of them castings and impact-tested grades. They are chosen mainly for their toughness at low temperature, so the group often appears on cold service where ordinary A105 is not permitted.

Reading the ratings

A Class 300 flange in Group 1.2 is rated 750 psig at 100 °F, 605 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. Group 1.1 carbon steel is rated 740 psig at 100 °F, so this group starts level. It passes carbon steel at 100 °F, where it is rated 750 psig against 740 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.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 1.2?

A350 LF6 Cl. 2, A216 WCC, A352 LCC, A352 LC2, A352 LC3, A203 Gr. B, A203 Gr. E.

What is a Class 300 Group 1.2 flange rated at 600 °F?

605 psig (41.7 bar). At 100 °F the same flange is rated 750 psig (51.7 bar).

Other material groups

Group 1.1 Group 2.1 Group 2.2 Group 2.3 Group 1.9 Group 1.10 Group 1.15