To be continued from this chapter “Pipe pressure rating“, I’d like to introduce to you about the fitting pressure rating.

Note:

Flanges, Gaskets, Valves, Weld fittings are designed as CLASS

Typically, there’re three type of Fitting CLASS rating:

According to ASME B16.5, are made in seven primary Pressure Classes:

150 300 400 600 900 1500 2500

The concept of flange ratings likes clearly. A Class 300 flange can handle more pressure than a Class 150 flange, because a Class 300 flange are constructed with more metal and can withstand more pressure. However, there are a number of factors that can impact the pressure capability of a flange.

The Pressure Class or Rating for flanges will be given in pounds. Different names are used to indicate a Pressure Class.
For example: 150 Lb or 150 Lbs or 150# or Class 150, all are means the same.

Base on type of material group – see this topic, we can find out the temperature rating according to ASME B16.5 from PRESSURE TEMPERATURE RATING TABLE.

Example for Group 1.2

Maximum Allowable non-shock Pressure (psig)
Temperature (^oF)	Pressure Class (lb)
	150	300	400	600	900	1500	2500
	Hydrostatic Test Pressure (psig)
	450	1125	1500	2225	3350	5575	9275
-20 to 100	290	750	1000	1500	2250	3750	6250
200	260	750	1000	1500	2250	3750	6250
300	230	730	970	1455	2185	3640	6070
400	200	705	940	1405	2110	3520	5865
500	170	665	885	1330	1995	3325	5540
600	140	605	805	1210	1815	3025	5040
650	125	590	785	1175	1765	2940	4905
700	110	555	740	1110	1665	2775	4630
750	95	505	675	1015	1520	2535	4230
800	80	410	550	825	1235	2055	3430
850	65	320	425	640	955	1595	2655
900	50	225	295	445	670	1115	1855
950	35	135	185	275	410	685	1145
1000	20	85	115	170	255	430	715