ANSI B16.5/ASME-B16.47 rates the pressure of a class based on the materials of engineering and the design temperature

API specifies allowable materials elements and gives it a particular pressure rating

The difference between ASME/ANSI and API may be the fabrication materials and an increased rated API operating pressure.

ANSI B16.5/ASME-B16.47 flanges are generally used in industrialprocess systems handling water steam, |air flow and gas. API flanges happen to be manufactured for high durability operating refinery devices goods such as essential oil and explosive gases.

API 6A - TYPE - 6B
	2000PSI		3000PSI		5000 PSI
size	Flange OD	Thickness	Flange OD	Thickness	Flange OD	Thickness
2 1/16"	165	33.4	215	46.1	215	46.1
2 9/16"	190	36.6	245	49.3	245	49.3
3 1/8"	210	39.7	240	46.1	265	55.6
4 1/16"	275	46.1	290	52.4	310	62
5 1/18"	330	52.4	350	58.8	375	81
7 1/16"	365	55.6	380	63.5	395	92.1
9"	420	63.5	470	71.5	485	103.2
11"	510	71.5	545	77.8	585	119.1
13 5/8"	560	74.7	610	87.4
16 3/4"	685	84.2	705	100.1
20 3/4"			855	120.7
21 1/4"	815	98.5



API 6A - TYPE - 6BX

	2000PSI		3000PSI		5000 PSI		10000 PSI		15000 PSI
size	Flange OD	Thickness	Flange OD	Thickness	Flange OD	Thickness	Flange OD	Thickness	Flange OD	Thickness
1 13/16"							185	42.1	255	63.5
2 1/16"							200	44.1	285	71.5
2 9/16"							230	51.2	325	79.4
3 1/16"									355	85.8
3 1/8"							270	58.4
4 1/16"							315	70.3	445	106.4
5 1/18"							360	79.4
7 1/16"							480	103.2	655	165.1
9"							550	123.9	805	204.8
11"							655	141.3	885	223.9
13 5/8"							770	168.3	1160	292.1
16 3/4"							870	168.3
18 3/4"					675	112.8	1040	223.1
21 1/4"					770	130.2	1145	241.3
26 3/4"					905	165.9
30"					990	181
	1040	126.3	1100	161.2
	1120	134.2	1185	167.1