ASME/ANSI FLANGES

Our flanges are designed according to the ASME/ANSI B16.5, B16.47 series A and B standard, which covers different dimensions, tolerances, materials, pressure-temperature ratings, and testing requirements for pipe flanges and flanged fittings within a certain size range and pressure class.

What is ASME B16.5 Flange?

ASME B16.5 is a critical standard that specifies requirements for pipe flanges and flanged fittings. It covers sizes from NPS 1/2 through NPS 24 for pressure classes 150 to 1500, and up to NPS 12 for class 2500. The standard details pressure-temperature ratings, material specifications, dimensions, tolerances, and marking requirements. It applies to components made from cast or forged materials and includes specifications for various flange types like slip-on, threaded, and weld neck flanges. This standardization ensures consistency across industries, facilitates proper component selection, and maintains safety in piping systems.

Key Features of ASME B16.5 Flange

Standard Scope

ASME B16.5 constitutes the fundamental engineering standard governing steel pipe flanges and fittings in industrial applications. This specification encompasses dimensional ranges from NPS 1/2 through NPS 24, establishing comprehensive requirements for pressure containment systems. The standard systematically addresses pressure classes ranging from 150 through 2500, implementing precise technical parameters for each classification.
Engineering Parameters:

• Dimensional Specifications: NPS 1/2 – NPS 24
• Pressure Classifications: 150, 300, 600, 900, 1500, 2500
• Configuration Types: Weld neck, slip-on, blind, socket weld flanges

Pressure-Temperature Correlations

ASME B16.5 establishes definitive pressure-temperature relationships across all pressure classes. The standard implements systematic derating factors that correlate operating pressures with temperature variations, ensuring operational integrity across diverse service conditions.Operating Parameters:

• Class 150: Maximum allowable pressure 285 PSI at ambient conditions
• Class 300: Operating limit 740 PSI at standard temperature
• Class 900: Design pressure 2220 PSI at reference conditions
• Operational Range: -29°C to 538°C with specified derating factors

Material Specifications

The standard delineates precise material requirements, correlating mechanical properties with service conditions. Material selection criteria incorporate mechanical strength, temperature limitations, and corrosion resistance factors, ensuring optimal performance under specified operating conditions.Material Classifications:

• Carbon Steel: ASTM A105, A216 (specified yield and tensile requirements)
• Stainless Steel: ASTM A182, A240 (corrosion-resistant applications)
• Low-Alloy Steel: ASTM A350 (low-temperature service)
• Specialty Alloys: Application-specific requirements

Testing Methodology

ASME B16.5 implements systematic testing protocols based on dimensional and pressure class parameters. Hydrostatic testing requirements vary proportionally with nominal pipe size, establishing minimum hold times for pressure verification.Test Specifications:

• Hydrostatic Test Pressure: 1.5× design pressure at 38°C
• Hold Time Requirements:

NPS ≤ 2: 60-second minimum
NPS 2½-8: 120-second minimum
NPS ≥ 10: 180-second minimum

Temperature Parameters

The standard establishes critical temperature thresholds affecting pressure ratings and material selection. Temperature considerations encompass both elevated service conditions and cryogenic applications, with specific requirements for material validation.Thermal Considerations:

• Class 150: Enhanced analysis above 200°C
• Higher Pressure Classes: Additional verification above 400°C
• Cryogenic Service: Material qualification below -29°C
• Impact Testing: Mandatory for sub-zero temperature service

Component Identification

ASME B16.5 mandates specific identification requirements ensuring complete component traceability. Marking protocols facilitate proper material verification, pressure class confirmation, and dimensional validation.Identification Requirements:

• Manufacturer Identification
• Material Specification
• Pressure Classification
• Dimensional Data
• Standard Designation
• Supplementary Requirements (as applicable)

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ASME b16.5 Flange Dimensions

ASME b16.5 Slip On Flange Dimensions - Pressure Class 150 to 1500

Class 150

Class 300

Class 600

Class 900

Class 1500

Class 150

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	90	60.3	16	4	M14	9.6	22.5	30	14
20	3/4	26.9	100	69.9	16	4	M14	11.2	27.5	38	14
25	1	33.7	110	79.4	16	4	M14	12.7	34.5	49	16
32	1 1/4	42.4	115	88.9	16	4	M14	14.3	43.5	59	19
40	1 1/2	48.3	125	98.4	16	4	M14	15.9	49.5	65	21
50	2	60.3	150	120.7	18	4	M16	17.5	61.5	78	24
65	2 1/2	76.1	180	139.7	18	4	M16	20.7	77.6	90	27
80	3	88.9	190	152.4	18	4	M16	22.3	90.5	108	29
100	4	114.3	230	190.5	18	8	M16	22.3	116.0	135	32
125	5	139.7	255	215.9	22	8	M20	22.3	143.5	164	35
150	6	168.3	280	241.3	22	8	M20	23.9	170.5	192	38
200	8	219.1	345	298.5	22	8	M20	27.0	221.5	246	43
250	10	273.0	405	362	26	12	M24	28.6	276.5	305	48
300	12	323.9	485	431.8	26	12	M24	30.2	328.0	365	54
350	14	355.6	535	476.3	30	12	M27	33.4	360.0	400	56
400	16	406.4	595	539.8	30	16	M27	35.0	411.0	457	62
450	18	457	635	577.9	33	16	M30	38.1	462.0	505	67
500	20	508	700	635	33	20	M30	41.3	513.5	559	71
600	24	610	815	749.3	36	20	M33	46.1	616.5	663	81

Class 300

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	95	66.7	16	4	M14	12.7	22.5	38	21
20	3/4	26.9	115	82.6	18	4	M16	14.3	27.5	48	24
25	1	33.7	125	88.9	18	4	M16	15.9	34.5	54	25
32	1 1/4	42.4	135	98.4	18	4	M16	17.5	43.5	64	25
40	1 1/2	48.3	155	114.3	22	4	M20	19.1	49.5	70	29
50	2	60.3	165	127	18	8	M16	20.7	61.5	84	32
65	2 1/2	76.1	190	149.2	22	8	M20	23.9	77.6	100	37
80	3	88.9	210	168.3	22	8	M20	27	90.5	117	41
100	4	114.3	255	200	22	8	M20	30.2	116	146	46
125	5	139.7	280	235	22	8	M20	33.4	143.5	178	49
150	6	168.3	320	269.9	22	12	M20	35	170.5	206	51
200	8	219.1	380	330.2	26	12	M24	39.7	221.5	260	60
250	10	273	445	387.4	30	16	M27	46.1	276.5	321	65
300	12	323.9	520	450.8	33	16	M30	49.3	328	375	71
350	14	355.6	585	514.4	33	20	M30	52.4	360	425	75
400	16	406.4	650	571.5	36	20	M33	55.6	411	483	81
450	18	457	710	628.6	36	24	M33	58.8	462	533	87
500	20	508	775	685.8	36	24	M33	62	513.5	587	94
600	24	610	915	812.8	42	24	M39X3	68.3	616.5	702	105

Class 600

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	95	66.7	16	4	M14	14.3	22.5	38	22
20	3/4	26.9	115	82.6	18	4	M16	15.9	27.5	48	25
25	1	33.7	125	88.9	18	4	M16	17.5	34.5	54	27
32	1 1/4	42.4	135	88.4	18	4	M16	20.7	43.5	64	29
40	1 1/2	48.3	155	114.3	22	4	M20	22.3	49.5	70	32
50	2	60.3	165	127	18	8	M16	25.4	61.5	84	37
65	2 1/2	76.1	190	149.2	22	8	M20	28.6	77.6	100	41
80	3	88.9	210	168.3	22	8	M20	31.8	90.5	117	46
100	4	114.3	275	215.9	26	8	M24	38.1	116	152	54
125	5	139.7	330	266.7	30	8	M27	44.5	143.5	189	60
150	6	168.3	355	292.1	30	12	M27	47.7	170.5	222	67
200	8	219.1	420	349.2	33	12	M30	55.6	221.5	273	76
250	10	273	510	431.8	36	16	M33	63.5	276.5	343	86
300	12	323.9	560	489	36	20	M33	66.7	328	400	92
350	14	355.6	605	527	39	20	M36X3	69.9	360	432	94
400	16	406.4	685	603.2	42	20	M39X3	76.2	411	495	106
450	18	457	745	654	45	20	M42X3	82.6	462	546	117
500	20	508	815	723.9	45	24	M42X3	88.9	513.5	610	127
600	24	610	940	838.2	51	24	M48X3	101.6	616.5	718	140

Class 900

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	120	82.6	22	4	M20	22.3	22.5	38	32
20	3/4	26.9	130	88.9	22	4	M20	25.4	27.5	44	35
25	1	33.7	150	101.6	26	4	M24	28.6	34.5	52	41
32	1 1/4	42.4	160	111.1	26	4	M24	28.6	43.5	64	41
40	1 1/2	48.3	180	123.8	30	4	M27	31.8	49.5	70	44
50	2	60.3	215	165.1	26	8	M24	38.1	61.5	105	57
65	2 1/2	76.1	245	190.5	30	8	M27	41.3	77.6	124	64
80	3	88.9	240	190.5	26	8	M24	38.1	90.5	127	54
100	4	114.3	290	235	33	8	M30	44.5	116	159	70
125	5	139.7	350	279.4	36	8	M33	50.8	143.5	190	79
150	6	168.3	380	317.5	33	12	M30	55.6	170.5	235	86
200	8	219.1	470	393.7	39	12	M36X3	63.5	221.5	298	102
250	10	273	545	469.9	39	16	M36X3	69.9	276.5	368	108
300	12	323.9	610	533.4	39	20	M36X3	79.4	328	419	117
350	14	355.6	640	558.8	42	20	M39X3	85.8	360	451	130
400	16	406.4	705	616	45	20	M42X3	88.9	411	508	133
450	18	457	785	685.8	51	20	M48X3	101.6	462	565	152
500	20	508	855	749.3	55	20	M52X3	108	513.5	622	159
600	24	610	1040	901.7	68	20	M64X3	139.7	616.5	749	203

Class 1500

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	120	82.6	22	4	M20	22.3	22.5	38	32
20	3/4	26.9	130	88.9	22	4	M20	25.4	27.5	44	35
25	1	33.7	150	101.6	26	4	M24	28.6	34.5	52	41
32	1 1/4	42.4	160	111.1	26	4	M24	28.6	43.5	64	41
40	1 1/2	48.3	180	123.8	30	4	M27	31.8	49.5	70	44
50	2	60.3	215	165.1	26	8	M24	38.1	61.5	105	57
65	2 1/2	76.1	245	190.5	30	8	M27	41.3	77.6	124	64

ASME b16.5 Weld Neck Flange Dimensions - Pressure Class 150 to 2500

Class 150

Class 300

Class 600

Class 900

Class 1500

Class 2500

Class 150

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	90	60.3	16	4	M14	9.6	15.5	30	46
20	3/4	26.9	100	69.9	16	4	M14	11.2	21	38	51
25	1	33.7	110	79.4	16	4	M14	12.7	27	49	54
32	1 1/4	42.4	115	88.9	16	4	M14	14.3	35	59	56
40	1 1/2	48.3	125	98.4	16	4	M14	15.9	41	65	60
50	2	60.3	150	120.7	18	4	M16	17.5	52	78	62
65	2 1/2	76.1	180	139.7	18	4	M16	20.7	66	90	68
80	3	88.9	190	152.4	18	4	M16	22.3	77.5	108	68
100	4	114.3	230	190.5	18	8	M16	22.3	101.5	135	75
125	5	139.7	255	215.9	22	8	M20	22.3	127	164	87
150	6	168.3	280	241.3	22	8	M20	23.9	154	192	87
200	8	219.1	345	298.5	22	8	M20	27	203	246	100
250	10	273	405	362	26	12	M24	28.6	255	305	100
300	12	323.9	485	431.8	26	12	M24	30.2	303.5	365	113
350	14	355.6	535	476.3	30	12	M27	33.4	–	400	125
400	16	406.4	595	539.8	30	16	M27	35	–	457	125
450	18	457	635	577.9	33	16	M30	38.1	–	505	138
500	20	508	700	635	33	20	M30	41.3	–	559	143
600	24	610	815	749.3	36	20	M33	46.1	–	663	151

Class 300

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	95	66.7	16	4	M14	12.7	15.5	38	51
20	3/4	26.9	115	82.6	18	4	M16	14.3	21	48	56
25	1	33.7	125	88.9	18	4	M16	15.9	27	54	60
32	1 1/4	42.4	135	98.4	18	4	M16	17.5	35	64	64
40	1 1/2	48.3	155	114.3	22	4	M20	19.1	41	70	67
50	2	60.3	165	127	18	8	M16	20.7	52	84	68
65	2 1/2	76.1	190	149.2	22	8	M20	23.9	66	100	75
80	3	88.9	210	168.3	22	8	M20	27	77.5	117	78
100	4	114.3	255	200	22	8	M20	30.2	101.5	146	84
125	5	139.7	280	235	22	8	M20	33.4	127	178	97
150	6	168.3	320	269.9	22	12	M20	35	154	206	97
200	8	219.1	380	330.2	26	12	M24	39.7	203	260	110
250	10	273	445	387.4	30	16	M27	46.1	255	321	116
300	12	323.9	520	450.8	33	16	M30	49.3	303.5	375	129
350	14	355.6	585	514.4	33	20	M30	52.4	–	425	141
400	16	406.4	650	571.5	36	20	M33	55.6	–	483	144
450	18	457	710	628.6	36	24	M33	58.8	–	533	157
500	20	508	775	685.8	36	24	M33	62	–	587	160
600	24	610	915	812.8	42	24	M39X3	68.3	–	702	167

Class 600

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	95	66.7	16	4	M14	14.3	–	38	52
20	3/4	26.9	115	82.6	18	4	M16	15.9	–	48	57
25	1	33.7	125	88.9	18	4	M16	17.5	–	54	62
32	1 1/4	42.4	135	98.4	18	4	M16	20.7	–	64	67
40	1 1/2	48.3	155	114.3	22	4	M20	22.3	–	70	70
50	2	60.3	165	127	18	8	M16	25.4	–	84	73
65	2 1/2	76.1	190	149.2	22	8	M20	28.6	–	100	79
80	3	88.9	210	168.3	22	8	M20	31.8	–	117	83
100	4	114.3	275	215.9	26	8	M24	38.1	–	152	102
125	5	139.7	330	266.7	30	8	M27	44.5	–	189	114
150	6	168.3	355	292.1	30	12	M27	47.7	–	222	117
200	8	219.1	420	349.2	33	12	M30	55.6	–	273	133
250	10	273	510	431.8	36	16	M33	63.5	–	343	152
300	12	323.9	560	489	36	20	M33	66.7	–	400	156
350	14	355.6	605	527	39	20	M36X3	69.9	–	432	165
400	16	406.4	685	603.2	42	20	M39X3	76.2	–	495	178
450	18	457	745	654	45	20	M42X3	82.6	–	546	184
500	20	508	815	723.9	45	24	M42X3	88.9	–	610	190
600	24	610	940	838.2	51	24	M48X3	101.6	–	718	203

Class 900

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	120	82.6	22	4	M20	22.3	–	38	60
20	3/4	26.9	130	88.9	22	4	M20	25.4	–	44	70
25	1	33.7	150	101.6	26	4	M24	28.6	–	52	73
32	1 1/4	42.4	160	111.1	26	4	M24	28.6	–	64	73
40	1 1/2	48.3	180	123.8	30	4	M27	31.8	–	70	83
50	2	60.3	215	165.1	26	8	M24	38.1	–	105	102
65	2 1/2	76.1	245	190.5	30	8	M27	41.3	–	124	105
80	3	88.9	240	190.5	26	8	M24	38.1	–	127	102
100	4	114.3	290	235	33	8	M30	44.5	–	159	114
125	5	139.7	350	279.4	36	8	M33	50.8	–	190	127
150	6	168.3	380	317.5	33	12	M30	55.6	–	235	140
200	8	219.1	470	393.7	39	12	M36X3	63.5	–	298	162
250	10	273	545	469.9	39	16	M36X3	69.9	–	368	184
300	12	323.9	610	533.4	39	20	M36X3	79.4	–	419	200
350	14	355.6	640	558.8	42	20	M39X3	85.8	–	451	213
400	16	406.4	705	616	45	20	M42X3	88.9	–	508	216
450	18	457	785	685.8	51	20	M48X3	101.6	–	565	229
500	20	508	855	749.3	55	20	M52X3	108	–	622	248
600	24	610	1040	901.7	68	20	M64X3	139.7	–	749	292

Class 1500

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	120	82.6	22	4	M20	22.3	–	38	60
20	3/4	26.9	130	88.9	22	4	M20	25.4	–	44	70
25	1	33.7	150	101.6	26	4	M24	28.6	–	52	73
32	1 1/4	42.4	160	111.1	26	4	M24	28.6	–	64	73
40	1 1/2	48.3	180	123.8	30	4	M27	31.8	–	70	83
50	2	60.3	215	165.1	26	8	M24	38.1	–	105	102
65	2 1/2	76.1	245	190.5	30	8	M27	41.3	–	124	105
80	3	88.9	265	203.2	33	8	M30	47.7	–	133	117
100	4	114.3	310	241.3	36	8	M33	54	–	162	124
125	5	139.7	375	292.1	42	8	M39X3	73.1	–	197	156
150	6	168.3	395	317.5	39	12	M36X3	82.6	–	229	171
200	8	219.1	485	393.7	45	12	M42X3	92.1	–	292	213
250	10	273	585	482.6	51	12	M48X3	108	–	368	254
300	12	323.9	675	571.5	55	16	M52X3	123.9	–	451	283
350	14	355.6	750	635	60	16	M56X3	133.4	–	495	298
400	16	406.4	825	704.8	68	16	M64X3	146.1	–	552	311
450	18	457	915	774.7	74	16	M70X3	162	–	597	327
500	20	508	985	831.8	80	16	M76X3	177.8	–	641	356
600	24	610	1170	990.6	94	16	M90X3	203.2	–	762	406

Class 2500

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	135	88.9	22	4	M20	30.2	–	43	73
20	3/4	26.9	140	95.2	22	4	M20	31.8	–	51	79
25	1	33.7	160	108	26	4	M24	35	–	57	89
32	1 1/4	42.4	185	130.2	30	4	M27	38.1	–	73	95
40	1 1/2	48.3	205	146	33	4	M30	44.5	–	79	111
50	2	60.3	235	171.4	30	8	M27	50.9	–	95	127
65	21/2	76.1	265	196.8	33	8	M30	57.2	–	114	143
80	3	88.9	305	228.6	36	8	M33	66.7	–	133	168
100	4	114.3	355	273	42	8	M39X3	76.2	–	165	190
125	5	139.7	420	323.8	48	8	M45X3	92.1	–	203	229
150	6	168.3	485	368.3	55	8	M52X3	108	–	235	273
200	8	219.1	550	438.2	55	12	M52X3	127	–	305	318
250	10	273	675	539.8	68	12	M64X3	165.1	–	375	419
300	12	323.9	760	619.1	74	12	M70X3	184.2	–	441	464

ASME b16.5 Socket Weld Flange Dimensions - Pressure Class 150 to 900

Class 150

Class 300

Class 600

Class 900

Class 150

Nominal size		Steel pipe outer diameter A	Flange outer diameter D		Connection size				flange thickness C	Flange inner diameter B1		Socket			Flange neck big end N	Flange height H	Theoretical weight Kg
DN	NPS				Bolt hole center circle diameter K	Bold hole diameter L		Bolt hole Quantity n(pieces)				B2		U
15	1/2	21.3	90	88.9	60.3	16	15.7	4	9.6	15.5	15.7	22.5	22.4	10	30	14	0.42
20	3/4	26.9	100	98.6	69.9	16	15.7	4	11.2	21	20.8	27.5	27.7	11	38	14	0.59
25	1	33.7	110	108	79.4	16	15.7	4	12.7	27	26.7	34.5	34.5	13	49	16	0.81
32	1 1/4	42.4	115	117.3	88.9	16	15.7	4	14.3	35	35.1	43.5	43.2	14	59	19	1.07
40	1 1/2	48.3	125	127	98.4	16	15.7	4	15.9	41	40.9	49.5	49.5	16	65	21	1.36
50	2	60.3	150	152.4	120.7	18	19.1	4	17.5	52	52.6	61.5	62	17	78	24	2.1
65	2 1/2	76.1	180	177.8	139.7	18	19.1	4	20.7	66	62.7	77.6	74.7	19	90	27	3.33
80	3	88.9	190	190.5	152.4	18	19.1	4	22.3	77.5	78	90.5	90.7	21	108	29	3.9

Note: The inner diameter B1 of the flange is determined by the wall thickness of the steel pipe. The user should indicate it when ordering. The flange inner diameter B1 listed in the table is equivalent to a steel pipe with a wall thickness of Sch40

Class 300

Nominal size		Steel pipe outer diameter A	Flange outer diameter D		Connection size				flange thickness C	Flange inner diameter B1		Socket			Flange neck big end N	Flange height H	Theoretical weight Kg
DN	NPS				Bolt hole center circle diameter K	Bold hole diameter L		Bolt hole Quantity n(pieces)				B2		U
15	½	21.3	95	88.9	66.7	16	15.7	4	12.7	15.5	15.7	22.5	22.4	10	38	21	0.66
20	¾	26.9	115	98.6	82.6	18	15.7	4	14.3	21	20.8	27.5	27.7	11	48	24	1.15
25	1	33.7	125	108	88.9	18	15.7	4	15.9	27	26.7	34.5	34.5	13	54	25	1.4
32	1 ¼	42.4	135	117.3	98.4	18	15.7	4	17.5	35	35.1	43.5	43.2	14	64	25	1.75
40	1 ½	48.3	155	127	114.3	22	15.7	4	19.1	41	40.9	49.5	49.5	16	70	29	2.55
50	2	60.3	165	152.4	127	18	19.1	8	20.7	52	52.6	61.5	62	17	84	32	2.93
65	2 ½	76.1	190	177.8	149.2	22	19.1	8	23.9	66	62.7	77.6	74.7	19	100	37	4.4
80	3	88.9	210	190.5	168.3	22	19.1	8	27	77.5	78	90.5	90.7	21	117	41	5.92

Class 600

Nominal size		Steel pipe outer diameter A	Flange outer diameter D		Connection size				flange thickness C	Flange inner diameter B1	Socket			Flange neck big end N	Flange height H	Theoretical weight Kg
DN	NPS				Bolt hole center circle diameter K	Bold hole diameter L		Bolt hole Quantity n(pieces)			B2		U
15	1/2	21.3	95	88.9	66.7	16	15.7	4	14.3	–	22.5	22.4	10	38	22	0.76
20	3/4	26.9	115	98.6	82.6	18	15.7	4	15.9	–	27.5	27.7	11	48	25	1.29
25	1	33.7	125	108	88.9	18	15.7	4	17.5	–	34.5	34.5	13	54	27	1.55
32	1 1/4	424	135	117.3	98.4	18	15.7	4	20.7	–	43.5	43.2	14	64	29	2.06
40	1 1/2	48.3	155	127	114.3	22	15.7	4	22.3	–	49.5	49.5	16	70	32	3.00
50	2	60.3	165	152.4	127	18	19.1	8	25.4	–	61.5	62	17	84	37	3.67
65	2 1/2	76.1	190	177.8	149.2	22	19.1	8	28.6	–	77.6	74.7	19	100	41	5.35
80	3	88.9	210	190.5	168.3	22	19.1	8	31.8	–	90.5	90.7	21	117	46	7.06

Class 900

Nominal size		Steel pipe outer diameter A	Flange outer diameter D		Connection size				flange thickness C	Flange inner diameter B1	Socket			Flange neck big end N	Flange height H	Theoretical weight Kg
DN	NPS				Bolt hole center circle diameter K	Bold hole diameter L		Bolt hole Quantity n(pieces)			B2		U
15	½	21.3	120	120.6	82.6	22	22.3	4	22.3	–	22.5	22.4	10	38	32	1.8
20	¾	26.9	130	130	88.9	22	22.3	4	25.4	–	27.5	27.7	11	44	35	2.41
25	1	33.7	150	149.3	101.6	26	25.4	4	28.6	–	34.5	34.5	13	52	41	3.55
32	1¼	42.4	160	158.7	111.1	26	25.4	4	28.6	–	43.5	43.2	14	64	41	4.02
40	1½	48.3	180	177.8	123.8	30	28.4	4	31.8	–	49.5	49.5	16	70	44	5.45
50	2	60.3	215	215.9	165.1	26	25.4	8	38.1	–	61.5	62	17	105	57	10.2
65	2½	76.1	245	244.3	190.5	30	28.4	8	41.3	–	77.6	74.7	19	124	64	13.9

ASME b16.5 Threaded Flange Dimensions - Pressure Class 150 to 300

Class 150

Class 300

Class 150

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	90	60.3	16	4	M14	9.6	15.5	30	46
20	3/4	26.9	100	69.9	16	4	M14	11.2	21	38	51
25	1	33.7	110	79.4	16	4	M14	12.7	27	49	54
32	1 1/4	42.4	115	88.9	16	4	M14	14.3	35	59	56
40	1 1/2	48.3	125	98.4	16	4	M14	15.9	41	65	60
50	2	60.3	150	120.7	18	4	M16	17.5	52	78	62
65	2 1/2	76.1	180	139.7	18	4	M16	20.7	66	90	68
80	3	88.9	190	152.4	18	4	M16	22.3	77.5	108	68
100	4	114.3	230	190.5	18	8	M16	22.3	101.5	135	75
125	5	139.7	255	215.9	22	8	M20	22.3	127	164	87
150	6	168.3	280	241.3	22	8	M20	23.9	154	192	87
200	8	219.1	345	298.5	22	8	M20	27	203	246	100
250	10	273	405	362	26	12	M24	28.6	255	305	100
300	12	323.9	485	431.8	26	12	M24	30.2	303.5	365	113
350	14	355.6	535	476.3	30	12	M27	33.4	–	400	125
400	16	406.4	595	539.8	30	16	M27	35	–	457	125
450	18	457	635	577.9	33	16	M30	38.1	–	505	138
500	20	508	700	635	33	20	M30	41.3	–	559	143
600	24	610	815	749.3	36	20	M33	46.1	–	663	151

Class 300

Nominal size		Steel Pipe outer diameter	Connection size					flange thickness	flange inner diameter	flange neck big end	flange height
DN	NPS	A	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C	B	N	H
15	1/2	21.3	95	66.7	16	4	M14	12.7	15.5	38	51
20	3/4	26.9	115	82.6	18	4	M16	14.3	21	48	56
25	1	33.7	125	88.9	18	4	M16	15.9	27	54	60
32	1 1/4	42.4	135	98.4	18	4	M16	17.5	35	64	64
40	1 1/2	48.3	155	114.3	22	4	M20	19.1	41	70	67
50	2	60.3	165	127	18	8	M16	20.7	52	84	68
65	2 1/2	76.1	190	149.2	22	8	M20	23.9	66	100	75
80	3	88.9	210	168.3	22	8	M20	27	77.5	117	78
100	4	114.3	255	200	22	8	M20	30.2	101.5	146	84
125	5	139.7	280	235	22	8	M20	33.4	127	178	97
150	6	168.3	320	269.9	22	12	M20	35	154	206	97
200	8	219.1	380	330.2	26	12	M24	39.7	203	260	110
250	10	273	445	387.4	30	16	M27	46.1	255	321	116
300	12	323.9	520	450.8	33	16	M30	49.3	303.5	375	129
350	14	355.6	585	514.4	33	20	M30	52.4	–	425	141
400	16	406.4	650	571.5	36	20	M33	55.6	–	483	144
450	18	457	710	628.6	36	24	M33	58.8	–	533	157
500	20	508	775	685.8	36	24	M33	62	–	587	160
600	24	610	915	812.8	42	24	M39X3	68.3	–	702	167

ASME b16.5 Lap Joint Flange Dimensions - Pressure Class 150 to 600

Class 150

Class 300

Class 600

Class 150

Nominal size		Steel Pipe outer diameter	Flange outer diameter		Connection size				flange thickness	Flange inner diameter	Flange neck big end	Flange height	Rounded comers	Butt welding ring		Theotical weight
DN	NPS	A	D		Bolt hole center circle diameter K	Bolt hole diameter L		Bolt hole quantity n(pieces)	C	B	N	H	R1	high H	outer diameter d	Kg
15	1/2	21.3	90	88.9	60.3	16	15.7	4	11.2	22.9	30	16	3	51	34.9	0.38
20	3/4	26.9	100	98.6	69.9	16	15.7	4	12.7	28.2	38	16	3	51	42.9	0.55
25	1	33.7	110	108	79.4	16	15.7	4	14.3	34.9	49	17	3	51	50.8	0.76
32	1 1/4	42.4	115	117.3	88.9	16	15.7	4	15.9	43.7	59	21	5	51	63.5	1.01
40	1 1/2	48.3	125	127	98.4	16	15.7	4	17.5	50.0	65	22	6	51	73.0	1.3
50	2	60.3	150	152.4	120.7	18	19.1	4	19.1	62.5	78	25	8	64	92.1	2.03
65	2 1/2	76.1	180	177.8	139.7	18	19.1	4	22.3	78.5/75.4	90	29	8	64	104.8	3.25
80	3	88.9	190	190.5	152.4	18	19.1	4	23.9	91.4	108	30	10	64	127.0	3.81
100	4	114.3	230	228.6	190.5	18	19.1	8	23.9	116.8	135	33	11	76	157.2	5.25
125	5	139.7	255	254	215.9	22	22.4	8	23.9	144.4	164	36	11	76	185.7	6.02
150	6	168.3	280	278.4	241.3	22	22.4	8	25.4	171.4	192	40	13	89	215.9	7.4
200	8	219.1	345	342.9	298.58	22	22.4	8	28.6	222.2	246	44	13	102	269.9	12.1
250	10	273	405	406.4	362.0	26	25.4	12	30.2	277.4	305	49	13	127	323.8	16.4
300	12	323.9	485	482.6	431.8	26	25.4	12	31.8	328.2	365	56	13	152	381.0	26.1
350	14	355.6	535	533.4	476.2	30	28.4	12	35.0	360.2	400	79	13	152	412.8	34.5
400	16	406.4	595	596.9	539.8	30	28.4	16	36.6	411.2	457	87	13	152	469.9	44.6
450	18	457	635	635	577.9	33	31.75	16	39.7	462.3	505	97	13	152	533.4	48.7
500	20	508	700	698.5	635.0	33	31.75	20	42.9	514.4	559	103	13	152	584.2	61.6
600	24	610	815	812.8	749.3	36	35.1	20	47.7	616.0	663	111	13	152	692.2	86.6

Class 300

Nominal size		Steel Pipe outer diameter	Flange outer diameter		Connection size				flange thickness	Flange inner diameter	Flange neck big end	Flange height	Rounded corners	Butt welding ring		Theotical weight
DN	NPS	A	D		Bolt hole center circle diameter K	Bolt hole diameter L		Bolt hole quantity n(pieces)	C	B	N	H	R1	high H	outer diameter d	Kg
15	1/2	21.3	95	88.9	66.7	16	15.7	4	14.3	22.9	38	22	3	51	34.9	0.62
20	3/4	26.9	115	98.6	82.6	18	15.7	4	15.9	28.2	48	25	3	51	42.9	1.1
25	1	33.7	125	108	88.9	18	15.7	4	17.5	34.9	54	27	3	51	50.8	1.33
32	1 1/4	42.4	135	117.3	98.4	18	15.7	4	19.1	43.7	64	27	5	51	63.5	1.65
40	1 1/2	48.3	155	127	114.3	22	15.7	4	20.7	50.0	70	30	6	51	73.0	2.44
50	2	60.3	165	152.4	127.0	18	19.1	8	22.3	62.5	84	33	8	64	92.1	2.83
65	2 1/2	76.1	190	177.8	149.2	22	19.1	8	25.4	78.5/75.4	100	38	8	64	104.8	4.25
80	3	88.9	210	190.5	168.3	22	19.1	8	28.6	91.4	117	43	10	64	127.0	5.78
100	4	114.3	255	228.6	200.0	22	19.1	8	31.8	116.8	146	48	11	76	157.2	9.55
125	5	139.7	280	254	235.0	22	22.4	8	35.0	144.4	178	51	11	76	185.7	12.2
150	6	168.3	320	279.4	269.9	22	22.4	12	36.6	171.4	206	52	13	89	215.9	15.5
200	8	219.1	380	342.9	330.2	26	22.4	12	41.3	222.2	260	62	13	102	269.9	24.1
250	10	273	445	406.4	387.4	30	25.4	16	47.7	277.1	321	95	13	254	323.8	34.4
300	12	323.9	520	482.6	450.8	33	25.4	16	50.8	328.2	375	102	13	254	381.0	50.4
350	14	355.6	585	533.4	514.4	33	28.4	20	54.0	360.2	425	111	13	305	412.8	70.9
400	16	406.4	650	596.9	571.5	36	28.4	20	57.2	411.2	483	121	13	305	469.9	89.5
450	18	457	710	635	628.6	36	31.75	24	60.4	462.3	533	130	13	305	533.4	111
500	20	508	775	698.5	685.8	36	31.75	24	63.5	514.4	587	140	13	305	584.2	137
600	24	610	915	812.8	812.8	42	35.1	24	69.9	616.0	702	152	13	305	692.2	204

Class 600

Nominal size		Steel Pipe outer diameter	Flange outer diameter		Connection size				flange thickness	Flange inner diameter	Flange neck big end	Flange height	Rounded corners	Butt welding ring		Theotical weight
DN	NPS	A	D		Bolt hole center circle diameter K	Bolt hole diameter L		Bolt hole quantity n(pieces)	C	B	N	H	R1	high H	outer diameter d	Kg
15	1/2	21.3	95	88.9	66.7	16	15.7	4	14.3	22.9	38	22	3	76	34.9	0.72
20	3/4	26.9	115	98.6	82.6	18	15.7	4	15.9	28.2	48	25	3	76	42.9	1.25
25	1	33.7	125	108	88.9	18	15.7	4	17.5	34.9	54	27	3	102	50.8	1.5
32	11/4	42.4	135	117.3	98.4	18	15.7	4	20.7	43.7	64	29	5	102	63.5	2
40	11/2	48.3	155	127	114.3	22	15.7	4	22.3	50.0	70	32	6	102	73.0	2.92
50	2	60.3	165	152.4	127.0	18	19.1	8	25.4	62.5	84	37	8	152	92.1	3.55
65	21/2	76.1	190	177.8	149.2	22	19.1	8	28.6	78.5/75.4	100	41	8	152	104.8	5.23
80	3	88.9	210	190.5	168.3	22	19.1	8	31.8	91.4	117	46	10	152	127.0	6.95
100	4	114.3	275	228.6	215.9	26	19.1	8	38.1	116.8	152	54	11	152	157.2	14.4
125	5	139.7	330	254	266.7	30	22.4	8	44.5	144.4	189	60	11	203	185.7	24.3
150	6	168.3	355	279.4	292.1	30	22.4	12	47.7	171.4	222	67	13	203	215.9	28.5
200	8	219.1	420	342.9	349.2	33	22.4	12	55.6	222.2	273	76	13	203	269.9	43.1
250	10	273	510	406.4	431.8	36	25.4	16	63.5	277.4	343	111	13	254	323.8	70.5
300	12	323.9	560	482.6	489.0	36	25.4	20	66.7	328.2	400	117	13	254	381.0	86.1
350	14	355.6	605	533.4	527.0	39	28.4	20	69.9	360.2	432	127	13	305	412.8	100
400	16	406.4	685	596.9	603.2	42	28.4	20	76.2	411.2	495	140	13	305	469.9	145
450	18	457	745	635	654.0	45	31.75	20	82.6	462.3	546	152	13	305	533.4	177
500	20	508	815	698.5	723.9	45	31.75	24	88.9	514.4	610	165	13	305	584.2	225
600	24	610	940	812.8	838.2	51	35.1	24	101.6	616.0	718	184	13	305	692.2	318

ASME b16.5 Blind Flange Dimensions - Pressure Class 150 to 2500

Class 150

Class 300

Class 600

Class 900

Class 1500

Class 2500

Class 150

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	90	60.3	16	4	M14	9.6
20	3/4	100	69.9	16	4	M14	11.2
25	1	110	79.4	16	4	M14	12.7
32	1 1/4	115	88.9	16	4	M14	14.3
40	1 1/2	125	98.4	16	4	M14	15.9
50	2	150	120.7	18	4	M16	17.5
65	2 1/2	180	139.7	18	4	M16	20.7
80	3	190	152.4	18	4	M16	22.3
100	4	230	190.5	18	8	M16	22.3
125	5	255	215.9	22	8	M20	22.3
150	6	280	241.3	22	8	M20	23.9
200	8	345	298.58	22	8	M20	27.0
250	10	405	362.0	26	12	M24	28.6
300	12	485	431.8	26	12	M24	30.2
350	14	535	476.3	30	12	M27	33.4
400	16	595	539.8	30	16	M27	35.0
450	18	635	577.9	33	16	M30	38.1
500	20	700	635.0	33	20	M30	41.3
600	24	815	749.3	36	20	M33	46.1

Class 300

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	95	66.7	16	4	M14	12.7
20	3/4	115	82.6	18	4	M16	14.3
25	1	125	88.9	18	4	M16	15.9
32	1 1/4	135	98.4	18	4	M16	17.5
40	1 1/2	155	114.3	22	4	M20	19.1
50	2	165	127.0	18	8	M16	20.7
65	2 1/2	190	149.2	22	8	M20	23.9
80	3	210	168.3	22	8	M20	27.0
100	4	255	200.0	22	8	M20	30.2
125	5	280	235.0	22	8	M20	33.4
150	6	320	269.9	22	12	M20	35.0
200	8	380	330.2	26	12	M24	39.7
250	10	445	387.4	30	16	M27	46.1
300	12	520	450.8	33	16	M30	49.3
350	14	585	514.4	33	20	M30	52.4
400	16	650	571.5	36	20	M33	55.6
450	18	710	628.6	36	24	M33	58.8
500	20	775	685.8	36	24	M33	62.0
600	24	915	812.8	42	24	M39X3	68.3

Class 600

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	95	66.7	16	4	M14	14.3
20	3/4	115	82.6	18	4	M16	15.9
25	1	125	88.9	18	4	M16	17.5
32	1 1/4	135	98.4	18	4	M16	20.7
40	1 1/2	155	114.3	22	4	M20	22.3
50	2	165	127.0	18	8	M16	25.4
65	2 1/2	190	149.2	22	8	M20	28.6
80	3	210	168.3	22	8	M20	31.8
100	4	275	215.9	26	8	M24	38.1
125	5	330	266.7	30	8	M27	44.5
150	6	355	292.1	30	12	M27	47.7
200	8	420	349.2	33	12	M30	55.6
250	10	510	431.8	36	16	M33	63.5
300	12	560	489.0	36	20	M33	66.7
350	14	605	527.0	39	20	M36X3	69.9
400	16	685	603.2	42	20	M39X3	76.2
450	18	745	654.0	45	20	M42X3	82.6
500	20	815	723.9	45	24	M42X3	88.9
600	24	940	838.2	51	24	M48X3	101.6

Class 900

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	120	82.6	22	4	M20	22.3
20	3/4	130	88.9	22	4	M20	25.4
25	1	150	101.6	26	4	M24	28.6
32	1 1/4	160	111.1	26	4	M24	28.6
40	1 1/2	180	123.8	30	4	M27	31.8
50	2	215	165.1	26	8	M24	38.1
65	2 1/2	245	190.5	30	8	M27	41.3
80	3	265	203.2	33	8	M30	47.7
100	4	310	241.3	36	8	M33	54.0
125	5	375	292.1	42	8	M39X3	73.1
150	6	395	317.5	39	12	M36X3	82.6
200	8	485	393.7	45	12	M42X3	92.1
250	10	585	482.6	51	12	M48X3	108.0
300	12	675	571.5	55	16	M52X3	123.9
350	14	750	635.0	60	16	M56X3	133.4
400	16	825	704.8	68	16	M64X3	146.1
450	18	915	774.7	74	16	M70X3	162.0
500	20	985	831.8	80	16	M76X3	177.8
600	24	1170	990.6	94	16	M90X3	203.2

Class 1500

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	120	82.6	22	4	M20	22.3
20	3/4	130	88.9	22	4	M20	25.4
25	1	150	101.6	26	4	M24	28.6
32	1 1/4	160	111.1	26	4	M24	28.6
40	1 1/2	180	123.8	30	4	M27	31.8
50	2	215	165.1	26	8	M24	38.1
65	2 1/2	245	190.5	30	8	M27	41.3
80	3	240	190.5	26	8	M24	38.1
100	4	290	235.0	33	8	M30	44.5
125	5	350	279.4	36	8	M33	50.8
150	6	380	317.5	33	12	M30	55.6
200	8	470	393.7	39	12	M36X3	63.5
250	10	545	469.9	39	16	M36X3	69.9
300	12	610	533.4	39	20	M36X3	79.4
350	14	640	558.8	42	20	M39X3	85.8
400	16	705	616.0	45	20	M42X3	88.9
450	18	785	685.8	51	20	M48X3	101.6
500	20	855	749.3	55	20	M52X3	108.0
600	24	1040	901.7	68	20	M64X3	139.7

Class 2500

Nominal size		Connection size					flange thickness
DN	NPS	Flange outer diameter D	Central circle diameter K	Bolt hole diameter L	Number of bolt holes n	Bolt Th	C
15	1/2	135	88.9	22	4	M20	30.2
20	3/4	140	95.2	22	4	M20	31.8
25	1	160	108.0	26	4	M24	35.0
32	1 1/4	185	130.2	30	4	M27	38.1
40	1 1/2	205	146.0	33	4	M30	44.5
50	2	235	171.4	30	8	M27	50.9
65	2 1/2	265	196.8	33	8	M30	57.2
80	3	305	228.6	36	8	M33	66.7
100	4	355	273.0	42	8	M39X3	76.2
125	5	420	323.8	48	8	M45X3	92.1
150	6	485	368.3	55	8	M52X3	108.0
200	8	550	438.2	55	12	M52X3	127.0
250	10	675	539.8	68	12	M64X3	165.1
300	12	760	619.1	74	12	M70X3	184.2

Material:

Carbon Steel, Stainless Steel, Aluminum, Nickel Alloys

Custom Flange

Our custom flanges are made to specific sizes and materials for unique applications. Can be modified from standard designs or created from scratch to meet various industry requirements.

Compliance Certificates

Why Choose LONGAN Flange?

Expertise in Flange Manufacturing: Longan Flange specializes in producing a wide range of flanges and custom non-standard products, ensuring we meet diverse industry needs with precision.
Advanced Manufacturing Capabilities: With over 100 CNC lathes, 10 machining lathes, and 16 high-precision machining centers, we leverage advanced technology for efficient and high-quality production.
Rigorous Quality Assurance: Our independent laboratory equipped with 15 testing devices ensures extensive testing of each flange, guaranteeing they meet specifications and providing reliable performance.
Commitment to Customization and Standards: We offer tailor-made solutions while adhering to established industry standards, ensuring seamless compatibility and exceptional quality tailored to your project requirements.

Frequently Asked Questions (FAQs)

What determines a flange's pressure class rating?

A flange’s pressure class rating depends on multiple factors. The primary determinants are operating temperature and material group. ASME B16.5 provides specific pressure-temperature rating tables for different material groups. For example, a Class 150 carbon steel flange rated at 285 PSI at ambient temperature will have reduced pressure capabilities at elevated temperatures. The standard covers seven pressure classes: 150, 300, 400, 600, 900, 1500, and 2500.

How do material specifications affect flange selection?

Material selection critically impacts flange performance and compliance. ASME B16.5 categorizes materials into specific groups: carbon steel, low-alloy steel, and high-alloy steel. Each material group has distinct pressure-temperature ratings. For instance, ASTM A105 carbon steel exhibits different pressure capabilities compared to ASTM A182 stainless steel, even within the same pressure class. Material selection must consider service conditions, corrosion resistance, and temperature requirements.

What are the mandatory marking requirements for ASME B16.5 flanges?

ASME B16.5 requires specific identification markings on all flanges. These include the manufacturer’s name or trademark, material specification designation, pressure class rating, and nominal pipe size. For ring-type joint flanges, additional markings must indicate the ring number. These markings ensure traceability and proper installation, appearing on the flange’s outer rim or other visible location.

How does temperature affect flange pressure ratings?

Temperature significantly influences flange pressure capabilities. As temperature increases, the maximum allowable working pressure decreases. For example, a Class 150 flange rated for 285 PSI at ambient temperature might only handle 150 PSI at 500°F. ASME B16.5 provides detailed pressure-temperature rating tables for each material group, requiring careful consideration of both operating temperature and pressure requirements.

What are the dimensional standards for ASME B16.5 flanges?

ASME B16.5 specifies precise dimensional requirements for flanges from NPS 1/2 through NPS 24. These dimensions include face-to-face length, outside diameter, bolt circle diameter, and bolt hole size. The standard provides both metric and imperial measurements. As pressure class increases, certain dimensions like bolt circle diameter and flange thickness increase while maintaining consistent bore dimensions.