Flange Dimensions Class 600

Class 600 flanges per ASME B16.5 are used in high-pressure piping systems such as hydrocarbon processing, gas transmission, and high-pressure steam services. At ambient temperature, a Class 600 carbon steel flange (ASTM A105) is rated for approximately 102 bar (1,480 psi). The following table provides the key dimensions for Class 600 welding neck flanges from NPS 1/2 to NPS 24.

Class 600 Flange Dimensions (ASME B16.5)

NPS	Flange OD (inch)	Flange OD (mm)	Thickness (inch)	Thickness (mm)	Bolt Circle Dia (inch)	Bolt Circle Dia (mm)	Bolt Hole Dia (inch)	Number of Bolts	Bolt Dia (inch)	Raised Face Dia (inch)	Raised Face Dia (mm)
1/2	3.75	95.3	0.56	14.2	2.62	66.5	0.62	4	1/2	1.38	34.9
3/4	4.62	117.5	0.62	15.7	3.25	82.6	0.75	4	5/8	1.69	42.9
1	4.88	124.0	0.69	17.5	3.50	88.9	0.75	4	5/8	2.00	50.8
1-1/4	5.25	133.4	0.81	20.6	3.88	98.6	0.75	4	5/8	2.50	63.5
1-1/2	6.12	155.4	0.88	22.4	4.50	114.3	0.88	4	3/4	2.88	73.2
2	6.50	165.1	1.00	25.4	5.00	127.0	0.75	8	5/8	3.62	92.1
2-1/2	7.50	190.5	1.12	28.4	5.88	149.4	0.88	8	3/4	4.12	104.6
3	8.25	210.0	1.25	31.8	6.62	168.1	0.88	8	3/4	5.00	127.0
3-1/2	9.00	228.6	1.38	35.1	7.25	184.2	1.00	8	7/8	5.50	139.7
4	10.75	273.1	1.50	38.1	8.50	215.9	1.00	8	7/8	6.19	157.2
5	13.00	330.2	1.75	44.5	10.50	266.7	1.12	8	1	7.31	185.7
6	14.00	355.6	1.88	47.8	11.50	292.1	1.12	12	1	8.50	215.9
8	16.50	419.1	2.19	55.6	13.75	349.3	1.25	12	1-1/8	10.62	269.7
10	20.00	508.0	2.50	63.5	17.00	431.8	1.38	16	1-1/4	12.75	323.9
12	22.00	558.8	2.62	66.5	19.25	489.0	1.38	20	1-1/4	15.00	381.0
14	23.75	603.3	2.75	69.9	20.75	527.1	1.50	20	1-3/8	16.25	412.8
16	27.00	685.8	3.00	76.2	23.75	603.3	1.62	20	1-1/2	18.50	469.9
18	29.25	742.9	3.25	82.6	25.75	654.1	1.75	20	1-5/8	21.00	533.4
20	32.00	812.8	3.50	88.9	28.50	723.9	1.75	24	1-5/8	23.00	584.2
24	37.00	939.8	4.00	101.6	33.00	838.2	2.00	24	1-7/8	27.25	692.2

Notes

• All dimensions are per ASME B16.5-2020 for welding neck (WN) flanges with raised face (RF). Other flange types (slip-on, blind, socket weld, threaded) share the same outer diameter, bolt circle, bolt hole, and bolt size values; flange thickness may differ.
• The raised face height for Class 600 flanges is 6.4 mm (1/4 inch) and is included in the thickness values shown above.
• Bolt diameters refer to the stud bolt nominal size per ASME B16.5. The corresponding bolt hole diameter is drilled 1/8” larger than the bolt size (for bolt sizes up to 1”) or 1/4” larger (for bolt sizes over 1”).
• Metric conversions are rounded to one decimal place. Always refer to the latest edition of ASME B16.5 for the controlling dimensions.
• For Class 600 flanges with ring type joint (RTJ) face, the flange thickness is greater than the raised face values shown. Refer to ASME B16.5 Table 16 for RTJ flange dimensions.