Flange Size Chart Reading ASME B16.5 Dimension Tables

Mastering ASME B16.5 Flange Dimensions

A flange size chart ensures proper fit-up, bolt alignment, and gasket seating. Misreading tables leads to costly mistakes.

Key Dimension Parameters

NPS

Nominal Pipe Size (not actual OD for 14 inch+)

Class

Pressure rating: 150, 300, 600, 900, 1500, 2500

Outside Diameter

Overall flange diameter

Thickness

Flange thickness at hub

Bolt Circle

Diameter through bolt hole centers

Number of Bolts

Increases with NPS and class

Class 150 Dimensions

NPS	OD	Thickness	Bolt Circle	Bolts
1/2	3.50	0.44	2.38	4
1	4.25	0.56	3.12	4
2	6.00	0.69	4.75	4
4	9.00	0.81	7.50	8
6	11.00	0.94	9.50	8
8	13.50	1.06	11.75	8
10	16.00	1.12	14.25	12
12	19.00	1.19	17.00	12

Class 300 Dimensions

NPS	OD	Thickness	Bolt Circle	Bolts
1/2	3.75	0.56	2.62	4
1	4.88	0.69	3.50	4
2	6.50	0.88	5.00	4
4	10.00	1.12	7.88	8
6	12.50	1.38	10.62	8
8	15.00	1.56	13.00	8
10	17.50	1.69	15.25	12
12	21.00	1.81	18.50	12

Common Mistakes

1. Confusing NPS with actual dimensions
2. Mixing pressure classes (150 won’t bolt to 300)
3. Ignoring facing type (RF vs RTJ)

Songhai Flange provides dimension tables and CAD drawings for all products.

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