Flange Size Chart Reading ASME B16.5 Dimension Tables

2026-04-12
grama
115

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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