Manufacturing Standard Guide

ASME B16.5 Pipe Flanges Standard & Pressure Classes

Technical specs, pressure-temperature ratings, facing types (RF, RTJ, FF), and bolt hole dimensions for ASME B16.5 pipe flanges in Class 150 to Class 2500.

Pressure Classes & Dimensional Scope (ASME B16.5 (NPS 1/2 to 24))

Class 150 & 300

Standard commercial & industrial process plant flanges.

Class 600 & 900

High-pressure oil & gas transmission lines.

Class 1500 & 2500

Subsea and ultra-high pressure steam power plants.

Nominal Pipe Size (NPS) Dimension Overview

NPS (Inches)Outside Dia (mm)Class 150 / 2000 RatingClass 300 / 3000 RatingClass 600 / 6000 Rating
1/2"89 mmClass 150 (4 Holes)Class 300 (4 Holes)Class 600 (4 Holes)
1"108 mmClass 150 (4 Holes)Class 300 (4 Holes)Class 600 (4 Holes)
2"152 mmClass 150 (4 Holes)Class 300 (4 Holes)Class 600 (8 Holes)
4"229 mmClass 150 (8 Holes)Class 300 (8 Holes)Class 600 (8 Holes)

Frequently Asked Questions (ASME B16.5 (NPS 1/2 to 24))

What size range is covered by ASME B16.5?

ASME B16.5 covers flange sizes from NPS 1/2" up to NPS 24". Sizes 26" to 60" are governed by ASME B16.47.

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