ANSI B16.5 Vs. ASME B16.5 – What’s The Difference?

Both ANSI B16.5 and ASME B16.5 refer to the same standard for pipe flanges and flanged fittings, but the naming has evolved over time. Here's a clear breakdown of their relationship and key details.

1. Historical Background

ANSI B16.5 (Older Name):

Previously published by the American National Standards Institute (ANSI).

Widely used in the 20th century (e.g., ANSI B16.5-1981, ANSI B16.5-1996).

ASME B16.5 (Current Name):

Now maintained and published by the American Society of Mechanical Engineers (ASME).

The standard was transferred from ANSI to ASME, but the technical content remains largely the same.

Key Takeaway:

✅ ANSI B16.5 = ASME B16.5 (just different naming conventions over time).
✅ All modern editions are ASME B16.5 (e.g., ASME B16.5-2020).

2. Technical Content Comparison

The standard covers:

Flange dimensions (NPS ½" to 24").

Pressure classes (150, 300, 400, 600, 900, 1500, 2500).

Materials, tolerances, marking, and testing.

3. Which One Should You Use?

For new projects: Always use ASME B16.5 (the latest edition, e.g., 2020).

For legacy systems: Some old drawings/specs may still reference ANSI B16.5, but the dimensions are identical.

Common Misconceptions:

❌ "ANSI B16.5 and ASME B16.5 are different standards."
✅ They are the same standard, just rebranded.

❌ "ANSI B16.5 is outdated."
✅ It's not outdated-just renamed. The latest version is ASME B16.5.

4. Key References

ASME B16.5-2020 – Current edition for flanges and flanged fittings.

ASME B16.47 – For larger flanges (NPS 26" to 60").

ASME BPVC Section II – Materials referenced in B16.5.

Final Summary

Conclusion: Use ASME B16.5 for all new designs, but know that references to ANSI B16.5 are still valid (just older versions of the same standard).

Would you like a comparison with other flange standards (e.g., ASME B16.47, EN 1092-1)? Let me know!