ASME B16.5 vs B16.47 Flange Comparison

When selecting flanges for industrial piping systems, understanding the difference between ASME B16.5 and ASME B16.47 standards is crucial. These standards define the dimensions, pressure-temperature ratings, and material requirements for flanges, but they apply to different size ranges and applications.

Overview of ASME B16.5

ASME B16.5 is the most commonly used standard for pipe flanges and flanged fittings. It covers sizes from NPS 1/2 through NPS 24. This standard is widely applied in chemical plants, refineries, and power generation facilities where pipe sizes typically fall within this range. It includes pressure class ratings of 150, 300, 400, 600, 900, 1500, and 2500.

Key characteristics include:

• Covers sizes up to 24 inches.
• Standard for most general industrial applications.
• Well-established pressure-temperature ratings.

Overview of ASME B16.47

For larger diameter piping, ASME B16.47 is the governing standard. It covers large diameter steel flanges from NPS 26 through NPS 60. This standard was developed to address the needs of pipelines and larger industrial processes that require flanges larger than the 24-inch limit of B16.5. B16.47 flanges are available in pressure classes 75, 150, 300, 400, 600, and 900.

ASME B16.47 is further divided into two series: Series A and Series B.

Series A vs. Series B: What's the Difference?

Understanding the distinction between Series A and Series B is vital for proper fitment and system integrity.

ASME B16.47 Series A (MSS SP-44)

Series A flanges are thicker, heavier, and stronger than Series B flanges. They generally have larger bolt circle diameters and larger bolts. Series A flanges are often preferred for new construction projects where the extra weight and cost are justified by the increased robustness. They were originally known as MSS SP-44 flanges.

ASME B16.47 Series B (API 605)

Series B flanges are more compact, lighter, and typically less expensive than Series A. They have smaller bolt circle diameters and use smaller bolts. These flanges are often used in refurbishment work or non-critical applications where space and weight are constraints. They were originally known as API 605 flanges.

Critical Note: Series A and Series B flanges are NOT interchangeable. Attempting to mate a Series A flange with a Series B flange will result in misalignment of bolt holes and potential leakage.

Selection Criteria

When choosing between these standards and series, consider the following:

• Size: If your pipe is 24 inches or smaller, use ASME B16.5. For 26 inches and above, use ASME B16.47.
• Application: For high-stress, large-diameter applications, Series A is often the safer choice.
• Compatibility: Always verify the existing flange type when replacing components to ensure the bolt patterns match.

For a wide range of high-quality flanges that meet these rigorous standards, explore our catalog of Stainless Steel and Carbon Steel Flanges.