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ASME B16.5-2025

Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard
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ASME B16.5-2025

Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24 Metric/Inch Standard

PUBLISH DATE 2025
PAGES 274
ASME B16.5-2025

Purpose and Scope of ASME B16.5-2025

ASME B16.5, Pipe Flanges and Flanged Fittings: NPS 1/2 through NPS 24, is arguably the most widely used component standard in the piping industry worldwide. Its primary function is to provide a single, consistent set of technical and dimensional criteria for metallic flanges and flanged fittings, ensuring that a flange produced by any compliant manufacturer will correctly and safely mate with another component of the same specification.

The scope of the standard covers flanges and flanged fittings for nominal pipe sizes (NPS) from 1/2 through 24 inches (DN 15 through DN 600). It covers the full spectrum of technical requirements, including:

  • Pressure-Temperature (P-T) Ratings: It defines the maximum allowable working pressure for a flange at a given temperature. These ratings are organized into seven standard pressure classes: Class 150, 300, 400, 600, 900, 1500, and 2500 (with Class 2500 limited to smaller sizes).
  • Materials: It groups accepted materials (e.g., carbon steel, alloy steel, stainless steel) with their corresponding ASTM specifications and links them to the P-T rating tables.
  • Dimensions and Tolerances: It specifies all critical dimensions, including outside and inside diameter, bolt circle diameter, bolt hole size and quantity, flange thickness, and hub dimensions.
  • Flange Types and Facings: Covers various flange types (Weld Neck, Slip-On, Threaded, Lap Joint, Blind) and facing types (Raised Face, Flat Face, Ring Type Joint).

Application and Use

ASME B16.5 is foundational for engineers, manufacturers, and fabricators in nearly every industrial sector that uses pressurized fluid systems. It is used to govern the procurement and assembly of pipe-to-equipment connections, valve installations, and piping break points for maintenance:

  • Piping Designers: They use the P-T tables to select a flange's material and pressure class based on the system’s operating conditions (temperature and pressure).
  • Manufacturers: They use the detailed dimensional tables to manufacture flanges and fittings that are guaranteed to fit the designated pipe size and bolt pattern, ensuring product compatibility worldwide.
  • Construction Crews: They rely on the standard for correct assembly, ensuring the specified gaskets and bolting materials are used to create a leak-tight flanged joint that will safely contain the process fluid.

Because of its comprehensive nature, B16.5 is typically specified directly in government regulations and referenced by all major ASME Piping Codes (e.g., B31.1, B31.3, B31.8) as the definitive source for component design and ratings for flanges in the NPS 1/2 to NPS 24 range.

SDO ASME: American Society of Mechanical Engineers
Document Number B16.5
Publication Date May 30, 2025
Language en - English
Page Count 274
Revision Level
Supercedes
Committee
Publish Date Document Id Type View
May 30, 2025 ASME B16.5-2025 Revision