ANSI Flange Standards
American National Standards Institute standards for industrial flanges and pressure-boundary components. Relationship to ASME specifications and applications.
ANSI Standards Overview
Understanding ANSI Standards
ANSI (American National Standards Institute) is a standards coordination body that develops and adopts standards from various technical committees. Many ASME standards are also published as ANSI standards.
ANSI B16.5 and B16.47 standards are essentially ASME standards that have been adopted into the ANSI catalog. They specify the same pressure ratings, materials, dimensions, and requirements.
ANSI vs ASME
In practical application, ANSI B16.5 and ASME B16.5 are the same standard. ASME is the technical society responsible for developing and maintaining the standard, while ANSI serves as the approval and coordination body for national standards.
When specifying flanges, referencing either ANSI or ASME standards is equally correct and will result in identical components.
ANSI B16.5
- • Sizes: 1/2" through 24" NPS
- • Classes: 150, 300, 400, 600, 900, 1500, 2500
- • Types: Blind, weld neck, slip-on, socket weld, threaded, lap joint
- • Temperature range varies by material group; see ASME B16.5 Table 2 for the specific material in service
ANSI B16.47
- • Sizes: 26" through 60"+ NPS
- • Series: A and B designs
- • Multiple pressure classes
- • Large diameter applications
ANSI B16.9
- • Wrought steel butt welding fittings
- • Elbows, tees, reducers, caps
- • Sizes 1/2" through 60" NPS
- • Matching ASME specifications
Key Characteristics
ANSI standards for flanges emphasize compatibility, interchangeability, and broad industrial applications.
Material Flexibility
ANSI B16.5 covers carbon steel, stainless steel, and alloy steel with detailed specifications for each.
- ✓ ASTM A105 (carbon steel)
- ✓ ASTM A350 (low-temp service)
- ✓ ASTM A182 (stainless/alloy)
- ✓ Custom alloys approved
Pressure Classes
Standard pressure classes with temperature derating curves for proper application selection.
- ✓ 150 through 2500 classes
- ✓ Temperature derating tables
- ✓ Impact testing for low-temp
- ✓ Full pressure-temperature documentation
Interchangeability
ANSI standards ensure that components from different manufacturers are dimensionally and functionally compatible.
- ✓ Bolt hole patterns standardized
- ✓ Dimensional consistency
- ✓ Facings standardized
- ✓ Multiple supplier compatibility
Applications & Industries
ANSI flanges are widely specified across industrial applications throughout North America and globally.
Oil & Gas
ANSI standards are primary specifications for oil and gas pipeline systems, processing plants, and equipment interfaces.
High-pressure systems, variable temperatures, corrosive environments.
Power Generation
Steam piping systems, cooling water loops, and high-pressure/high-temperature applications in power plants.
ANSI covers materials and temperatures required for power systems.
Chemical & Refining
Process systems, chemical transfer piping, and specialized applications in chemical manufacturing and refineries.
Material variety and flexibility for diverse chemical environments.
ANSI Relationship to Other Standards
ANSI & ASME
ANSI B16 standards are identical to ASME B16 standards. ASME develops the technical content, ANSI provides official national approval and coordination.
Learn More →ANSI vs International
ANSI standards use class ratings (PSI-based) while DIN/EN use PN ratings (bar-based). Both widely accepted globally.
Compare Standards →Need ANSI-Compliant Flanges?
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