ANSI Class Flanges

The added strength of an ANSI certified flange contributes to high performance mechanical systems, structures, and assemblies across the United States and around the world. Tested and certified to meet the specifications of the American National Standards Institute, ANSI Class Flanges carry the organization’s seal of approval for the toughest jobs.

What is ANSI?

Originally formed in 1918, the American National Standards Institute is headquartered in Washington, DC, and is widely recognized as the American organization responsible for overseeing the national standards and conformity assessment system for products, services, processes, systems, and personnel.

ANSI works domestically with American government agencies and organizations, as well as with international entities, to make ANSI standards useful around the world.

Prior to the creation of ANSI, standards for engineering and equipment such as flanges were developed by the American Institute of Electrical Engineers (AIEE or IEEE), the American Society of Mechanical Engineers (ASME), the American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME), the American Society of Civil Engineers (ASCE), and the American Society for Testing and Materials (ASTM International) as members of the United Engineering Society, or UES.

ANSI B16.5

ANSI B16.5 -1996 is the official standard for ANSI Class Pipe Flanges and Flanged Fittings, applied specifically to those made from cast or forged materials, as well as blind flanges and some reducing flanges crafted in cast, forged, or plate. It covers evaluations and standards for the following characteristics, noted in both metric and U.S. units of measure:

  • Pressure-temperature ratings
  • Materials
  • Tolerances
  • Dimensions
  • Marking
  • Testing
  • Methods of designating openings

ANSI standard flange dimensions are designated as 150, 300, 400, 600, 900, 1500, and 2500, in sizes NPS 1/2 through NPS 24.

ANSI Class Flange Types

Regardless of size or specification, flanges are fundamentally designed to close, cover, connect, or support pipe systems. The six common types of ANSI Class Flanges, including:

  • Slip-on, in both ring and hub style, to fit over a pipe
  • Weld neck, machined to match a pipe’s inside diameter and attached via welding
  • Blind, for sealing the end or opening of a piping system or vessel
  • Lap joint, to pair with stub end fittings for applications demanding dismantling
  • Threaded, to fit pipes with external threads without the need for welding
  • Socket-weld, to provide ideal inside flow with the use of a socket fit and top weld 

Material Grades and Performance

The most common material grade for ANSI Class Flanges is forged or cast, unless otherwise specified.

Industries and Applications

The strength and durability represented by ANSI standards for flanges is valued in both domestic and international industries of all kinds. Common industries and applications include:

  • Food processing and manufacturing (ANSI-NSF is a unique food-safe family of specifications)
  • Valves, vessels, and industrial pumps
  • Waterworks and municipal pipe systems
  • Heating systems and heat exchangers
  • Plumbing and mechanical systems
  • Fire protection services
  • Power plants and the nuclear power industry
  • Oil, gas, and chemical assemblies
For more information on ANSI Class Flanges, or to learn more about custom flanges for particular specifications, contact the Coastal Flange team today.