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ANSI Class Flange Types

1. 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.

2. 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.

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.

ANSI B16.5 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.

Forging-Stainless-Steel-Flange production line image
4. ANSI Class Flange Types

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

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

5. Industries and Applications

The strength and durability represented by ANSI standards for flanges is valued in 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

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