Flanges according to ANSI standard

ANSI flanges, also known as American standard flanges or ANSI/ASME flanges, are pipe connectors manufactured to common US dimensional and pressure specifications. In our store you will find these flanges made exclusively from stainless steels — including acid-resistant and heat-resistant grades — suitable for industrial and commercial piping systems.

What are ANSI flanges and where are they used?

An ANSI flange (often called a pipe flange or industrial flange) is a flat or raised ring that joins pipe sections, valves and equipment to create a pressure-tight system. Flanges allow easy assembly, disassembly and maintenance without cutting pipes. They are used across many sectors: offshore and oil & gas, petrochemical plants, water and wastewater treatment, food & beverage and pharmaceutical processing, HVAC and building services, automotive and general fabrication — from small workshop jobs to large industrial installations.

Common flange types and features

• Weld neck – long tapered hub for high-strength welded connections, used where fatigue or high pressure is a concern.
• Slip-on – slides over the pipe and is fillet-welded; easier to align and weld in place.
• Socket weld – pipe is inserted into a socket and fillet-welded; suitable for smaller bore high-pressure systems.
• Threaded – screwed on to a threaded pipe; useful for low-pressure, non-weldable situations.
• Blind – solid plate used to close the end of a piping system or a pressure vessel opening.
• Lap joint – paired with a stub end; used where frequent dismantling is required.

Flange face finishes and sealing options also matter: common face types include Raised Face (RF), Flat Face (FF) and Ring Type Joint (RTJ). These affect gasket choice and sealing performance.

Materials and steel grades

We supply ANSI flanges only in stainless and speciality steels. Typical materials include:

• Stainless steel (austenitic) — e.g. AISI 304 (EN 1.4301) for general corrosion resistance and good formability.
• Acid-resistant stainless — e.g. AISI 316 / 316L (EN 1.4401 / 1.4404) for improved resistance to chlorides and acids; common in chemical, food and marine environments.
• Heat-resistant stainless — e.g. AISI 310 / 310S for elevated-temperature applications such as furnaces or heat exchangers.

(We use commonly accepted US and European designations so you can match material grades to project specifications. If you need a specific EN or ASTM number, our product pages and datasheets list exact material certificates.)

Standards and pressure classes

When people say “ANSI flanges” they generally refer to flanges produced to American dimensional and pressure standards (ANSI/ASME). Typical pressure classes you will see include Class 150, 300, 600, 900, 1500 and 2500 (ASME/ANSI B16.5 for pipe flanges up to 24" is a common reference). Choosing the right class depends on design pressure, temperature and flange size.

How to choose the right ANSI flange

• Match the flange type to the installation needs (weld neck for high pressure, slip-on for simple assemblies, blind to close off lines).
• Pick the correct material for medium compatibility: use 316/316L for corrosive or marine environments, 310 for high-temperature service, and 304 for general non-corrosive use.
• Confirm pressure class and size — flange ratings (150, 300, etc.), nominal pipe size (NPS) and bolt pattern must match mating components.
• Choose an appropriate flange face (RF, FF, RTJ) and gasket type for reliable sealing.
• Check welding and installation requirements — some flanges require full butt welds, others are socket- or fillet-welded or threaded.

Who buys ANSI flanges?

Customers include mechanical and piping engineers, maintenance teams, fabricators, contractors, shipyards and distributors. Our flanges serve one-off workshop projects as well as long-term industrial procurement for sectors such as oil & gas, chemical processing, food production, pharmaceuticals, power generation and building services across the UK and internationally.

Why choose stainless and speciality steel ANSI flanges from us?

• Material traceability — materials and certificates provided so you can verify grade and compliance.
• Wide selection of flange types, pressure classes and face finishes in stainless, acid-resistant and heat-resistant steels.
• Technical support — help selecting the correct flange, material and gasket for your application.

If you are looking for ANSI flanges, industrial flanges, pipe flanges or stainless steel flanges for a specific project, contact us with your nominal pipe size (NPS), pressure class, flange type and required material grade — we’ll recommend the correct American standard flanges for your needs.