Specifications

How ASTM B366 works

ASTM B366 is a fittings specification for nickel and nickel alloys. Rather than repeating each alloy's composition, it requires the fitting to be made from starting material that meets the relevant product specification – for alloy 625, for example, B444 pipe or B443 plate – and adds requirements for forming, heat treatment, welding and examination. The fitting is designated with a B366 grade code and the alloy's UNS number, and the mill test certificate refers back to the starting material's heat. The composition of the alloys is therefore the same as for Inconel pipe and plate:

Nickel includes cobalt where stated in the standard. Footnotes as given in each ASTM specification.

Fitting types

• Elbows – 45°, 90° and 180°, long and short radius.
• Tees – equal and reducing.
• Reducers – concentric and eccentric.
• Caps and stub ends for lap joint flanges.
• Forged fittings – socket weld and threaded elbows, tees, couplings, plugs and bushings.
• Olets – weldolets, sockolets and threadolets.

Manufacturing and testing

Seamless fittings are formed from seamless Inconel pipe and larger welded fittings from plate, then heat treated – annealed or solution annealed as the alloy and service require – and machined to ASME B16.25 bevels. Welds in welded fittings are examined as the specification requires. Each fitting is dimensionally checked and marked with the manufacturer's identification, specification and alloy, size, schedule and heat number. Liquid penetrant examination, radiography, positive material identification and third-party inspection can be added to the order, and fittings can be supplied to NACE MR0175 / ISO 15156 on request.

Welding Inconel fittings

Inconel fittings are welded to Inconel pipe with matching or over-alloyed nickel filler metal, low heat input and clean joint preparation – contamination by sulphur, lead, phosphorus or zinc from paints, crayons and cutting fluids can cause hot cracking. Joint bevels for nickel alloys are often more open than for steel because the molten weld metal is less fluid. Post-weld heat treatment is not normally needed for corrosion service in 625. Where Inconel fittings join stainless or carbon steel, a nickel filler suitable for the dissimilar joint is used.

Ordering

Please state the fitting type, standard, size and reducing size, schedule, alloy and UNS number, seamless or welded, quantity and any supplementary tests or inspection.

Choosing seamless or welded Inconel fittings

Small and medium Inconel fittings are normally made from seamless B167 or B444 pipe. Large-diameter elbows, tees and reducers may be formed from B168 or B443 plate and welded, with the welds examined and the fitting heat treated as B366 requires. For high-pressure or cyclic service, specifications often require seamless fittings up to a stated size and full radiography of welds in larger fittings. Please send the project specification with the enquiry so the construction and examination match it.

Applications and related products

Inconel pipe fittings are used in furnace and heat-treatment piping, flare and exhaust systems, chemical and petrochemical plants, offshore and subsea oil and gas, flue gas desulphurisation and power plants. They connect Inconel pipes and tubes with Inconel flanges, bolted with Inconel fasteners. We also supply Inconel sheets and plates, Inconel round bars and Inconel wires. See all fitting materials on the pipe fittings page and alloy guidance on the Inconel page.