Nickel Alloy Fittings

Nickel alloy fittings cover the range of elbows, tees, reducers,
caps, stub ends and forged fittings produced to ASME B16.9 (butt weld),
ASME B16.11 (socket weld and threaded) and MSS SP-43, in grades from
commercially pure Nickel 200/201 through Inconel 600/625/718, Monel 400 and
K-500, Hastelloy C-276 and C-22, Incoloy 800 and 825, and the specialist
low-carbon nickel-molybdenum alloys. This page is the technical entry point
for the fitting side of our supply. The pipe and tube range is covered
separately in our
nickel alloy pipe and tube
category.

For the fitting forms by type rather than by grade, see
nickel alloy butt weld
fittings, our forged
socket weld fittings and our
forged threaded
fittings. Flanges that pair with this range are in
nickel alloy flanges.

Which specification governs a nickel alloy fitting

The fitting form and the governing document are chosen together, and the
material specification decides which fitting class applies. Four documents do
most of the work:

Fitting classes: what S, W, WX and WU mean

ASME SA-403 assigns a class to every wrought austenitic stainless fitting
grade, and the class states both the construction and the nondestructive
examination. The same four designations are used across the stainless and
nickel alloy fitting families.

Ordering by class matters because it fixes what the mill is obliged to
demonstrate before shipment. A Class S fitting is supplied on the basis of
its material and dimensions alone; a Class WX fitting carries a radiographic
record. The CR grades of SA-403, which follow the MSS dimensional and rating
standards rather than the ASME ones, have no class designation at all.

Grades and the material specification behind each one

The trade name on a drawing does not identify the material. What
identifies the material is the grade designation in the specification, and
that designation also fixes the fitting class that may be ordered. The table
below lists the grades carried in our stock programme against the
specification that governs them.

Sizes, schedules and the dimensional standard behind them

Fitting dimensions are governed independently of the material. The
centre-to-end dimensions of a butt weld elbow are fixed by the nominal size
in ASME B16.9 and do not change with the schedule; only the wall thickness,
and therefore the weight, follows the schedule. Fittings are normally
matched to the pipe they are welded to, so the pipe dimensional standard and
the fitting dimensional standard are chosen together.

Every pipe dimensional figure we publish is taken from the ASME Section II
reprints of ANSI B36.19 rather than from a trade table: the seamless
reprint is ASME SB-829, the welded reprint is ASME SB-775, and the
stainless and duplex pipe reprint is ASME SA-790 Appendix X1.1. The three
reprints agree row for row across all 25 sizes.

What to write on the purchase order

A fitting order that cannot be manufactured is a scheduling problem
before it is a commercial one. The following fields are the ones that
actually determine whether the mill can quote and what the buyer receives.

• Product form and size – elbow, tee, reducer, cap, stub end, and the
  nominal size, with the wall thickness schedule stated separately.
• Governing dimensional standard – ASME B16.9, ASME B16.11 or
  MSS SP-43, named explicitly.
• Material specification and grade – the grade designation from the
  specification, not the trade name.
• Construction class – seamless, or welded with the NDE stated:
  Class S, W, WX or WU.
• Heat treatment condition – annealed or solution annealed where the
  specification distinguishes them.
• Testing and inspection – hydrostatic test, and whether radiography
  or ultrasonic examination is required beyond what the class already
  obliges.
• Documentation – EN 10204 3.1 mill test certificates, and whether
  third-party witness inspection is required.
• Marking – the specific marking standard required on the fitting
  itself.

Applications and grade selection

The grade is decided by the corrosion mechanism, not by the temperature
alone. Monel 400 is the classical choice for seawater and hydrofluoric acid
service. Hastelloy C-276 and C-22 cover mixed and strongly oxidising acid
media. Inconel 625 combines chloride resistance with high strength and is
used both offshore and in chemical plant. For sour service, the selection is
a joint decision between the corrosion allowance and the material
requirements of the applicable service code, and that decision should be
recorded on the order rather than left to the supplier.

Related product ranges

For the full catalogue, see our
nickel
alloy round pipe and tube,
nickel
alloy raised face flanges,
nickel
alloy cold drawn bars and
Incoloy
825 plate, sheet and strip. Product availability, minimum order quantity
and delivery terms are confirmed with a quotation against your own grade,
size and inspection requirement.