Specifications

Types of stainless fittings

• Elbows – 45°, 90° and 180° in long and short radius.
• Tees – equal and reducing, and crosses.
• Reducers – concentric and eccentric.
• Caps for closing line ends.
• Stub ends – long and short pattern, for lap joint flanges.
• Forged fittings – socket weld and threaded elbows, tees, couplings, unions, plugs, bushings and swage nipples.
• Olets – weldolets, sockolets and threadolets for branch connections.

The most requested grade has its own page: SS 316 pipe fittings.

ASTM A403 classes

ASTM A403 grades carry a class that shows how the fitting was made and examined. Class S fittings are made from seamless product; class W fittings are welded, with radiography of welds made by the fitting maker; class WX fittings have all welds, including those in the starting pipe, radiographed; and class WU fittings have their welds ultrasonically examined. The class appears after the grade, for example "WP316L-S" or "WP304-W", and should be stated in the purchase order, because many piping specifications call for seamless fittings in small sizes and permit welded fittings in larger sizes.

Material properties

Butt-weld fittings are formed from pipe or plate of the corresponding grade and then solution annealed, so their chemical and mechanical requirements follow those of the starting material. Forged fittings to ASTM A182 have the requirements shown below; the mill test certificate gives the actual values for each heat.

Low-carbon grades F304L and F316L have a lower carbon limit; nitrogen and other elements as given in the standard.

Values for solution-annealed forgings.

For grade descriptions, see the stainless steel material page.

Manufacturing, testing and marking

Elbows are hot or cold formed on a mandrel from pipe, tees are formed by hydraulic bulging or extrusion, and reducers by pressing; all are solution annealed, pickled and machined at the ends to ASME B16.25 bevels. Forged fittings are hot forged from bar and machined. Each fitting is dimensionally checked and marked with the manufacturer's identification, grade and class, size, schedule or pressure class and heat number. Supplementary tests – intergranular corrosion testing to ASTM A262 Practice E, liquid penetrant examination, radiography of welds – can be added to the order, and fittings can be supplied to NACE MR0175 / ISO 15156 on request.

Ordering stainless fittings

Please state the fitting type, the dimensional standard, the size (with branch or reducing size), the schedule matching the pipe, the material grade and class (for example WP316L-S), the quantity and any supplementary tests. For forged fittings, give the class and the end type. If you also need pipe and flanges, sending the full line list lets us match heats and certificates across the package.

For hygienic service, fittings can be supplied with polished bores; for very low-pressure duties, MSS SP-43 light-weight fittings reduce weight and cost.

Applications and related products

Stainless steel pipe fittings are used in chemical and petrochemical plants, refineries, fertiliser and pharmaceutical units, food, dairy and beverage processing, water treatment, desalination and marine systems. They are installed with stainless steel seamless pipes, welded pipes and tubes, stainless steel flanges and fasteners. For fabricated supports and equipment we also supply stainless plates, sheets, coils, round bars, wires, circles, rings, angles, channels and flats. All fitting materials are on the pipe fittings page.