ASTM A403 WP316 Stainless Steel Fittings – WP316-S / W / WX Buttweld Fittings
ASC LLP, Mumbai, supplies ASTM A403 WP316 stainless steel fittings: seamless and welded buttweld elbows, tees, reducers, caps and stub ends to ASME B16.9, from ½” to 48″. In addition, every fitting comes with an EN 10204 3.1 certificate. See also our full range of stainless steel fittings.
What are ASTM A403 WP316 Fittings?
ASTM A403 (ASME SA403) is the specification for wrought austenitic stainless steel piping fittings used in pressure piping. The prefix WP means a wrought pipe fitting made to ASME B16.9 or B16.11 dimensions, while 316 is the 17Cr-12Ni-2.5Mo grade (UNS S31600). As a result, WP316 fittings match ASTM A312 TP316 pipe.
The molybdenum gives better pitting resistance than WP304, especially in chloride-bearing water and chemicals. For welded systems in corrosive service, however, the low-carbon WP316L is often preferred, so many fittings are dual certified WP316/316L.
A403 WP316 Fittings – Quick Facts
- Specification: ASTM A403 / ASME SA403, Grade WP316 (UNS S31600)
- Classes: WP316-S, -W, -WX and -WU; in addition, CR for light-wall fittings
- Dimensions: ASME B16.9, B16.28 and MSS SP-43
- Sizes: ½” to 48″ NB, from SCH 5S to XXS
- Strength: 515 MPa tensile, while yield is 205 MPa min
- Matching pipe: ASTM A312 TP316
Types of A403 WP316 Buttweld Fittings
- Elbows: 45°, 90° and 180° in long radius (1.5D) and short radius (1D), as well as 3D and 5D bends.
- Tees: equal and reducing tees, in addition to crosses.
- Reducers: concentric and, for pump suctions, eccentric reducers.
- Caps and stub ends: similarly, end caps and MSS SP-43 / ASME B16.9 stub ends for lap-joint flanges.
ASTM A403 WP316 Classes – S, W, WX, WU and CR
| Class | Construction | Weld examination |
| WP316-S | Seamless | None, because there is no weld |
| WP316-W | Welded | Radiography of welds made by the fitting maker; however, pipe-maker welds need not be radiographed |
| WP316-WX | Welded | All welds radiographed |
| WP316-WU | Welded | All welds ultrasonically examined instead |
| CR | Light wall to MSS SP-43 | Examination to the lighter CR requirements |
The class should always be stated on the order. For example, critical lines often specify WP316-S or WP316-WX, whereas utility lines may accept WP316-W.
A403 WP316 Fitting Sizes & Schedules
| Size range (NPS) | Typical schedules |
| ½” – 2″ | 5S, 10S, 40S, 80S, 160, XXS |
| 2½” – 12″ | 5S, 10S, 40S, 80S, 120, 160, XXS |
| 14″ – 24″ | 5S, 10S, 20, 40S, 80S |
| 26″ – 48″ | welded, to required wall thickness |
Buttweld fitting dimensions follow ASME B16.9; meanwhile, short-radius elbows follow B16.28 and light-wall fittings follow MSS SP-43. Wall thickness matches the connecting pipe schedule.
A403 WP316 Mechanical Properties
| Property | A403 WP316 |
| Tensile strength, min | 515 MPa (75 ksi) |
| Yield strength (0.2%), min | 205 MPa (30 ksi) |
| Elongation, min | 28% (longitudinal) |
| Hardness | Not specified in A403 |
A403 sets no hardness limit for WP316; therefore, any hardness requirement must be added by the purchaser. Tensile results are taken from the starting material or from the fitting, as the specification allows.
A403 WP316 Fittings Specifications
| Item | Details |
| Specification | ASTM A403 / ASME SA403, Grade WP316 |
| Starting material | Seamless or welded pipe, or alternatively plate or forgings in 316 |
| Heat treatment | Solution annealed at 1040 °C (1900 °F) min, then rapidly cooled |
| Dimensions | ASME B16.9, B16.28; alternatively, MSS SP-43 for light wall |
| Ends | Bevelled to ASME B16.25, or plain for socket systems |
| Certificate | EN 10204 3.1; in addition, 3.2 and third-party inspection on request |
ASTM A403 WP316 Chemical Composition
| Element | WP316 (%) |
| Carbon (C) | 0.08 max |
| Manganese (Mn) | likewise 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulphur (S) | also 0.030 max |
| Silicon (Si) | 1.00 max |
| Chromium (Cr) | 16.0 – 18.0 |
| Nickel (Ni) | 10.0 – 14.0 |
| Molybdenum (Mo) | 2.00 – 3.00, which improves pitting resistance |
| Iron (Fe) | Balance |
WP316 vs WP316L vs WP316H vs WP304
| Grade | Carbon (%) | Main feature | Typical choice |
| WP304 | 0.08 max | No molybdenum | General service, at lower cost |
| WP316 | 0.08 max | 2–3% Mo | Chlorides and chemicals |
| WP316L | 0.030 max | Low carbon, so welds resist sensitisation | Welded systems in corrosive service |
| WP316H | 0.04 – 0.10 | Higher carbon for creep | Hot service above about 500 °C |
For stabilised grades, see A403 WP321 and WP347 fittings, as well as the A403 WP fittings overview.
Applications of ASTM A403 WP316 Fittings
| Industry | Typical WP316 fitting use |
| Chemical processing | Process piping for acids and chlorides, while temperatures stay moderate |
| Pharmaceutical & food | Clean process lines, often with polished or electropolished bores |
| Oil & gas | Utility and chemical-injection piping, as well as instrument lines |
| Water treatment | Desalination pre-treatment and, similarly, brackish water lines |
| Pulp & paper | Bleach and chemical lines, for example in washing stages |
WP316 resists chlorides better than 304. However, warm seawater can still cause pitting, so super duplex or 6Mo fittings are used there. Matching items include 316 pipe, 316L pipe and 316 flanges.
Why Buy A403 WP316 Fittings from ASC LLP?
- Traceable material: EN 10204 3.1 certificates with heat number, class and test results.
- Correct class advice: help choosing S, W, WX or WU, because the piping code decides the class.
- Complete packages: fittings together with pipe and flanges in the same grade.
- Export packing: finally, fittings are end-capped and packed in wooden cases.
For the general grade page, see our stainless steel 316 fittings.
Frequently Asked Questions – ASTM A403 WP316 Fittings
What is ASTM A403 WP316?
In short, it is a wrought 316 stainless steel buttweld fitting made to ASTM A403, usually to ASME B16.9 dimensions.
What does WP316-S, W or WX mean?
S is seamless and W is welded with the fitting maker’s welds radiographed. WX, by contrast, means all welds are radiographed, while WU means all welds are ultrasonically examined.
What are the mechanical properties of A403 WP316?
It needs 515 MPa (75 ksi) tensile and 205 MPa (30 ksi) yield minimum, with 28% elongation. However, A403 sets no hardness limit.
What pipe is used with WP316 fittings?
Normally ASTM A312 TP316 or TP316L pipe, together with A182 F316 flanges.
What is the difference between WP316 and WP316L?
WP316L has 0.030% max carbon, so welds resist sensitisation. As a result, dual-certified WP316/316L fittings are common.
Are A403 WP316 fittings suitable for seawater?
They are better than 304, but warm seawater can still cause pitting. Therefore, super duplex or 6Mo fittings are usually chosen.
What dimensions do A403 WP316 fittings follow?
ASME B16.9 for most buttweld fittings, B16.28 for short-radius elbows and MSS SP-43 for light-wall fittings.
Global Supply
ASC LLP supplies ASTM A403 WP316 stainless steel fittings from Mumbai to customers in India, the Middle East, Europe, Africa, the Americas and South-East Asia. To get a prompt quotation, simply send your enquiry with fitting type, size, schedule, class and quantity.
Countries We Export To
UNITED STATES, EUROPE, UK, UAE, SAUDI ARABIA, OMAN, KUWAIT, JORDAN, QATAR, INDONESIA, MALAYSIA, BRAZIL, SPAIN, ITALY, FRANCE, GERMANY, BAHRAIN, SRI LANKA, AZERBAIJAN, AUSTRALIA, AUSTRIA, PHILIPPINES, TURKEY, RUSSIA, IRAN, IRAQ, CANADA, KOREA, JAPAN, YEMEN, FINLAND, ZIMBABWE, HUNGARY, PORTUGAL, VIETNAM, MOROCCO, THAILAND, SOUTH AFRICA, MEXICO, SINGAPORE, GREECE, KUWAIT, POLAND, NEW ZEALAND, SWEDEN, SWITZERLAND, BELGIUM, BHUTAN, BANGLADESH, TAIWAN, ROMANIA, CAMBODIA, KAZAKHSTAN, AFGHANISTAN.
