What Is ASTM A403 WP316?
WP316 is the molybdenum-bearing austenitic stainless buttwelding fitting grade within ASTM A403. It is the standard choice when 304-type fittings show pitting in chloride, marine or chemical service.
Temperature Range
Rated up to 538°C per the stainless pressure-temperature basis of the ASME B16.9/B16.5 tables.
Material Group (per ASME B16.5)
WP316 fittings pair with Group 2.2 (16Cr-12Ni-2Mo) flanges in ASME B16.5 systems.
Corrosion Resistance
Per the Schweitzer tables (Type 316/316 L row), WP316 resists a wider range of media than WP304 — especially chloride, brine and mildly reducing streams — while still not being suitable for concentrated hydrochloric acid. It is the default upgrade for coastal, wastewater and chemical plant piping.
Typical Applications
- ASME B16.9 stainless fittings for coastal and marine piping
- Chemical, pulp & paper and wastewater process lines
- Heat-exchanger and instrumentation connections
Chemistry & Mechanical Properties
Composition and mechanical properties per ASTM A403 — consult the standard for exact limits. 3.1 mill certificates supplied.
Related Standards
- ASME B16.9 — Buttwelding Fittings (NPS 1/2–48)
- ASME B16.5 — Pipe Flanges
- ASTM A403 WP304 — 18Cr-8Ni Fittings
- ASTM A182 F316 — Stainless Forgings
- Buttwelding Elbows
- Equal Tees
FAQ
Why choose WP316 over WP304?
Molybdenum gives better pitting and crevice corrosion resistance in chloride, brine and marine environments.
What temperature range does WP316 cover?
Up to 538°C per the stainless pressure-temperature tables.
Is WP316 suitable for seawater?
Much better than 304; for full immersion consider duplex (F51-class) fittings — send us your conditions.
WP316 or WP316L?
Use WP316L for welded fabrication without post-weld annealing; it carries the Group 2.3 lower-strength rating.
What does WP316 mean?
WP stands for wrought piping (fittings), grade 316 — the molybdenum-bearing austenitic stainless buttwelding fitting grade in ASTM A403.
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