6.000" x 4.000" 12ga Butt-Weld Concentric Reducer - (31W) - Polished OD/ID - 316L Stainless

316L STAINLESS BUTT-WELD CONCENTRIC REDUCER (31W) FOR MARINE EXHAUST & SANITARY SYSTEMS

PNW Sanitary 316L Butt-Weld Concentric Reducers are built for applications where corrosion resistance matters most. The molybdenum in 316L gives it substantially better resistance to chlorides and saltwater than 304 stainless, making these reducers a natural fit for marine exhaust systems and any fabrication exposed to salt spray, seawater, or condensing exhaust gases. The low-carbon "L" grade limits carbide precipitation in the weld zone, helping each joint hold its corrosion resistance after welding.

MARINE EXHAUST APPLICATIONS

Raw-water cooled exhaust systems create hot, wet, chloride-rich conditions that cause pitting and crevice corrosion in lesser alloys. 316L concentric reducers let you step between exhaust diameters while keeping the entire system in one corrosion-resistant alloy, and the concentric design keeps the flow path centered to minimize turbulence. Typical uses include:

• Stepping exhaust diameter at mixing elbows and risers
• Transitions into mufflers, water lift boxes, and through-hull outlets
• Marine generator exhaust
• Adapting between tube sizes in custom wet and dry exhaust systems

SANITARY APPLICATIONS

These reducers are 3-A Certified and polished to a 32Ra sanitary finish on both ID and OD. They provide hygienic, permanent transitions between tube sizes in CIP systems, product transfer lines, and high-purity process piping for food, beverage, brewing, dairy, and pharmaceutical applications, and are compatible with leading sanitary brands.

FEATURES:

• 316L Stainless Steel (low-carbon, molybdenum-bearing)
• Greater resistance to saltwater and chloride corrosion than 304
• 3-A Certified; polished OD & ID (32Ra)
• Concentric design keeps the flow path centered
• Capped and cleaned for sanitary protection

QUALITY & MATERIAL CHECK: All PNW Sanitary fittings undergo in-house Positive Material Identification (PMI) with a SciAps X-550 handheld XRF spectrometer to confirm alloy chemistry and support traceability.

FABRICATION TIPS: For the best corrosion resistance in marine service, weld with 316L filler and back-purge with argon to protect the inside of the weld. Removing heat tint and passivating finished welds helps restore the protective surface layer.

BUILD A COMPLETE 316L SYSTEM: Pair these reducers with our 316L Stainless Tube, 316L Butt-Weld Elbows, and 316L Butt-Weld Tees.

LOOKING FOR SANITARY FITTINGS? This reducer is also available on our sister site, PNW Sanitary, along with a full line of sanitary fittings, butt-weld reducers, gaskets, and 316L sanitary tube.

CROSS-REFERENCE