Large stainless equipment for treatment plants: troughs, weirs, clarifier components, and dosing skids, welded and rolled to hold tolerance across long spans and pickled and passivated in-house to hold their corrosion resistance. 304L, 316L, and duplex 2205, built in a dedicated stainless-only production space in Oak Harbor, Ohio.
Northern Manufacturing fabricates custom stainless steel equipment for municipal water treatment plants, industrial wastewater facilities, and OEMs building treatment systems. Common materials: 304L for potable water service, 316L for chlorinated or mildly corrosive environments, and duplex 2205 for high-chloride or seismically loaded applications. All work runs through our 40,000 sq ft stainless-only production space in Oak Harbor, Ohio, where dedicated tooling prevents carbon contamination on corrosion-critical assemblies.
60+ AWS-certified welders. ISO 9001:2015 certified (AVU Registrations). ASME BPVC Section IX qualified welding procedures for austenitic (P8) and duplex (P10H) stainless. In-house pickling and passivation per ASTM A380/A967 in a 55-foot spray booth. CWI on staff.
Equipment We Build for Water and Wastewater
Troughs & Weirs
Long-span stainless troughs for clarifiers and settling basins. Northern's longest single trough: 100 feet of 304L, held straight within 1/8 inch end-to-end.
Chemical Dosing Skids
Skid-mounted stainless systems with piping, valving, metering pumps, and containment, fabricated as a unit and tested before shipment.
Clarifier & Thickener Components
Rake arms, baffles, weir plates, and overflow structures in 304L or 316L.
Filter Housings & Membrane Frames
Structural stainless fabrications supporting filtration modules, built to tight dimensional tolerances for field alignment.
Storage Tanks & Mixing Vessels
Atmospheric and low-pressure tanks in 304L, 316L, or duplex 2205 depending on the chemical environment and chloride exposure.
Pipe Spools & Process Piping
Prefabricated pipe spools with full weld documentation and fit-up verification before shipment.
Stainless Grades for Water Service
Most projects arrive with the grade already specified, and we build to it; when the spec is open we will point you to a starting grade for the service, but the value we add is in the fabrication. Grade choice tracks chloride content, temperature, and whether the equipment contacts potable water or process wastewater. Duplex 2205 delivers roughly twice the yield strength of 304L at comparable corrosion resistance, which allows thinner wall sections on large tanks and reduces both material cost and installation weight. The trade-off is fabrication discipline: duplex requires controlled heat input and interpass temperatures to maintain the 50/50 austenite-ferrite balance.
| Grade | Chloride range | Typical application | Strength vs. 304L |
|---|---|---|---|
| 304L | Low chloride (under 200 ppm) | Potable water contact, structural supports | Baseline |
| 316L | Moderate chloride (200 to 1,000 ppm) | Chlorinated process water, chemical dosing | Similar |
| Duplex 2205 | High chloride (above 1,000 ppm) | Seawater-cooled systems, brine contact, seismic loading | ~2x yield strength |
Welding for Corrosion-Critical Service
Every weld on a water-contact surface is a potential corrosion initiation site. Northern controls weld quality through ASME BPVC Section IX qualified procedures for both austenitic (P8) and duplex (P10H) stainless.
For austenitic grades, we control heat input to prevent sensitization in the heat-affected zone. For duplex, we maintain interpass temperature and use ER2209 matching filler to preserve the ferritic-austenitic microstructure. Ferrite content is measured on production weldments, not just test coupons.
Surface Restoration and Passivation
Post-weld pickling removes heat tint, embedded iron, and surface contamination that would otherwise initiate corrosion in service. Our 55-foot spray booth handles entire assemblies in one pass per ASTM A380 and ASTM A967. No sectioning, no re-welding after treatment. For equipment entering potable water service, free-iron verification per ASTM A380 confirms the absence of surface contamination before the assembly ships.
