Northern Manufacturing fabricates industrial stainless steel ductwork, scrubber components, exhaust stacks, and SCR reactor housings for power generation, chemical processing, pulp and paper, mining, and wastewater treatment plants. Material selection runs from 304L and 316L through duplex 2205, AL-6XN, and Hastelloy C-276 for the gas streams that destroy standard grades. Welding procedures are qualified per ASME BPVC Section IX across austenitic, duplex, and nickel-alloy material groups, including dissimilar-metal transitions between them.
The work runs through a 160,000 sq ft indoor facility in Oak Harbor, Ohio, with 60+ AWS-certified welders across 78 welding stations. ISO 9001:2015 certified (AVU Registrations). A Certified Welding Inspector oversees the welding program, and assemblies finish with pickling and passivation per ASTM A380/A967 in our 55-foot spray booth.
Why Industrial Duct Fails
Air handling and pollution control systems concentrate everything that attacks metal. Process gases condense into acids that thin plate and drive localized pitting. Chlorides combine with heat and residual stress to crack standard austenitic grades. Abrasive particulate erodes elbows and transitions from the inside. And a leak is not a maintenance item: escaped process gas wastes energy, exposes employees, and puts the plant’s EPA and OSHA standing at risk.
Every one of those failure modes traces back to two decisions made before fabrication starts: the alloy and the weld procedure. Those are the two decisions we spend the most time on with your engineers.
What We Build for Air Handling and Pollution Control
- FGD absorber ductwork and components. Fabrications for flue gas desulfurization systems, where condensing acid chemistry sets the alloy choice.
- SCR reactor housings and ammonia injection grids. Structures that house and feed the catalyst systems converting NOx into nitrogen and water.
- Large-diameter ductwork. High-volume duct runs, transitions, and elbows, with section breaks engineered around transport limits.
- Cyclone collectors and baghouse housings. Custom housings for dust capture and filtration systems.
- Fan housings for hot service. Housings built to shield industrial fans from process heat and corrosive carryover.
- Abrasion-resistant duct. Hardened carbon steel duct for particulate-heavy airstreams in mining and bulk material transport, fabricated separately from our stainless-only space.
Matching the Alloy to the Gas Stream
The cheapest duct is the one you only buy once. We help your engineers match the grade to the conditions at each point in the system instead of defaulting to one alloy everywhere.
| Service condition | Grade | Why |
|---|---|---|
| Dry particulate, ambient to warm air | 304L | The baseline workhorse where chemistry is mild |
| Condensing acids, washdown, moderate chlorides | 316L | Molybdenum addition resists pitting that takes out 304L |
| Chloride stress-corrosion-cracking risk | Duplex 2205 | SCC resistance plus roughly twice the yield strength of 316L |
| Warm, high-chloride scrubber zones | AL-6XN | Super-austenitic grade for chloride service where 316L pits |
| Aggressive mixed-acid or reducing-acid chemistry | Hastelloy C-276 / C-22 | Nickel alloys for the zones that consume everything else |
304L and 316L plate is stocked from 20 gauge through 1 inch with 2-day availability from our distributor network; heavy plate through 2 inches is available within 5 days. Duplex and the specialty grades are sourced per project.
Welding for Corrosive Service
A duct system is only as corrosion-resistant as its weld zones. Our procedures are qualified per ASME BPVC Section IX for austenitic stainless (P8), duplex 2205 (P10H), and nickel alloys including Hastelloy C-276 and C-22 (P43) and AL-6XN (P45), plus the dissimilar-metal combinations between them, so a 316L duct run can transition into an AL-6XN scrubber section under a qualified procedure instead of an improvised one.
Heat input is controlled to the WPS, filler is over-matched to the parent material (ER2209 on duplex 2205, for example), and ferrite measurement is available on duplex work. Weld integrity is verified per your drawing: visual, dye penetrant, radiographic, and ultrasonic examination run under a Certified Welding Inspector and ASNT SNT-TC-1A Level III oversight. After welding, pickling per ASTM A380 strips heat tint and the chromium-depleted layer beneath it, and passivation per ASTM A967 restores the passive layer across the full assembly.
Built at Scale, Proven Before It Ships
Duct packages are big, and the expensive failure mode is discovering misalignment at the site. Our 160,000 sq ft facility has the floor space to fit up complete duct runs, and where field fit-up risk matters we dry-fit mating sections against inspection drawings before release. Section breaks are engineered around real transport constraints, so what leaves the dock is what bolts together at the plant.
Featured Project: Power Plant Exhaust Ductwork
A regional power generation facility needed replacement exhaust ductwork with large-diameter sections that had to mate to existing in-plant flanges during a scheduled outage, with zero tolerance for forced alignment on site. We laser-cut the flat patterns, rolled the sections to diameter, seam-welded them with robotic and manual GTAW, and dry-fit every assembly against its mating section before release. Field crews installed the run without rework.
Quality Documentation
Every ductwork project ships with a turnover package assembled under our ISO 9001:2015 quality system:
- Material Test Reports (MTRs) traced by heat number from mill cert to finished section
- Weld maps with WPS references for every joint, plus welder qualification records
- NDE reports (VT, PT, RT, UT as specified on your drawing)
- Dimensional inspection reports to your drawing tolerances
- Pickling and passivation certification per ASTM A380/A967
- Certificate of Conformance (CoC) to your purchase order requirements