Most duct is a sheet-metal contractor's job. The large, heavy, welded pieces on a data center air path are not, and buying them from a fabricator with enclosure tolerances is faster and tighter.
Sourcing ductwork & plenums for a data center project? Call 601.892.5017 or email collin.t@fabtekindustries.com — send the drawings and the spec and we quote to print.
- Split the duct scope: standard spiral and light-gauge to the sheet-metal shop, heavy welded pieces to the fabricator.
- Specify pressure class, leakage class and construction standard; gauge alone is not a spec.
- Qualify on panel folding, long-seam welding and fixtured assembly; plenums seal or they cost fan energy forever.
- Buy hangers and supports with the duct.
What you are buying
Air-cooled data centers move very large volumes of air through air-handling galleries, fan walls and plenums, and the metal on that path is closer to enclosure fabrication than to commercial duct: heavy-gauge trunk duct with flanged joints and stiffeners, room-sized welded plenum boxes, fan-wall support frames, transitions from air handlers to the hall, outdoor intake and exhaust hoods, and the welded frames that carry dampers and louvers in the wall. The mechanical engineer specifies the construction standard and pressure class; the fabricator cuts, forms, welds and finishes to it.
Where it sits in the project
Mechanical contractors buy the heavy pieces their sheet-metal shop cannot handle; developers and GCs add them to the mechanical steel package. The pieces are needed when the air handlers set, which is after the structure and before the hall is commissioned, and large plenums often have to go in before walls close.
What to put in the RFQ
| Duct drawings | Shop drawings or design drawings with dimensions, connections and access requirements |
|---|---|
| Construction standard | SMACNA pressure and leakage class, seam and joint type, stiffener requirements |
| Material and gauge | Galvanized, aluminum or stainless; gauge by component; plate for frames |
| Plenums and frames | Panel layout, access doors, fan-wall frame loads, damper and louver frame dimensions |
| Finish | Mill finish, powder coat color for exposed pieces, passivation for stainless |
| Supports | Trapeze hangers, saddles and floor stands, with attachment details |
| Shipping | Knock-down vs. assembled sections, match-marking, size limits for the building opening |
How to qualify a fabricator
- Panel folder and press brakes sized for long skins. Plenum panels are long and heavy; short brakes mean more seams.
- Welded-seam experience. Enclosure and tank welding translates directly to welded duct and plenums.
- Trial assembly. Large sections assembled and match-marked in the shop before knock-down.
- Leakage testing. Where the spec calls for it, the fabricator should be able to test before shipment.
Lead time, sequencing and delivery
Release plenums and fan-wall frames early enough to go in before walls close; release trunk duct and fittings with the air handlers. Ship match-marked sections sized to the building opening, with hangers and supports on the same trucks.
Common mistakes
- Specifying gauge without pressure class. The class drives seams, joints and stiffeners.
- Sending heavy plenums to a light-gauge shop. Expect seams, leaks and a long lead time.
- Forgetting the opening. A plenum that does not fit through the door is field-assembled badly.
- Exposed duct in mill finish. If it is visible, specify the powder coat.
How FabTek supplies it
FabTek fabricates heavy-gauge ductwork and plenums on the panel folders, press brakes and welding cells that build its enclosures, at four plants in Hazlehurst, Mississippi, powder coated in-house where the duct is exposed and shipped with hangers and supports from the same floor.
Frequently asked questions
What duct belongs with a metal fabricator instead of a sheet-metal contractor?
Heavy-gauge welded trunk duct, large plenums, fan-wall frames, hoods, and damper and louver frames: pieces that need panel folding, long-seam welding and enclosure-level tolerances.
What is SMACNA pressure class?
A classification of duct construction by the static pressure it is built to hold, which sets seam type, joint type, gauge and stiffener spacing. The mechanical engineer specifies it.
Can heavy duct be powder coated?
Yes. Exposed duct, plenums and hoods are commonly powder coated to the project color; concealed galvanized duct is usually mill finish.
Who fabricates data center plenums and fan-wall frames?
FabTek Industries fabricates welded plenums, fan-wall support frames and heavy trunk duct at its Mississippi plants for mechanical contractors and developers.
