REFINERY AND PLANT TURNAROUND DUCT FABRICATION
Turnaround duct work is the most schedule-sensitive fabrication there is. The unit is down, every hour of the outage is costing production, and the window was planned months in advance. Fabrication has to be finished and staged before the outage opens, because there is no recovering time once it does. JMC builds welded heavy-gauge industrial duct for that work from Pascagoula, MS.
Industrial duct is also a different product than commercial HVAC duct, and it is worth being precise about the difference.
Published August 5, 2026 · JMC Fabrication
Commercial HVAC duct moves conditioned air at low to medium static pressure, built to SMACNA with mechanically sealed joints. Industrial process duct often moves something else entirely: dust, fume, hot gas, or corrosive exhaust, at higher static and sometimes under negative pressure. The construction follows the process specification rather than SMACNA.
That drives heavier gauge, welded and leak-tight seams rather than slip-and-drive, and material selection based on what is passing through the duct and at what temperature. Carbon steel for many services, stainless where corrosion demands it. Where combustible dust is involved, the design carries requirements that go well beyond airflow.
The result is a product that looks more like pipe work than sheet metal work in how it is fabricated and inspected, which is a reasonable fit for a shop whose other core capability is pipe spool fabrication.
Nearly every construction decision differs:
| Attribute | Commercial HVAC duct | Process and industrial duct |
|---|---|---|
| Governing document | SMACNA | Process specification |
| Material | Galvanized steel | Heavy-gauge carbon or stainless steel |
| Seams | Slip-and-drive, flanged | Welded, leak-tight |
| Pressure | Low to medium static | High static, positive or negative |
| What is moving | Conditioned air | Dust, fume, hot or corrosive gas |
| Inspection | Construction class records | Weld inspection per the specification |
Four scopes that recur on refinery and plant projects:
- Dust collection duct: Welded heavy-gauge duct for material transport and dust collection systems, built to the system design pressure and the requirements the specification carries.
- Fume and process exhaust: Corrosion-resistant exhaust duct where the service demands it, typically stainless, welded for leak tightness.
- High-temperature and high-static ductwork: Heavier construction and reinforcement for service conditions outside the commercial range.
- Ventilation and make-up air: Plant ventilation and make-up air duct tied into facility airflow balancing, often long-run and large-volume.
The defining fact about a turnaround is that the install window is fixed and short, and the cost of missing it is not the cost of the duct. It is the cost of the unit staying down. So the fabrication plan works backward from the window rather than forward from the award.
That means detailing and approval finish early, material is on the floor early, fabrication completes before the outage opens, and the entire package stages until the field can take it. JMC's 50,000 square feet of covered storage across three warehouses is what makes staging a whole package practical rather than shipping it early into a plant laydown yard.
It also means planning for the changes that turnarounds always produce. Once a unit is opened, conditions get discovered, and pieces need modification or replacement on no notice. Being an hour from the Gulf Coast plant corridor rather than several states away is the difference between a same-day fix and a lost shift.
- The outage window dates, which drive the entire schedule backward
- The process specification covering duct construction, material, and pressure
- What the duct is conveying, and at what temperature
- Weld inspection and documentation requirements the specification names
- Material traceability requirements, including mill certificates
- Access and rigging constraints that limit section size
- Whether pipe spools are in scope alongside the duct
Does JMC fabricate industrial and process duct?
Yes. Oil and gas and industrial work is one of JMC's core markets, and the shop builds welded heavy-gauge duct for dust collection, fume and process exhaust, and high-static or high-temperature service in carbon and stainless steel.
How is process duct different from commercial HVAC duct?
It follows the process specification rather than SMACNA, uses heavier gauge and welded leak-tight seams rather than mechanically sealed joints, and is built for higher static pressure and for whatever the system is actually conveying. Material selection follows the service and temperature.
Can JMC fabricate to a turnaround window?
The approach is to work backward from the window, finishing fabrication and staging the package before the outage opens rather than fabricating during it. Whether a given window is achievable depends on lead time from award and current shop loading, so send the outage dates and the scope and JMC's project management will give a real answer.
Can JMC stage a full package until the field is ready?
Yes. The Pascagoula facility has 50,000 square feet of covered storage across three warehouses, which means a completed package can stage at the shop instead of sitting in a plant laydown yard for weeks before the outage.
What happens when conditions change once the unit is open?
That is expected on turnaround work. Proximity is what makes it manageable: JMC is on the Mississippi Gulf Coast, within reach of the Gulf Coast plant corridor including Mobile and New Orleans, so a modification or replacement piece can often be fabricated and back on site same day or next day.
Can JMC supply duct and pipe spools on the same turnaround?
Yes. Pipe spool fabrication is a core capability alongside duct, so both can come from one shop on one schedule rather than from separate vendors that have to be coordinated against the same outage window.