Stainless rectangular exhaust
Laboratory/process exhaust
Before you start
- Confirm stainless grade, duct gauge, reinforcement, pressure and service requirements, companion angle or welded flange detail, compatible gasket, fasteners, and sealant.
- Inspect rectangular sections for bowed panels, bent flanges, damaged reinforcement, contamination, and mismatched hardware.
- Keep sections on padded dunnage and use clean gloves and dedicated tools.
- Verify laboratory or process-exhaust requirements before making any field substitution.
Tools and materials
Stainless rectangular duct, stainless companion angles or welded flanges, compatible gasket and sealant, stainless fasteners, padded supports, clean clamps, drift pins where appropriate, dedicated stainless tools, level, and isolated trapeze hardware.
Lay it out
- Establish centerline, elevation, flange access, reinforcement orientation, and support locations.
- Keep joints clear of supports, walls, and equipment so all sides can be bolted, welded, sealed, and inspected.
- Mark airflow and service-sensitive sections before lifting.
Set and support it
- Use stainless or properly isolated trapezes sized for the rectangular section.
- Support both pieces level and square before bringing the flanges together.
- Do not use bolts or clamps to pull a racked or wrong-size section into shape.
Make the connection
- 1
Clean and inspect the flange faces and gasket surfaces.
- 2
Apply the approved gasket to the required flange face.
- 3
Bring the sections together level and square.
- 4
Align holes and install compatible stainless hardware loosely.
- 5
Tighten in an alternating pattern so the flange remains flat.
- 6
Complete approved seam sealing or welded areas.
- 7
Verify reinforcement and supports remain correctly installed.
Check the install
- Flanges remain flat and square with even gasket compression.
- All bolts and washers are compatible stainless or specifically approved.
- No galvanic contact or iron contamination is present.
- Panels and reinforcement remain straight.
- Seams and joints are sealed for the process service.
Common mistakes
- Using plated or carbon-steel hardware on stainless.
- Overtightening one corner and bowing the flange.
- Using clamps to force a twisted section into alignment.
- Applying ordinary duct sealant without checking process compatibility.
Stop and ask
Stop for mixed-metal fasteners, unknown gasket or sealant chemistry, damaged reinforcement, wrong stainless grade, or a field condition that requires forcing the flanges together.