Corrosive fume exhaust is where galvanized duct goes to die. Plating shops, pickling lines and laboratory fume systems all eventually standardize on polypropylene duct — it is light, seamless-smooth inside, and immune to the acid mist that eats metal systems from the inside out. Here is a practical guide to specifying it.
Pick Diameters for Velocity, Not Habit
Keep transport velocity around 8–12 m/s for general fume duty: fast enough that condensing droplets are carried along instead of pooling, slow enough to keep fan power and noise reasonable. Our round duct runs DN75 for single bench take-offs up to DN1200 for main headers, so branch-to-header transitions can follow the airflow math rather than whatever pipe is on hand.
Flanged vs. Socket-Welded Joints
Socket or butt welding gives the cleanest permanent runs. Use flanged joints — PP flanges with EPDM gaskets — wherever you will ever want to open the line: at fans, dampers, scrubber inlets and every 10–15 m of straight header. A duct system you can unbolt is a duct system that gets maintained.
Don’t Forget the Accessories
- Butterfly dampers or blast gates on every branch for balancing.
- Condensate drains at low points — fume systems always collect liquid somewhere.
- Flexible connectors at the fan to break vibration paths.
- UV-stabilized or painted duct for rooftop runs — plain PP chalks under years of direct sun.
Why Buy Duct and Fittings from One Factory
Mixed-source systems leak at the interfaces: an elbow a millimeter over size here, a flange drilled to a different pattern there. Because our duct, elbows, tees, reducers and flanges come off the same two production lines to one dimension table, everything actually fits on site — which is cheaper than any unit-price saving from shopping the parts separately.
Send your duct schedule (diameters, lengths, fitting counts) to jinhaofeng298@163.com or WhatsApp +86 186 1558 6932 and we will quote the full system, packed for container shipping.