Welded grease duct is bowing or binding when it heats up
Hot welded duct can move. If supports are locking it rigid with no movement path, stop and get an approved support/expansion detail before hangers, welds, or structure get damaged.
Do not just tighten hangers harder on a hot grease duct that is trying to move.
Check
Confirm where the duct is bowing, binding, rubbing, or cracking hangers/supports.
Check if the run has rigid clamps at multiple points with no movement path.
Look at hangers, shaft penetrations, wrap, cleanouts, and nearby combustibles/structure.
Verify the support/expansion detail in the approved drawings and submittals.
Stop startup/cover if movement is damaging supports or rated/fire-wrap conditions.
Steps
Confirm where the duct is bowing, binding, rubbing, or cracking hangers/supports.
Check if the run has rigid clamps at multiple points with no movement path.
Look at hangers, shaft penetrations, wrap, cleanouts, and nearby combustibles/structure.
Verify the support/expansion detail in the approved drawings and submittals.
Stop startup/cover if movement is damaging supports or rated/fire-wrap conditions.
Say this to your foreman
The welded grease duct is bowing/binding at [location] when hot. I checked supports and movement path. Do you want sliding supports, expansion detail, or engineer/detailer direction before we lock this run in?