Do not use hold-down clamps like a vise on thin duct skin.
Check
Look for crushed bottom skin, flange gaps, or corner leaks.
Check whether clamps are bearing on a joint or flange corner.
Add approved cushion/isolation where required.
Tighten evenly without oil-canning the duct.
Retest leak/noise if the joint was distorted.
Steps
Look for crushed bottom skin, flange gaps, or corner leaks.
Check whether clamps are bearing on a joint or flange corner.
Add approved cushion/isolation where required.
Tighten evenly without oil-canning the duct.
Retest leak/noise if the joint was distorted.
Say this to your foreman
The hold-downs at [location] are crushing the duct/flange and opening a leak. Do you want me to back them off, add isolation pads, and reseal/retest the joint?