Why does a volume damper leak when it is bolted metal-to-metal into a sleeve?

Metal-to-metal damper frames can leak around the perimeter. Back it off, clean the faces, add the approved gasket/seal detail, re-tighten evenly, and retest.

['A damper frame bolted into a sleeve without gasket or seal can leak around the entire perimeter even if the fasteners are tight.', 'Find the leak path, unbolt only as allowed, clean both faces, install the approved gasket/sealant detail continuously around the frame, tighten evenly, and retest under fan pressure.']

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