What's the correct way to seal a flex duct connection (zip tie vs. metal band vs. tape/mastic)?

1. Pull back the outer insulation jacket and fiberglass layer to expose the inner plastic core sleeve. 2. Slide the inner core sleeve over the sheet metal collar at least 2 inches. 3. Secure the inner core to the metal collar using a heavy-duty nylon tension tie (zip tie) tightened down with an approved tensioning gun tool, or use a metal hose clamp. 4. Seal the joint with mastic or approved foil tape, then pull the fiberglass insulation blanket back over the connection and secure the outer

['1. Pull back the outer insulation jacket and fiberglass layer to expose the inner plastic core sleeve. 2. Slide the inner core sleeve over the sheet metal collar at least 2 inches. 3. Secure the inner core to the metal collar using a heavy-duty nylon tension tie (zip tie) tightened down with an approved tensioning gun tool, or use a metal hose clamp. 4. Seal the joint with mastic or approved foil tape, then pull the fiberglass insulation blanket back over the connection and secure the outer jacket with a secondary zip tie or tape.']

Stop if

• Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

Steps

• Stop and verify the approved detail, manufacturer instructions, foreman direction, and project specs before touching it.
• Pull back the outer insulation jacket and fiberglass layer to expose the inner plastic core sleeve.
• Slide the inner core sleeve over the sheet metal collar at least 2 inches.
• Secure the inner core to the metal collar using a heavy-duty nylon tension tie (zip tie) tightened down with an approved tensioning gun tool, or use a metal hose clamp.
• Seal the joint with mastic or approved foil tape, then pull the fiberglass insulation blanket back over the connection and secure the outer jacket with a secondary zip tie or tape.

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