TinnerFlow
Grease Duct Systems ยท Grease Exhaust Systems

Grease duct transition at hood

Hood collar transition

Life-safety system.
The approved design, adopted code, qualified procedure, and exact manufacturer instructions control this installation.
ConnectionWelded hood collar or listed adapter
SupportIndependent support not carried by hood

Before you start

  • Grease duct is a fire/life-safety system. Verify the approved design, adopted code, hood and fan requirements, listed enclosure or shaft details, and inspection hold points before fabrication or installation.
  • Confirm the hood model, hood collar, approved duct connection, transition dimensions, hood listing, enclosure or wrap details, and independent support requirement.
  • Verify the transition does not block hood service, fire-suppression components, lights, filters, or access panels.
  • Inspect the hood collar and transition ends before lifting.
  • Do not field-modify the hood or collar unless the approved manufacturer detail permits it.

Tools and materials

Approved hood transition, welding equipment or exact listed adapter system, independent supports, fit-up clamps, level, marker, joint materials, enclosure or fire-wrap components, and finish protection.

Lay it out

  1. Establish the hood collar centerline and transition orientation from the approved hood submittal.
  2. Check the transition route to the main grease duct and verify service clearances around the hood.
  3. Place supports so no transition or main-duct load transfers to the hood shell.

Set and support it

  1. Install independent support for the transition before closing the hood connection.
  2. Protect the hood finish and fire-suppression components during welding or assembly.
  3. Hold the transition square to the collar without pulling or distorting the hood.

Make the connection

  1. 1

    Verify the hood collar and approved connection method.

  2. 2

    Set the supported transition in alignment with the hood collar.

  3. 3

    Clamp and inspect the fit without stressing the hood.

  4. 4

    Complete the continuous welded joint or exact listed adapter connection.

  5. 5

    Connect the transition to the downstream grease duct.

  6. 6

    Complete the required enclosure, wrap, or clearance treatment.

  7. 7

    Inspect the hood, joint, support, and nearby service components.

Check the install

  • The hood shell and collar remain undistorted.
  • The transition carries no weight through the hood.
  • The connection is liquid-tight and uses the approved method.
  • Hood service and fire-suppression components remain accessible.
  • Required enclosure or wrap is continuous.

Common mistakes

  • Using the hood collar as the support for the transition.
  • Pulling a misaligned transition into place and distorting the hood.
  • Field-cutting or welding the hood without manufacturer approval.
  • Blocking filter, suppression, or service access.

Stop and ask

Stop if the hood listing or submittal does not show the proposed connection, the collar is damaged or mislocated, independent support is missing, or field welding would affect hood components or finish.