Grease duct 90-degree elbow
Change of direction
The approved design, adopted code, qualified procedure, and exact manufacturer instructions control this installation.
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 elbow construction, radius or geometry, drainage direction, joint type, access requirement, and fitting support.
- Check whether the elbow can be cleaned from existing access points or requires a dedicated access opening.
- Inspect the throat, heel, seams, and connection ends for damage or internal obstruction.
- Verify the elbow will not create an unapproved grease pocket.
Tools and materials
Approved grease-duct elbow, welded or listed joint components, dedicated fitting support, level or laser, access door when shown, soft lifting equipment, marker, inspection light, and welding or listed-system tools.
Lay it out
- Mark inlet, outlet, top, throat, heel, and drainage direction before lifting.
- Confirm both centerlines and the cleaning-access path.
- Keep enough clearance around the fitting for joint completion, inspection, and enclosure.
Set and support it
- Support the elbow body near its center of gravity.
- Keep both adjoining runs independently supported.
- Hold the fitting against rotation until both joints and supports are complete.
Make the connection
- 1
Set the elbow at the correct orientation and drainage direction.
- 2
Align and complete the inlet joint.
- 3
Recheck the outlet centerline, fitting rotation, and low-point condition.
- 4
Bring the outlet run into alignment without twisting the elbow.
- 5
Complete the second liquid-tight joint.
- 6
Install the required access door or cleaning opening.
- 7
Load the supports and verify the fitting does not roll or create a pocket.
Check the install
- The elbow drains as intended and creates no inaccessible low pocket.
- Both joints are liquid-tight and inspected.
- The throat and heel are undamaged and unobstructed.
- Cleaning access is usable.
- The elbow body is independently supported.
Common mistakes
- Rolling the elbow to make the downstream run reach.
- Supporting the fitting only from one adjoining section.
- Creating a low pocket at the heel with no approved access.
- Closing enclosure before the complete joint and access arrangement are inspected.
Stop and ask
Stop if the elbow creates an inaccessible grease pocket, cannot maintain the approved drainage path, lacks required cleaning access, or violates the listed or welded system design.