Elbows & Offsets ยท Elbows & Offsets
Rectangular compound offset
Horizontal and vertical shift
ConnectionFlanged joint
SupportDedicated engineered support
Before you start
- Confirm the shop-detailed compound fitting matches the horizontal and vertical shifts shown in the field.
- Mark top, inlet, outlet, rotation, and both target centerlines before lifting.
- Verify the fitting has a clear load path and enough room for the full rotated body.
- Do not treat a compound offset like a fitting that can be spun until it almost reaches.
Tools and materials
Shop-detailed compound offset, approved flanged joint components, gasket, fasteners, sealant, laser, level, tape, marker, controlled lifting equipment, clamps, and dedicated fitting support.
Lay it out
- Establish both target coordinates in plan and elevation.
- Transfer the required fitting rotation to the floor.
- Mark the balance point and support location.
Set and support it
- Install the dedicated support before closing both joints.
- Rig the fitting so its rotation can be controlled.
- Support both adjoining runs independently.
Make the connection
- 1
Set the fitting at the marked rotation and support point.
- 2
Connect the first end while holding the fitting at the correct coordinates.
- 3
Recheck both horizontal and vertical target centerlines.
- 4
Bring the second run into alignment without twisting the fitting.
- 5
Complete the second flanged joint.
- 6
Seal required seams and joints.
- 7
Load the supports and verify the fitting has not rotated.
Check the install
- Both target planes and centerlines match the field coordinates.
- The fitting is not twisted or forced.
- Seams and flanges are unstressed.
- The support carries the fitting at its balance point.
- Both joints are fully seated and sealed.
Common mistakes
- Rotating the fitting until one end reaches and throwing the other end off.
- Trying to field-correct a shop-detail error with the flange bolts.
- Supporting only one end.
- Installing without marking top and rotation.
Stop and ask
Stop if the field dimensions do not match the fabricated compound fitting, or if the fitting must be twisted, cut, or forced to reach both coordinates.