Apprentice Q&A · #357Why does a drive cleat pop off a tight 45-degree elbow throat?
2nd YearGREEN · Standard CorrectionDrive Cleat on 45° Throat
Short answer
The inside throat of an angled fitting can be under tension. Align and clamp the flanges before driving the cleat, and trim/detail only as approved.
Field answer
On a tight rectangular 45°, the inside throat joint may not sit as relaxed as a straight duct joint. If the flanges are not compressed and aligned, the drive can buckle or pop off instead of sliding home.
Use clamps or tongs to flatten the joint, check the cleat length, and drive it square. If the cleat or flange needs field trimming, keep it clean and approved so the joint still seals mechanically.
What to check first
- Check whether flanges are aligned and seated.
- Look for the drive bottoming out at corner seams.
- Clamp the throat joint flat before driving.
- Check cleat length and end clearance.
- Seal only after the drive is mechanically seated.
Do not do this
Do not beat a drive cleat until it buckles and leaves the throat joint loose.
Why it matters
A popped drive cleat leaks, rattles, and can open up when the system starts.
Ask foreman
The drive cleat is popping off the inside throat of this 45 elbow. I can clamp the flanges flat and reset the cleat, but it may need a small approved trim. Do you want me to correct it now?
Text this wording
Final direction belongs to the foreman, approved drawings/specs, manufacturer instructions, pressure/material schedule, employer policy, and AHJ/code requirements.