TinnerFlowTinnerFlow™
Apprentice Q&A · #357

Why 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

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

Related Field Rescue route

Open routeBack to Q&A

Final direction belongs to the foreman, approved drawings/specs, manufacturer instructions, pressure/material schedule, employer policy, and AHJ/code requirements.