Why do trapeze hangers need lock/jam nuts?
1st YearYELLOW · Check FirstMissing Jam Nuts
Short answer
Single nuts can walk under vibration. Use the proper support nut and lock/jam-nut setup at the rod/strut connection per shop standard.
Field answer
You assemble a dual-rod Unistrut trapeze hanger bracket on the ground, threading the lower nuts tightly onto the bottom of the strut rail, but you forget to install the secondary top backing jam-nuts against the channel face.
Single nuts can walk under vibration. Use the proper support nut and lock/jam-nut setup at the rod/strut connection per shop standard. The likely recovery is to check the condition, correct prep/setup if it is within your assignment, and bring the foreman clean information before the work creates rework overhead.
What to check first
- Check each rod end for support nut and lock nut.
- Verify nuts are tightened against each other.
- Confirm the strut is level after tightening.
- Look for rods that can spin loose by hand.
- Recheck after equipment startup if vibration is present.
Do not do this
Do not leave a trapeze supported by loose single nuts.
Why it matters
Jam nuts keep the hanger from slowly backing off and sagging the duct.
Ask foreman
You missed the top jam-nuts on those trapeze rods. Fan vibration will cause those single nuts to slowly back off and sag the duct. Double-nut every connection point to lock those rails solid.
Related Field Rescue route
Final direction belongs to the foreman, approved drawings/specs, manufacturer instructions, pressure/material schedule, employer policy, and AHJ/code requirements.