Hangers, Bracing, and Seismic Protection
Domain 6: Hangers, Bracing, and Seismic Protection
This domain tests support and restraint: hanger spacing, attachment, sway bracing, flexibility, and seismic separation. The controlling idea is that pipe must stay in place under gravity and earthquake motion without transferring load to sprinklers.
Core rules
- Hanger spacing depends on pipe size. A 1-inch pipe is commonly limited to 12 ft; 1.5-inch to 14 ft; 2-inch to 16 ft; larger sizes increase in steps per NFPA 13.
- Hangers must be attached to structural members or approved supports; they are not interchangeable with sprinkler spacing.
- Seismic bracing uses lateral and longitudinal sway bracing. Lateral bracing is typically spaced at no more than 40 ft; longitudinal bracing at no more than 80 ft, with exceptions.
- Flexible couplings and seismic separation assemblies protect piping where it crosses building joints.
Worked example
A 1.5-inch branch line has a maximum hanger spacing of 14 ft. If sprinklers are spaced at 12 ft, hangers should be placed at 12 ft so each hanger supports at the sprinkler location and the 14 ft limit is not exceeded. The reasoning: the tighter of the two limits governs.
Traps
- Using the hanger spacing table as a sprinkler spacing table.
- Omitting lateral bracing because the pipe is “small.”
- Forgetting seismic separation at building joints.
- Attaching hangers to nonstructural or unapproved elements.