Vertical Drops

A vertical drop describes pipe that normally extends down from an overhead run of pipe and connects to a piece of equipment, usually through some type of flexible coupling connector. The drop can also extend horizontally. If the pipe drop is less than or equal to one half the transverse restraint spacing, no further restraint is required provided that there is a transverse restraint at the end of the horizontal run.

The restraint installation angle for transverse and longitudinal cable and strut restraints may be between 0° and 60°as measured from the horizontal. Image courtesy of Kinetics Noise Control

Longitudinal restraints may be attached to the pipe with a pipe clamp slightly rotated to miss the hanger rod. Image courtesy of Kinetics Noise Control

Strut type longitudinal restraints may also be attached to the pipe with a pipe clamp, which is rotated to miss the hanger rod. As with the transverse restraints, the installation angle may vary from 30° up to a maximum of 60°.

Hanger rods, which are very long or very small in diameter, may require rod stiffeners to prevent buckling. Image courtesy of Kinetics Noise Control

Hanger rods for isolated pipe at restraint locations must be fitted with uplift limit stops applied to the hanger rod just below the isolation hanger. Typically this consists of a nut and washer, which are adjusted to provide a gap not to exceed ¼-in. between the washer and the bottom of the isolation hanger. When top mounted cushions of neoprene or fiberglass are provided, a gap, not to exceed ⅛-in. is required at the top of the isolation hanger. This treatment is valid for all isolated pipe and duct.

Isolation hangers at seismic restraint locations are fitted with uplift limit stops. Image courtesy of Kinetics Noise Control

Hot Water Pipe Restraint

Hot piping, whether it is steam or domestic hot water, presents certain problems when designing seismic restraints due to the fact that the piping grows in length as it heats up. Only one longitudinal restraint is permitted on a run to avoid problems created by the expansion of the pipe. Runs that are longer than the permitted longitudinal restraint spacing will require an expansion compensator to allow additional longitudinal restraints.

Restraint Attachment

Unless provisions are made for relative movement, the pipe restraints must be attached at approximately the same elevation in the building as the pipe hangers.