Why do I need to provide restraints on equipment that is hung 12″ or less from the ceiling?
Although from a philosophic viewpoint it would seem that the rules stated in the questions above should apply to equipment, this is not the case. Equipment behaves more erratically than piping or ductwork during a seismic event because it is more local in nature. Large distributed systems like pipe and duct will tend to move laterally or even exhibit relatively minor variations in the vertical loads but will not tend to rock. Localized components like equipment will rock and as such can generate considerably higher tensile loads in the support system. In some cases this may not be an issue, but there are definitely situations where the installation geometry will develop loads that can cause failure(s) in the support system.