Most vibrator manufacturers have specific instructions included in their manual for proper installation. Typically, this involves skip-welding channel up the side of the hopper. The channel should extend most of the sloped vertical run of the hopper. Orientation of the vibrators should be shaft horizontal. Location of the vibrators should be in the lower portions of the bin, roughly 1/3rd up the sloped portion vertical height. Also, setup the controls so that the vibrators ONLY RUN when you are emptying. (No reason to run them unless material flow is needed.)
Use good motor protection, like solid-state overloads, since vibrators suffer excessive load if run under high-amplitude conditions, such as on empty bins or upon flimsy mounting. Excessive amplitude will cause motor O/L events.
Mount plates should be flat, and Grade 8 bolts used. After 1-2 hours operation, double-check the bolt tightness, and periodically check these again.
Ideally, this minimizes the run time of the vibrators, minimizes their amplitude (they are supposed to cause a "liquifying" or "flow-ability" of the material in the hopper, causing the material to vibrate, not the vibrator, per se), while maximizing the flow of material and the lifetime of the bin.
BK