Modern Solutions for Bulk Material Flow
Linear vibrators activate material inside chutes or bins by delivering heavy blows to the outer steel walls of the structure. Historically, the earliest method of achieving vibration was through hammering. By striking the chute or bin walls, this action disrupts the adhesive force between the material and the wall surface. However, this repetitive hammering often damages the wall surface, leaving marks known as "hammer rash," exacerbating the very issue it aimed to resolve. Moreover, swinging a sledgehammer poses risks of injury to plant personnel. 
To mitigate these drawbacks, the piston vibrator was developed as a non-impact alternative. A pneumatic piston (or linear) vibrator uses plant air to move a piston back and forth inside a casing. Depending on the design, the piston may strike the wall or oscillate with sufficient mass to flex the wall. In either case, the vibrator transfers energy through the wall to the material inside, effectively breaking the adhesion and facilitating material flow.
This method, more controlled than hammer strikes, is particularly effective for handling sticky, coarse, or high-moisture materials. A practical test involves squeezing a handful of material into a ball—if it retains its shape upon release, linear vibration is likely the optimal choice. 
Installation typically involves mounting the piston vibrator on the exterior of the vessel or chute, targeting areas prone to buildup or blockage inside. These vibrators are commonly affixed to a steel channel on the chute wall to distribute force across a larger surface area, thereby enhancing efficiency while safeguarding against structural fatigue. Most linear vibrators are powered by plant air and can be operated remotely via solenoid or locally with a manual on/off valve.
Selecting the appropriate vibrator depends on the weight and properties of the material in the chute or sloped section of bins or hoppers. A general guideline suggests applying 1 newton per 1 kilogram (1lbf / 10 lbm) of material weight inside the chute. This general rule assumes the material is flowable and has a density below 1,440 kilograms per cubic meter (90 lbm/ft³). More force will be needed for materials of high density or moisture or of low density. While the ratio above is acceptable for materials between 640–1440 kilograms per cubic meter (40–90 lbm / ft3), materials with higher or lower bulk densities require different ratios.
The length of the mounting channel and the thickness of the chute wall should be tailored to the specific application's material weight and characteristics. Applications falling outside standard parameters may require specialized engineering considerations. Calculating linear force is essential for correctly applying a vibrator to a chute.
Post-installation, air-powered vibrators require tuning to match application requirements by adjusting air pressure and/or flow rates to maximize their impact on bulk material flow.