subject: Industrial Vibrators for Powder & Bulk Solids [print this page] Material flow problems in bins, hoppers, and silos are common. These problems are caused by a high level of friction between the material and the bin wall, and high cohesive strength within the material. Wall friction is dependent upon the wall angle, wall material, smoothness, temperature, moisture, corrosion, abrasive wear, and the time the material remains at rest in the cone where the problem exists. Cohesiveness is affected by material properties, including moisture content.
Flow problems can occur, such as bridging or rat holing. Solving these problems is essential for efficient production and accurate material inventory management. In many cases Industrial Vibrators are employed to break the friction between wall and material, as well as material cohesiveness, to promote material flow from the bin.
There are two basic types of industrial vibrators: rotary and linear. Rotary vibrators are characterized by an unbalanced mass rotating around a centre point. The result is a centrifugal force output at a given frequency. Rotary vibrators include ball, ring, turbine, and motor-driven eccentric types.
An unbalanced mass is useful for calculating the centrifugal force output, and it is used for sizing a vibrator for use on a bin. It is even used for sizing applications, such as vibratory screens and feeders, with a known feed rate.
Rotary vibration is best applied to drier products that tend to bridge and rat hole. The objective with rotary vibration is to make the bin wall as rigid as possible and transmit vibration directly into the material. A rigid mount will help keep the frequency and force output higher, thereby making the vibrator more efficient.
Linear vibration is obtained by oscillating a mass back and forth on one axis, which results in force output (impact) as the piston decelerates and changes direction at the end of each stroke. Three types of linear vibration exist: continuous impacting, continuous non-impacting, and single impacting. Continuous impacting are those, which oscillate continuously and provide an impact similar to a blow from a hammer at the end of each stroke. Continuous non-impacting vibrators have the same continuous operation, but there is no impact.
Linear vibration is best for promoting flow of moist or wetter materials. The objective is to move the wall back-and-forth ("oil canning"). This movement is beneficial for dislodging wet, sticky materials from the bin wall.
