Bin Activators
A bin activator consists of an inverted cone or baffle suspended across the outlet hopper with supports. There is an annular space between the inverted cone and the outlet hopper through which the material from the bin/silo can flow towards the outlet hopper. The entire assembly oscillates in a horizontal elliptical plane at frequencies ranging from 10 to 50 Hz (typically 30 Hz) and amplitudes ranging from 1/16 to ½ inch. Single or dual exciters can be used to impart vibrations. The inverted cone serves three purposes:
- Imparts force into the bulk to break potential arches.
- Reduces stresses in the outlet region by shielding flow over the outlet.
- Provides a slot-like outlet and pseudo-plane flow, offering a favorable flow shape.
Some vendors provide additional baffles or venting in the outlet hopper to assist flow and prevent compaction. The intensity of vibration can be changed by moving the eccentric weights on the drive motors. Desirable discharge rates can be achieved by suitable combination of width of annular space, outlet size, vibration frequency/amplitude and on-off cycles. There is lack of consensus amongst various vendors regarding on-off cycling of bin activators. On one hand, vibrating product for extended periods with the outlet closed can result in compaction and arching problem so is best avoided, but constant cycling of the unit can result in mechanical failures.
The resonant frequency of isolated assembly is usually lower than the operating frequency. Therefore, the unit will often pass through a resonant “shudder” when the motor is stopped and the machine is running down. For frequent cycling operations, a motor breaking control system is recommended. This will minimize resonant vibrations that can damage mechanical components and weigh cells (if installed).
Common Applications
Bin activators have been successfully adapted and applied to various industries:
Chemical Industry
Explosion proof motors, self cleaning design, corrosion resistant design
Agricultural Products
Steeper cones for deeper penetration into the bulk material for light and springy product
Diary/Food Industry
Smooth stainless material of construction, sealed cones, FDA compliant materials for flexible boot
Coal/Foundry Industry
Abrasion resistant design and high temperature components
Advantages
- Reduces effective outlet size as compared to gravity flow design. Makes it easier to interface with a feeder.
- Helps to restart material flow after long duration (time consolidation) or discharge caked material
- Reduces overall headroom requirement by using shallower cone