Bag Unloader Type – Paddle Agitators vs Live Fluidization
Questions to consider on choosing a paddle agitator vs. live fluidizer:
Efficiency – some materials, mostly salts and acids (crystalline particles) may not be affected by paddle agitation, especially where the material has been exposed to humidity. They become a solid block of material that the paddles just move back and forth, there simply isn’t enough energy to break the material up to promote flow.
Conversely, the live fluidizer (just like what is used in every silo in the world) is perfectly set up to break the bond between the particles and create mass-flow. The vibrator we use at FormPak is a 1,500# force unit, which is rarely set at more than 50% of maximum (these are adjustable force units).
Effectiveness – due to the design, the paddle machines can only agitate sections on each side of the bulk bag. This leaves tremendous dead zones in the corners of the big bag.
The fluidization pan activates the entire bottom of the bag, and its hopper bottom shape forces all of the material out of the bag and into the downstream process.
Maintenance – because there are so many parts (solenoids, cylinders, hinged plates, etc.) the long term cost of these machines can be very significant.
Fluidizing style machines typically require no spares, and will last decades without any maintenance.
Sanitation – because of the bearings, hinges, clevis joints, pins, etc., the paddle style units are extremely difficult to clean (hinges in particular are nearly impossible to insure against infestation).
The fluidizing pan is 100% sheet steel (typically stainless) and can be completely enclosed and polished, leaving no areas for infestation or material build up.
Safety – this is by far the most important item in consideration in choosing between these styles of machines – regardless of industry, material, or application. One of the more recent developments is that several end users of paddle machines have been asked by OHSA or their insurance carrier to build guarding around the paddle agitator system. This is due the pinch points and crushing potential of these units. If an operator reaches their hand between the bag and an actuated paddle, the results can be devastating; the same is true of the plates where the hinge from the frame causing pinch points for fingers, skin, or clothing.
Fluidization systems have none of these dangers or risks.
Buyers may wish to consult their safety team or a loss-prevention expert before purchasing a system that may require custom guarding once installed.