Vibrating Empty Bins

Vibrating empty bins?  Don’t do it.

When you have a bulk solid material that flows unreliably or difficultly you will need to employ a flow aid of some type. Typically you can vibrate or use air. We aren’t going to discuss these two in detail here, just the use of vibration and the proper method to control vibrator type flow aids.  Vibrating empty bins?  Don’t do it.

Bulk solids that have high cohesion or adhesion levels will have difficulty flowing through a bin.  Using steep bin walls can help, but often a flow aid is needed, and many times the type chosen is an industrial vibrator. Vibrators come in a variety of types, sizes and usually either pneumatic or electric driven. Before using industrial vibrators, often a laborer would go to the bin having the flow problem (rathole/bridge) and bang or hammer the bin at the location of the flow problem.  This method, though it can work, can damage the bin, is inaccurate, and labor intensive. An industrial vibrator replicates this manual action of banging on the bin wall on a potentially automatic basis. Industrial vibrators can put energy into the material through the bin wall at various levels of frequency and amplitudes to accomplish the task of promoting material flow, depending on the material, the flow problem, the bin structure design and the environment.

The use of industrial vibrators to break up material flow problems in a bin is counter-intuitive, correct?  Doesn’t vibrating the container pack the material in it? Yep.  But at the correct frequency and energy level vibration, like aeration, separates the bulk solid particles, thereby promoting material flow.  It also breaks the bond between the bin wall and the material particles.  This means vibration can counteract both adhesion (material clinging to bin walls) and cohesion (material particles adhering to each other).

So, process control of industrial vibrators. How should you control them?  Run them all the time, right?  No! Operate an industrial vibrator only when needed.  Remember, that high energy as a result of frequent banging can damage the bin material, welds and even the mount that the vibrator is attached to. So, when there is a flow problem run the vibrator until the flow problem is gone and then stop the vibrator.  Also, pulse the vibrator on/off to give the material a chance to move once the particles are separated by the vibration. One thing you don’t want to do is run the industrial vibrator when the bin is empty of material, which is why you should not run it continuously. Why?  Because you can damage the bin and anything attached to it, like level sensors which are often in the proximity of an industrial vibrator installed on a bin. Take a look at this video to see the result of vibrating and empty bin with a level sensor attached.  How long will the mechanical and electrical structure in that level sensor last?  Let’s not find out.  Vibrating empty bins?  Don’t do it!