Dear Emma,

Might I suggest that you read a paper prepared by Prof Alan W Roberts. The title is Concepts of Feeder Design and Performance in Relation to Loading Bulk Solids onto Conveyor Belts. This paper was presented at Beltcon 9 conference in South Africa in 1997.

This will answer all your questions.

It is available at the following site:

www.saimh.co.za/beltcon/Beltcon9/paper925.htm ■

The important feature to get right with a belt feeder is the hopper interface design. This should extract from the whole length of the outlet slot and have a size adequate to prevent arching, but not so large as to apply large over-pressures to the belt.

To ensure the predictability of the system it is useful to include at least a short depth of mass flow construction for the hopper outlet section and cut back the side inclined faces at an increasing height from the belt, from a small clearance at the back of the outlet slot to the minimum bed depth at final extraction. This shape will provide an increasing width of outlet slot to secure progressive draw from the opening and allow the material to form a inclined transition arch as it changes direction, thereby radically reducing the drag-out load on the belt. Alan Roberts has published many papers on the mechanics of belt feeders and I endose the suggestion for anyone interested in belt feeders to review this work.

Lyn Bates ■

Remember to leave enough space under the feeder to allow for ease of cleaning. Feeders especially apron feeders are messy and difficult cleaning can be a major maintenance factor. ■

Dear Emma

I am in posession of a paper published many years ago Titled: "Designing to Customer Requirements". It is about designing long slot hoppers. The specifics of slot height are briefly noted. It covers a tonnage range from 1200 to 6600 t/h. It highlights reclaim problems and offers a solution, based on test work, and model building of train unloading systems and long slot reclaim hopper/feeders. The paper also highlights the problem TUNRA and others consultants had in tryng to predict the proper design and getting it wrong.

I received this paper from a friend who also has the problem in not knowing the publication source. You may find it in a search engine. The author is Otto van Rensburg. At the time of publication, he was Principal Engineer, Materials Handling, BHP Engineering. I am going to inquire with BHP and Hatch ( old BHP Engineering) of more detail.

TUNRA may know the source.

The paper references a number of train unloading configurations put into practice and later visited to update difficulties, efficiency, maintenance, etc.

Conveyor Dynamics, Inc.(CDI) will soon publish a paper on this very subject (Designing Hoppers and their Feeders) using Discrete Element Method (DEM) modeling.

As Mr. Mulani noted, particle size is a critical parameter, as is moisture, size distribution, rheology (cohesion, adhesion), compaction and plasticity action, time in storage before reclaiming, and the many geometric factors.

One key factor noted in the paper, that is now parcticed in silo and bin reclaim designs is the use of pressure reducing beams and staged reclaim layers.

The solution would not be appropriate for large lump products. Could you share more of the project details?

I will scan the paper and send it to your email. At present, I am on a business trip and cannot do it at the moment.

With Kind Regards,

Lawrence Nordell

President

Conveyor Dynamics, Inc.

website: www.conveyor-dynamics.com ■

Referring to the material depth on belt feeder, please see the following points :

1) The first factor affecting the depth is material lump size.

2) The second consideration is that, the depth should be such that the grip between material and belt is more than the skirt board drag force

3) The other important issue is to select material bed width and height in such a manner that there is least (reasonable) power demand.

4) The belt speed should be restricted to 0.20 mps if very abrasive material and upto 0.40 mps if non abarasive material like coal.

If possible, the material from hopper should not directly fall / rest on belt feeder (this is not a must, and there are many belt feeders with material directly resting on belt). Also, hopper outlet length should be kept minimum to reduce material dead load on belt, and power.

Regards,

I G Mulani.

Author - Book 'Engineering Science and Application Design for Belt Conveyors'.

Email : parimul@pn2.vsnl.net.in ■