A belt feeder is designed to extract material from beneath a head of material above it. The material load above it and the head pressure always exist until all of the material is depleted. The material extracted must be sheared from the material above. This requires large driving forces and results in a constant abrasion of the material on belt. The belt feeder is a volumetric flow control means. An adjustable gate is used to control the height dimension of the flow area (skirt gage sets the width). The feeder is often equipped with a variable speed drive that can interact with feedback from a downstream belt scale. The belt feeder mst run at slow speed otherwise it will abrade away prematurely.

A belt conveyor recieves the material cleanely from a free falling flow. There is no head pressure nor the associated shearing forces. The belt conveyor transfers the flow as it comes. It does not attempt to regulate it. Belt conveyor speeds can be much faster.

I hope this explanation helps.

J. A. Dos Santos ■

The information provided by Mr. Dos Santos is correct for those belt feeders that are used to feed conveyors from bins, silos, et cetera where a constant uncontrolled feed is used.

Other belt feeders are used in non-shear applications as a means to control the feed to the main conveyor(s) in a belt friendly fashion. That is, the feeder minimizes load impact on the conveyor and delivers the load at a speed matching that of the conveyor. These belt feeders do not require greater horsepower and their primary purpose is to act as a sacrificial belt system, so that the longer conveyor belt does not need to be changed frequently due to loading or load induced mistracking damage.

Both types of belt feeders are conveyor systems in their own right.

With the conditions you described, I do not believe that a belt feeder is required. However, you should ensure that the chuting arrangement delivers the material in a controlled manner.

Regards,

Dave Miller ■

A further note,

Both of the above arecorrect. Maybe Joe's response is the more common. An additional condition of many belt feeders is the skirt drag magnitude. Many feeders have a higher than normal bed depth. The hydraulic pressure from the bin/ stockpile load acts on the skirt side walls. These forces can be quite significant, depending on: material contact height with the skirts, length of skirts, appeture design at the shear zone exit, and the shear zone hydraulic pressure which comes from the Rankine side wall pressure. CEMA gives reasonable treatment. Prof. Allan Roberts publications in Bulk Solids Handling and other give a more definitive analysis. BELTSTAT also givea a reasonable treatment. The most accurate treatment is done by Discrete Element Method (DEM) modeling.

Lawrence Nordell

Conveyor Dynamics, Inc.

Bellingham, WA, USA

ph 360/671-2200

email nordell@conveyor-dynamics.com

web www.conveyor-dynamics.com ■

a belt feeder is typically used and located at a loading position, generally as the live bottom of a feed or surge hopper and it's specific function is two fold.

one: to receive the impact load of the feed material, generally designed with much tighter spacing of the idlers in a short span and or utilizing a slider bed design to take the impact of the material. The belt feeder then, discharges onto a normal field conveyor setup.

Depending on the harshness or nastiness or sheer weight or abrasiveness of the feed material..........other devices may in fact need to be explored. Example: Electro magnetic pan feeders as the transition point or brute force feeders or reciprocating plate feeders and all have their specific niche applications.

check out: www. assinck.com or email me at bael@golden.net ■

can you advise the weight per cu ft of the material as this is highly important.

I would assume 100# cu ft range.........for the sand...

question: why bin activators? I assume because material is hanging up....or not freely discharging.........which seems odd for free flowing material.

Maybe you do need a more POSITIVE means of moving the material out which a belt feeder or other device meant for this purpose would certainly, easily achieve. ■

Good Day Johnp

I note from your details that you are based in WA and operate in the mineral sands business. I am Perth based and would be pleased to visit you to discuss your feeder issue in more detail. We have experience in bulk handling of all types of mineral sands in WA. Please e-mail me if you wish to discuss this further, sdavis@hatch.com.au.

Regards ■

From the information given about the material flow condition there would appear no difficulty in using the hopper to the belt as a feeder. The extra belt load on a conveyor 30 meters long will be small if the interface with the feed hopper is designed right and tracking should not be affected. The geometry of the hopper may be partly dictated by the inlet size required to accept the loading conditions from a front-end loader and partly by the interface with the belt to minimise belt loading and control the outlet rate. Even with free flowing materials there is considerable merit in forming a progressive extraction pattern onto the belt and form an increasing taper along the belt of the dynamic arch of the transition from the hopper convergence to the outlet. These steps provide a smooth transfer from the hopper contents onto the belt and draws material away from the side skirts. An inverted Vee insert along the length of the hopper is also useful to reduce belt loads during initial loading and during flood discharge conditions. This also spreads the flow channel and helps to clear the corners of the hopper. More sophisticated designs of hopper shape, control gate and skirt plates would not appear to be justified for this relatively small duty. ■

Dear John,

You are mentioning that the material flow from hopper to belt-feeder / conveyor is by 200 DN Nozzle. Please describe in few sentences what is implied by nozzle and how it functions.

Also, whether you have single or more number of feed points on 30m feeder / conveyor. Solution also depends upon this.

Regards,

I G Mulani.

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

parimul@pn2.vsnl.net.in ■