Dear Mr. Hugo Lombaard,

You have given the conveyor basic data and also about the material data previously and as on now. But you have not mentioned the difficulties you are facing in operating this conveyor. You might have better response if you mention the problem.

As I can guess, the change of material from dry to wet concrete type material should cause the difficulty about capacity because such material will have low repose / surcharge angle. Also, the material will not be stable laterally on belt, so it might affect the stability of belt in curved zone. What about the troughing angle? One might have to also think about increasing the troughing angle if permissible. As I can think, you might have to check this conveyor for capacity, lateral stability, cleaning aspect etc.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Hello,

I've not had much experience with gold ore, but I understand in the mid 70's a coal company in the western US had a overland transfer of coal from a mine to a powerplant in which they added water and pumped the coal and water combination. I'll check my sources, but I believe it was in Kayenta, Arizona.

Just thinking off the cuff, you might try blending in a mineral like bentonite to change the charateristics of the ore slurry into a more manageable consistency. Bentonite is used in a number of processes and is also used to make clumping kitty litter. I dont have a clue if it is found in South Africa, but would be a quick fix.

regards,

Todd Dietrich ■

With the saddling up link I would like to introduce myself to you.

"www.hans-lauhoff.de"

With pleasure I present an offer to you. ■

Hello

It could be also that the belt / idler frictional resistances maintaining stability when the system is dry, are not there when the system is very wet.

Considerable and additional setting up may be required for wet conditions.

P Holt

Dosco Overseas Eng ltd. ■

Hello Wawiel....

On horizontally curved conveyors, the idler frames are normally tilted forwards a couple of degrees in plan view, and super-elevated on the inside of the curve. (In your case probably about 4 to 5 degrees).

Due to the belt tension in the curve, there is more load on the wing roll inside the curve. Because of this, the centralising effect due to the forward tilt is greater in the direction towards the outside of the curve, due to the extra load on the inside wing roll.

This together with the super-elevation can cause the belt to train very nicely for most operating conditions.

In your case, the wet ore is simply slumping towards the outside of the curve due to the super-elevation of the idler frames, and to a very small extent due to the centrifugal force around the curve.

As such, there is now too much load on the wing roll to the outside of the curve, and this is de-training the belt towards the inside of the curve, which is the last thing you want. The belt will climb up the super-elevation, and the material will keep to the lowest point like pulling a table cloth from under a plate on a leaning table.

If you can't get rid of the excess water, and get the moisture content to less than about 17% by mass, then you have a a bit of a problem.

You could try removing the de-training angle in plan on the outside roll, but always remember that the conveyor must also track nicely when empty.

Do you have the details of the super-elevation and the forward tilt? Also what capacity are you running at and what type of belt is it?

LSL Tekpro ■

In addition to Grahams clues (which I fully agree to) it would have a positive effect if one could reduce the belt tension in the curved area by setting a booster drive in front of the curve.

That way the belt will not climb up the super-elevation that much. ■

Hello Hugo,

You have received lots of good advice and the use of dewatering chutes would definitely be of assistance. A local (RSA) example of dwatering chutes can be found at Matla Colliery (installed underground by Nepean SA).

As an example of a horizontally curved conveyor which runs well even under reasonably wet conditions you could get information on the Namaqwa Sands trunk conveyor which is unsheeted and runs along the sea shore accumulating both occasional rain and early morning mist.

This conveyor was designed by Graham Spriggs of Tekpro.

Regards,

Adi Frittella

Afripp Projects

famfrit@global.co.za ■

Hello again Hugo,

Some further thoughts.

I have viewed the conveyor awhile ago. The design needs to be reviewed and the equipment specification must be brought in-line with the designers specifications.

As I remember the initial fault was an incorrect banking of the idlers, rectified by superelevating the opposite side.

It was obvious that the mine maintenance staff had attempted to rectify the problems by doing field modifications which had not been successfull in reducing the spillage or (primarily) in improving the tracking through the curve.

Thus the initial task must be to 'go back to basics' and check the design parameters.

There are many successfull horizontally curved conveyors around the Witbank/Secunda coalfields installed and designed by (amongst others) Bateman, C-Kit, LSL/Tekpro, Conveyor Dynamics, Roymec, Krupp, ATD. I am sure that the users and

designers of these systems would share their experiences on the transportation of 'wet' material with you.

Regards,

Adi Frittella

Afripp Projects ■

Dear Rekhawar,

See previous posting by Matt Crocker.

The purpose of the chute is to remove water from the product stream. Its functioning is reliant on the difference in trajectories between free water and product at the transfer point.

Regards,

adi ■

Hugo,

Is it possible for you to increase belt speed easily? If you have enough installed power, a speed increase will reduce the profile on the belt and reduce tensions. An adjustment (reduction) of the superelevation angle will then be possible.

Regards

Peter Burrow ■

Mr. Burrows:

Your speed increase may not be possible with a wet material. The centripetal force acting on the material may cause it to discharge off the belt in the curves outer radius.

Lawrence Nordell

www.conveyor-dynamics.com ■

Amen to comments by Mr. Spriggs, Obser, Croker, Fratelli (Adi). In order to find a solution that doesn't de-water the product to stability one must return to basic analysis of the conveyor.

Belt wander calculations include empty belt wander at full load, end to end or local full load. This is not an oximoron as it approximates behavior of a short empty run between an otherwise continuously loaded belt. In such a case empty belt wander is allowed to be more dramatic knowing that the required correction under load is delivered by the load (a small load only needs a small correction to not spill, and so on). The problem in this case (not considering other problems that may exist) is that the material is a fluid (for belt wander purposes) and makes no (or little) contribution to correcting the alignment. The dramatic empty belt wander that is calculated is thus realized but unfortunately it is realised at the point where there is a load. Solving this problem requires tension, curve and banking combinations, anywhere on the horizontally curved belt line, that will not allow dramatic belt wander of the empty belt even at full load tensions. This problem may or may not be solvable with the existing conveyor path but I have outined the approach that must be pursued to determine this.

I hope this is helpful.

Joseph A. Dos Santos ■