Dear Mr. Subra:

I suspect that more information is required. If I understand your description, you have one load chute feeding a conveyor (without spillage) and this feeds the next conveyor in line at the first transfer station (again without spillage); then you have three more conveyors and transfer stations (all without spillage); and a final conveyor that delivers the meal to a chute. It is at the discharge chute where spillage is occuring.

If this scenario is correct, the problem is likely to be with your client's chute design. If the "spillage" problem is one of carry-over, it is likely that the belt cleaners are inadequate, or there is not sufficient space for them to work properly.

If you would provide more detail, or a sketch, I (and probably many others) would be in a better position to make suggestions.

Regards, ■

Dear Mr. Subra

I would be happy to review your drawings if you would care to send me copies. Photographs would also be quite helpful. Since Perth is only a few hours flight away, it would also be possible to arrange a visit if required.

Regards,

Peter Donecker ■

Dear Mr. Subra,

It is necessary to check design of transfer point (i.e. Material trajectory, material path in chute, material loading on skirt board, skirt board length, idler spacing, belt tension etc). After checking these, one can arrive at remedial measures. Belt scraper alone does not contribute in this matter.

Either you should analyze yourself, or take services from concerned experts.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor

Advisor / Consultant for Bulk Material Handling Systems.

Email : parimul@pn2.vsnl.net.in ■

Dear Mr. Subra:

As the spillage is occuring at the various transfer points, it suggests one of the following:

[1] overloading

[2] off center loading

[3] improper or mal-adjusted skirting

[4] belt sag between idlers

[5] run-back at the back-end of the loading area

If overloading, the answer is obvious (reduce the load rate or increase the receiving belt speed).

If off center loading, consider a chute reconfiguration or baffle (direction) plates.

If improper or poorly adjusted skirting, consider a different skirt system (you can contact me for a list of possible alternatives), or adjusting the existing skirting.

If belt sag, consider more belt tension (note that this can cause other problems), more impact idlers, a UHMWpe slider arrangement in lieu of the angled troughing idlers, or an impact slider bed instead of the impact idlers.

If material is flowing backwards on the belt, improve your back skirt system or install a capture box.

There are other possibilities, but these are the most likely.

Hope this helps. ■

Mr. Subra

The problem you describe can be quickly mathematically modelled using the Discrete Element Method (DEM) to clearly resolve the nature of spillage. Individual granular particles contact physics and flow regime are mathematically simulated.

Stagnation zones, or buildup are visulaized.

Any transfer chute system can be analyzed with any mix of particle size groups. Your problem can be quickly resolved including:

1. spillage

2. tracking

3. rip protection

4. dust generation

5. noise generation

6. belt wear

We are specialists in such modeling and would be pleased to offer our assistance.

Visit our website: www.conveyor-dynamics.com

In the comming months we will post a number of chute configurations resulting from limestone, copper, iron ore, coal, and fine cement. We are publishing some of the techniques at Beltcon 12 in South Africa in July.

Lawrence NOrdell

Conveyor Dynamics, Inc. ■

Dear Mr. Subra:

The drawing you attached helps in that it gives an overview of the transfer station. Unfortunately, it does not give any details on the skirting system.

I presume that there is metal/flexible material skirt arrangement that is supposed to prevent spillage from the 250mm gap between the top of the belt and the bottom of the chute, and that this arrangement extends past the chute to a point where the material has had a chance to settle on the belt.

The diagram does indicate a potential for off center loading on the belt -- but I cannot confirm this without feeding belt speed and normal loading information.

Regards, ■

Dear Mr. Subra,

Take a look at our webpage at www.overlandconveyor.com or www.applieddem.com. You should be able to get a brochure from our site under the numerical modeling that will give you an idea of what is needed to do Chute analysis and what we have done in the past to solve some of the problems that you describe.

Also, if you would like to talk about this in more detail please feel free to contact me directly at 303.716.0569 or via email at dewicki@overlandconveyor.com

Best regards,

Grzegorz ■

Dear Mr. Subra,

Also a quick comment on the 90 degree transfer point. With out knowing what the velocity and tonnage of the material is I can not give you an exact anwser but i am assuming that the material comes of the head pulley and goes to the far side and than rides that skirting high and spills over the edge and also if the seal between the skiriting and belt is poor than it will blow past it as well.

The Chute Analysis will easly show that and there is an easy geometry fix for that and getting the material to flow down the center of the chute and load the recieving conveyor down the cennter and even if the skirting is poor that should not be the problem if the material flow is managed properly unless you have way too much material and overloading the belt.

If you are interested in Chute Analysis or what it can do you can see some movies of them on our webpages....

Best regards,

Grzegorz "Greg"

www.overlandconveyor.com (look under numerical modeling)

www.applieddem.com ■

DEAR SUBRA,

I have viewed the chute design. I have not formally analyzed it in detail. Does "Raw Meal" mean limestone rock, hot clinker, or calcined and ground cement? The chute geomentry has many flaws. I offer the following comments on potential problems and CDI's offer to help/fix:

1. Off-center loading due to 2.4 m high material impact on the receiving belt, based on the material trajectory and drop height. The material appears to land on the far side of the chute centered 1000 mm (ranging from 850-1100 mm based on CEMA) away from the discharge pulley. The true trajectory will be more defused.

2. Off-center loading will cause mal-tracking from belt being pushed off its idler centerline from granular side-thrust ,or if cement, significant aeration of product that leads to reduced bulk density and high dusting

3. Off-center loading will cause the material to be assymetrically loaded which can cause spillage and belt mis-tracking separate from points 1 and 2.

4. Extreme belt wear, if the product has reasonable lump size and/or shaarp edges > 4 inch (100 mm) due to high, direct vertical impact causing granular cutting and sliding , in receiving belt direction, to accelerate material on receiving belt and/or impact gouging damage if the granular particle sizes have reasonable mass or have sharp edges> 100mm diameter.

5. High dust generation due to high velocity gradient caused by vacuum generated behind falling particles and gas turbulence from sharp impact and gas with dust exspunging from granular field

6. High impact causing granular scattering and belt-to-skirt dialation which leads to flushing of fine particles under skirt containment

7. Potential product degradation

8. Belt cleaning and discharge of refuse back onto receiving belt is non-existent, not shown, or not properly shown .

9. proper dust seals designed to be separate from containment side skirts and void of pressure from impact action

10. Action of loading may cause a reverse surcharge angle - ie. a negative angle which will lead to overfilling of the belt.

11. I assume from the chute dimensions the belt is either 1000 or 1050 mm wide. Given the material density is about 1200 kg/m or higher the 1050 mm belt works. If the belt is smaller or the density is lighter then it would appear the belt cross-section is beyond a reasonable load limit.

These are potential problems. More information is required. I believe this is sufficient for you to validate if a need exists to get professional assistance. There is no doubt that all the above negative conditions can be eliminated using Discrete Element Modeling (DEM). Materials of construction should be factored into your decision to satisfy expected maintenance reduction.

CDI offers this design service (DEM model, design, fabricate, and install or assist) together with a guarantee of performance on:

1. spillage containment

2. belt tracking

3. belt wear life improvement

4. dust reduction

5. liner wear control and specification on liner materials

6. reduction in maintenance

7. idler life increase

8. reduction in noise generated

9. proper chute dimensioning to control flow and belt cleaning residue

We are available to aid with mathematical DEM modeling and identifying the correct chute design solution.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com

. ■

Dear Mr Subra,

I have run a quick calculation of the discharge trajectory at 1.7m/s through the Helix Delta-T Conveyor Design program. The co-ordinates of the trajectory from the Centre line of the pulley are listed below. (Calculation No, time in sec, Fall distance, horizontal distance from centre of pulley)

19/05/2003 Discharge Trajectory Page 1



Helix Technologies Pty Ltd



Project Cement Chute Problems Client Mr M Subra



Conveyor Discharge Trajectory Report



Belt Speed 1.7 m/s Number of Calc 20 increments



Discharge Radius 0.318m

Co-ordinates Measured from Pulley Centre Line



Calc Time t Fall H Distance X



No sec m m



0 0.000 0.295 0.119



1 0.040 0.261 0.183



2 0.080 0.212 0.246



3 0.120 0.147 0.309



4 0.160 0.067 0.372



5 0.200 -0.029 0.435



6 0.240 -0.141 0.498



7 0.280 -0.269 0.561



8 0.320 -0.412 0.624



9 0.360 -0.571 0.687



10 0.400 -0.745 0.750



11 0.440 -0.936 0.813



12 0.480 -1.142 0.876



13 0.520 -1.363 0.939



14 0.560 -1.601 1.002



15 0.600 -1.854 1.065



16 0.640 -2.123 1.128



17 0.680 -2.407 1.191



18 0.720 -2.707 1.254



19 0.760 -3.023 1.317



20 0.800 -3.354 1.380

You may wish to plot these co-ordinates on your drawing. There is also a sketch attached showing this path.

If you wish to change the input details, you can download a copy of the demonstration version of the delta-T software from our website at http:www.helixtech.com.au and use it to re-do your calculations. This download and the use of the demo software is free of charge.

Yours sincerely

Peter Burrow

Attachments

cement conveyor discharge chute (JPG)

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Dear Mr. Subra

Below is the data provided above by Mr. Burrow plotted against your chute drawing. From this general location of the impact point can be seen.

Depending on the nature of the ore, it may tend to form a rhino-horn at this region, or it may just fan out. Also shown below is a top view of a 1/10 th physical scale model of a chute of similar geometry with a similar impact position. In this case, the degree of side loading was at its worst when the loading was low.

This kind of chute can be easily simulated by scale modelling, and its behaviour under different situations observed.

With regard to skirting systems, there are some very effective and easily maintained systems available in Perth, which are widely used our mining operations. If you would like me to provide details of these, please contact me directly.

Attachments

topview (JPG)

■

Since only one attachment appears to have come through, I am making a second post with the other picture attached.

Attachments

cement1 (JPG)

■

Dear Mr. Subra,

If you and your client would like to do the analysis of the chute and the material flow to come up with the right geometry for the new chute or the changes to it to get the right material flow I will be more than happy to help you with this.

Also, If you and your client would like a list of refrences and chutes to see that we have done I will be more than happy to do that as well.

Please do feel free to take a look at our webpages and download the the brochure about numerical modeling/ Discrete Element Methods (DEM). This might give you a better feel about what it is that we do and how we model the material flow.

Web page: www.overlandconveyor.com or www.applieddem.com

Also if you like you can contact me direclty at dewicki@overlandconveyor.com

Best regards,

Grzegorz

303.716.0569 ■

Mr. Subra,

From the data provided I would expect the bulk of the material to hit the back of the chute approximately 1 meter below the top of the feeding belt, and then deflect down to the receiving belt with the majority of the material landing in the center and to the right (#3) side of the belt. Given the powdery nature of meal, I would not expect this chute arrangement to give you too many problems in terms of belt wear or belt mistracking.

Therefore, the more likely cause of your spillage situation is likely to be an inadequate skirting arrangement, coupled with insufficiently supported belt. There are a number of suppliers offering quality solutions for this problem. To see the variety available, access web sites of companies such as Martin Engineering, Rema, et al; and then ask them for recommendations on containing very fine material.

If this has become a major annoyance, call in a reputable supplier or consultant and have them do an analysis. From my long-distance viewpoint: I would suggest that you use a dual skirt system that allows fines to get past the inner seal, but not the outer seal; consider the use of UHMWpe to support the belt edges in the skirting area; and extend the length of the skirting system

Hope this helps. ■

Hi,

From our raw meal transport experience, we make the following suggestions

ESS durt tracker primary scrapers are good - esp. for reversing belts.

We also use ESS sec. scrapers - type depends on application.

For loading skirts - we use ESS 2000 skirt sealing system on reasonable wide belts - these work very well. The loading zone features impact table/support rollers and also dust collections.

Belt speed should not be over 1.6m/sec typ.

Belt condition is important for good belt cleaning - where is the carryback occuring, do U have cracks in the belt??

Belt scrapers will never be 100% effective...maintenance is also important.

Drag scraper conveyors are good if well designed but these are the transport device...U still need to have a good cleaner...

Also - consider the chute angle - back wall...do U have a carry back issue or an issue with chute buildups and pull thro by the belt.?

Try adding lagged (45Duro) conveyor rollers with bend pressure idlers on top to help remove more material. They do work.

Also - consider removing the return idlers or using RDRT type rollers.

All of the above will help.

James Morrish

Eng. Manager

Queensland Cement Ltd. ■

Dear Mr. Subra,

Please mention the name of the equipment, which is feeding on to the conveyor. Whether flow from that equipment is steady or dropping unevenly in surge. The conveyor is supposed to carry material as it reaches to the belt, without material dead layer under feed chute (i.e. it should not be fed in a manner similar to belt feeder). Such situation can also create spillage.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor

Email : parimul@pn2.vsnl.net.in ■

Dear Mr. Subra,

I understand you have four feeding points on single conveyor, that means there are four skirt boards on conveyor.

I have also seen your drawing. In this context, I comment / suggest as below :

1) Material should not fall directly on belt. The material should preferably, first land on sloping plate and create velocity towards receiving conveyor. This you can do by introducing / rectifying one side of chute (in 700 mm height), using 50 degree slope.

2) Chute and skirt board should have flanged connection, forming enclosed construction.

3) Your skirt board width seems to be narrow. Its width needs to be between 66% to 70% of belt width.

4) If there are four feed points on single conveyor then clarify whether each feed point is creating 25% capacity or 100% capacity etc. The skirt board needs to be profiled such that material from earlier feed point passes through successive feed-points under least turbulence / deformation. The material incoming end of skirt board needs to be flared to cover material on belt, without ploughing. Even skirt board will have vertical and inclined plates.

5) The belt should be under proper tension all the time, with close pitched idlers under skirt-board, say value less than 1% etc.

6) A better option to minimize the problem, is to use comparatively wider belt or comparatively higher speed for such conveyor so that the material cross section ensures sufficient edge clearance on belt and thereby least interference between incoming material and skirt board (i.e. to avoid ploughing)

Trust this will help you to tackle the problem.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyor

Email : parimul@pn2.vsnl.net.in ■

Dear Subra,

I had posted prior comments on your request to gain understanding on the transfering of Raw Meal. I possed a question: what is raw meal? You did not answer.

Talking to people in-the-know, they say typically Raw Meal is the term used for the product after blending and fine grinding to a P80 of 75 microns.

Handling 75 um requires special care not discussed by the above. The material will entrain gas, swell the flow stream, will not settle immediately, spill upon exiting the skirt zone, and cause great dust generation.

If this is your product, then CDI has produced a novel procedure for controlling the Raw Meal flow behavior to minimze dust, spillage, and entrained gas.

As a side note, the material flow trajectories offered by others would not accurately predict the Raw Meal stream trajectory. Fine powders < 75um @ P80 do not obey the CEMA typical trajectory.

Flushing added flow streams onto the main collector belt will exacerbate the problem.

CDI offers to assist in designing the best fit for purpose transfer chute design and offer a guarantee that it will meet the design objectives or you owe nothing for the services.

Although I and others have commented on the typical trajectory path impinging on the far vertical surface, and the affects of this condition, this may become more difficult to handle due to the flow stream size fraction. Wear and belt training are the least of your worries.

Lawrence Nordell

Conveyor Dynamics, Inc.

website: www.conveyor-dynamics.com

email: nordell@conveyor-dynamics.com ■

I am sure that they are not conveying raw meal powder on a belt conveyor. It has to be raw materials going to the raw mill. There will be collection conveyors or a collecting belt from 3 or 4 weighfeeders.

I think that Mr Subra has now got enough info to let him act as a good consultant to his client. 3 pages of replies is testament to this.

James Morrish ■