Your question suggests a dichotomy philosophy. Why? You can load on an incline of choice until the product becomes unstable, causes unnecessary harm to receiving belt, or other unacceptable behavior.

There are restrictions such as drop height, orientation, ability to place vertical concave curve. The driving factors should be ability and economics.

There are, as you are aware, many factors that govern the degree of inclination such as: fines with moisture, granular shape, aeration, chute design , and other factors that have been addressed many times in this forum.

Since this has been the focus of many comments and recommendations, do you wish to address a new point? Why 8 and 15 degrees? Why not 5 through 20 degrees or by product type and physical properties? ■

It is advisable to keep the conveyor receiving end horizontal rather than having any inclination, provided total belt length can be suitable as per layout constraint. In case of inclined belt at the receiving end, due to material turbulence, skirt board friction, belt friction, material friction, idler friction resistances go up resulting more belt tension and more power requirement. However, some economics may be calculated to decide less inclination angle depending on material flow properties.

Overall belt inclination angle is guided by the material flow charecteristics, troughing angle, surcharge angle, moisture content and size (mm) of the material.

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Hello Banerjee..

The incline factor relates to the loading point only.

Simple as that!

Regards

LSL Tekpro ■

Dear Mr Banjeree..

It is not really a question of where does the extra material go. It is far more simple than that.

For example, suppose you load a belt on the horizontal and get 25 degrees surcharge angle, and it gives you a cross sectional area of 1m squared...in the vertical plane.

Suppose then you do the same again but loading at 15 degrees.

Again you get 25 degrees surcharge angle, and again it gives you a cross sectional area of 1m squared...**but**only**in**the**in**the**vertical**plane**.

The actual capacity of the conveyor however works on the cross sectional area at *right*angles*to*the*belt* i.e. Q=A x V in the direction of belt travel. This would be around 09m squared for A at 15 degrees loading.

It is therefore quite clear that it is the loading angle that determines the usefull area of cross section. Once loaded however this area stays much the same.

On coal over 12km I have measured only 1 degree reduction in surcharge, and sometimes even less than that.

Simple way to look at it is try loading at 90 degrees..effective area in vertical plane =0m squared, inclination factor=0.

Regards

LSL Tekpro ■

Dear Mr. Banerjee,

Inclination factor is not applicable to loading point only. For belts on inclined conveyors the theoretical quantity carried has to be reduced by a constant factor depending on the angle of inclination. This constant factor for different inclination angle are as below:

Incl. angle 2 4 6 8 10 12 14 16 18

Const. factor 1.0 0.99 0.98 0.97 0.95 0.93 0.91 0.89 0.85

While calculating the effective pull this reduced quantity has to be considered. Effective pull = g*fric. coeff*(m+mb+mr)+/- g*m*sin(angle). Also add peripheral forces from scrapers and cleaning devices.

I would like to add that for any conveyor design discharge point at any transfer point is very critical. It is important to ensure that the discharge materials on the receiving conveyor is settling down properly and does not find any difficulty picking up the speed of that conveyor. So, it may need adequate design attention for take up travel, pulley wrap angle, chute design, skirt board length and height selection, suitable scraper .........

Thanks,

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Dear Rabi Kundu...

Once the material is loaded say horizontally onto the belt, please enlighten us all, and explain in your opinion what happens when the load negotiates an incline.

As we understand it, according to you, the theoretical burden has to reduce, as you apply the slope factor not only at the loading point.

As we all know in practice, this is not the case, and normally what gets on the belt at one end...comes off the other end.

Except for a badly designed tripper, and extremely lightly loaded belts, I have never in 35 years seen material fall off a belt due to a change in inclination.

Do enlighten us all

Thanks

LSL Tekpro ■

Graham,

I think you have led too sheltered a life.

Material, usually larger lump, can dislodge from a loaded belt when its position, shape, idler agitation, and support stability are exceeded.

I believe you have not considered the dual slopes that make up the maximum rilling (surcharge) angle. The maximum rilling angle is the resultant of the belt's incline slope and the surcharge crossectional slope. They combine to produce a material slope angle greater than the aforementioned individual angles. As such, a high surcharge angle, loaded on the horizontal plane, can lead to less stability on the incline as does happen with larger lump.

I do not dispute your general comment on crossectional loading that the burden will not reduce. ■

Hi Larry..

Thanks for your comments.

I can see what you are getting at in theory, but in my quite long (but albeit sheltered!) career in materials handling, I have never seen a lump fall of a properly designed and loaded belt, due to a change of belt inclination.

(As such I still maintain the slope factor only relates to the loading point for fines as well as for lumpy material for the reasons I have tried to explain.)

For my overland conveyors (normally loaded on the flat), I never take the slope factor into consideration. Even with significant undulations along the way, and I have never had lumps fall off en-route. The lumps don't even fall off with the inclines compounded with horizontal curves.

Quite often, the client exceeds the theoretical maximum design capacity these belts. The lumps still don't fall off!

Regards to you..

LSL Tekpro ■

Dear LSL Tekpro,

As you know that material cross sectional area reduces with more inclination angle. Conveying capacity = V * A. So, with less cross sectional area conveying capacity reduces. Now, if the conveyor profile is horizontal to incline, design capacity should be enough to cater inclined situation. If not so, there is a possibility of accumulating material at the receiving end of the conveyor as the conveyor will not be able to discharge enough material due to less carrying capacity at the inclined zone.

The above problem could happen, if the conveyor runs at its design capacity. If the conveyor runs at below capacity, the above problem may not happen.

Thanks,

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To further the discussion with Graham,

Belts with inclines and declines exceeding 14 degrees and carry lumps of significance (can hurt when hit). We find, many have spillage all along the belts. The largest contributor is the leading and trailing loads on declines and inclines respectively. I don't believe I have seen a plant without such spillage.

The stability angle, spoken of above, is more severe that the rilling angle. The leading and trailing end loads have the dual angles of sloope and axial angle of the load at the ends. ■

Quite so Larry..

A very lightly loaded inclined belt causes roll back and spillage (nothing to do with the de-rating slope factor though).

I think to clear the apparent confusion and spell it out so all can understand, we have to distinguish between two basic loading criteria namely:

- De-rating due to loading angle (slope factor)

- Maximum allowable incline (due to material size and characteristics)

These are two seperate criteria.

To try and combine the two causes all the confusion, and one can easily go off at the wrong tangent, as can be seen above.



LSL Tekpro ■

Graham,

To belabor the point, the German Standard 22101, for many years, had a correction factor for the slope effect. The crossectional load had to be reduced by the correction factor:

correction factor =cube of cos(slope angle)

This was a part of the standard for about 40 years. It did not mention whether the belt was loaded on the flat or incline. One could make various interpretations. My point is that it was recognized. I have given my reasons for the need and have witnessed incline spillage in many mines for both reasons stated.

I am not up to date on DIN today, are you? Does it matter?

I do not see the mutual independence between slope angle transport crossection and material properties.

I think you are misunderstanding surface rilling geometry from crossectional area of transport. I also believe DIN was correcting for the rilling effect and not the arguement of flat vs incline transport crossectional area. ■