Conveyor Turn Design 1

[elinwood]

I just got into the Bulk Material Handling world and I'm baffled by the design of conveyor belt when it turns. I have a civil engineering background and I'm used to seeing super-elevation on a road such as this:

http://www.urbanaut.com/3-car train elevated on curve - closeup-Vashon croped.JPG

I was just talking to my coworker and to them it sounds so easy to understand why the conveyor belt system's superelevation is the other way around:

http://img.ehowcdn.com/article-new/ehow/images/a05/dv/41/define-conveyor-belt-800x800.jpg

Anyone care to explain ? I've been looking online and also on eng-tips and i can't find anything...

 

[Compositepro]

The tilt or super-elevation of the conveyor has nothing to do with making the turn. It is so baggage slides to the side so it is easier to reach and pick-up. On a road the tilt is the other way so the vehicle does not slide to one side.

 

[dvd]

Is the photo related to the question? How is baggage handling involved in bulk material handling? Not exactly a clear connection.

 

[elinwood]

The photos are there to illustrate the different slopes when turning. As far as I understand it, the first photo is typically what happens when designing a turn. The second photo is to illustrate what my coworkers were telling me. I couldn't find a photo specifically to coal conveyors but my coworkers were telling that it's similar to the second photo. I've asked 2 engineers about this and didn't get a clear answer.

 

[dvd]

Are you referring to something more like this?

If so, the belt runs up the tight side on the idlers to balance forces. Think about a string that is running down the center of the idlers while slack, and then think about what happens to it when it gets pulled tight. It pulls toward the inside of every curve, not the outside.

 

[elinwood]

So if I understand this correctly, the slope isn't to mitigate the centrifugal force on the coal like it is on the car driving on a road. Rather, the slope is so that the belt doesn't "sag" along the idler while turning due to the lack of tension.

Thanks for the explanation.

 

[Walterke]

Sounds reasonable. Since most conveyor belts don't travel very fast, the centrifugal force is probably not a very important factor.

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[dvd]

Look at chapter nine of CEMA belt conveyor for bulk handling 6th edition.

 

[PersonalProfile]

Similar to the above, centripetal force is generally negligible in conveying, if you drew a FBD the conveyor is trying to merge towards to the center of curvature and hence the idlers are banked to resist this.

Regards,
Lyle

 

[georgiasurplus]

On roads and bridges you are trying to keep the load on top of them, and no other support, with the slope varying with the severity of the turn, this helps the vehicle make an easier turn (caster, camber, suspension characteristics, etc., etc.). In a conveyor configuration the belts, chains, etc. are traveling inside the supports "side loading" the conveyor rails during turns and usually with a means of support for the product.