Conveyor material backflushing

[turnyourbassdown]

Hello,
I was recently given a project to assess what needs to be done about a raw material (limestone and gypsum) conveyor "backflushing" (12 degree incline). By backflushing I mean the following: material rides too high on the belt and it moves backwards and causes spillage off to the sides. It is not possible to reduce the angle of incline.

Belt speed estimate: 685 feet / minute (3.5 m/s, 7.8 mph)
material size: 1-3" diameter
belt width: 48"

I am not sure how to calculate the maximum allowable speed of conveyor belts, I assume it varies with material type and density. If the belt speed is increased, material depth is decreased while tons/hour stays the same.

Does anyone have any other suggestions on how to prevent the material from falling back down the incline? Since we can't reduce the angle of the conveyor, and the current chain drive system is already problematic at current RPM, I am searching for alternatives.

Also, if anyone knows how to calculate conveyor volumetric utilization %, that would be useful.

Your help is greatly appreciated.

L

 

[swearingen]

Your best bet is to start with CEMA - the Conveyor Equipment Manufacturers Association. They have a manual that covers most subjects on conveyor design, including volumetric utilization numbers.

One option would be to replace the belt with a ribbed belt. This will probably require some major retrofitting, however.

An (expensive) option is a cap belt. It's essentially an upside down conveyor that rides on top of the material only on the incline, helping to keep it compacted. It will require its own drive and support, of course.

Other than that, I don't think there's too much you can do besides lowering the incline for that size material. If it was finer, I'd suggest methods of wetting and/or compacting, but those don't generally work on large diameter material.

 

[dvd]

Pretty good forums with multiple knowledgable conveyor people at:

http://www.bulk-online.com/Forum/index.php

and

http://www.powderandbulk.com/cgi-bin/yabb/YaBB.pl?board=general

 

[diskullman]

Any chance that you could attach come cleats to the belt? Anything to interfere? You could look at the Tach-A-Cleats in the Flexco catalog.

Russell Giuliano

 

[turnyourbassdown]

The cleats seem to be a good idea. However, the scrapers/cleaners will no longer work. How are cleated belts automatically cleaned of debris?

 

[PeterCharles]

"How are cleated belts automatically cleaned of debris?"

VERY BADLY!!

And you'll have to change your return idlers.

 

[turnyourbassdown]

Why will the return idlers need to be changed? It seems the best option for cleaning cleated belts is a rolling brush, but with moist material this will likely be messy.

Back to the drawing board for options, still seems like speeding this belt is the best way to alleviate current spillage.

 

[berkshire]

turnyourbassdown (Industrial)
Just a thought, can you change out the inclined portion of the belt conveyor for a drag link conveyor?