What size are the pebbles?

How many?

What distance?

What is the loading method?

What is the water content?

What happens to your scats should give you some clue.

Are the pebbles paramagnetic?

Over to you for now. Others might need more information. ■

Hello,

Published literature does not mention pebble, but often mentions gravel, pebble, for which usable inclination is as below for regular belt conveyor:

An American source: Upto 12 deg.

An Indian source: Upto 15 - 17 deg.

An European source: Upto 12 deg.

If you have apprehension that you are concerned with pebble of special type i.e. more spherical and more smooth than usual, then get it tested (or make your own test) for repose angle, and accordingly deduce allowable inclination.

Higher speed and lesser troughing angle will tend to influence allowable inclination marginally, on lower side.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

Author of Book : Belt Feeder Design And Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Pune, India.

Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

In general though rule of thumb, any pebble type material you should look at loading flat or near flat then going up to 12 degrees plus or minus a couple of degrees depending of the rollability (if that is a word) of your material. You also need to look at properly introducing your material or limiting your conveyor speed help settle your material on the belt properly.

As noted in a different post elsewhere I have seen DRI pellets running at 15 degrees (loaded at 15 also) and it makes for a very messy conveyor with a lot of clean up required. I installed a conveyor for DRI loading at 3 degrees and ramping up to 13 degrees. I would have preferred lower angles but were were space limited. Material is loaded in the direction of the belt and centered. The client is happy with the installation.

The problems with materials that roll is not during normal operation but when the conveyor trips with material on the belt. If your slope is too steep you can end up with quite a mess. You also want to be careful when starting the belt when it is full. Intermittent loading for batch processes can be problematic also where the last bit of material has nothing to keep it from rolling backwards. I little bump over an idler and it starts to roll back on the belt ( and fall off) until more material is introduced behind to push it forward. ■