belt conveyor power calcualtion (round section belting)

[luisss749]

Hello

Im designing a belt conveyor/classificator for fruits/vegetables, you can see a video of this kind of conveyors in:

https://www.youtube.com/watch?v=hAKtQbKkijM

as you can see the conveying surface is provided by several round section belts, i already made a power calculation for: empty belt conveyor, move the charge horizontally and for accelerate the belt conveyor, now i have some questions i hope you guys can help me with:

1. Im using the same design approach that for trough belt conveyors is this admissible for this kind of conveyors?
2. for the power calculation empty belt/move charge horizontally, i'm using the friction coeff. of 0.033 (the same as for trough belt conveyors idlers) but im using flanged ball bearings (shaft diameter=20mm) what you recommend me?
3. right now i have not considered the friction between belts and sheaves, any tip of how to incorporate this to the power consumption and for the belt tension calculation?

Thanks in advance

Luis Salazar

 

[berkshire]

Looking at your classifier I would think that equations for a flat belt conveyor would be more appropriate. One thing that was not clear was , is the conveyor sorting to the end, and just picking out leaves and stems in the intervening baskets, or were the round section belts fanning out to sort by size?
B.E.


You are judged not by what you know, but by what you can do.

 

[luisss749]

Hello Berkshire

1.- I guess the belts are fanning out, i've seen some videos where they put containment boxes under the belt to catch the different sizes falling from the inferior trays.

2.- Taking a closer look to the formulas they can be applied for flat belt too, in resume:
a)obtain the weight W=w1+w2+wn
b)multiply the weight for a idler friction coeff Ff=W*mu
c)multiply that force by the lenght of the conveyor this give us the work=Force*distance
d)with the linear speed and the lenght i can get a time to empty the belt time=distance/speed
e)power = work/time

 

[berkshire]

Luisss, I have attached a link to a set of pulley friction formulas , you say you have not considered friction between the belts and sheaves this may help , or you may find it to simplistic :

http://www.statics.marcks.cc/friction/pdf/belt_friction.pdf

Good luck
B.E.

You are judged not by what you know, but by what you can do.

 

[luisss749]

Hello Berkshire

I already made some calculation for the tensions, here the site i found:

http://www.thecementgrindingoffice.com/belt5.html

, is basically the same info of your link (now i know where comes the k factor i have seen some many times in belt conveyor formulas/tables).
Now i just need help to decide if the idler friction coeff. from trough idlers is ok for this kind of conveyor (ive seen they use the same fro flat belts), i read in a text book a friction coeff of 0.001 to 0.005 for ball bearings, i also find a value of 0.001 to 0.0015 for the same kind of bearings, i found this in a NTN document (google: NTN 2200tech)
Besides that there is something else, i would like to verify the diameter of the belts for the worst case, imagine 3 paralell belts separated 3in and supported between 2 idlers with a separation of 12in, now im considering that over that arrangement there will be 3 spheric object with a knowed diameter and density (3 medium potatoes of 3in with a weight of 225 gr each), the key of this design is to find the diameter that ensures that the belts dont separate apart by effect of the weight of the load, the weight of the belts (taking in consideration the tension of the belt) and let the product fall between the belts, this considering the caracteristics of the round belt material (PU85A) any tip or resourse you can suggest me find the solution to this problem?

Regards

Luis Salazar

 

[berkshire]

Luisss,
I am afraid you are on your own on this one unless somebody else in here has specific information on round belts, You are now looking at the horizontal deflection of the belts under an applied load, You should also look at flange height of your pulleys to make sure a large object spreading the belts/strings. does not cause them to jump the pulleys. I think you are going to have to do some of this work by test and re iteration.
Most of my experience is in flat belt conveying or roller conveying not where you are going with this.
B.E.

You are judged not by what you know, but by what you can do.