Hello Serhey

When I first designed a horizontally curved conveyor about 25 years ago, I was concerned that I must not have too much fill of material, simply because it was curved.

I took the conservative approach

Suffice to say that it was not long after I commissioned it that the owner used the spare capacity to get even more coal through.

So in other words it was running full to the brim,, but with no problems at all.

Last year the conveyor was speeded up from 4.1m/sec to about 5.6m/sec for yet more throughput, but it is still running fine.

What you have to watch out for is belt resonance in the curve, whatever the speed, but for my money, I would run your belt at 5.6m/sec and have a generous loading.

You can always speed it up later when the client wants the inevitable more throughput, belt resonance permitting.

Make sure the belt is designed to track within about 80mm of centre-line whatever the weather or load coditions (side guide rollers are absolutely forbidden in a good design!!)

Cheers

Taggart LSL Tekpro ■

Hi there..

Re: "still a little worrying about material spillage, since we have some inclination and centrifugal force" ...

I was worried about such things and that is why I went the conservative route. However, when I commissioned that one all those years ago, I was surprised to find that the centrifugal force, Idler super-elevation etc., had no visible effect at all.

Re: Method of calculating horizontal curves, I did it almost all from first principles, and calculated all the forces involved.

This included the inward detraining forces from the curve as well as the force required to actually bend the steelcord belt into the polygon shape round the curve (I calculate the differeing stress in each individual cord across the width of the belt). These have to balance out with the outward forces from the super-elevation combined with the additional outward frictional forces you get from tilting the super-elevated idler rolls forward.

This last bit was where I got some useful help from a researcher, who measured the variation in sideways forces of a belt on an idler roll with respect to the angle the roll is from normal to the belt.

To assist with the numerous calculations involved, I simply used sub-routines on my BBC 32kb computer (at least it was a step up from my ZX81!)

Cheers

Taggart LSL Tekpro ■

Hello Serhey..

I will have a look in my dusty old records for the test results which formed the key to the design of my conveyor horizontal curves.

Actually, without this testwork and empirical information, I don't see how you can do proper calculations.

What worries me these days is that I have come across many new conveyor design software packages of late, and even tried them out. But I have noticed to my horror that they are extremely poor when it comes to the horizontal curves, so be careful!

Cheers

Taggart LSL Tekpro ■

Originally Posted by Serhey778

Dear colleagues

Let me ask you a question for real professionals. I know there are probably a number of "studies" for this kind of calculations, but I am more than sure that practical experience might be slightly different.

I am working on about 7 km downhill conveyor with horizontal curve for coal. From budget point of view, I am directed on 42" belt. It looks like I am getting too high CEMA area, about 95% at 5.6 m/sec belt speed. I also was recommended to go no higher than 70% CEMA area at approximately 7.5 m/sec speed. This looks too fast for me. Probably, theoretically, using 70% CEMA area we are on safe side, but is that high speed not a concern? Especially for horizontal curve.

I really would like to hear some comments based on existing similar case.

Please help, any suggestions are appreciated

Thank you for your attention

Dear Mr Serhey,

You can go for even 7.5 MPS belt speed,but,that will necessitate extremely good quality idlers manufactured out of seamless tubes with rigorous inspection and testing.Presently,the idler manufacturer can supply you such needed finely balanced idlers on sample basis,but,I have every doubt that the manufacturing process has reached maturity level to offer idlers on a large scale commercially, suitable for 7.5 MPS.

With the above in view,Our company,who are a major consulting engg company in India,does not recommend long distance conveor speed more than 4.5 MPS at this moment.May be we shall recommend a little higher speed in the next project and shall gradually look for even higher when we find commercially idlers are available to suit such higher speed.

Also,we donot recommend more than 70% loading in the conveyor to ensure that material does not spill out at curvatures due to centrifugal forces.However,a possible alternative could be to provide a slope at the curvature points as is the practice in highways.

Regards,

D S Mallick ■

Hello Mallick..

How on earth can you say you do not recommend more than 70% loading because of the curve?? I have proved this to be nonsense in practice.

And how can you say that we should bank the belt like a motorway to reduce spillage??

The camber of a motorway is the opposite way from that of a horizontally curved conveyor!!

Bank the conveyor inwards and the belt will de-train immediately.

And as for your maximum belt speed, I give up!

Taggart LSL Tekpro ■

Adani has 7.5 mps 6000 t/h conveyor operating for more than two years now, designed by Conveyor Dynamics, Inc.(CDI). We have designed multiple systems in other parts of the world with horizontal curves, 7.5 mps and high tonnage. Ask Adani for an invitation to see the conveyors in operation in Ahmedabad, India at their Mundra Port. We are doing the same at their Dahej Port with a 14 km that is elevated and curved. ■

Originally Posted by Graham Spriggs

Hello Mallick..

How on earth can you say you do not recommend more than 70% loading because of the curve?? I have proved this to be nonsense in practice.

And how can you say that we should bank the belt like a motorway to reduce spillage??

The camber of a motorway is the opposite way from that of a horizontally curved conveyor!!

Bank the conveyor inwards and the belt will de-train immediately.

And as for your maximum belt speed, I give up!

Taggart LSL Tekpro

Dear Mr Taggart,

Thanks for your response.

Regarding belt speed,I reiterate that it is related to the quality of manufacturing and testing facility available with the manufacturers.With the present status in India,4.5 MPS is a reasonable figure.As the manufacturing quality improves,higher speed can be recommended.This may appear to be nonsense to you-but,this is a fact.

Regarding belt loading,once again,this is related to quality of manufacturing and erection workmanship.If 70% looks to be too conservative,one can go for 75% to 80%-but,not more than that with the level of manufactuing/erection available here.

As regards training of belt in the curvature zones,We apply"Banking and tilting".While giving reference of highways,what I meant was that certain provisions are needed to prevent toppling of cars.Similarly,certain provisions are also needed for high speed belt conveyors to keep the belt trained in the curvature area.

Thanks and regards,

D S Mallick ■

Originally Posted by D S Mallick

Dear Mr Serhey,

..............to ensure that material does not spill out at curvatures due to centrifugal forces.However,a possible alternative could be to provide a slope at the curvature points as is the practice in highways.Regards,

D S Mallick

Dear Graham,

Please don't give up. Super-elevation deserves to be reinvented and centrifugal forces along curves of 800m might just throw rocks out if the speed increases enough. On second thoughts I've just given up as well.

Time to overhaul the keypads & correct upper F sharp on my Sax. ■