Hello Urutxurtu,

As belts differ from manufacturer to manufacturer (and from type to type by any given manufacturer), your best bet is to get this information from the belt manufacturer of your choice.

Regards, ■

Hello Urutxurtu,

Mr. Dave Miller has already provided some information and suggestion.

This reply is addressed to the people who are not familiar with horizontal curved conveyors.

1) One often thinks that radius of curvature will be small in such conveyor, and conveyor can be made to fit into jig jag path in the plant. It is not so. The radius of curvature happens to be in kilometers (either full or fraction of km). It is like railway.

2) When the belt is horizontally curved, the tension in the belt tends to shift it towards the center of curvature i.e. belt will try to shift, on idlers towards the center.

3) The belt tendency to shift is to be counteracted by specific positioning of the idlers. The idlers are positioned in horizontal and vertical orientation so that the force arising from the idlers and gravity will counter balance the inward force arising from the belt tension. Thus, the stability of the belt is achieved on curved path.

4) The belt stability is to be analysed for various situations i.e. part load, full load, starting, stopping etc.

Above are basic considerations in such conveyors.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Search Bulk Solids Handling (BSH) past publication such as Grimmer, Tooker, ....

Jo Bahr (sic) published the earliest concept in 1959 out of Friberg University in East Germany. Bahr used only friction to steer the belt.

Prof. Grimmer published the use of super elevation, I believe in 1963. Others have republished the basic physics of his work till this day. Problems with Grimmers concept: a)assumes belt to be a monolithic structure regardless of load or no-load - this concept does not account for change in reactions when belt plus material undergo a traverse shift, b) does not account for change in belt surface forces with vertical and horizontal curves, c) does not account for reaction forces and junction between wing and center roll with varying degrees of belt construction, d) does not account for shifting of load cross-section as material rills from high banking angles and cross section moves to settle in lowest swale point. Grimmers concept gets in the ball park but the idea of having a monolithic variable density belt across the width can result in unacceptable errors.

I believe Garren Tooker published in BSH many years ago on finding the pivot for transverse rotation that allows belt and material to laterally shift. Although we do not follow his approach, and do use our own derivation.

To know who is right, you need to see the field data vs theory. This is not normally published either for IP reasons or because the interested party has not got it quite right.

Modern physics must take into account the potential for the belts outer curve from lifting off (curling), and the inside from buckling. The belt stiffness properties must be considered. Belt reaction before and after the horizontal curve is not published. Belt mistracking from cross-sectional shifting and its effect on downstream terminal equipment is not noted. There are other factors are not found in any publications.

Some use belt steering by using forward tilt ( Jo Bahr) and super-elevation (Grimmer). Wet belt including, slimes, et. al. can have profound effects on belt tracking when employing friction control and does separate idiologies of design.

Modern curve engineering allows tighter radii. Some of these techniques are not published.

Then there is the use of pivoted idler frame and support mass to be included in the belt transvers displacement calculation such as the publishing of Prof. Franz Kessler in Austria.

I appologize for any mispellings.

Good Luck

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Reinhard

You did not reference the most contraversial paper on horizontal curves.

Dr. Olaf Klupfel's 1982 (??) BSH published reference regarding the New Caledonia SLN installation. Poor Olaf got pounded in the German courts, for his inventive engineering/photos of this installation and other topics. REI became noted for their engineering of the Curvoduc. The curve is a Klupfel design when he worked for Beumer Sr. as their engineering manager.

He published the Mea horizontal curved conveyor work to gain some recognition for his accomplishment. He was left alone to commission it and correct its nasties ( control related) to make the curves work.

He did all the conveyor engineering without computer and used the principles of Grimmer.

There are a lot of fascinating stories about the selection of the engineer, its engineering, commissioning, and claims to the design, and claims in the German courts.. You ought to get Dr. Klupel to to a autobiography.



Its still running today. A little rusty in spots. SLN still think its a great design. I wonder if they know who engineered it?

This was one of BSH's first publications, is it not?

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Hello Gabriel..

I agree that a friction coefficient of .6 for a dry belt on new rolls is seemingly high.

But if you look closely at what I wrote above you will see that I take a range of values from .1 to .6 and my computer simulation for the idler configuration must give suitable results for the whole range, and limit belt wander to 25mm each way.

I also wrote:

"One of the secrets here is to predict the friction factor of the belt on a forward tilted wing roll. From my curved conveyors I have found the value to be from zero to about half what you expect it to be, from zero to four dergrees in plan"

Regards

LSL Tekpro ■

Hi there Urutxurtu (and Manny)

It is actually a very interesting exercise to calculate the behaviour of the belt in the curve from first principles. (but you absolutely must get your first ones audited by someone who has successfully done many before though)

The de-training forces (inwards to centre of the curve) must obviously be balanced with de-training (outwards to the outside of the curve) for normal conditions, taking the force needed to bend the belt into consideration as well.

You have to analize the vertical, horizontal, and resultant forces on each roll.

The wander must then be calculated for all extremes of loading, vertical radii and weather conditions for loaded, empty, starting, stopping etc. (This is where your computer becomes extremely handy)

I then normally select the horizontal radius, the super-elevation and the forward tilt, such that the belt wander for all the above conditions is limited to 25mm each way.

One of the secrets here is to predict the friction factor of the belt on a forward tilted wing roll. From my curved conveyors I have found the value to be from zero to about half what you expect it to be, from zero to four dergrees in plan. (I have found two degrees to be the best in practice.)

What you expect it to be is from mu=0.1 in the mist and rain on shiny rolls to mu=0.6 on a nice sunny day on new idler rolls.

By so doing, for normal operations, the belt tracks around the curve like Shumacher around the Nurberg ring!

In fact, I always maintain that a well engineered curved conveyor tracks better than a straight one.

So Manny, please inform your crowd of doubting Thomas's that there is realy nothing to fear, if the curve is designed by the right person and, as Adi has pointed out in another thread, the idler frames are made and fitted as per the orientation of the design.

There are now numerous examples to see.

Good luck

LSL Tekpro ■

Manny..

Two examples of tight horizontal radii here in South Africa are:

Conveyor Q10 at Landau Witbank R= 1200m and R=1300m

Conveyor B18 at Goedehoep R=1000m

Lots at 3000m, as well as the dual-carry-conveyor where I swopped the top and bottom strands over in 290m of groundline using six horizontal 3000m curves compounded with four vertical curves. This is at Namakwa Sands Western Cape.

Regards

LSL Tekpro ■

Manny,

There are a number of Australian installations. A sub 3 km radius is Warkworth, just north of Sydney:

Product ...................... Coal

Tonnage .................... Dual 150 and 600 t/h (from memory) Radii .......................... Multiple 1200 and 1400 m

Length ....................... Length 4 km

Installed .................... About 4 years ago

Speed ........................ Dual 1.5 m/s and 6.5 m/s

For more information contact: Dave Bagient, engineering mgr. at Barclay Mowlem, in Sydney, his phone number is: 02-9855-1782.

Its the photo on our web page.

Lawrence Nordell

www.conveyor-dynamics.com ■

Peterman & Prax offered another interesting perspective in their paper, "Long Distance Conveyors with Roller Guided Edges".

Refer to Bulk Solids Handling Volume 18 Number 2 April June 1998 ■

I developing the equations, and reviewing the work by Grimmer et al, consider how the following would be analysed.

* Steel cord belt.

* There are no steel cords above the middle or outer wing rolls. The only steel cords are above the inner wing. Ie a very poorly manufactured belt. They ran out of cables.

* The inner wing is vertical ie 90 deg to the horizontal.

* Would this belt go around a very small curve?

Gary James

Bulk Handling Innovation ■

Hi,

the first detailled and quite comprehensive publication on the theory of horizontally curved belt conveyors is (at least to my knowledge!):

"Auslegung und Betrieb kurvengängiger Förderbänder mit normalen Fördergurten" (Teil 1, Theoretische Grundlagen) and (Teil 2, Beschreibung einer ausgeführten Anlage) in fördern und heben 22 (1972) Nr. 3 and 4 (page 107-111 and 174-178) by Klaus-Jürgen Grimmer, Leoben, and Bernhard Beumer jr., Beckum

It dates back to 1972 and is, unfortunately, in German language only. The two Gentlemen compiled what was long time used as the basis for many conveyor calculations. Certainly, it was just considering static conditions as if the belt would have endless time to reach a certain position on the track. Dynamic calculations were introduced many years later. And also the question, how quick moves a belt in the lateral direction under a certain temporary loading condition on icy idlers was not really considered...

This may have led to some surprises during start-up and braking. But finally, the conveyor installations calculated as per that theory were running.

Holger Lieberwirth ■