I am not confident my comments will be valuable, however this was discussed previously in modern history:

https://forum.bulk-online.com/archiv...p/t-25981.html

I suspect the links will include some references.

Also the following may be of interest:

http://www.beltcon.org.za/docs/b1204.pdf

Regards,

Lyle ■

Sir,

the successful application of Horizontal and Vertical curved trough conveyors has been developed since 1960's. (e.g.: Bell Bay, Tasmania)

Vertical curve is very common, horizontal curve less common but usually confined to overland applications between (say) 3km (e.g. South Blackwater - Kenmare OLC; QLD Aust design 1995; decommissioned 2005) to 13km (e.g.: Crinum-Gregory OLC with 3 separate horizontal curves; design circa 1997).

The designs are generally successful and not "troublesome", however may need periodic expert adjustment to maintain tracking.

Certainly the operational costs to maintain the horizontal curved conveyor performance are less than the civil work to enable a straight trace.

Sometimes there are environmental considerations and the trace must avoid a significant heritage or wildlife zone - so going around with the curve is the viable option.

Tracking for the curves is generally achieved by super-elevation of the trough and return idlers.

The curves are generally 1 - 2 km radius; quite gentle...

Hope this helps; you're welcome to contact me with any specific queries.

ray ■

This is also common in underground tunneling projects. Careful attention to curve radius as well as application of correctly spaced and banked idler sets through the curve can help prevent major spillage and belt damage/failures. ■

Mr. Ganesh,

Horizontally curving troughed belt conveyors have been employed successfully for many years. The number of installations are too numerous to list. Some generalizations have been made by respondents but these don't represent limitations. The rules are pretty basic. The curves must conform to radius of curvature constraints that ensure that no part of the belt is subject to over stress nor slack condition and the belt must not wander far from its centerline of the curve keeping the belt and the material well within the edges of the troughing idlers. The belt tension and the horizontal curve induces a radial load towards the center of the curve. That radial load must be offset by the gravitational loads on the slopes of the idler's wing rolls which tend to center the belt. Super elevation of the idler base at the inside of the curve can be used to offset the radial load but, because the tension varies as well as the loading, there is an amount of tolerable belt wander laterally. In this regard the radius of the horizontal curve dictates itself.

One respondent limits the radius of horizontal curves ti 2 km. There is no such limit and there is no limit in the length of conveyor that can benefit from horizontal curves. We have done multiple conveyors with multiple curves including a two way conveyor that carried material at both belt strands (upper carrying and lower return). Our horizontal curve radii have been as tight as 300 meters and this does not represent a limit,

Joe Dos Santos ■

Hello,

The belt conveyor curvature in vertical plane is a very common feature and is well known. Such radius is required when conveyor changes its inclination. Concave curvature is needed at the point where conveyor inclination changes from lower value to higher value. Conversely, convex curvature is needed when inclination changes from higher value to lower value.

The belt conveyor can also have curvature in horizontal plane. Such curvature radius happens to be in kilometers (2 - 4 km, etc.). The in-plant system do not have space for such a radius, and so in-plant conveyors will rarely have horizontal curved conveyors. The horizontal curved conveyors are mostly cross country conveyors (long distance conveyors).

In horizontal curved conveyor, belt tends to shift towards its curvature centre, due to belt tension, unless counter-acted by other force. Only idlers are in contact with the belt, and therefore only idlers can apply counteracting force as well as stabilising force to keep the belt at proper position. In such conveyors, the idlers construction and installation are manipulated so that belt remains at its place within permissible limit.

Such conveyors are designed such that they have very gradual start-up, and have proper drive distribution so as to keep the magnitude of belt tension and its variation bare minimum, for better stability of belt. Deeper troughing idlers are more suited.

The design analysis for belt stability at curvature is done very carefully considering empty and loaded condition of belt, for the situation steady running, starting and stopping.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 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 ■

Originally Posted by I G Mulani

......Such curvature radius happens to be in kilometers (2 - 4 km, etc.).......

......Only idlers are in contact with the belt, and therefore only idlers can apply counteracting force as well as stabilising force to keep the belt at proper position........

Dr. Mulani, I respectfully take issue with the above two points of your post.

There is no limit on the radius of a horizontal curve. As I said in my previous post, I personally have designed very successful horizontal curves with radius as low as 300 meters.

The forces that counteract the miss-aligning radial forces are largely gravitational. (This is analogous to the banking of a the curves at a high speed race track though in that case the radial force is centripetal and outward). Deep troughing idlers as well as super elevation of the idlers at their inside supports exploit the gravitational load causing a counteracting net outward force. The latter is regardless of miss-alignment. The only counteracting idler traction that we exercise is a slight forward tilt. This does not enter into our belt wander calculation and is by its nature reactive to misalignment.

Joe Dos Santos ■

Hello,

Thanks to our long time friend Mr. Joseph A. Dos Santos for his posting. It provides opportunity to make the subject issue more clear and informative.

I clarify that the mentioned concave radius ‘2 - 4 km etc.’ is a very general information. The adjective ‘etc.’ implies other values as well. Obviously, the concave radius value will be as per designer’s choice, on case to case basis, less or more, and buyer’s concurrence. One managing with less radius will have business reward in some of the cases (all installations will not have acute space constraint).

I have deliberately used comprehensive statement ‘idler construction and installation manipulation’. This implies regularly used manipulations such as idlers banking, idlers skew placement, side rollers tilt, garland idler troughing angle variation or any other means as applicable.

The purpose of my posting is also to inform to those who are not familiar with the equipment, that it is just a belt conveyor but designed more sophistically for belt stability. This may promote its use in the interest of all.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 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 ■

While reviewing a Job for ARAMCO in the Persian gulf region I was advised by the Main Contractor's people that the banking was necessary to keep material on the belt to counter centrifugal force.

I tried to explain fugo - I flee and peto - I seek but realised that I was talking to the wall. I found it politic - petare - to flee.

I patented a troughed conveyor which had integral covers top and bottom and could provide any required banking angle and still maintain true radial alignment of every single idler set. Batemans had an earlier, very similar, system but without integral covers. My gadget could be made on a press brake and spot welded at site. No bolts and sod all steelwork weight. Then I realised I preferred trucking alternatives and binned it. But if anybody is interested they're welcome. ■

The same Main Contractor wanted to know why I didn't agree with his proposal to wrap the belt into a tube configuration around the bends and then open it up to a troughed profile along the straight. Work can be really enjoyable sometimes; especially when its tax free! ■

Hi John,

I wouldn't mind taking a look. My Email address is listed below. Along those lines you may remember the Binder (Voest Alpine) system with the hung swinging idler set (carrying and return) that basically tilted in direct relation to the inward radial load caused by the belt tension and inverse relation to the gravity loads that worked against that tilt. Years ago I proposed the lazy man's horizontally curving conveyor using quite over-sized deep-trough five-roll garland idlers. I never pursued it and I suspect it would be costly. In the end there is no substitute for the deep understanding and the due diligence of a complete and thorough analysis that allows one to use the same economical equipment that is used on any well designed conventional conveyor. ■