What is the wind speed?

Thirteen metres of travel is very short and acceleration time should also be mentioned: for track wear purposes because power is related to speed.

Hopper water volume is confusing. Please confirm what surcharge is expected.

What are the height considerations? This affects wheel loads during wind and acceleration influences, particularly if the driving wheel lifts. You might need drives at both ends.

Endless rope haulage might be easiest. But beware: I had to rectify a short travel rope haulage system in a steelworks. Overspill from the melt in the ingot molds was burning through, and sometimes capturing, the haulage ropes. ■

Best regards Roland. Sax is in Java, I'm in Brexitland.

I overlooked the reversible conveyor.

Dear Mr. Ganesh Reddi,

A reversible conveyor with an incline at both, or one, end for a straight loadable length of 13m seems very elaborate. The single incline with reverse also seems impractical for a variety of reasons. I will assume that both ends of the conveyor are inclined and therefore there will be 2 vertical curves. The required straight length will be much greater than the 13m for loading, especially if the elevated discharge height serves any useful purpose. If you can provide room for such a conveyor OK: but I would consider raising the whole show to feed a straight reversing conveyor. This would greatly simplify the take up arrangement and reduce the floor space required.

Please remember that structural steel is much cheaper than rubber and further remember that it is incumbent upon a conveyor designer to minimse the number of pulleys because there the rubber lagging is not so cheap and the machining costs are considerable. ■

I am still mystified by the need to reverse a conveyor which is lifted at one end only.

Now is seems the conveyor moves in unison with the hopper. In such a situation tyres are/should be out of the question. Sidewall flexing means that to stabilise the discharge point the conveyor should be fitted with retractable outriggers. Of course you can do that: complicated though it is. The other problem is hold down. With rails, besides improved alignment, there is the facility to provide rail clamps and storm anchors. Gusts of 180kmh^-1 are severe and rails are almost mandatory. Wheel diameters for such a machine are usually 700mm. Pin the hopper to the conveyor of course and prepare a loading table to examine the stability in crosswinds. Your biggest risk is losing drive wheel contact under onshore wind. This could prevent you reaching the storm anchor. Anemometers only monitor storm conditions: they are unable to accurately forecast the storm. Depending on your situation i.ts might help to look at 2 speed drives.

I regularly encounter 150mm lateral movement during the engagement of a trailer kingpin along a 9m wheelbase. That's in still air!

Check your valley angles against your perceived conveyor width. Don't forget to consider the conveyor side boards: necessary to prevent belt lift off.

Show us a drawing, please.

Hi Roland,

I thought 'Brexitland' on the spur of the moment. It is very confusing indeed. Metrication will persist. We might even be fully metric one day and replace miles with km. ■

Hello,

Earlier participants have already given useful information. Some addition from my side is as below:

Stockyard system sometime includes movable hopper, fed by movable reclaiming (feeding) equipment / machine.

I presume that the arrangement has rail mounted traveling hopper, which is fed by independently moving feeding equipment, and there is no mechanical connection between the two. The traveling hopper will encounter following resistances during its travel:

1) ‘Rolling resistance’, as referred by railway. For railway this is about 10 lb/tonne. Here you may take around 10 kg/tonne, as condition will not be so good as railway. If the hopper mobile machine mass is Mo kg, then this resistance R1 = 10 x (Mo divided by 1000), kgf.

2) Slope resistance if track has gradient say y:100, then this resistance R2 = Mo x (y divided by 100), kgf.

The track could be horizontal in general, even then locally certain gradient is considered according to the quality / anomaly / tolerance for construction.

3) When the machine moves, it has to overcome the material rubbing resistance in skirt board. This resistance R3 = Skirt board resistance considered in conveyor design.

4) Feed table operational resistance. Even when conveyor is stand still and hopper is moving, the hopper drive has to overcome the feed table resistance. Account for resistance R4 as per this phenomenon.

5) Wind resistance. The ISO guideline (or practice) for mobile machine (hopper) is that the equipment is supposed to operate routinely even when wind speed is up to 72 kmph. The resistance R5 is equal to wind force on the hopper machine projected area perpendicular to track.

6) The travel drive along with rail clamps for anchoring should hold the machine safely in storm condition. Machine is not supposed to travel in higher velocity wind.

7) Crabbing resistance R6 considering the flange rubbing at 2 corners of the machine is as below:

R6 = 0.025 x Mo kgf.

8) The drive power / size should be suitable for resulting machine acceleration, acceleration time and resulting thermal stresses for electrical - drive system.

9) Machine stability during starting, steady running and stopping operation. This can have implication on drive size / type if hopper is tall.

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 ■