PUSHING A BELT WOULD BE A QUANTUM LEAP.

Less seriously; but again...quoting Lord Kelvin "We only know what we can measure." So give some numbers!

Remembering!!!!

1 is impossible

2 & 3 are the same.

So we're a bit spoilt for choice; aren't we? ■

Well, it doesn't take Sherlock Holmes to deduce that you can't push a rubber band very far.

1 is not the best way because the tension fluctuations are excessive.

2 is better because its simpler

3 is wrong because the tensions are functions of e^„‰ƒÆ & should not work out at 50/50.

If you really have the set up described then you have the GTU in the wrong place. It should be in the middle & horizontal. Monsoon rain in the pit is presumably the raison d'etre of the shed.

Manufacturers of bucket wheel stacker reclaimers tend to know a bit about yard conveyors & have presumably told you what is best already. I cannot understand that you would source separately; unless you are buying a used machine without the yard conveyor it is leaving behind? ■

Duel drive is preferred. That will allow tensions on carrying side (either direction) managable. You have a gravity take up. Is the movement of Take-up pulley in horizontal plane with wire rope going over a systemof pulleys to the top of take up tower.

AC frequency control drive motors on both the ends will be better for smooth start upin both direction.

Vinayak Sathe Tel: +91 832 2538294 ■

We have designed many successful dual direction systems. Key features need to be defined in order to make a proper recommendation including: tonnage in each direction, total length, speed, and downstream surge controls to name a few.

Drives at both ends are a good option with a takeup in between can be applied only if the belt is long enough to justify dual remote drives. The trade-off is in the added belt tension, structural costs etc., verses drives, controls, electric house, maintenance, etc. THere must be an incentive to build a more complex system. All three concepts have merits.

THe least beneficial is the dual drive located at one end. unless you consider a fourth option to place the vgtu between the dual drives.

There are other options, but more of your plant and production criteria needs to be known. ■

Dear Mr. Polstar,

From conveyor design point of view, you can design conveyor by considering any arrangement of drive. But in case of yard conveyors equipped with stacker-reclaimer machine, the important consideration is to have minimum tension at the concave curvature of the machine. If this is not done, the tripper portion of stacker-reclaimer machine and thereby the complete machine will be large. This is not economical.

Therefore, the usual practice as I know, is to decide the power required by the conveyor and place two number of drives, one at tail end and one at head end. As per the experience on this matter, the drive size at each end is nearly 75% of total requirement then yard conveyor is to be designed considering varying situation ranging from equal power shared at both the ends to the 75% and 25% power sharing at each end. The analysis of conveyor response in varying situations needs exhaustive design analysis.

75% mentioned above is not a rigid figure. It can be said as say 65% to 75% depending upon the available sizes of the motor. I do not think you will gain anything by putting dual drive at both the ends. The actual analysis considers the need of the machine and economy and proper functioning of the yard conveyor.

While making the design and analysis one has to also see for the various positions of the travelling machine.

Regards,

Ishwar G Mulani.

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

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

THe concave curve is only in the higher tension region with a fully extended stacker. As such there are other factors that may be considered for such a design.

First, to minimize curve liftoff,the smallest amount of power/belt tension should be passed through the GTU.

An equally powered head and tail will not accomplish this. THe curve will see half the motor power (tail drive) plus GTU tension plus belt resistance tension to extension position. The curve tension is near 1.66 of the total tractive tension (TE).

Second, there are two ways to minimize the tension at the concave vertical curve, if this becomes an issue.

1. Use a dual gravity takeup about a fixed drive located at the tail. With this concept, the belt tension at the concave curve will be GTU tension plus belt resistance tension to curve. The curve tension is nearly 1.33 times the total tractive tension (TE).

2. USe a one way clutch on each head and tail with each operating in opposite rotations. This has roughly same result as point 1 with a 1.33 TE.. ■

Originally Posted by I G Mulani

Dear Mr. Polstar,

From conveyor design point of view, you can design conveyor by considering any arrangement of drive. But in case of yard conveyors equipped with stacker-reclaimer machine, the important consideration is to have minimum tension at the concave curvature of the machine. If this is not done, the tripper portion of stacker-reclaimer machine and thereby the complete machine will be large. This is not economical.

Therefore, the usual practice as I know, is to decide the power required by the conveyor and place two number of drives, one at tail end and one at head end. As per the experience on this matter, the drive size at each end is nearly 75% of total requirement then yard conveyor is to be designed considering varying situation ranging from equal power shared at both the ends to the 75% and 25% power sharing at each end. The analysis of conveyor response in varying situations needs exhaustive design analysis.

75% mentioned above is not a rigid figure. It can be said as say 65% to 75% depending upon the available sizes of the motor. I do not think you will gain anything by putting dual drive at both the ends. The actual analysis considers the need of the machine and economy and proper functioning of the yard conveyor.

While making the design and analysis one has to also see for the various positions of the travelling machine.

Regards,

Ishwar G Mulani.

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

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916

Dear Mr. Mulani,

Where can I find more information about yard conveyors?

In reversibale yard conveyors with dual drive (one on tail and the other on head), is it possible one drive working and the other off? ■

Please consider the belt line first. That is the basis of conveyor design, or it used to be.

There will be a single reversible boom conveyor feeding onto the reclaim mode and also fed from the tripper during stacking mode.

How will the 2 heights be accommodated? You need a separate elevating conveyor for stacking and a kneeling tripper to feed the said elevating conveyor. This will dramatically reduce vertical curve issues and so forth. You need to accommodate the kneeling geometry within the take up mechanism. But what size of pile are you expecting from a 10m tripper elevation anyway? I am perplexed at how most respondents have assumed that one belt can feed to and receive from another belt without some elaboration involving elevation discrepancies. There is much ado about powering a belt before the issue of how the material gets onto the belt is clarified.

Also consider that when the boom is up-luffed in the reclaim mode there will be precious little headroom for any tail chute. ■