Dear Gentlemen

Not to get too involved with the whole issue of the design around a reversible conveyor.

But I would like to state that there is a solution to belt tracking on a reversible conveyor.

After many years of manufacturing our SureGuide systems we finally decided to tackle this problem.

As stated the alignment of all components on a reversible system is vital as most corrections made in the fwd direction will come back to haunt you in the rev direction.

For this reason we took our standard proven single directional products and looked at what was needed to make them work in reverse. The solution has come about by using a very simple product set ( 1 x frame for the Troughing side and 1 x return roller on the return belt.)

The system constantly reads belt direction and when belt direction is changed 3 small linear actuators convert the system to adapt to the new running direction.

Now we know the apprehension most have with using electronic,hydraulic or pneumatic devices on conveyors, but our system only uses the electrical part for 20 sec everytime the belt direction changes. Thereafter the system is a fully mechanical belt tracking system.

If there is any interest please feel free to contact me.

mark@sureguide.co.za

Mr Spriggs please send my regards to Mr Shortt when you see him. He has visited our company in Krugersdorp a few years back and I usually see him at the Electra Mining.

Kind Regards

Mark Hupertz ■

Hello all

This thread has been around for a while.

Sorry about the tracking idler comment earlier I was not thinking.

Wonder however if you could have tracking idlers that jack up and down depending on which way the belt is going. Have not really thought about this just thought I would put it out there.

Obviously getting all idlers aligned is preferable.

I also came across a Semperit belt called ‘Autostable’ (name from memory) anyone got any comments on this. This belt self tracks from memory it uses a large transverse cord on the centre idler only.

Waloni I am interested in receiving some information on your product.

Gareth Blakey

blakeyg@conwag.com ■

Go and look at www.tru-trac.com. We have utilised these tracking idlers on large capacity overland coal conveyors with great success - return side just before tail pulley). They will work on reversible belts as well. ■

Is this a belt conveyor, screw conveyor, chain conveyor ?? ■

So far its a double-sided tripper belt conveyor.

I think you are talking about a shuttle conveyor. If so it should be reasonably symmetrical. Cleaners must be suitable for the reversing belt. It will have to be isolated from personnel so that you can immediately restart it in the opposite direction after you have stopped it. Accelerating & decelerating the shuttle involves providing capacity to contain incoming material flux which should not be temporarily halted while the shuttle reverses. To acheive this you can optionally make the belt wider than required by the normal operating condition or else provide overhead storage. The latter will also require that the shuttle has larger capacity than the feeding conveyor. Your choice depends on the frequency of stop starts & the ability of the receiver to accommodate the material surges.

If its not a shuttle then forget what I just said. ■

Hi DJolley

I designed a 115 meter long shuttle conveyor for a capacity of 6000 t/h. Beltwith 2000 mm beltspeed 2,9m/sec.

The project has been realised last Januar and is Located in the

Antwerp Harbour (Belgium)

The conveyor has two cooperating drives on both pulleys.

A special chute directs the product into the direction the shuttle conveyor is running at that specific moment.

For training we installed 2 special training idlersets in the return part of the belt. The loading point has stationairy impact idlers.

Can I help you with more detailed information ?

Kind regards

Johan Brands ■

Not to rain on you but:

I would strongly advise thee to investigate the US patent office as there are many patents both USA and international for shuttle conveyors for livestock feeding and you may end up with a barister/lawyer visiting you for patent theft if this is something you are serious about designing, doing, building and selling or manufacturing. ■

I fail to see the relevance of US litigation in the outer real world. If US lawyers wish to start chasing shuttle conveyors instead of ambulances it is their own silly prerogative.

Coca Cola took Sainsbury's to court because the copy was claimed to be too near the branded product. Result; by admitting Sainsbury's copy was so near, Coca Cola pushed Sainsbury's sales through the roof; & lost the case as well.

Brands, your chute sounds interesting. Don't forget to patent it. ■

To my knowledge there has not been any publication on the reversible double ended tripper.

CDI has designed and had installed many reversible double ended tripper conveyors for stockpile reclaiming of iron ore port operations in Brazil with our partner MGS (Voest Alpine). These are not shuttle conveyors.

There is no patent infringement to my knowledge.

Length, tonnage, speed and idler spacing can exacerbate the design. One key difficulty is how to control the take-up. Should you have a gravity or fixed? The dynamics of long conveyors, with large tonnage and higher speeds can cause the belt tension to collapse at the base of the tripper with the carry side belt then pushing or festooning under the tripper frame. THis festooning has ocurred during starting and stopping. It can ocurr with single ended trippers as well.

Given a typical TUP system, in one direction or the other, the conveyor must drive through the TUP for all operating conditions. This can lead to complications.

As has been noted, they often have drives on the end pulleys. Some trippers are collapsable when the product must travel over the tripper location. ■

Hi Daniel..

Don't know of any literature, but I suggest you make it reversible in the normal way, and simply fit garland idlers, (also in the normal way).

You don't really need any literature, and good alignment is the key to any reversible belt.

Regards

LSL Tekpro ■

Dear Mr. Daniel,

The specific nature of your application is not clear i.e. whether it is plain reversible conveyor or reversible shuttle conveyor or whether it is 30 m long or 300 m long etc.

As said earlier, such conveyor should be designed as per usual design for the conveyor. If it is a single drive then you have to design accordingly considering reversible running of the belt and consequent tensions in different situations. If it is a long reversible conveyor with multiple drive, then design accordingly for their reverse rotations, that means tensions are to be decided for forward running and reverse running cases and various components including take-up should be matching to the conveyor functional needs.

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 ■

Hi DJolley

Can't seem to find your message ■

Hey Daniel,

So you have been given the task of designing this conveyor.

I hope you are not still planing on reusing the offset idlers on the existing conveyor.

It may work putting the offset idlers in alternating directions and I have heard about it being done before.

The best way to make a conveyor reversable would be to align all of the idlers perfectly. Perfectly is a tall order and is impossible but high quality and ufortulantly costly procedures should be used for the instalation of the idlers to ensure that they are alinged as perfectly as possible.

Barring this your only hope would be to use a number of tracking idlers through the system.

Have Fun

blakeyg@conwag.com

Gareth ■

Daniel..

Just use the proven method...Garland idlers for reversable conveyors.

Forget training idlers.

Regards

LSL Tekpro ■

Graham,

I was not aware that Garland idlers are a proven method for reversable conveyors.

Can you please cite a reference or explain why this is so.

Best Regards,

Gareth ■

Gareth..

Thisis a copy of an e-mail I sent to Daniel on this subject

I hope it is of interest to you..

"Good morning Daniel..

I must admit that I have not come across a reversible conveyor with two trippers on it, but I see no reason why it can't work, if the pulleys are 100% aligned. (I have seen a non-reversible conveyor with three trippers on it though!)

The point is that you cannot train the belt in either direction.

If a pulley is not 100% aligned and if you train the belt by compensating by adjusting an adjacent pulley for example, then when you run in reverse, the belts behaviour will be different, and it will tend to de-train.

This would apply to the idlers as well.

You are stuck with the required alignment accuracy of the pulleys, but you don't have to be in the same boat with the idlers.

This is because you can use garland idlers, which are considerably more forgiving in practice.

It is for this reason that a lot of shiftable conveyors use the garland idlers. After shifting, the idlers are normally not that well aligned, but the belts still run OK.

My friend Graham Shortt has made a conveyor reversible, and replaced the fixed idlers with garland ones on brackets to facilitate this. This worked.

I made an existing belt reversible in Namakwaland and still used fixed idlers. I only just got away with it.

I will look for photos of such reversible installations. I know of one in Witbank here on a reversible yard belt with garland idlers. I believe there is also a reversible yard belt on fixed idlers in Phalaborwa. This is a fairly narrow belt which does not help, but I hear it works.

The other thing is therefore the belt which must be straight, well spliced, and as heavy as possible.

Hope this helps

Cheers

Graham"

LSL Tekpro ■

If the conveyor is not shiftable, you do the client a diservice using garland type idlers.

You throw away between 1 and 2% of your electric power with the added drag from the forward motion of the idler set. We have measured this in the oil sands in Canada.

What a pile of rubbish about not being able to operate the conveyor in both directions with standard idler frames.

Look at the kinematics of the garland. It inherently misaligns the idler wing rolls in the direction of belt motion. The only thing that steers the belt is its offset weight. Mr. Spriggs should know from years of experience that the center roll rocks forward which makes the connecting wing roll fleet angle induce misalignment.

Garlands are used to correct for exaggerated errors between adjacent idler frame positions that otherwise would introduce high and damaging stresses in idler frames and supports. They are not a belt alignment wonder. ■

Did you get out of bed on the wrong side this morning Larry?

Please read what I said properly, and maybe learn from the actual experiences of others like Graham Shortt like we do.

LSL Tekpro ■

Mr. Spriggs,

Exactly what message are you preaching: "The point is you cannot train the belt in either direction"? "Either direction" means this way or that way? A bit of a puzzle?

I noted a first principles reason why the application is not sound. I am eager to hear the counter arguement other than "he said".

This concept has be discussed in earlier forum dialog. Some have perfectly respectable experience with well aligned and non-tilted rigid idler frames.

I claim that conventional idlers can be superior to garland when correctly applied.

Certainly, poor installations beg to be corrected no matter the methods used. Just because someone makes an improvement, does not imply it is the only method.

Yes, we all stand to learn from others, and for those who are willing, they will become the wiser. ■

Mr. Spriggs,

I do agree that tracking idlers are a no no with reversible conveyors. ■

I found that if you train a belt to run in one direction, especially due to the idiosyncrasies of the belt and the variation of the load thereon, then you make things worse for operation in the reverse direction.

You therefore have to either align 100% and don't touch anything thereafter (do not train the belt) or better still, simply use garland idlers because they tend to align the belt well in practice even without training whatever the load.

That is what I was preaching ... Here endeth the lesson.

Regards

LSL Tekpro ■

Dear Mr. Spriggs,

Your description of aligning idlers indicates using idler forward tilt to adjust the belt tracking. Thus, when reversing the belt motion, the idler is in a backward tilt and mistracks the belt acting more like a garland. Certainly, this is a bad idea.

This is the old method. Modern belts do not use idler tilt to track the belt. When belts preferentially wet one belt bottom surface, such wind and rain, the tilt friction is lost and the belt goes in unpredictable paths.

Modern belt tracking is done by first accurately positioning the idlers normal (right angle) to the belt longitudinal axis in the vertical and plan view directions. Second, the mistracking is accomplished by altering the stringer and not the idler. This preserves the belt axis normal attitude while adjusting for vertical misalignment. No horizontal alignment is allowed.

I do note that you did not respond to "First Principles" lesson. ■

huh?? Since when have I said you can you reverse a belt on forward tilting idlers?? When I made the Namakwa conveyor reversable, I accurately packed the idler frames to be perpendicular to the belt. That's how I just got away with it. Next time I will use Graham Shortt's adapter brackets method to fit garlands for such a retro-fit.

LSL Tekpro ■

My last word,

Read your quote: "I found that if you train a belt to run in one direction, especially due to the idiosyncrasies of the belt and the variation of the load thereon, then you make things worse for operation in the reverse direction. "

A reader can conclude you tilt the rollers to train the belt in one direction. Most knowledgable readers agree with the quote and that its no good for bi-direction.

You also make my point if the belt is installed correctly its can be operated in both directions.

I think other forces are at work.

Gone elsewhere to a less perfect world. ■

My last word..

You have lost me completely ... so goodnight Larry.. sleep well

LSL Tekpro ■