Originally Posted by jishnubhel

In one of our projects, we have a conveyor of L=523m and H=44.7m. We are facing belt run out/sway near the take up pulley. We have tried adjusting the counter weights and checking the alignment many times, but are not able to arrest the sway. Sometimes belt is moving wayward in one direction, sometimes in the other. Is it technically OK to use guide rollers on the edge of take up pulley frame (sketch attached) inorder to arrest the belt sway? Yes there are chance of rubbing of the edges of belt, but in case if I keep contact with one side belt in contact with the roller, the roller will also be free to rotate and hence rubbing chances can be reduced.Attachment 44052

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Not a good idea period as the belt could wander far enough that the belt

will become wedged and either trip a circuit breaker or tear apart.

Your belt issues could be occurring for a number of reasons.

1. OLD stretched belt

a. new belt may be needed or section cut out and new splice made.

2 lousy splicing job

a.splice may be separating if it is mechanical

b. vulcanized splice may be stretching at joints

3.HOUSEKEEPING - not enough shoveling/vacuuming of fines under return path of idlers to the tail pulley

4.Tail pulley plugged with dust

5. V plow at tail pulley flipped upside down-it does happen!!!

6. belt in dire need of training

7. geometry of entire belt flight may be off and need to be centered again

a. wandering pulleys sliding to one side or the other just a little bit affecting belt travel.

8. bad transition idlers with frozen idlers affecting belt travel due to drag

you need to tell us more if you want more help

Help us, to help us help you!!!!!

The lid of the basket holding this King Cobra must be tied down and fixed

as it will cause a lot of pain and down time.

The fix may be as simple as watching the belt pulling the emergency stop after this section passes through

IF and only IF one section of belt wanders. Other wise start at number 1.

Chances are you are either overloading the belt or its past its useful life. ■

Going back and forth is a very strong indication of a poor belt splice. If it was in the structure it would move over and stay. Watch for a splice just after the wandering starts then after the splice goes by it should start to go the other way. The rollers are a bandaid for the real problem and not solving the problem. Analyse the system and the belt completely before you put any rollers on. If you do put the rollers on you can guarantee your belt will be much narrower in a year or so.

My money is on No. 2. Leon. ■

As suggested by others, I propose you fix the actual issue [and again, if you provide the forum with more details, it may be able to provide some additional assistance with this].

I propose it is not appropriate to attach "guide rollers" to the take up as this will reduce the take up's ability to freely travel.

Regards,

Lyle ■

Originally Posted by jishnubhel

In one of our projects, we have a conveyor of L=523m and H=44.7m. We are facing belt run out/sway near the take up pulley. We have tried adjusting the counter weights and checking the alignment many times, but are not able to arrest the sway. Sometimes belt is moving wayward in one direction, sometimes in the other. Is it technically OK to use guide rollers on the edge of take up pulley frame (sketch attached) inorder to arrest the belt sway? Yes there are chance of rubbing of the edges of belt, but in case if I keep contact with one side belt in contact with the roller, the roller will also be free to rotate and hence rubbing chances can be reduced.Attachment 44052

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This response mainly deals with steel cord construction. The principle is the same for fabric.

Best approach is to find source. Mark the belt when it moves left then reverses to the right. See if the same section has repeat behavior. Time it. If it repeats between marks, which we believe will be the case, there is an error in belt construction either in parent belt or at splice.

The belt can have a number of these errors or alignment anomalies. Some may be small enough to be acceptable vs. getting new belt or new belt sections. This depends on the warranty owner agreed to with supplier. Better belt specifications have teeth that protect client and gives client negotiating power.

There are many ways the belt tracking can occur. One is the direction of travel in factory construction. If installer did not observe or supplier did not mark direction of travel at factory, then the balance of cord/fabric tensions may force change in tracking. When we first installed Channar 20 km overland, with steel cord construction, we observed/measured (using digital encoders) 5-6 belt sections 600 m/roll that tracked over 150 mm off center. The errors where measured to be repeatable to within a few mm over each 20 km lengths on each of two belts. We had to cut the 600 m lengths and reverse them. Once done belt tracked.

Another tracking anomaly I have witnessed: belts with internal construction errors. X-Ray verified construction cord crossing or wandering within the belt that leads to tracking errors. Even though the belt construction specification set the tracking limit and the supplier exceeded the limit he was forgiven by the owner since it did not hit steel.

If the error occurs along the length in a given section, this indicates the conveyor supported earth has moved/settled or heaved. ■

Not knowing conveyor length, I add the following to the above posting. It is possible the ore can cause belt side travel and eventually results in take-up tracking error. This is a bit more remote, but, with knowledge of tracking pattern can be deduced and observed in ore on belt favors flow offcenter that changes with feed. This will not likely repeat in an accurate manner. ■

Hello,

Firstly see that bend pulleys and take-up pulley shafts are parallel and at right angle to belt travel. Mostly this should avoid the misalignment problem.

The use of 2-roll return idlers in place of flat return idlers near take-up can also improve the alignment. Any misalignment running on such 2-roll idlers (that is in this zone) will create aligning force on the belt. See that the gap between 2 rolls should be bare minimum to avoid pinching of belt and such idler should not be very close to bend pulleys. It should follow the rule for transition distance.

Regards,

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 ■

Take a look on Foundation's book from Martin Engineering which include detailed description of belt tracking. ■

Dear Jishnubhel,

There is a very simple and inexpensive way to solve this problem permanently and it lies in how you designed your counterweight. If you detach the weight box from the pulley carriage and insert a a simple bridal arrangement such that you re-attach the weight centrally below the pulley carriage you have no need for guide rolls or anything as the counterweight is always acting centrally. I see this problem all the time and cannot understand why designers continually attach weight boxes as addendum's to the pulley frame and then try crude alignment devices to keep everything straight when all it takes is a simple arrangement that suspends the weight centrally and the potential for problems is eliminated.

Cheers

Colin Benjamin

Gulf Conveyor Systems Pty Ltd

www.conveyorsystemstechnology.com ■

Dear Colin,

Would you please show bridal arrangement in an sketch. ■

This reply box does not allow me to do a drawing but the concept is very simple, attach 2 wire ropes to the edge of the pulley cradle using U bolts and then have them come together centrally and from this central point attach the weight box

Cheers

Colin Benjamin ■

Hello Mr Collin;

Is there any other way of hanging the counter weight box under the carriage pulley,

besides the common one of having it attached to the bottom of the carriage pulley frame?

Kind Regards

Paul Chigwenya ■

Dear Roland,

I think this sketch doesn't guarantee that the counterweight will be positioned centrally, because ropes are divided and they can have different length. ■

Hi Roland,

Thanks for the sketch that I did not provide. Getting the rope lengths right is not that hard. You can achieve the same thing by making the a steel structure that allows the weight to be centrally mounted or you can have a centrally located rope that runs through a series of sheaves onto the remotely positioned counter weight. The key issue is apply the counter weight centrally and you eliminate the need for guide rails and eliminate or almost so the likelihood of the the take-up system being a source of poor belt tracking

Cheers all

Colin Benjamin

Gulf Conveyor Systems Pty Ltd

www.conveyorsystemstechnology.com ■

Dear Roland,

Of course I know this is sketch and I mean the idea. If it was a single rope (instead of one), the counterweight will be always in the middle.

Meanwhile many thanks from you to draw Mr. Colin idea so that we can discuss about it. ■

Hi Roland,

I have used the design and variations to this theme virtually all the time. In fact what has surprised me is why it has not been a universal approach and it is so logical and eliminates a potential maintenance issue as far as pulley alignment and maintenance of the guides

Cheers

Col ■

Hi Roland,

Normally we design the bridal as a simple equilateral triangle unless we have height or length restrictions. As for wind, have a few tonne suspended of a rope you need a mighty wind to create problems and I would suggest there would be more problems than a swaying counterweight to worry about. In such circumstances there is usually a lock down and such masses are fixed using tie down ropes. If you are concerned you can surround the weight box by structure or column constraints but in this instance they are not guide rails just constraints in case of wind. Build up from spillage etc. onto the weight box is not an issue

Cheers

Colin Benjamin ■