In regard to your belt problem, first you need to install training idlers to help the belt track properly.

Second you need to survey the belt installation to make sure the drive units and tail pulleys are centered.

Third you need to make sure the belt splices-if they are mechanical splices are square-meaning they are not slightly off at an angle.

Fouth, you need to make sure your splices are not being stretched by the belt take up pressure, if you use a hydraulic take up to maintain tension, but most of all you need to make sure the troughing and return idlers are straight on and not causing the belt to track off and tear in to the steel work, even if they are a little off they will cause damage especially when loaded, also check the tail pulley and head and drive pulleys in regard to their general condition-meaning pulley lagging and bearings-if you have a bad tail pulley bearing or lagging it will create a lot of drag and it will cause problems.

I also can not emphasise this enough- make sure you train the conveyor belt from the tail pulley to the head pulley so it tracks properly!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

And finally you should make sure your conveyor belt is not stretched out as this will also create tracking/alignment problems that can not be fixed with out replacing the conveyor belt.

lzaharis ■

Hello Michele,

Please mention the belt width, troughing angle, capacity and center to center distance of the conveyor. It seems you are referring to some short conveyor.

The above information will help to narrow down the possible reasons of the lateral movement.

Regards,

Ishwar G Mulani.

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

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

You need to separate the operating and construction variables that cause transverse shifting. The belt can shift from internal construction anomolies, varying forces during running operation, such as noted by lzaharis, or by external forces such as settlement, wind, moisture, sun thermal expansion, variations in load crossection and its placement, to name a few.

Conveyor Dynamics, Inc. (CDI) developed and lateral measurement device using digital encoders and a roller wand assembly.

We placed wands on both sides of the overland belts, during commissioning, in a low tension zone. The low tension zone amplifies tranverse motion due to construction errors.

The encoder signal can resolve to about a 0.5 millimeter of belt lateral displacement. The encoder output is digitally recorded, as the belt is rotated, for two or more revolutions.

The signal can show many types of construction defects such as dog-leg splices, cord placement errors in steel cable belt, errors in belt construction from tension member pretensioning in the factory, and installing the belt in reverse direction to its manufacturing.

This procedure allows you to separate construction variables from operating variables.

I am sure others have added points to make.

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Aded point:

Belts can have internal damage from operation that may or may not be visible that weaken the elasticity balance across the width. This can come from impact damage to one side, from tracking errors that yields the tensile member on one side, usually at the splice, and from geometric asymmetric anomolies produced and the factory.

LKN ■

mikycampo,

If I understand your question correctly, you have indicated that the belt mistraining is only at, or near, the splice (joint, junction).

Normally, a belt will mistrain there if the splice is crooked or if there is a bow in one of the belt sections. There are other possibilities, but these two are the most common.

To determine if which is most likely, you can do a centerline through the splice area - taking measurements approximately 20 feet before and after the splice. Also, do a centerline just in the splice area; one from the mid-point of the splice to approximately 20 feet in front of the splice; and one from the center of the splice to approximately 20 feet behind the splice.

If the splice is centered on the overall centerline, everything is straight - and you have to look for another cause of the problem. If the splice is centered with either the leading belt section or the trailing section, the splice is likely straight, and a section of the belt is probably bowed.

A quick way to come up with the same information is to watch the belt as it moves. If the belt moves to one side and then back as the splice passes any given point, there is a problem in that area. To determine if the problem is with the splice or with one of the belt ends, watch the movement. If the splice is centered on the movement it is probably a poor spliced. That is the belt will start to move approximately 20 to 30 feet before the splice and be back on track approximately 20-30 feet after the sploice has passed. If the belt moves over approximately 40 feet before the splice and moves back 20 feet after the splice, the lead belt end is probably bowed. The same applies for a bowed trailing end (i.e. starts to move approximately 20 feet before the splice and moves back 40 feet after tyhe splice has passed.

Hope this helps. ■

Dear Michele,

My answer may be too late for you now, but nevertheless I would like to submit you enclosed an excerpt of a book written by my company MARTIN ENGINEERING, explaning in detail the problems, reasons and solutions concerning belt mistracking.

with best regards

Uwe Schneider

MARTIN ENGINEERING GmbH

Attachments

pages 1-5 of ch15 - keeping the belt on track (ZIP)

■

Hi Michele,

Belt wandering should be taken up very seriously and with an immediate effect.

Based on my knowledge wandering can happen because of

- poor belt splicing, (i think the entire forum commented)

- side roller supports not dimensionally erected (or damaged) and alligned

- off-centered feeding at the inlet on the belt and one side segrrated lumps

- deposition of foreign paritcles (or product) on the guide rollers

- uneven roller wear (if abrasive particles)

In addition, even after so many suggestions if your problem still persists then I would request you to write to me and send in the installation photographs at

amresh@gmx.net

Regards,

Amresh Mehta ■

Dear Mr.Mikycampo,

Belt moves laterally due to following reasons:

1. Off-center loading.

2.Improper chute design.

3.Out of roundness of idler.

4.Erection of idler are not proper.

Regards.

A.Banerjee ■

Ciao Michele,

As I understand it the belt is used to extract waste created in a tunnell boring operation. This generally implies a moving (either extending or retracting) conveyor tail end with many splices (joints) required due to the varying length of conveyor.

You indicate that the lateral wander is between two splices - on this basis I would suggest that Dave Miller's method would be best to confirm whether the splice is correctly made and to establish whether there exists 'bowing' in the belt.

However, take good note of all the suggestions and recommendations as maintaining good tracking will significantly improve belt operating efficiency.

Regarding the use of 'self aligning' idlers - these are a remedy and do not treat the root cause. Apply the recommendations given and the belt will run centrally without the need for 'self aligning idlers'

Regards,

Adriano (Adi) Frittella ■