Dear Mr. Sonksen:

Without seeing the system, it is extremely difficult to give recommendations. Also, more information is required.

Is the conveyor a troughed system, or is it a flat belt feeder conveyor? Is the conveyor uni-directional, or does it run in both directions? Is the belt driven at the discharge end, on the return run, or is it tail driven? What are the enevironmental conditions (heat, dirt, wind, etc.)? How is the belt being loaded (in center, in-line, to one side, etc.)? What type of take-up system is used (gravity, pneumatic, screw, etc.)? How much take-up force is used? Is the conveyor aligned? Is the belt bowed?

Any of these can factors can through the belt tracking off.

From your description, it appears that the belt runs true when unloaded, but not when a load is applied. From this, the first two items that I would look at are loading geometry and belt tension.

Good luck in resolving it.

If you wish to discuss it in greater detail, feel free to contact me.

Regards, ■

Adding to the previous posting: Fabric belt may have a weft and warp bias error to the weave. As the belt tension is increased, the bias error alters the tracking trend that the installer used during initial empty belt startup. Further, if the belt does not have crowned pulleys, the errors in mfg. can induce changes in tracking as noted. In lighter belt construction, crowning is specified to aid in tracking.

Lawrence Nordell

President

Conveyor Dynamics, Inc.

Bellingham, WA, USA 98225

ph 360/671-2200

fx 360/671-8450

email: nordell@conveyor-dynamics.com ■

Additional items to check:

1. Is belt cupped? (curvature across face of belt) Cupping reduces contact between roller and belt and prevents rolling components from steering belt.

2. Does belt have camber? (banana like curve to belt) often confused with a crooked splice.

3. Loading conditions to check for are offcenter, segregated, or surge. ■

You state that "the smallest gravel or dirt (10-20mm) tracks the belt sideways". Are you saying that when the belt is loaded it mistracks but when there is no load the belt runs straight? ■

Dear Mr. Sonksen,

Earlier respondents have provided certain information / possibilities. Additionally, you can also check / try the following.

It is difficult to give specific solution based on the limited information.

1) Check the pulleys alignment i.e. their axes should be at right angles to the conveyor center line. Pulleys axes should be parallel to conveyor plane.

2) Idler position adjustment in vertical and horizontal plane, for alignment of belt.

3) Material loading needs to be at the center of belt.

4) Belt should be joined in such a manner that the belt is pressing the conveyor pulley uniformly i.e. proper joint.

Many technical publications of the belt suppliers specifically give few pages for belt misalignment and possible corrective action. You can try such remedies if you have such publications / leaflets from your supplier of the belt.

Regards,

Ishwar G Mulani.

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

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 5882916 ■

We believe our SG210/50 Sureguide Belt Centralising Return Pulley would solve your problem.

We can offer this unit at Euro 1560-00 ex factory

Please visit our websit to view the product.

www.waloni.com

Attachments

sureguide cutaway (JPG)

■

Dear Mr. Sonksen:

Hopefully you have already corrected the mistracking problem.

If not, I suggest that you have someone conduct a system study on the conveyor to evaluate all parameters. Typically, this can be done by a factory representative of the belt manufacturer or by an independent (consultancy firm or belt service company). Although most of the factors affecting belt tracking have been mentioned by the various posters, there are more. A study should uncover the root cause of the problem and allow your user to take corrective measures.

If you wish to tackle the problem on your own, there are a number of tracking method publications available from the belt manufacturers and industry trade groups.

Although I have not seen the conveyor in question, I suspect that the problem lies with one of the following:

[1] conveyor alignment problem

[2] loading zone problem

[3] belt problem [4] splice problem

[5] tension problem

[6] environment problem

If you have specifics on the conveyor, you can contact me directly by e-mail for assistance, or deal with anyone you have confidence in. Your first two steps, however, should be to evaluate the system yourself to look for obvious problems, and to have the belt manufacturer look at the system to get their input.

Regards, ■

ALthough others have commented on the loading zone and product placement, I would like to add a bit.

Look at the product flow stream leaving the discharge system. It may be that the discharge stream that impacts onto the conveyor has a horizontal transverse force vector ( transverse shifting force ).

If the product stream, viewed in plan within the transfer chute, is turning at an angle to the receiving belt, then the above comment is highly likely.

View the product stream in elevation, down the axis of the receiving belt, as it falls through the chute. If the stream appears to have a trajectory that does not fall in-line with the receiving belt, then I believe the product's impact is pushing the belt off its center.

The short nature of the conveyor will increase sensitivity the mal-tracking from many sources.

There are still many other conditions which many produce the mal tracking behavior. The afore-mentioned may be easily verified and reported back to stop further hunting expeditions.

LOL,

LKN ■

Sorry for this added point of clarification:

The product stream impacting onto the conveyor is the only point of interest. Product may take a varied path like a careening billard ball within the chute. Its only the thrust, at the point of impact, that counts.

LKN ■

Just gotta add another comment.

If my comment proves to be correct, then the fix requires the flow stream to be directed into alignment with the receiving belt before product impacts.

I'll say no more.

LKN ■

A 2100 mm wide belt would probably have transverse fabric joints. If these joints are not balanced w.r.t. the centerline then you could have problems of tracking. Any specification for conveyor belts stipulate this parameter and one needs to be certain that the belt supplier adopted the specified constraints.

Good luck. ■