Sounds like your belt has a concave vertical curve. You need to lower the belt tension by:

a) lower peak motor torque during startup cycle such as by adding a fluid coupling or voltage resistant starter

b) increase the apparent or physical drive belt over pulley wrap angle that will allow a reduction in take-up tension such as ceramic lagging or increase pulley wrap with a snub or second drive.

c) add drive inertia to retard peak drive energy and belt tension - not a good choice for this small system

d) select a motor with a lower pullout torque

I believe item 1 is a good bet ■

To give you good advise you need to tell us a lot more about the installation such as trough angle of the idlers, is the system skirted and how, is there a vertical curve etc. Tracking problems with a conveyor belt can be caused by many things.

Col Benjamin ■

Guess I got my orientation fuzzed up.

Belt mistracking can be caused by either an external alignment error or from construction anomolies within the belt. Try to isolate the cause.

It would be helpful to know when this effect occurs. Is the belt loaded? Since it occurs during starting, what are the differences in product loading or belt's 360 degree position/orientation?

Not all self-aligning idler rolls help tracking until the belt edge hits the side guide roller. Some cause mis-aligment till the side guide rolls are engaged. You need to study the alignment mechanism.

Try marking the point the belt travels to the side. See if it often repeats at the same location.

Moisture and temperature can play a part in tracking influence along with idler alignment and features such as forward tilt. If one side is wetted, then the idler steering friction is altered.

There are many components that can cause misalignment. Colin named two. As he said you need to provide more details. ■

jnaneswar,

As indicated by Colin and Larry, there are too many variables to provide answers with the information you have provided.

As this is a "major" problem for you, I suggest that you ask the belt manufacturer and conveyor installer/designer to do an evaluation for you. Alternatively, there are a number of consulting experts available to you.

The use of rigid guide rollers help to contain the belt, but are not a good long-term answer, as they can damage the belt edges and contribute to the mistracking problem.

You should be looking at basic system alignment, system design, belt construction, operating conditions, and environmental conditions.

Regards, ■

From the information you have given the folowing needs to be checked;

a) The skirt system. Please make sure that the rubber skirt does not contact the belt but is maybe 1-2mm above the belt. If material is getting trapped underneath the skirts, the design of the skirting system could be an issue. Skirt systems that contact the belt can create a different pressure on one side of the belt relative to the other and this can cause atracking issue such as you have described.

b) The 700mm belt. Was it slit from a wider width and is it possible the belt is thicker on one side relative to the other.

c) Make sure all the idlers and the pulleys are square to the belt.

d) I am presuming that the tracking off to one side occurs under no load. If it is occuring as the belt is being loaded then centralise the loading and make sure it is flowing onto the belt in the direction of belt travel.

Given you have installed a 700mm belt onto a 650mm system I expect the most logical cause will be to do with the skirting system and the need to ensure that there is not a differetial contact pressure. Idler, pulley alignment second and the belt third.

Hope this helps

Col Benjamin ■

Jnaneswar

Do you know the specification of your belting?

The belt needs to be designed for proper troughability. Too heavy a belt on a narrow conveyor can cause the problems you are experiencing. As Dave Miller suggests have your belt supplier or a consultant analyse your system to determine if the existing belt is suited and if not they can give you a correct specification.

We once experienced similar problems with a steel cord belt that had cross cables for rip protection and would not allow the belt to trough properly and we could never track it. We replaced the belt with a nylon/polyester ply belt and the tracking problems immediately went away.

I get the feeling that from what you are describing that this may very well be your problem.

Good luck,

Gary Blenkhorn ■