In reality there may be a minor change in power requirements because the indentation resistance may be effected. This may be a slight increase if the cover grade is decreased and more if the new covers are high temperature rated while the existing are not. Having noted this, I do note that CEMA does not recognize any such diferences.

If this is a long overland conveyor with little or no net elevation and marginal installed power there may be slight cause for concern. If it is an elevating, sloped conveyor with adequate connected power there is no cause for concern.

There may be other issues of concern related to the elastic and permanent stretch properties of the belt, belt bending stiffness and belt weight. This effects adequacy of take-up travel, transition distances, pulley diameters. There may be other considerations that don't come to mind right now.

Joseph A. Dos Santos, PE ■

Hello Shane,

Changing a belt from that designed for the system to another style can create unexpected problems, Mr. Dos Santos has indicated. Conversely, since you are considering a change, I assume that you have experienced problems with the original belt choice.

You should ensure that you are dealing with the technical department of a reputable belt manufacturer before making changes. It may also be of benefit to contact Mr. Lawrence Nordell?s company, as they have apparently done studies on power consumption studies on various belt systems. If you do contact Conveyor Dynamics (www.conveyor-dynamics.com), it will be necessary to give them full belt and conveyor specifications.

As far as power consumption is concerned, the belt construction, cover material, and total belt weight will all have an impact. Using standard formulae for calculating power requirements will help ? but these tend to be somewhat generic in nature. Therefore, the calculations can be off when specialty belts are concerned.

Good luck with your research and with your replacement belt. ■

Hello Shane,

Firstly, what is the length of the belt conveyor? If the belt conveyor is short, the terminal resistances form substantial proportion, which is of fixed nature. Following points are more crucial than effect on power rating, (often you might have margin in the existing drive unit):

1) Suitability of tension rating (belt joint rating). Three ply joint efficiency will be less compared to 5 ply joint efficiency.

2) Existing pulleys diameter should be adequate.

3) Impact absorption capability of carcass should be adequate (if you are dealing with lumpy material)

4) Effect on required concave radius if new belt happens to be of lighter in weight.

5) Other issues as mentioned by earlier respondents.

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 ■

Shane

Apart from belt weight, belt flexure and rolling friction will affect power demand - these are of significance for long conveyors.

Increase of cover thickness will have bearing on your power. Suggest to consider low friction bottom cover if the conveyor is long and power is of concern.

Best Regards

Janusz Wala ■

Dear shane

please indicate following data before doing any analyses

1.0 Existing belt tension rating

2.0 New belt tension rating

3.0 Existing belt Wieght wight/m

4.0 New belt weight/m

5.0 Existing belt Idler roller diameter

6.0 Available Margin in existing Motor rating

In case of motor margin is not available then pl donot go for higher bottom cover Thickness

A R SINGH ■

Shane,

The answer is yes, but most of the programmes we have to design conveyors with will not give you an accurate answer. It is about belt flexure and rubber distortion especially over the idlers. The major impact will be any change in belt weight unless the belt is quite long.

Col Benjamin

Gulf Conveyor Systems ■

Your query and the responses demonstrates an awareness in the industry that there will likely be differences in demand power with differences in belt construction, and that fabric belts are notorious for consuming more power than steel cord belts.

The answer to your question is somewhat complex. First, fabric belt rolling efficiency has not been of significant academic interest because it is usually applied to belts with lower tension ratings, wrt steel cord, implying shorter lengths where the power differences tend to be smaller. Note, historic methods used to calculate power are usually very conservative.

Second, the belts fabric stiffness or resistance to bending deformation and flexural hysteresis during deformation must be measurable when comparing the two belts of interest.

Third thicker belt covers increase the bending stiffness which reduces flexural hysteresis but also increases the hysteretic loss due to idler indention strain.

Fourth, and probably more important, as an overall indicator, is the specification of the belt's cover compound viscoelastic strain hysteresis index evaluated with the fabric and skim coat viscoelastic strain hysteresis indexes. These indexes can be measured in a laboratory and ranked.

Fifth, the operating temperature spectrum may favor one compound over others. You must evaluate the benefits and limitations associated with minimum temperature (most often) that sets belt strength and power verses the operating range and frequency of temperatures which will define the operating costs.

This last point is now beginning to define, to owners and operators, the true cost comparisons of belting and is directing the future of belt specifications.

If all rankings tend to favor one or more new manufacturers over your present application then it is safe to assume you will be better off with the new belt. Ask the manufacturer for the cover, skim coat and fabric viscoelastic properties at a fixed strain with your temperature spectrum. As a simple approximator, ask for the viscoelastic tan delta value at the minimum temperature. Lowest value wins.

Ranking worst case conditions answers your question. What about cost of ownership? What if one belt is cheaper than the others but has a significant overall cost penalty for ownership?

The newest sixth edition of CEMA has a new method that claims to make this analysis. CDI has made initial assessments of this technique and find they likely under estimate true belt power. However, it may portend the near term public access to viscoelastic power analysis. ■