Marks on the belt

Posted in: , on 23. Oct. 2006 - 14:40

I have recently come across a new rubber belt having some defects on the surface. Photo is attached. If any one of you have come across such defect before, I'll appreciate to understand from you, what might be the possible causes and what corrective action is suggested.



Re: Marks On The Belt

Posted on 23. Oct. 2006 - 01:00

The photo did not get attached. Hence trying again.




photo3 (JPG)

Conveyor Belt Condition

Posted on 23. Oct. 2006 - 04:35

Originally posted by sdas

The photo did not get attached. Hence trying again.




since you have stated that it is a new rubber belt but not

whether it is on the carry or return side or whether it is in service

It looks exactly like a conveyor belt that was not cured properly

when it was woven/glued/pressed/ assembled at the "master

slitter" assuming that the master slitter was where it was


Re: Marks On The Belt

Posted on 23. Oct. 2006 - 04:43

Is this in the top cover or bottom cover?

First thought is that the very surface of the cover is unable to contract after becoming stretched as it passes around the drums. Could be that the compound on the surface is a little different than that underneath, or its coming into contact with something that is prematurely aging the very top surface of the belt. I've seen it often with cracks in the very top layer of the cover, normally with heat resistant belt, but this seems like the exact opposite, where the top part has actually stretched more and is unable to return to it's normal shape.

Is the belt, by any chance, a PVC solid woven belt with a synthetic rubber cover, mostly found in underground mining?

How thick are the covers?

Re: Marks On The Belt

Posted on 23. Oct. 2006 - 06:05

Dear Shri Das,

I am not clear from the query whether you are seeing the surface marks on a brand new belt or on the belt after some use in plant.

If such marks are on brand new belt, then it is a manufacturing defect.

However, if such marks have appeared after some use of belt then better you inform about the application main features, such as material being handled, lump size, temperature, belt speed, width, belt cover grade, type of carcass. This information will help the respondents to look for some reason and possibly to make some suggestions.


Ishwar G Mulani.

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

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email :

Tel.: 0091 (0)20 25882916

Re: Marks On The Belt

Posted on 24. Oct. 2006 - 01:41

Do these cracks appear to follow a steel cord pattern? I anticipate they are on the bottom cover. I have seen many belts with similar cracks. There are a range of conditions that can create such a pattern.

The cracks typically are not deep and will not grow much deeper with age.

There is no corrective action if it is a poor cure or is ozone induced short of replacement.

If they are longitudinal, as I guess, they are tensile failures in the tranverse direction or across the width. If so, then you must ask, how can a tensile failure occur across the width. Shrinkage, or impairment of the rubber such as an ozone or surface hardening action during curing.

If the cracks are on the bottom cover, try to bend the belt to see the depth. I expect the depth is no more than 1.5 mm. Observe the cracks in the region of the wing-to-center roll bend zone. If the crack depth is no greater in this area, then you should have no worries for the moment.

All this is all conjecture, since you provide little information on the details, which are many.

Lawrence Nordell Conveyor Dynamics, Inc. website, email & phone contacts: phone: USA 360-671-2200 fax: USA 360-671-8450

Re: Marks On The Belt

Posted on 24. Oct. 2006 - 01:47

If the cracks are longitudinal, observe the cracks seem to be uniform across the width even out to the edge where there is little stress from any working action.

Again, no data to make a more definitive observation. I could be off by miles.

Lawrence Nordell Conveyor Dynamics, Inc. website, email & phone contacts: phone: USA 360-671-2200 fax: USA 360-671-8450

The Possible Reasons On The Manufacturing Procedure

Posted on 24. Oct. 2006 - 07:44

The reason on the manufacturing process may be as follows:

1> There may be cross reinforce steel breaker, and the breaker is not very good handled when processing with the belt.

2> The rubber are not vulcanized perfectly(may becasue the vulcanizing time is not enough long), and when passing the drum, the pleats are formed out.

3> The raw material is not good,reclaimed rubber compound is too much in the total mixing of rubber.

The reasons above is the possible resons in the manufacturing procudure.

Best regards,


Sales Director



Qingdao Huaxia Rubber Industry Co,.Ltd

Zhengyang Road Chengyang District

Qingdao City China




Luke Sales Director Qingdao Mingtai Rubber Products Co.,Ltd web: [url][/url] linkedin:[url][/url]

Cover Crazing.

Posted on 30. Oct. 2006 - 11:53

Hi SD,

I have come across similar defects from manufacturing and service related operations (but will not commit an answer). Would you advise the belt specifications, manufacturing method and age (date of manufacture and date of service)?

These details will assist our learned friends in identifying probable cause and provide some answers and possible rectifications.

Kind regards,

Peter Thorpe

Some More Information.

Posted on 30. Oct. 2006 - 12:36

Thanks a lot for all of your answers.

The belt is a new one and yet to be installed in the line.

The problem is only on the bottom cover.

It is a EP 630/4 belt.

The scratch marks comes only when the belt is bent and when straight, it almost goes off.

Top cover does not have any problem.

Bottom cover thickness is 1.6 mm.

If any one can tell me why this has happened & how this can be over come, it will be highly benifical to us.



(not verified)

Re: Marks On The Belt

Posted on 7. Dec. 2006 - 02:11

Some belt manufacturers cure the belt using siliconised paper, usually on the bottom side of the belt. The non-uniform shrinkage of such paper are known to leave crack-like impressions on the cover after curing. Such impressions are completely harmless and disappear within hours of belt operation.

However, in my experience, such impressions are random in nature and unlike the marks photographed, which are rather uniform.

If these marks are transverse, I cannot think of a more likely answer than overcuring (localised or otherwise). What is the rubber hardness in the affected zone ? Is it significantly higher than the top cover hardness ?


Re: Marks On The Belt

Posted on 12. Dec. 2006 - 04:33

Hi SD,

Could you measure the depth of these marks? (you have mentioned a pulley cover thickness of 1.6mm) as well as providing the above requested hardness within the areas of interest and hardness of the general belting.

Kind regards,

Re: Marks On The Belt

Posted on 17. Jul. 2009 - 05:34

deffective belt send it back to the suppliers the bonding between the carcass is not right most probbably the carcass was not treated before it was molded with the rubber it will not show on the top cover because of the rubber thikness difference

Belt Cracks

Posted on 18. Jul. 2009 - 08:22

Dear Sdas,

Already asked your belt furnisher?

If yes, could you please forward the answer to this forum?



Alexandre Costa Calijorne Caltra Projetos & Consultoria Ltda [url][/url] [email][/email] phone/fax: +55 31 2555-9097

Re: Marks On The Belt

Posted on 18. Jul. 2009 - 10:28

the original post is almost 3 years old I am sure he has it corrected by now.

thread closed.

Gary Blenkhorn
President - Bulk Handlng Technology Inc.
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