Have you checked the whole conveyor system particularly in return side and impact area condition?

Rgds,

Endri ■

The photographs are interesting indeed.

They would suggest that the belt was reeved on the ground. This could typically happen if the belt was removed from the conveyor for some reason when a reel was not available or there was no device available for reeving and then re-installed.

This is possible on second hand belting or factory rejects that have found their way back into the market. The later is a distinct possibility since the manufacturers stamps appear to have been removed and replaced with inserts. ■

Dear sganesh,

The photos show the pulleys are too small a diameter for the number of plies/cover thicknesses and also appear to be over-tensioned.

It would appear that somewhere the belt is being stressed around too tight a radius bend which is de-laminating the belt and cracking the top cover crosswidth wise. This does not look like impact damage. It could be the belt was old prior to being fitted and has hardened above the Shore grading, or it may be the incorrect belt (chemical composition) was supplied.

Check your pulleys for diameter. the smallest diameter pulley should be at least 850mm @80% tension for this belt type. Please check with your belt supplier for the correct diameters and please give ALL the parameters of the conveyor as they can do a realistic analysis and make a detailed comment for you. ■

Dear sganesh,

Looks like the belt was pulled a little too far on the press in the factory after vulcanising and before the next pressing.

This gives a very short section (which ends up as a line across the belt) where it is not properly vulcanised and gives failure as per your photographs.

Regards

LSL Tekpro ■

I tend to agree with some of the responses. Could be a pulley issue. Find that sometimes OEMs, best designs are trumped by budget restraints, therefore going small on the pulleys. Also could be a cold zone area as previosly noted. However this is usually repaired prior to leaving the factory.

There are non destructive testing for entire length of belt, but is costly & time consuming with X-Ray. ■

Taking a second look at the photographs (I did not scroll down last time) I need to add to the conclusion previously drawn.

You would get similar damage if a nip angle when round a pulley however in most cases the nip angle creates a spiral on the pulley and diagonal damage on the belt. This rules out the nip angle but does suggest that the belt was folded or incorrectly clamped on the first example 5F 1.55.

The second example appears to be a factory splice where the calendaring has not been completed correctly. Factory splices have no external distinguishing marks. ■

The only way to know for sure is X-ray of entire belt. The right service or equipment can detect as much as a finger print inside a belt. This is time consuming & expensive. What I see is similar to the prior comment, a fabric splice in the calendaring process. Hard to detect unless is breaks loose. The widthwise crack shows up when the fabric splice comes loose/fails. Saw it at a steel mill before. they wanted to know why it wasn't detected previosly and called it a factory splice. Well, these are not easily detected untill the failure ocurs. Then you go back to the manufacturer. ■

Dear Sganesh,

Ply separation originates from poor quality control during manufacture. This can be due to delinquent manufacturers or night shift manufacture where a hot chocolate and warm bench replace the overseeing of manufacture. Once the belt is rolled the only chance to detect such a problem is when it is being pulled onto the conveyor but that is extremely unlikely. The defect usually only makes itself known when combined with poor conveyor design or poor installation. It shows up when convex radii is too tight, transitions are incorrect or more often when the conveyor comprises of a mixture of inline and off set idlers e.g. at a mass meter. That said the separation can be noticed days or weeks before catastrophic failure. So who is to blame for your problem? Well I'm afraid just about everyone is from the manufacturer to the belts man responsible for maintaining the conveyor. ■

Though the evidence points to poor quality belting as the cause of your problems it is advisable to do a design audit of each conveyor to ensure that it is properly designed particularly with regard to:

- Proper transition distances

- Radius of curvature constraints ensuring

- at convex curves:

- belt edges are not overstressed

- Belt middle is not relaxed or buckled

- visa versa at concave curves

- Pulleys diameters are properly sized

- In the case of successive drive pulleys that they have sufficient distance between to allow relaxation of the rubber, about one second of travel distance

- etc

Joe Dos Santos ■