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Thread: Belt Cover Cracking

  1. #1
    Steve Davis

    Steve Davis, B.Eng., P.Eng., CEng, CPEng, FIMechE, FIEAust

    Principal Advisor

    RioTinto

    RioTinto

    Belt Cover Cracking

    Hi all,
    Thought I would see if anyone else has experienced (and has a potential solution for) the issue of very fine cracks appearing in the covers of conventional troughing belts carrying alumina. Alumina can be up to 60 degC max but is usually less than this, around 40 degC. Belts are outside, but covered. Temperature between perhaps 10 and 40 degC ambient.

    The cracks appear fairly soon after installation and don't seem to get worse, maintaining a pace with cover wear.

    Ultra fines appear to get trapped in the cracks and polish the surface of the idler rolls. The fines are released when the belt passes around pulleys and the cracks open creating dust.

    Thanks for any comments.

  2. #2
    Hi Steve

    Cover cracking is typically from excessive heat but can also be caused by UV rays. Even under cover it is not 100% protected.

    Questions that can be asked are:
    1- Was the correct cover compound selected for the application?
    2 - How was the belt stored prior to installation? Storing outdoors and not wrapped can start the process early.
    3 - What are the belt tensions? Higher tensions can speed up the process.

    Good luck in your search for answers.

    All the best
    Gary
    Gary Blenkhorn
    President - Bulk Handling Technology Inc.
    gblenkhorn@bulkht.ca
    http://www.bulkht.ca

    Offering Conveyor Design Services, DEM Flow Simulation Services, Conveyor Transfer Design Services, SolidWorks Design Services for equipment layouts and Software for the Bulk Material Industry.

  3. #3
    Steve Davis

    Steve Davis, B.Eng., P.Eng., CEng, CPEng, FIMechE, FIEAust

    Principal Advisor

    RioTinto

    RioTinto

    Cover Cracking

    Hi Gary,
    Thanks for the guidance.

    Temperature is a possible concern for the first belts in this system but it is normally controlled and the alumina would cool by the time it travels the full system.

    UV is a possibility, but the identical length and exposure bauxite belts are fine. My experience of UV cracking is a dry brittle appearance and deeper more widely spread cracks than these, but I agree these could be related.

    Belt cover selection is likely the issue, and I suspect this could be the cause. The original belts were replaced with "equivalent" lower cost belts. As is often the case the history is vague.

    Will keep digging.

    Regards

  4. cover up..

    Hello Steve,

    I got it correctly that the belts in question are these on the alumina side and not those on the bauxite side of the process?
    Now, Al is chemically very reactive, so that the material might alreday influence the surface of the belt. Characteristically, this should then happen only to the carrying side of the belt. If ozone or UV rays are the issue, the effect should be somehow spread further around rthe full belt surface.
    As the cracks (transversal ones only, or also longitudinal cracks?) dont grow in depth, a force or pulley diameter cause seems not so likely.
    Regards
    R.

  5. #5
    Steve Davis

    Steve Davis, B.Eng., P.Eng., CEng, CPEng, FIMechE, FIEAust

    Principal Advisor

    RioTinto

    RioTinto

    Cracked belts

    Hi Roland,
    You are correct, just alumina.
    The cracking is only on carry side, and I believe it to be due to either temperature, which should be in acceptable limits at below 50C, or some form of reaction between the rubber and alumina.
    The conveyor design, pulley sizes, tensions etc. maintenance and tracking are all good so I doubt it is this.

    Has anyone else seen a similar effect with alumina, and is there a cover rubber that is more resistant to the effect?

  6. Quote Originally Posted by SteveDavis View Post
    Hi Roland,
    You are correct, just alumina.
    The cracking is only on carry side, and I believe it to be due to either temperature, which should be in acceptable limits at below 50C, or some form of reaction between the rubber and alumina.
    The conveyor design, pulley sizes, tensions etc. maintenance and tracking are all good so I doubt it is this.

    Has anyone else seen a similar effect with alumina, and is there a cover rubber that is more resistant to the effect?
    Roland,

    Is the belt you are using EPT for temperature resistance ?
    We experience the same issues in alumina transfer here. Eventually the polishing of the carry rollers will shear them. Have you tried rumble rollers & air knives on bend pullies etc to remove fugitive dust as this does reduce dust.

    Jason
    Knowledge , is simply what is waiting to be discovered and used.

  7. #7
    Steve Davis

    Steve Davis, B.Eng., P.Eng., CEng, CPEng, FIMechE, FIEAust

    Principal Advisor

    RioTinto

    RioTinto

    Cracked Belts

    Hi Jason,
    Are you at QAL?
    Can I put you in touch with the operation that has these issues?
    You may be able to pool experiences.
    Thanks Steve

  8. Quote Originally Posted by SteveDavis View Post
    Hi Jason,
    Are you at QAL?
    Can I put you in touch with the operation that has these issues?
    You may be able to pool experiences.
    Thanks Steve
    Steve,

    No issues here, drop me your E mail address & we will go from there.
    Send to:
    gibbsj@qal.com.au

    Jason
    Knowledge , is simply what is waiting to be discovered and used.

  9. #9

    Carry cover cracking

    To Roland’s point, Alumina is very reactive to belt covers. In addition to potential negative affects from heat, Alumina creates a drying affect. It draws the plasticizers out of the rubber compound. Unless the compound is formulated to resist durometer creep, cracking will continue until the remainder of the covers begin to lose adhesions and break away from the carcass. Hope this is helpful.
    Buddy Wilson
    General Manager - WV/VA Operations
    Fenner Dunlop ECS

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