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Thread: Hot Splicing Problem

  1. #1
    Gary Blenkhorn
    Bulk Handling Technology Inc.

    Professional Experience 40 Years / 5 Month Gary Blenkhorn has 40 Years and 5 Month professional experience

    Discussions 102 Gary Blenkhorn acceded to 102 discussions, Publications 0 Gary Blenkhorn Blenkhorn released 0 publications

    Know-How Design (317) Gary Blenkhorn used this tag 317 times, Belt Conveyors (135) Gary Blenkhorn used this tag 135 times, Software (56) Gary Blenkhorn used this tag 56 times

    Hot Splicing Problem

    We are experiencing top cover vulcanized splicing problems with a plybelt.

    The belt is a 2 ply 660 fabric with 3/16x3/32 covers and has 8 hot vulcanized splices and 5 of these have a deteriorating top cover after only 4 months. The conveyor is a 42" belt, 2300 feet c/c, 64 foot lift, 1500 TPH of rock salt in an underground mine, ambient temperature is 68-70 F year round. There is a belt scraper on the head pulley, the scraper was checked for proper tension by the scraper manufacturer.

    I have heard different splice technicians say that the salt does something to the splice kit rubber during the splicing process.

    Does anyone have any info on the chemical reactions during hot vulcanizing of the rubber compounds of MSHA F?

    Gary Blenkhorn

  2. Hot splicing problem

    Hi Gary,

    Sorry but I am unable to advise on your hot vulcanising problem as we supply the cold-cure repair alternative to hot splicing ( Eli-Flex ).

    I recall you contacted us a while ago interested in Eli-Flex for your belt repairs.

    Did you ever get the info and samples you requested from our distributors ?.

    Please let me know.

    Best Regards,
    Aram Friedrich
    Eli-Chem Resins U.K Limited

  3. Hi Gary,

    Without knowing the recipe of the MSHA F cover compound being used in the splice area it is difficult to state that there is a chemical reaction between your airborne salt and the green rubber. If there is a reaction, it is likely to be with one of the catalysts used and not with the base rubber itself. If so, the cure rate would slow but not be stopped.

    The best source for an answer to your question is the manufacturer of the splice materials, not the splice technicians.

    To offer a personal opinion ? site unseen: if the cover rubber is peeling off in the splice area and the rest of the splice materials are holding, the likely causes are (1) contamination during the splice lay-up; (2) the use of old splice materials; (3) improper vulcanization; or (4) incompatible materials. Although it is possible that an adverse chemical reaction has occurred, it is not likely.

    As far as the effect of salt, or sodium chloride solutions, on cured rubber is concerned, you should not have a problem at your operating temperatures. Natural Rubber and SBR compounds can experience some swelling (less that 1%) at elevated temperatures (212F).

    If you want to discuss in greater detail, give me a call or e-mail.

    Dave Miller
    ADM Consulting
    10668 Newbury Ave., N.W.,
    Uniontown, Ohio 44685 USA
    Tel: 001 330 265 5881
    FAX: 001 330 494 1704

  4. Hello Gary
    For what it is worth, we have had much better luck with cold splices. They don't look as good, but appear to be of greater strength, and seem to last better. Also you don't have the problem of the splicing kits going off with hot weather and time.
    You mention having only 2 plies. Do you know what procedure was used?

    Graham Spriggs

  5. Gary, a couple of things to check (may sound elementary) would be the direction of the splice, the pulley diameters used in the system and the trough angle.

    !. The splice direction should be layored so belt cleaning devices have a tendency to skim over the splice joint rather than digging into the splice.

    2. All pulley diameters should be of sufficient size to prevent the belt from being bent too sharply. This can put undue stress on the splice and cause failure.

    3. The maximum trough angle of the belt should be verified and compared with the actual trough angle being used. Bending the belt in this direction more than the belt was designed for can also cause splice failure.
    Larry J. Goldbeck
    Martin Engineering

  6. Gary,

    Is it possible that the overall thickness of the splice is thicker than the parent belt. The head cleaner tension may have been adjusted to suit the parent belt and if the thickness of the splice is greater than the belt it may be contributing to wear.

    A splice which is too thick may be caused by using skim rubber between the plies that is thicker that that in the parent belt during the vulcanising process

  7. #7
    Join Date
    Jun 03

    Splice Problems

    I do not have any experience with salt, but I would contact the belt manufacturer. Salt may have a leaching effect on the top cover and in combination with the heat of the vulcanizer may cause the top cover to harden and deteriorate faster. Over cooking a splice, alone, can harden the covers.

    I will be in your area in September if you would like me to inspect.
    Phone # 1-403-279-3877

    Brent Wheeliker
    Clemro Western

  8. Hot Splicing Problem

    Dear Gary Blenkhorn,

    in Germany the company Kali + Salz (potash and salt mines, approx. 2.5 billon Euro turnover) use differents technologies for the splicing with some good success:
    - hot splicing for EP 400, EP 630, EP 800 and EP 1000
    - cold splicing for P 1000 and P 2000
    - hot splicing for EPP 1000 (new standardized belt)

    In the underground mines it is impossible to avoid the contamination of salts during the hot splicing between the layers of rubber and textile plies. This little film of dust will weak the splice. The people told me that why they have a better experience with cold splicing even if the bench tests of the university of Hannover show another result. But it is the difference between theoritical test in a clean labor and the reality on the field. But it is difficult to make a cold splice with a 2 ply belt.

    The theoritical life time of the splice is 3 to 5 years but Kali + Salz have the same problems like you. I'm not sure but I think the real life time of a hot splice there is only 2 or 3 years and sometime less. Mostly Kali + Salz remove the conveyors after 2 or 3 years. That's why they decided to try using the Super-Screw fasteners because it's the first lacing system in the world that meet all requirements (dust proof, very quick and easy to installe, mechanical fixed with self taping screws, scraper compatible, elastic, wear resistant etc). After two years of experience, they told me that the life time of this fastener is approximately 20,000 hours with the conditions of Kali + Salz.

    You will see attached a picture of a Super-Screw after one removing the conveyor one year later.
    It is the real alternative for you !

    If you want further information you may conctact:
    MLT Inc.
    381 City View Heights
    WV 24740 Princeton (USA)
    Phone : +1-304-425-7161
    Email :


    Edgar Jakob
    Managing Director
    MLT GmbH

  9. Hot splicing problem

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