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Thread: Cold Vulcanizing vs Hot Vulcanizing

  1. One of the main factors involved in cold splicing is the down time needed to allow the splice to cure. In certain 24HR plants we service, the down time is not exceptable and therefor cold vulcanising is not an option.

    In 10 years of vulcanising i have never had a cold joint fail due to a splicing error. Correct splicing of a cold joint is far more critical, a great deal of care is needed when splicing as 'cut throughs' are harder to deal with also the area must be dust free, dry and all joint areas must be spotless also an adequate 'key' must be achieved on joint surfaces.

    I've also seen many ways of cold vulcanising. Some vulcanisers simply butt the top and bottom joint ends together and apply feathered edge strip over the top. This can cause problems when working in conjunction with primary and secondary scrapers due to the increased thickness of the finishing strip. You can also buff a taper into the top and bottom covers and add an inch or so onto the last steps and then sand the area flat once the joint is laid, this gives a direction of travel on the top cover and makes it much harder for the bottom to pick up, again finishing strips can be used to seal everything up.

    As previously mentioned, Cold joints are ideal for inaccessible areas and when a press cannot be used. The biggest problem i encounter is trying to convince the customer that a cold joint is as good as a hot joint. It seems cold joints have had a bad reputation, gained from bad workmanship and poor techniques, Yet i believe a well spliced cold vulcanised joint is almost / as good as a hot joint

  2. #32
    Originally posted by CJones

    The biggest problem i encounter is trying to convince the customer that a cold joint is as good as a hot joint. It seems cold joints have had a bad reputation, gained from bad workmanship and poor techniques, Yet i believe a well spliced cold vulcanised joint is almost / as good as a hot joint
    Is it as good or almost as good - it can't be both ways as you seems to indicate in your post.

    I have experienced very good success with cold joints on short low tension belts - but our operation has mostly long high tension belts and the risk of a cold joint is way too high to justify and therefore we go hot joints as recommended by the belt manufacturer.

  3. Sorry Gary, my post was slightly deceiving

    In all applications where i have installed a cold joint i believe it has performed as good as a hot joint would have, However there are, as you suggest, many variables to consider.

    I wil say this. If it is feasible to use a vulcanising press and adequat lift / access is available, then i will always hot vulcanise.

  4. Hi all..
    At last, someone who agrees with me about cold joints being good. I just love the bit about trying to convince customers in this regard....my experience in a nutshell.
    The customer always thinks he's right, and who are we to upset the customer? I don't know how many times I have been forced into designing something in a way that I know to be far from ideal, and later, the bad aspects always reflects against me and not him. Very frustrating.

    C Jones you are a breath of fresh air to this thread.
    Regards
    LSL Tekpro
    Graham Spriggs

  5. Thanks Graham

    I've read quiet a few threads on this forum and The information available is superb and to be honest a fair bit is lost on me.

    Technical data is superb and the belt manufactures certainly know what the best way to join their belts, However all that information is pointless if the workmanship is not adequate. Your vulcanisers could lay a perfectly square joint with the very best solutions and the appropriate step lengths, yet if the splicer has cut through in places the joint Will fail

    In weighing up the options over Hot versus Cold I would suggest this. Consult your belt supplier and ensure your using the best solutions, i always use SC2000, but more importantly make sure the workmanship is of the highest standard

  6. #36

    thecnical info

    hi guys,im a newby in this field but i know that you guys are the right person to help me.recently we had this conveyor vulcanizing bussiness that we are supposed to start, the group who invested are me Chysler diagnosti tech,an accountant a civil engeneer and a vulcanizing trained technician,we had the equiptment for hot joint from china, the problem was the trained thecnician bailed out on us ,so that leaves as hangging and we cannont afford so loose the money that we invested and since i'm the only 1 who is willing to do mechanical,i have to learn the trade quickly and with precission, so please tell me how to get hold of thecnical info such as how to do the splice,correct temp,time of curing,the types of joint, type of conveyor ,ect.or basiccally i want to start to know this trade,i'm from the Philippines in the far east. we would be very appreciative for your help............................................thanks in advance

  7. #37

    Re: thecnical info

    Originally posted by carwisetrading
    hi guys,im a newby in this field but i know that you guys are the right person to help me.recently we had this conveyor vulcanizing bussiness that we are supposed to start, the group who invested are me Chysler diagnosti tech,an accountant a civil engeneer and a vulcanizing trained technician,we had the equiptment for hot joint from china, the problem was the trained thecnician bailed out on us ,so that leaves as hangging and we cannont afford so loose the money that we invested and since i'm the only 1 who is willing to do mechanical,i have to learn the trade quickly and with precission, so please tell me how to get hold of thecnical info such as how to do the splice,correct temp,time of curing,the types of joint, type of conveyor ,ect.or basiccally i want to start to know this trade,i'm from the Philippines in the far east. we would be very appreciative for your help............................................thanks in advance
    this is not something that you can learn from a manual. Then you wonder why users get splice failures.

    All vulcanized splicing information is available from the belting manufacturers.

  8. As Gary has just mention it really isn't something you can be taught from the manual.

    All the technical data you'll need is out there and your belt supplier will advice on appropriate step lengths etc etc.

    At this present moment in time I am training a guy to spice. He's 6 months into his training and I still wouldn't let him anywhere near a joint without supervision. It really isn't a easy as it looks especially if your dealing with thicker / stronger belts

    My whole trust with a customer is based on the reliability of my joints and one joint failure would ruin that trust i have built up and for that reason I would strongly recommend you look for a trained splicer as you'll only get one chase in the working environment, joint failure can be a very costly mistake.

    Where are you based ?

  9. What about Super Screw

    Quote Originally Posted by TE-Anthony View Post
    My question is, what is the difference between or how to do you compare both these methods of vulcanizing?

    I am managing a team of belters who are specialized in cold vulcanzing, and it seems that more and more belts are converting to hot vulcanizing, and I am talking about just normal belts. Engineers/end-users claimed that hot vulcanized belt are far superior than cold vulcanized belts.

    I have explained to them that:

    1. Most of the cold vulcanized belts are non critical, since the users are not very confident of cold vulcanizing, the critical belts (such as the lifeline of the conveying system) are already using hot vulcanizing even though they are just normal belts. Thus, I explained that since most of the belts that are cold vulcanized are non critical, perhaps their maintenance people are not paying close attention to these cold vulcanized belts as they would with those that are hot vulcanized (since they are the critical ones).

    2. In addition, some of the cold vulcanized belts are recycled belts, 2nd hand belts that are resized and deemed fit for reuse. Thus, not 100% of all the belts cold vulcanized are new, compared to 100% of the hot vulcanized belts that are new.

    3. As you can see, there are many more reasons, factors that could cause a cold vulcanized belt to "sound" inferior to a hot vulcanized belt.

    It seems that it is hard for me to convince my customer to be more confident of cold vulcanizing. I am left without words to explain. I have planned to purchase a 1400mm 1800mm and perhaps a 2000mm hot press, however, in order to help my customer understand and to know the benefit of hot and cold vulcanize (cold vulcanizing is much cheaper to operate, since) I need some solid facts on these 2 methods. Any help? for some facts, studies showing a comparison of Cold Vulcanize vs Hot Vulcanize. Some as even gone as far as saying that cold vulcanizing is only 75% strength of a hot Vulcanize, is this true?

    a. We do not performing cold vulcanizing on hot belts, these are just normal belts.

    b. Common belts we deal with, Bridgestone & Yokohama.

    c. We have sufficient lacing tools and thus ensuring my cold splices are done correctly.

    d. We DO follow the "suggested & adviced" splicing guides as provided by each belt manufacturers.

    e. We use SC2000 vulcanizates and ensure non are expired.

    f. Our general step length/coverage for long & heavier belts are 1.5 x of width.

    With our proper vulcanizing technique, i do believe that cold vulcanizing are just as good as hot vulcanizing, and to say and assume that 88% failure of belts are of cold vulcanizing as indication that cold vulcanizing are far inferior compared to hot vulcanizing is not a fair comparison..

    Please help, if you have any facts, studies or even just experience of explaining the comparison of these 2 methods of vulcanizing please do post a reply.

    Thanks.
    We have found that we have helped countless mining, quarrying and crushing companies steer away from hot and cold vulcanising.
    Why have to spend thousands of dollars on splicing crews, travel time and accomodation, when in a matter of 2 hours anyone can fit up a super screw join for a fraction of the price and no downtime.
    They are available in Abrasive resistant, Heat resistant to 200 degC , FRAS and also anti magnetic for metal detectors.
    Welcome to the real world of conveying.

    David Cotton
    Director
    WA Belting Solutions

  10. New splicing material without solvents for cold splcing and hot splicing

    Dear TE Anthony, dear Bulkholics, dear readers,

    Since you started this threads in 2006, over 19,500 readers and 39 replies shows that this topic is particularly important and remains newsworthy in my opinion. Experts like Gary Blenkhorn, Lawrence K. Nordell, Dave Miller, Barry Chung, Bruce Baker among others, confirmed at least that hot splicing is normally better and that it cannot be replaced by cold splicing. In some cases even (finger splicing of monoply belts, steel cord belts) there is no definitive answer to cold vs hot splice. As former co-owner of MLT Minet Lacing Technology SA in France and Managing Director of former MLT GmbH in Germany I send a personal reply, suggesting to add the Super-Screw lacing in the comparison, which was developed by my father, a couple of years before.

    In the meantime, the technological competition between cold splicing and hot vulcanization has evolved and Super-Screw splicing has established as a recognized alternative technology for textile rubber belts. Probably everybody knows that some glues like the SC2000 have been meanwhile prohibited in Europe and in many other countries, proven to be a possible cause for cancer and disease due to the included trichloroethylene. Hence a new generation of rubber adhesives has emerged on the market. These are containing a new cocktail of solvents, which are classified as less dangerous and less toxic. Those solvents are mainly responsible for the way contact glues are working, all manufacturers have tried to find the best alternatives to optimize the pot time, the open time, while reducing the curing time to full functional strength. As a result, cold splicing has been generally improved and it’s now accepted that you don’t have to wait 24 hours before restarting a conveyor belt. Consequently cold splicing is becoming again more popular.

    But if we want to know whether cold splicing or hot splicing is better I think that it’s useful to understand how cold and how hot vulcanization are working.
    You might probably all now, rubber cement is mostly based on polychloroprene polymers dissolved in up to 85% solvents. The curing begins after application, without heat by evaporation of the solvents. Only after the solvent has largely evaporated the formation of crystalline structures of the chloroprene polymers can begin. An adhesion between the adhesive and the surface to be bonded and the cohesion within the adhesive is based on molecular interactions, such as Van-der-Waals interactions, and mechanical cohesion of the molecules in the glue and in the rubber, after the initial diffusion, with the help of the solvents. It means that after checking the initial adhesion with the usual finger back method, both prepared splice surfaces must be pressed firmly, to ensure that the crystalline structure will be pressed into each other, providing the required cohesion. Consequently you should improve the strength and the life time by using a press instead a double acting rollers as a compromise. In comparison: shoemakers are pressing a longer time with the same type of contact glue!

    Further point: the solvents that evaporates in the course of solidification of the adhesive provides an increasing occurring problem. On one side, the actual volatile solvents - even after banning trichloroethylene as proven carcinogenic - are generating health risks for the users, like Dizziness, nausea, headache, irritation of the mucous membranes and even organ damages. If you take a look on the safety data sheet of the news solvents (mostly a mixture of ethyl-acetate, cyclohexane, dichloromethane, Tetrachloroethylene, acetone, hexane, etc.) you will discover such words like: “suspected of damaging fertility”, “may be fatal if swallowed” etc. These statements should be even worse if manufacturers have to declare in the safety data sheet all included components with less than 0.1 %. On other side, the diffusion occurring with the support of solvents, leads not only to mechanical binding between the polychloroprene molecules of the adhesive, with the molecules of the rubber belt, but to interaction with the included softeners, additives etc. of the belt. This interaction remains active a long time after restarting the belt and leads to a fundamental instability.

    In comparison, the process of hot splicing uses vulcanization solutions which includes among various dissolved rubber compounds, various solvents, crosslinking chemical such as sulfur, peroxides and metal oxides, and vulcanization accelerators such as zinc oxides, 2-mercaptobenzothiazole or dithiocarbamates. The vulcanizing solution is applied to the rubber surface to be bonded and compressed with a vulcanization press at high pressure. And high temperature for more than an hour in some cases. The chemical reaction of rubber molecules, with the crosslinking chemicals, in the case of sulfur with formation of sulfur bridges, leads to the crosslinking of the rubber molecules. Additionally you have molecular interaction and diffusion process, which leads to a strong, a very stable cross-link, so that the belt can be put immediately under full load after cooling and reopening and dissembling the press.

    But even in hot splicing the volatile and harmful solvents plus sometimes toxic vulcanization accelerator involved, leads to similar problems as in the case of cold splicing, even if less pronounced. Furthermore, as already pointed out by the former repliers, the vulcanization requires a high investment, higher technical effort and skill. But sometime this technology cannot be used, e.g. in case of bad accessibility in confined area, or with small tension travel/take-up of the conveyor.

    For the last few years I have made some static and dynamic tests to compare both: I can confirm that the static pull resistance of a cold splice is the same as a hot splice if done correctly on the same multiply rubber belt in the same manner, according to DIN 22102. But it is clear that if you make a dynamic test, even with a simple L-shaped bench as I have, the hot splice is the long lasting one. But again, even if cold splices are potentially less good than hot splices I think that the evolution will go toward bonding.

    As a specialist of mechanical fasteners and manufacturer the most compact vulcanizing presses on the market, I understood that it is necessary to develop something new, to solve some of the actual problems. That’s why I decided several years ago, to start the development of an adhesive without any solvents and without any risks for the people and the environment and capable to combine the mode of action of cold splicing with the mode of action of hot splicing. This new developed and patented reaction glue provides a very stable cross-link, like a hot vulcanization but requires some changes of the method of use in comparison to usual contact glues:
    - Longer open time, allowing to make the job step by step and to close the splice immediately with no risks to have bubbles or after getting the required tacky if wished
    - Possibility to make a correction of the position or to reopen the splice for the same
    - Less sensitive to moisture, dust etc. during application
    - Short curing time at room temperature or very short time by using a heating source
    - The use of a narrow fixing unit or a light pressure press to ensure best result and to accelerate the curing time (quicker as a hot splice)
    - Possibility to use it for all types of belts and all types of splicing, including the repair of holes, surface damage and long rip repair
    - Use on a wider range of rubber compounds, on PVC, PU, fabric (no RFL and adhesion rubber required), metal (with no primer!), ceramic, etc.
    - Higher resistance to chemical, sun light, temperature etc. as normal cements with solvents

    Today I can confirm that the polymer glue Multiface achieve the same dynamic strength as a hot splice on our little dynamic bench and on trial tests and on field. Of course this is not a statistical statement and not a universal solution, but probably the most promising innovation on the splicing market with real improvement potential in the future.

    At least let me repeat what Barry Chunk wrote 12 years ago: “Hot or cold, a joint can only be as good as its preparation. Among others, an important contributory factor, in the case of fabric belts, lies in the buffing of the plies after peeling and in steel cords, the stripping of the strands... I feel any emerging findings would be purely academic and prove more useful to manufacturers in improving their products than to most of us doing field splicing. Even if we know, should we then accept the results as the Holy Grail or gold standard; I think not. As we have seen, there are simply too many factors that go into determining the life and quality of a field joint for us to draw a narrow conclusion.”

    In contradiction to this quote, I hope that you all want to start a trial and be convinced step by step, as you have done with the Super-Screw fasteners.
    I wish you a lot of fun while reading and analyzing my statements.
    Please let me know your comments on this subject.

    Examples of using Multiface .pdf

    Edgar Jakob
    Hejatex GmbH, Küstriner Straße 15, 94315 Straubing (Germany), Phone: +49-9421-96884-0, email: info@hejatex.com, www.hejatex.com YouTube: Hejatex or Multiface

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