Anthony

This subject has been discussed many times on the forum as per link below for one.

Use the search button above and enter "cold vulcanizing" and enjoy the reading.

I for one recommend hot over cold at our mining operation simply because 90% of our belts are high tension applications. I have used cold vulcanized splicing on short belts up to about 200' long but that would be my limit. Of course any splice cold or hot is totally dependant on the quality of the materials being used and the skills of the splicing technician.

My rule of thumb is to go with the belt manufacturers recommendation and follow them exactly. They know what materials work best with their rubber compounds.

https://forum.bulk-online.com/showth...5&pagenumber=1

Regards,

Gary Blenkhorn ■

It might be a daft question: but if the belt manufacturers could develop a satisfactory way to make the belts without heating the presses wouldn't they have done so by now? Maybe they have already. I never paid so much attention to belt manufacture, more to the astronomical price. ■

I get better results with cold splices, as SC2000 gives a very strong bond, and it also means that I don't have to spend a fortune on vulcanising presses.

My big wide fabric belt feeder belts are always cold spliced for example, and are subjected to massive start up pull out tensions. I have not had a single problem to date. Good job, as the wide hot presses cost $$$$.

Many people think that because a splice is hot it is better. I don't find this to be true in practice. I also get good life out of cold ones, as long as they are done properly and cleanly (very important).

Regards

LSL Tekpro ■

Although this may sound elementary, when considering splice failures, either cold (I lke to refer to these as chemical splices) or hot, one major problem is the direction the lap of the splice was made in the first place. The lap should be in the direction so belt cleaners and sealing systems will not "dig" into the splice and start peeling the top layer back. Also I have found that layering the belt slightly longer than recommended will increase the life of the chemical splice. ■

Dear Anthony,

I am not sure where you got the 88/12 stats from, but if the study involved someone trying to make a definitive conclusion on the superiority of hot splicing using unfiltered field data, then I wouldn't take it too seriously. This is because, as you have rightly pointed out, there are simply too many variables that would render such a call highly questionable.

However, all else being equal, the conventional wisdom that hot splicing is better than cold cementing may not be that far off after all. One of the most important aspects of splicing that has so far not been mentioned on this thread, and very often overlooked, is that of gage control. Hot splicing allows one to rebuild the belt in a way that cold cementing simply does not. Because of this, it makes the method suitable for a wider variety of belts. Then there are some belts such as steel cords and PVC (finger splicing) that cannot be done any other way.

Among the other aspects that contribute to this argument are jointing material compatibilty, preparation and service factor.

Hope this has helped.

Best regards.

Barry Chung ■

Old belt are not a good test unless the aged rubber is stripped from the splice. When belts age beyond 8 years the core gum in the splice has seen a large number of strain cycles. The strain cycles cause failure. The variance in attitudes of the respondents surely signifies lack of agreement that could be attributed to variance in procedures as well the specimen and personal biases.

Simple tests can be performed that may yield a conclusive answer. Large, expensive steel cord belts usually undergo splice destructive testing to quantify their dynamic efficiency.

The first test of two major tests is to make a laboratory coupon (strip) of a splice equivalent at a smaller scale. This consists of two sections of belt with the smaller scale steps, width and length. The coupons are strain cycled in a prescribed manner for all subjects including:

a) new, old and new to old belt

b) manufacturer A,B and C

c) hot and cold vulcanized

d) 30,40; 50 % cyclic loading levels to failure

e) any other tests perceived as relevant

Instron, MTS and others make test machines that can be programmed to apply the cyclic procedure that mimics the load pattern a splice undergoes for each cycle.

CDI has conducted many such tests as has Goodyear and Hanover.

The second is to fabricate endless loops and subject is to Goodyear's, or Hanover's close loop test machine. This procedure includes pulley-bending stresses.

A clear winner will emerge that stops further speculation. Typically, a minimum of 3 samples is needed for proper statistical tests to eliminate white noise (fabrication or sample construction error).

One would think this would have been, given the high costs of failure. ■

Dear TE-Anthony

With out a doubt Hot Splicing is Superior to Cold Splicing in all but a few cases, and I’m surprised to see comments to the contrary.

My reasoning for Hot Splicing as follows:

1/ With Hot you are basically using the same technique as when the belt is manufactured, heat, pressure and uncured fresh gum.

2/ It is a seamless join and even thickness.

3/ With a Hot splice, cure temperature, time and pressure is a standard from the manufacturer, where by the time for a cold join to be ready to be laid up / put together is up to the individual. Also the rolling / stitching in or the pressure applied to the cold splice is up to the individual and varies.

4/ Hot splice on new belt should last, done correctly, for the life of the belt, this could be 10 or 15 years in some cases.

5/ Ask any recognised Belt Installation Company what their time Guarantee is on Hot versus Cold, this should give you an idea on which they think is the better of the two.

I also noticed in this thread that there’s been Hot splice failure’s, I wouldn’t go blaming the Hot splice as such, I’d be having a closer look at the system, splice materials, splice temperature and pressure and of course the installers, in that order.

Now having said all that, cold splicing has its place and is very, very good, when done in the right conditions and with experienced, qualified technicians. ■

I agree with Mr. Baker,

It is not sufficient or prudent to lay blame without knowing the root cause for any failure.

Note, there are many more fabrication and field factors which must be controlled to produce a proper hot vulcanized splice than a cold chemical splice.

Usually, the cold splice has proper supervison due to its novel method, while there are many whan-a-bees that profess expertise in hot vulcanizing. ■

Gentlemen...

I still don't aggree that a hot splice is better than a cold one for fabric belts because:

- For a start I have had better results with the cold splices, especially for example with the fold-over "U-CON" belt which put splices to the real test.

- REMA TIP TOP, one of the splicing outfits here maintain that cold splicing is better.

- The bond between plies in a hot splice are just as susceptible to the dreaded ply separation as the rest of the belt. (This is not so when good old SC 2000 is used to bond the plies)

- There can be no doubt that our mining environment are generally tending towards the cold spice.

Regards

LSL Tekpro ■

Graham

When you do the cold splicing, how do you do your do you skives top and bottom, as a skived butt join, sealer strip / filler strip and do you use a repair band over the skives.

Matt

Was that the "20/20" or the “OTG” Warrantee?

For those of you outside of Australia the above abbreviations mean:

"20/20" - 20 minutes or 20 revolutions, which ever comes first, this includes cure time.

"OTG" - as soon as we’re “Out The Gate”

I’ll second that….. ■

G'day Matt,

I'm also interested to know the kinds of warranties offered down under. Over here, we generally offer a one year warranty for splicing new belts (hot and cold) and limited or none if its an old belt. However, should we discover that the quality of the belt, even new, is suspect, we will notify the client and accordingly also limit the warranty.

I have been following this thread and has come to a conclusion that this debate will never end given the wide range of field experience pointing both ways. Nevertheless, I'm confident there can only be one answer and one which can only be obtained through controlled lab tests as Nordell has suggested. While I'll be the first in line to want to know, 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.

Therefore, instead of debating the merits, I think we will gain more by exploring all these factors especially so that the uninformed reader will gain a better insight into the subject rather than relying on the anecdotal opinions of quack contractors.

All else aside, to me, 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. Just how much of the old rubber should we leave behind? And would this have a bearing if the belt were old or new?

One of the things that spring out is that most new major installations employ hot splicing on belts usually supplied by a single manufacturer which may provide an experienced company technician or trained local rep to supervise the jointing during construction. While I agree there may be exceptions, I have noticed these joints tend to last longer (one ran for 18 years and was still going until the belt was electively replaced) and the problems for the client usually do not begin until after this first batch of joints fail. Does this tell us something? With the wide variety of belts out there in the market and most splicing technicians, perhaps out of ignorance, employing essentially the same method for all joints, could this be contributing to Anthony's client's stats?

Regards.

Barry Chung ■

Hi Barry

You’ve bought up some good points and looks like you have just stoked up the fire, please take that as humour, not an anecdotal opinion.

Sounds as good as the 20/20 warrantee, if you can get away with it all the best to you but I’m surprised your clients accept that.

Generally you would warrantee a hot splice on a new belt for at least 3 to 5 years, or the life off the belt depending on its working environment.

Sand, Coal and other soft type ores with low or no impact would be in that range, 5 to life.

Hard rock mining environment would be more like the 3 – 5 years as the belt itself has a shorter service life.

Cold, I’d expect that you’d reduce all the above by 2 years or so.

I’m talking about Fabric belts here, Steel would be considerable more, say 2 or 3 times the above.

Used belting would be as you say, none or very little.

The contractor is responsible for the “many factors”, the environment, the people, the materials, the equipment and everything else that determines the outcome of the splice, and as such they must be able to stand behind their product 100 %, which in this case is the splice.

I’m sure the cold splice material manufacturer’s have this available, if I was manufacturing the product, the best selling point would be to have it tested against the hot splice and publish the results.

We’d still debate this of course.;-)

You’re absolutely correct in what you say, on major installations they generally employ a Quality Assurance person to oversee and supervise the splice and installation. so it’s done to the manufacturer’s specifications.

With a controlled environment [ Splice Shed / Shelter ], people [ assessed on the job], materials [ Belt manufacturers and in date ], equipment [ tested on the job], and everything else that determines the outcome of the splice.

With the QA involvement you would generally have a 100 % success rate, and a manufacturer’s and splice contractors warrantee for the life of the belt.

Its great insurance for the client, and also for the contractor. ■

Hi Bruce,

I really wasn't referring to anyone on this thread when I said "quack contractors" but was actually thinking of the many cut-throat freelance splicing outfits here when I wrote that. My deepest and most sincere apologies to all who may have taken offence.

I'm afraid we'll be driving ourselves to the poorhouse if we offered the same warranties here. This is largely due to the flood of cheap shoddy belts from manufacturers you've never even heard of, much less get the splicing specs from. Ever come across a new multi-ply belt where the only way to join is to use fasteners because all attempts to splice hot or cold failed? Or 3xEP100 plies stamped as EP400? Frightening isn't it. To answer your question, we don't always get away with not offering a warranty, which is why we have chosen to serve only the premium end of the market.

Best regards.

Barry Chung ■

It certainly is, not much you can do about it in the short term.

We went through a similar problem in Australia with cheap “shoddy” imports, took a while to sort out but the ones that really wanted the business improved their quality and the others are history.

One importer / distributor, would offer a free splice after the initial installation due to it stretching that much, but when it’s stretched past it’s limit something has to give, and it was the splices of course. ■

Dear Anthony,

I, as with many others of this forum, have done both cold and hot splices. My preference is heavily weighted to the hot splice technique, even though I have found that a PROPERLY CONSTRUCTED cold cure splice is just as strong as a properly constructed hot splice.

My reasoning is as follows:

1) a cold cure splice is more expensive for the end-user than a hot splice, when system down time is factored in. The cold cure splice should sit without tension for 24 hours once the splice is copmpleted. This down time cost far outweighs the extra equipment rental and rigging costs associated with hot splicing.

2) a hot splice is much more forgiving to construct than a cold cure splice, because of the pressure applied by the vulcanizer. This ensures that the cement and rubber used with the hot splice are properly compressed. When doing a cold splice, proper compression of the cement and cured rubber components is often difficult - resulting in voids which can expand and cause a splice faiulure.

As an additional note, any splice (cold or hot) should only be made with high quality materials which are approved by the belt manufacturer. Why take an unnecessary risk to save a few pennies when the cost of failure is so high?

Regards, ■

I posted the following question on the "Ask Lyn" forum the other day but did not get a response. Hope I might get some answers here.

"Is it common practice for belt manufacturers to build the up the full width of a ply using 2 or more separate pieces of fabric laid lengthwise? Section 6.7.1 of DIN 22102 Part 1 appears to allow this. My questions are

1. How will this affect the ultimate breaking and the overall lateral strengths of the belt compared say to one where the ply is constructed using a single piece of fabric?

2. How will this affect the lifespan of the belt given the possiblity of tear across and shear along the longitudinal joints.

3. How will the minimum pulley diameters, load support and troughability properties of the belt be altered.

4. Can a conventional n-1 stepped splice be performed assuming the carcass has more than 2 plies? Or are there any special requirements?"

Has anyone had any experience doing a splice on a belt like this? Appreciate your comments.

Regards.

Barry Chung ■

Hi Barry,

The practice of having longitudinal "seams" in particularly wide belts was very common place many years ago when standard fabrics were only manufactured 1200mm wide. It is less common now that modern looms allow manufacturers to purchase fabric up to 2000mm wide (and wider I believe). It was the availability of wider fabrics that moved belt manufacturers to make "slab" width stock effectively passing the problem over to the distributor. Anyway to your specific questions, yes I have had experience splicing and seeing belts with longitudinal fabric joins in operation. Basically there were no problems with their operation relative to belt made with full width fabric ie no mechanical differences, providing;

1) The longitudinal joins were made in a manner that did not create a flex point. In other words the joins were made such that they were spread in a manner that was balanced and did not overlay.

2) The belt had at least 4 plies unless it was very lightly loaded. The biggest concern was load support

3) The joins were made in a manner that avoided separation during manufacture and this was sometimes done by lightly stitching the joins

4) That the joins butted but definitely did not overlap. If they overlapped they usually generated a failure point.

Splicing was done normally, there were no precautions required unless a fault was found in the lay up of the fabric and this is no different to what you would do if you found a ply fold in a normal belt. The biggest concern I have had was with a particularly wide, very heavily loaded belt in a port operation where such joins did over time "hinge" and create a longitudinal crack in the belt and this is can only be compensated if full width fabric is not available by adding a ply to the specification. In other words my only concerns (other than when there were manufacturig faults) was load support.

All the best

Col Benjamin

Gulf Conveyor Systems P/L

PS a bit of the radar as far as cold slicing. In respect to this for what it is worth, cold splicing providing the cements used are from a quality manufacturer can give excellent results but there is a lot more risk. It requires better quality materials that are freah and the worker skills must be better. In other words there is less margin for error. ■

G'day Col,

Thank you for the insight. Really appreciate it.

Just one question though. You mentioned;

"The biggest concern I have had was with a particularly wide, very heavily loaded belt in a port operation where such joins did over time "hinge" and create a longitudinal crack in the belt ......"

Was the seam, in this case, located within or in close proximity to the junction gap and if not, was it riding over the centre or the wing roll?

To add to the comment in your footnote, I have found that although manufacturers like REMA lists the compatibility of both their hot and cold splicing materials to different base polymers, I have found they worked best for NR and OR belts but have had some problems in the past with HR and FR grades even though the base rubber was the same. Have you encountered this before?

Best regards.

Barry Chung ■

Hi Barry,

When you lay up longitudinal seams in belts you MUST know the idler configuration as it is most important that the longitudinal seams correspond to the mid-point of the carry idler face or as close as is possible. The sequence must also be such that no seams over lay each other. This is sometimes most difficult especially with 5 roll idler sets that are sometimes favoured with very wide belts given the idler weights. A combination of a 5 roll idler configuration and very heavy loads meant that the seams were too close to the idler junction and the fabric "hinged' and ply separation occurred along the joint. The whole issue became a very big problem as the belt manufacturer tried to rely on the fact that they were not told the idler configuration etc. 45 degree troughing especially with a very narrow Vee configuration to maximise load carrying also represents an bit of a challenge as you need to then locate seams along the wing idler sections without once again overlaying seams. Hope this helps

All the best

Col Benjamin ■

Hi again,

Missed your last comment. It all gets down to the base polymers in the rubber. Most cold curing cements are based on compatibility to natural rubber. As such SBR is AOK as are most neoprenes as chemically they are very similar as far as bonding is concerned. Most OR or oil resistant compounds are nitrile based (sometimes butyle) and neither are chemically compatible. As we are relying on a chemical bond we end up with very poor adhesions in such instances with cold curing systems that are set up for natural rubber. With FR compounds some belt manufacturers, rather than use a neoprene based compound, use chemical additives and rubber blends as neoprene is very expensive. Once again this can distort the normal chemical bonding, hence the hassles you had. All this pre-supposes that the belt splicer skill levels were high and materials were fresh.

regards

Col Benjamin ■

If I got only 2 to 3 years out of a cold splice, I would feed my splicer to the Lions!

Regards

LSL Tekpro ■

Dear TE-Anthony,

Our company group, Minet Lacing Technology, is not only a manufacturer of conveyor belt fasteners, but also of special belts (mainly truly spliceless belts i.e. thrower belts for speed up to 30 m/s and a capacity up to 1.800 m3/h), vulcanizing presses and accessories for vulcanizing service companies. During the last 60 years we have experienced the advantages, limits and disadvantages of the different splicing technologies.

The main difficulties of cold vulcanizing are the quality of the glue (depending of the formula, the condition of storage and the date of expiration), the conditions for doing the job (dust, humidity, mud, oil etc.) and last but not least, the skill of the operators. If your company is experienced with cold vulcanizing I suspect you don’t need more information about this subject.

In opposition, if you want to make a good hot vulcanizing you should take more attention on the quality of the belt. Be aware that a belt manufacturer have to juggle between a wide range of parameters, among them :

- variable fabrics from different suppliers (various material, weaves, strength wrap and weft, elongation etc.)

- the quality of the impregnation on the fabric and the adhesion cover between the layers (--> adhesion strength, elasticity etc.)

- the formula (several thousand compounds are available) and quality and the age of the uncured rubber

- the tolerance of every raw material (i.e. thickness of raw rubber)

- the process parameters during the belt manufacturing (temperature, pressure, time etc.)

- the quality of the manufacturing equipment

- etc.

Hot vulcanizing is not like metal processing, where it’s possible to keep an accuracy and constancy of 1/1,000 mm ! Sometime we manufacture in our very clean factory the same belt in the morning and afternoon with various results only because the atmospheric conditions (temperature and humidity) was different. Every belt manufacturer know the big problem of ply separation during the manufacturing, even with the most modern machines !

One point is that it must be possible to separate the plies and that the rubber must be re-vulcanisable one or two times in order to make the splice (also after a few years). It means that the vulcanization of the belt is only “half done”. So it means you need a reliable belt supplier and the raw material only from him to be sure !

Of course if you want to make a good hot splice you need also a team of specialized workers and a good vulcanizing press. Here is the next difficulty : due to the pressure of 10 bars or more and due to the high temperature you will discover that even strong traverses will bend in the middle like a banana (maybe up to one mm !). The result can be a big pressure difference between the middle and the edges of the belt and maybe a bad splice. Consequently, if you want to vulcanize very wide belts, you need to calculate a progressive vulcanizing tool (thicker in the center and thinner on the corners) or you need a press with a “water bag” as pressure system. Only a press with a hydraulic bag provides a constant pressure on all the surface regardless of eventual variation of the belt thickness.

Of course, the condition of working must be approximately the same as for a cold vulcanizing (no humidity, no dust, no oil, etc.) and you have to follow the recommendations of the belt manufacturer.

If I want to summarize I will say that hot splice is a good solution for long and wide belts with the guaranty that the construction will fulfill the function (wear resistance and pull resistance) and maintain the elasticity during all the life time of the rubber compound. On the other hand you need a very high investment (more than 100,000 USD for the press, the crane, the truck, etc.) and there is always a little risk of failure, even with the best quality insurance (see the number of vulcanizers in a open cast mine!).

For small and non critical belts, or for old belts, cold vulcanizing is a good solution, especially if the accessibility is bad and if you want to save a lot of money for the investment and for the education of your people. The biggest difference between hot and cold vulcanizing is that a glue will lost his elasticity after some years, so that the life time will be theoretically shorter.

Again, the challenge today is not to find the best technological solution but the most economic solution, depending of the application and the conditions in a specific country. That’s why we decided to develop the Super-Screw fasteners as a new technology among the traditional hot splice, cold splice and metal fasteners. There is no universal solution, all four technologies are somewhere the best solution, it’s up to you to make your own experience and to decide which one you want to use. ■

To Edgar Jakob:

I am truly intrigued by your spliceless thrower belt technology. Can you post your details on a new thread? It is always good to hear from somebody who knows their business.

johngateley@hotmail.com ■

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 ■

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. ■

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. ■

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 ■

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 ■

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. ■

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 ? ■

Originally Posted by TE-Anthony

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 ■

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.

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 ■