Re: Hot & Cold Splices - Pros & Cons
Hi Bernard,
I find your overview on hot and cold splicing very inconsistent.
1) Firstly the lay up of a hot or cold fabric splice is identical, the only difference is the vulcanisation/adhesion system being used hence the theoretical strength is the same. If you want to put a false step in to possibly increase the nominal splice strength you can with either method.
2) The most common failure modes be they hot or cold with fabric splices is incorrect cutting of the steps or incorrect buffing of the fabric. Common to both splice methodologies.
3) The selection of the best and freshest materials is a comon need. If the materials are poor or aged in both cases failures will occur.
4) The need for skilled practioners is common to both. We can agree on the fact that the lack of trade skills and poor workmanship is an issue world wide regardless of methodology used.
5) There is a difference in the time to do a cold versus a hot splice but against this is that it is chemically a hell of a lot easier to generate high bond strengths with uncured rubber systems than with cold curing cements. Consequently regardless of skills it is theoretically much easier to do a stronger splice with a hot vulcanised system.
There are agruments for and against but they need to be factually based
Regards
Col Benjamin
Gulf Conveyor Systems P/L ■
Re: Hot & Cold Splices - Pros & Cons
Hi Colin
I am some what confused when you say that the hot and cold splice is identical. From what I understand when doing a hot splice you have to take one ply out. With my cold splice as previously explained I leave all my plies.
Your version of the false step, is that the cover fill in with a breaker ply on the top and bottom bevels? As this will be where the ply was first extracted?
If you where to take the example I previously mentioned and draw it out on paper of a 4ply belt with a three step splice, and one with four steps. You will note the areas of weakness.
In your case where you add the false step, if correctly understood will work, but what about the end of your second and third step. Do you also add a false step in these areas of the splice?
In fact a conveyor belt is one long length of hot splice if you where to think of it. All the rubber covers, inner plies and skim rubber are all rolled out into a press. Curring of the inner rubber and covers take place. The plies are already treated for maximum adhesion between rubber and ply. Sections of the belt then gets tested for tensile strength example 1600/4 = 1600kN/mm.
Why with a hot splice is one subtracting a ply? Maybe they do it so the platens do not warp, or create an uneven flow of rubber during the curring process. And its 3minutes per 1mm time curring. Why is one trying to cure rubber covers already cured?
Do all our hot splices have all the ply steps? If so then this would be an exceptional strong splice.
If not then a splice either hot or cold not matching that of the tensile strength of the belt is very inconsistent.
Regards
Originally posted by Colin Benjamin
Hi Bernard,
I find your overview on hot and cold splicing very inconsistent.
1) Firstly the lay up of a hot or cold fabric splice is identical, the only difference is the vulcanisation/adhesion system being used hence the theoretical strength is the same. If you want to put a false step in to possibly increase the nominal splice strength you can with either method.
2) The most common failure modes be they hot or cold with fabric splices is incorrect cutting of the steps or incorrect buffing of the fabric. Common to both splice methodologies.
3) The selection of the best and freshest materials is a comon need. If the materials are poor or aged in both cases failures will occur.
4) The need for skilled practioners is common to both. We can agree on the fact that the lack of trade skills and poor workmanship is an issue world wide regardless of methodology used.
5) There is a difference in the time to do a cold versus a hot splice but against this is that it is chemically a hell of a lot easier to generate high bond strengths with uncured rubber systems than with cold curing cements. Consequently regardless of skills it is theoretically much easier to do a stronger splice with a hot vulcanised system.
There are agruments for and against but they need to be factually based
Regards
Col Benjamin
Gulf Conveyor Systems P/L
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Re: Hot & Cold Splices - Pros & Cons
Hi Bernard,
Unless you have some unique way of stepping the plies as you lay up your fabric belt the splice must lose the strength of one ply as compared to the parent belt. We do not "cut" a ply out when we do a hot splice, we do exactly the same way you do a cold splice. Look at the lay up of the steps and you will see why the splice strength has to be less. Could I suggest you refer to one of the major belt manufacturer's manuals on fabric splicing and if you follow their cut out and lay up techniques which is the same for hot and cold splicing you can explain how a cold splice can be theoretically stronger.
Col Benjamin ■
Re: Hot & Cold Splices - Pros & Cons
Hi Col
You are the first person I have come across that do not extract a ply when doing a hot splice. Maybe you can teach me some thing new. Trust me when I say I have looked at just about every belt manufactures manuals, all having the same hot splice procedures, subtract a ply.
How is it possible that you can leave all your plies when doing a hot splice. You obviously agree with me as far as tensile strength in a belt when concerned. My splice steps are straight forward.
Overland conveyors splice length =1.2 or 1.5 x belt width 4ply dived into 4 equal step lengths. EX:1000 mm belt width = 1.2 x 4 = 300mm steps.
Over all splice = 5 ply. Bais = 1third or some times 2thirds belt width pending on pulley sizes.
Bernard
Unless you have some unique way of stepping the plies as you lay up your fabric belt the splice must lose the strength of one ply as compared to the parent belt. We do not "cut" a ply out when we do a hot splice, we do exactly the same way you do a cold splice. Look at the lay up of the steps and you will see why the splice strength has to be less. Could I suggest you refer to one of the major belt manufacturer's manuals on fabric splicing and if you follow their cut out and lay up techniques which is the same for hot and cold splicing you can explain how a cold splice can be theoretically stronger.
Col Benjamin [/B][/QUOTE] ■
Re: Hot & Cold Splices - Pros & Cons
Hi Bernard,
There are no splice manuals printed that talk or even show you "extracting " one ply when doing a hot vulcanised fabric splice. You are mis-interpreting the manuals. The strength is one ply less, the splice is laid up EXACTLY the same for cold and hot splices. There are some alternative fabric splice patterns we sometimes use eg for solid woven belting or the mono and duo ply high strength fabric belts but for conventional plied fabric belts it has always been a simple lap joint with the only variation being the step lengths based on the fabric strength. This system has a splice stregth as I have said many times, one ply less than the parent belt.
Col Benjamin ■
Re: Hot & Cold Splices - Pros & Cons
Hi Collin
I would like to discuss this, as Pang,Nilos,Good Year, Dulop, Rema Tip Top, conveyor belt technology........... one ply extracted when hot splicing. As per my first post I mentioned that with high tension conveyor belts one should calculate the tension verses the belt tensile strength.
My email is gauteng@interflex.co.za and if you would like lets share these ideas. I will send you my version of how a hot splice fails on high tension. And I am very inquisitive to know your method. But really at the end of the day we are trying to stop splice failures.
I know you are in Australia, but here in South Africa I have witnessed splice failures of all sorts. Maybe its a new generation of splicers but so far splice failures is at its worst.
Why its never been made a trade, I will never know and it should be. Its casting the industry millions when a belt falls.
Send me your version of how you hot splice, and I will see if I can find fault. If I do not find fault then I apologize and have learnt some thing new.
Regards
Bernard
There are no splice manuals printed that talk or even show you "extracting " one ply when doing a hot vulcanised fabric splice. You are mis-interpreting the manuals. The strength is one ply less, the splice is laid up EXACTLY the same for cold and hot splices. There are some alternative fabric splice patterns we sometimes use eg for solid woven belting or the mono and duo ply high strength fabric belts but for conventional plied fabric belts it has always been a simple lap joint with the only variation being the step lengths based on the fabric strength. This system has a splice stregth as I have said many times, one ply less than the parent belt.
Col Benjamin [/B][/QUOTE] ■
Re: Hot & Cold Splices - Pros & Cons
Hi Bernard,
I will email direct to you some info, but I think your final comment on the "new generation" of splicers is very close to the mark
Col Benjamin ■
Hot Splice
Hi to all
I am a splicer/site manager on one of the Sasol plant in South Africa and today at 9 am I was notified of a splice failure on one of the belts and it was a hot splice.
I actualy hope to get some information because untill today I would have told any body who asked me to give my view to say if hot splice is better or not good I would have said its the best splice but I was proven wrong today seeing that I do inspections weekly and I didnt even know that there is a problem on this splice.
Can you please tell me what you think I should look when doing my inspections for I might be missing something.
Kind Regards
Dwaine Exall ■
Re: Hot & Cold Splices - Pros & Cons
I was about to comment on some issues mentioned, but halfway the story I stopped reading as the inconsistencies piled up. So I actually haven't read all but I would like to make some comments:
- static strengths of cold and hot joints can be equal as long as the correct procedures are followed
- dynamic strength (=lifetime) of hot joints still are higher than achieved any other way when tested on test rigs
Also there is a lot possible in the actual belt design. There is a huge difference in belt quality and in respect of splicing also in the used skims, splicing materials, fabric dips etc. For high tensile belts, other innerply skims can be used and also high adhesion materials and/or primers can be issued.. So there is actually a lot more to it than just the people on site joining the belt.
Especially a country like South Africa, due to big tenders focussed on lowest meter price only, it is flooded with the cheapest of cheapest belting products from local manufacturers, India and China, where in some cases the belts already delaminate because of low innerply adhesion, so how can you make a good splice in a belt like this...
(please note we are in no way associated with Dunlop South Africa, as they are no part of our worldwide Fenner Dunlop group)
Attachments
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Re: Hot & Cold Splices - Pros & Cons
i agree to what you say and do have one question asked to me by client this week.
He wanted to know that in the way that we can do an x-ray scan on a steelcord belt is there a way to do so on a ply belt. ■
Hot Vs. Cold Splicing
I do not agree that a cold splice is better or even being close to equally effective as a hot vulcanized splice.
1)Of all the splice manuals I have, as well as the many splices I have seen, I have never seen one that directs the splicers to remove a ply. Moreover, hot or cold, the step splice will only be partially as strong as the max PIW strength of the belt -even on an absolultely perfect splice. Thats just a matter of fact. This comes from cutting across the width of the belt & creating ply-cuts. (Example: 3ply 330 = 220PIW(66%) through the splice). ■
Re: Hot & Cold Splices - Pros & Cons
Further, in conveyor belt manufacture, we use heat & pressure to cure belting. Heat & pressure activate the polymers and chemical treatment of fabrics to create a mechanical as well as chemical bond. Both are required to create the adhesions necessary to get proper service life in the field. This holds true when splicing. The best bond comes from both mencanical & chemical bonds. To get these consistencies in splicing, procedures that mimick the original manufacturing process are best practice (hot vulcanized splicing) Most reputable manufacturers provide their own splice materials and splicing procedures for their proprietary products. Splice failures don't just occur at ply cuts in the splice without a trigger. As stated previously, many times fabric is knicked or steps are cut short or all of the virgin skim coat is buffed away. These are human errors, not an error of methodology. In regards to the weakness in the ply cut in the top & bottom fill-strip areas, a breaker fabric should be used to bridge this area and provide flexibility in the splice. I have yet to see a successful consistent success in cold splicing in North America.
Reputable splicing companies train their technicians via field experience and factory authorized training. This depends many times on what brand of belting the company represents as well. That being said, the technicians in the field should not have to worry about what tension the belt is running at. They only ned to know what type belt, what brand & make sure they are prepared ahead of time to have the proper splice materials & equipment to do the job. ■
Re: Hot & Cold Splices - Pros & Cons
Mr. Exall -
Fenner DUnlop has splicing & scanning services. We can scan steel cord belting as well as provide X-ray services on site too. However, to x-ray a fabric belt, it needs to be a specific spot on the belt. If there was an event that damaged the covers severley, the belt can be spotted-up in those particular locations & then x-rayed accordingly.
Buddy Wilson
Application Engineer/TSM-Southeast
Fenner Dunlop Americas ■
Re: Hot & Cold Splices - Pros & Cons
Good day Dwaine
Having read your message of the hot splice that failed, I can assure you that this is the first step in finding a far more effective method of splicing a plied conveyor belt. Having the experiance in splicing plied conveyor belts, I have proven that a cold splice is the way to go. Let me geuss, your hot splice cracked then snapped? Splice failures have caused millions of Rands in loss in production, and most technical experts are now turning around to put an end to this.
Sure you will hear of polymers and chemical treated fabrics, and the list goes on and on. Information about hot splicing fabric conveyor belts seams to be so advanced that most people are forgeting the basics. To put it simple, I urge all in favour of hot splicing to send their specifications or manuals to you. I will show you what all have missed, and I still cannot believe that some belting manufactures are supporting these hot splicing manuals. Hot splicing conveyor belts should only be implemented on a smaller scale, where exteam heat or oils are conveyed. If you are talking about overland or conveyors and high inclines, then a cold splice is the only method. I can discuss these issues with you, as i have conducted training of cold splice in South Africa and abroad. Infact I will be bring up hot and cold splicing with the SABS commity in the near future. Splicing of plied conveyor belt has fallen to a poor performance in our country and, are some splicers really trained??
I look forward in discussing this matter with you. Please feel free to contact me any time.
Kind regards
Bernard Laubscher
Technical Director
International Belting & Marketing
Email:gauteng@interflex.co.za
Mobile:083 264 5013 ■
Re: Hot & Cold Splices - Pros & Cons
Originally Posted by WilsonBW
1)Of all the splice manuals I have, as well as the many splices I have seen, I have never seen one that directs the splicers to remove a ply. Moreover, hot or cold, the step splice will only be partially as strong as the max PIW strength of the belt -even on an absolultely perfect splice. Thats just a matter of fact. This comes from cutting across the width of the belt & creating ply-cuts. (Example: 3ply 330 = 220PIW(66%) through the splice).
Just a qeustion I need to ask when assembling the press. Is the splice the same thickness as the belt? If so please explain how when not removing a ply. Surley it has to be to avoid bending the platterns in the press.
I have witneesed this first hand where the splicers are removing a ply which saves time having to remove the top or bottom covers.I have recieved a hot splicing manual from a certain well known member, who does not remove a ply when hot splicing. Example: a 3ply belt which is prepared in a three step stage. The top ply is bonded to the second ply and so forth. Then "tie cord" is bonded to the leading and trailing sides of the splice. What about in the center-inside the splice? This is apparent on all rated plied belts. Look at the ply lay out with in the hot splice you will note that there is a ply strength missing. Whether one removes a ply or not, there will always be a weak area in the join. My cold splices, I am using all my plies, and on the lower class belts, the splice is slighly thicker but never has posed a problem. On the higher class belts from 630 upwards, my splices are the same thickness or even thinner than the virgin belt. Your splice is 1/3rd weaker than the belt. The client's order stipulates a 330, why would one join the belt weaker than the design reqeust. My version of cold splicing is equal or may even be stronger than the class belt put into operation. Again a say that hot splicing in my opinion should only be limited to hot conveying apllications,where materials exceed the cold adhesion expectations. The problem is that the inferior hot splicing methods has unfortunatley been carried over to the cold splicing methods. Most engineers are totally against cold splicing for that reason. ■
Hot & Cold Splices - Pros & Cons
Hot and cold splice advantages and disadvantages
Hi to all
Having read all the opinions I am most certainly one for cold splicing. I was once a belt splicer and having studied design, and have sound knowledge on conveyor belt technology. One very important thing we have all missed when splicing a belt is to first identify the belt specification. Not doing so cost a mine R15000 000, and that was due to a hot splice. It took the men 24 hours to complete a 900mm splice, and then snapped two day later. Not forgetting that all the product had to first be emptied off the belt before they could get the two belt ends to meet.
The problem why we have splicing failures today is that it has never been made a trade. The only place in the world I heard that it is a trade is in Germany.
Since November last year I have been having to solve "splicers" problems. The one question a client asked me is, why is the one length of belting tracking different to the other? Simply because the one length is spliced upside down to the other length of belt.
The list goes on and on, and the list of all the splice failure are hot splicing. One cold splice failure recorded, and this was due to incorrect buffing or not enough. Two different type of adhesion's where used. The splice was not long enough and who knows how the splice was finished off.
There is no non critical belts, they are all critical in the industry. When a belt fails especially at the join, the splicer or the belt supplier looses no money. Its the user who has to bare the loss.
Going back to identifying the belt tensile strength, a belt splicer must adhere to first, before splicing. And this is where I find hot splicing at a major disadvantage.
Lets take an overland conveyor say a class 1600/4ply. This is where most splicers go wrong. They do not understand the term that is marked on the belt. They see no difference between a class 1600/4ply or class 1600/3ply belt.
Now if I were to hot splice this belt, one would have to subtract a ply. And as one gentleman said the hot splice comes out the same thickness as the belt. Great, the finished splice one can barely see. But here's the catch.
Hot splice
1600/4 - one ply = 3x120kN splice strength = 3 step
All the hot splice manuals indicate take one ply out. But the splice manuals do not give you the highest tension in the belt at a given point. Let say the highest tension at this given point is 155kn, due to increase in tonnages or surge loading.
155kn highest tension
- 120kn splice strength
= 35kn above splice strength
Over a long term the splice steps start to crack and in tern the splice length is shorter resulting in total splice failure.
It is important to find out by the designers or the engineers if they have this particular belt on record. Check and determine the highest tension and then decide which splice should be carried out.
I am not saying that this will happen to all the hot splices conducted, but one day it will catch up to who ever spliced the belt.
Splice lengths are also depended on the press length, and I find this a disadvantage as most splicing companies are only equipped with so many size presses.
Cold splice
1600/4ply all the plies = 4 steps = 40 kN per step
= 5kN higher than the high tension in the belt.
Now some will say that the splice will be thicker than the belt. Who cares, the only thing that will happen is that the scraper will wear off 2mm on the top cover. But I am concentrating on the belt which is the plies. Then one can increase the bias angle and slightly countersink the bottom bevel, so that the return plough will not catch the bevel and lift it.
On higher class belt with thicker inner rubber, one can buff the rubber to almost down to the plies. The splice in fact turns out sometimes as thick as the belt itself.
Some say they only give a guarantee for 3 to 6 months on their splicing. Where I came from my cold splices were life time guaranteed under normal working conditions.
Although I do not splice any more, I have spliced this method in most gold and platinum mines with success.
I too used Rema SC 2000 and I rate it the best in the world, and I agree that you need a dedicated team, to carry out a successful splice.
Hot splicing relies on heat and pressure. A cold splice on the other hand relies on pressure to escape air from center out , then impact with rubber mallets all over. This kind of interlocks the two sides of adhesion. Then leave on the splicing board to cure and must never be disturbed. Maximum time for my cold splicing to cure is four hours on overland conveyors, and two hours on small conveyors. 24 hours seams too much for curring, the longer your splice the stronger the contact area of bond. Some cold splices after four hours still cure when the belt is put into operation.
This method, I have used in any width of belt from 2500mm wide to as little as 300mm wide belts. The only disadvantage of a cold splicing is in extreme hot and oily conditions that need to be conveyed.
Mr Spriggs you are on the right track, just bare in mind tensions related to conveyor belt tensile strength. Find out what is the highest tension if on record, and then work your splice around that. 95% of any splice failures are steps cracking causing the splices to snap.
The other I need to comment about, is longitudinal joins in the fabric of conveyor belts. Conveyor belts are extensively tested after manufacturing. No make or brand of conveyor belt has ever failed in the years I have conducted surveys. Nor will these longitudinal joins have any adverse effect during load support.
If any thing I have ever seen, it is called Idler Junction Fatigue, where the belt is wedged between the support idler and the flat. More damage occurs during the load. The rubber cover splits then the plies split, which over time looks if there were a longitudinal join that failed.
Best regards to all
Bernard Laubscher ■