View Full Version : High Temperature Belt Splicing
We are experiancing permature splice failures in our elevated temperature belts. The conveyor belting in question is Semperit transtherm 400/3 TEB and we are using cold chemically bonded steped splices. We are not using hot valcanised splices since it is very difficult to get a contractor that has the correct equipment to do these.
My questions are:
- Should we insist on hot valcunised splices and if we do are there any special coumpounds that we should use?
- Can we keep on using cold splices and if we do are there any special compounds to use?
- Are there any mechanical splices that would be suitable considering that belt scrapers are used and that the produt is hot sand at a temperature of plus minus 160 degrees C?
4th May 2004, 21:16
How do you control points that can significantly influence splice capacity?
1. Splice design (step/finger/hybrid; dimensions)
2. Preparation procedure
3. Splice kit Mfg. components and validation for high temperature operation including being compatable with belt mfg. rubber and fabric.
4. Length of service before failure
5. Duty rating in percentage of design load in present use
6. Conveyor geometry, pulley sizes, and tonnage
7. Impact station design
8. In general, hot vulcanized splices are stronger than cold bonded.
9. yada yada
High temperature can/will adversly affect splice and rubber strength, typically above 65 C.
Other factors to consider with the cold cement include -
Curing time - depending on the brand of cement, you want to leave the belt for a minimum of two hours before applying tension.
This is especially true if the belt(splice) is become heated quickly after being put in service and the glue hasn't cured for an adequate period.
What brand of cement is being used?
What is your curing time?
How many coats are being applied?
Are the splice's peeling apart or breaking?
If your only alternative is to splice cold you need to ensure your procedures are spot on.
7th May 2004, 9:48
Without knowing the nature of your system(s) and splice failures, it is difficult to provide specific advise. As Larry Nordell has stated, using compatible materials is very important. As Shane has indicated, following proper splicing procedures is critical.
In general, cold cure splicing is the least forgiving of all the splice methods -- the technicians must do it correctly and the set time before use is extremely important.
You should confirm with your belt supplier that the splice materials used are acceptable. If they are, confirm that the material is fresh. Finally, play close attention to the splice method used by the contractor.
If you still experience problems, consider purchasing a dedicated vulcanizer for the system. The cost of equipment will be lower than repeated splice failures. Your 3-ply polyester/nylon carcass belt should be step spliced with a minimum step length being that recommended by the belt manufacturer (generally, you can safely increase the step length by 20% for added splice security).
As far as mechanical fasteners are concerned, there are a number of options available to you. Critical concerns with this type of splice method include the interaction with belt cleaners and skirting; and your plant's ability to conduct on-going maintenance of the splice(s).
7th May 2004, 16:05
Unfortunately the HR, Nitrile and most specialty Heat Resistant belts are extremely hard to keep together regardless of what specs you use. [ As others here have mentioned ]
It’s more luck than good management.
This is even more so with belts that have been in use for some time.
In regard to Vulcanising, the best method as a rule of thumb is hot vulcaniser for all type belts, cold vulcanising is great for light duty belts in perfect conditions.
There are several sites that will give you a background on what you should look for in regard to belt maintenance.
Details can be found at:
Goodyear @ http://www.goodyearindustrialproducts.com/conveyorbelts/main_pages/end_heavymining.html
Georgia Duck @ http://www.gd-enerka.com/gaduck/gaduck.nsf/navview/5?OpenDocument
In regard to fasteners I would give the Minet Super Screw fastener a try, its easy to install, can be used in conjunction with scrapers with some slight mods.
If using scrapers I would cut out the Top and Bottom covers. [ Counter sink the fastener ]
Install the fastener and use a poly type resin to seal the join.
You can find further info @ http://www.mlt-usa.com/
Hope this helps.
7th May 2004, 19:51
Most mfgrs. recommend hot vulcucaning for Heat Resistant belt splice to achieve full dynamic strength, as is noted in their belt strength and safety factor (usually SF= 10-12:1 breaking strength : working strength). The cure process (higher cure temperature) and materials differ from conventional splice kits.
The bond mechanics differ. Each mfg. has perfected their own process.
Mfgrs. kits may differ from splice contractor kits and render the splice less efficient wrt dynamic strength.
Needless to say they all claim a hot vulcanized splice is best.
Where do you find publications of cold bond dynamic strength to compare to hot vulcanization? I bet it is follows the Ozzy term: "suck-it-and-see".
Conveyor Dynamics, Inc.
8th May 2004, 1:33
The dynamic strength between the two types of vulcanising is not usually the issue. [ Excluding HR and speciality componds ]
Done correctly in perfect conditions, splice failure would not occur in either.
With cold vulcanising you do not have the leeway you have with hot vulcanising.
In general terms the weather, dust, humidity, tack [ To dry to wet ], pressure stitching or rolling and the technician’s experience has the major role, not the vulcanising method, more so with cold than hot.
Uniform and correct pressure over the splice area is rarely achieved cold, by using a vulcaniser this is achieved this 99% of the time.
As mentioned in an earlier post the rule of thumb would be:
Hot when ever possible for all types of belts.
Cold, when Hot is not an option and only on small, light duty systems in warm climatic regions.
16th May 2004, 11:38
I want to suggest to use the "Super-Screw fasteners" for this application. With a multiply synthetic textile structure, rubber as cover material and special self taping screw for fixing, this fastener meets the requirements of wear resistence and tensile strength. You may installe this fastener in biais (10 degree angle) directely on the carcass after removing the rubber of the belt on both side and by using a good power screw driver. Everybody can do it ! It's simple and very quick.
Like a hot splice, different covers (heat resistent, oil resistent, fire resistent, wear resistent, white FDA) allow to operate under various conditions.
Of course, this fastener is compatible with most of the scrapers is correctly installed like you can see on the picture.
You will find further information on our web site.
14th June 2004, 22:25
My company represents Sempertrans belting in North America, and I have spliced the TEB belt before.
As far as I know cold splicing is not recommended for this type of belt. Traditional cold splicing materials, including Sempertrans cold cement “Semfix” is not compatible with the high temperature resistant rubber.
The factory recommendation would be to perform a hot splice using their splice method and their splice materials. With heat resistant belts you are unlikely to have success using splice materials from other belt manufacturers because no two belt manufacturers heat resistant compounds are exactly the same.
I understand you problem of not having a contractor to perform hot splices. I have used the Heat Resistant Super-Screw that Mr. Jacob has suggested on many Sempertrans belts with excellent success. This product is very easy to install and last a long time. Is is an outstanding alternative to hot splicing and in my experience it is much less susceptible to failure than a cold splice, on any rubber compound.
It is recommended that you skive the covers using a hot knife if you with the fastener to be recessed. I have found that this is always the best way to install the Super-Screw to get the maximum life out of this fastener.
Break tests on this fastener are outstanding!
coreytroy - EBW, Australia
1st July 2004, 6:06
This issue of Splicing Heat grade belts has come up here in Australia also.
The Purpose of a Heat grade belt is for the Conveyor Belt apparent to be able to with stand the flow of product UP to the Rated Temperature of the Belt Type.
Ie CRHR 150Deg C
EPT/EPDM 180Deg C
and so on...
Extreme Heat Grade Belts as the T180/EPT/EPDM Require SCRUPULOUS ATTENTION given to the Environment and Preparation of the Splice.
Error with this WILL result in a Splice Failure.
For a Quality completed Cold Splice using say SC2000, it will be suitable for use UP TO 80Deg C.
Therefore: Why spend excess money for a needed Heat Grade Belt to say Handle 100 Deg Celcius, and Join it with a Splice that will ONLY handle 80 Degrees Celcius.
If 80 Degrees Celcius is not too Low of a Temperature for the product, then a simple 'M' Natural Rubber Belt would suffice, at a considerabley cheaper price.
Cold Splicing on Heat grade belt SHOULD NOT BE DONE.
Also from our experience HEAT GRADE Belt Construction has POORER Adhesion between the Fabric Layers and will prepare for splicing (stepped Splice) leaving Bare Fabric exposed to Bond to Bare Fabric, thus loosing the effective bond between rubber to rubber OR rubber to fabric.
14th July 2004, 13:38
I think you should directly convert to hot splicing using the EPDM vulcanizing material of the manufacturer of the belt which is the best way to do it.
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