Splices
Originally Posted by sganesh
Dear Experts,
How the lengths of Hot vulcanised joints in fabric belts are derived? For example, what will be the splice length of 500/3 and 1250/4 fabric belts? How are they derived? Do the derivations hold good for the cold vulcanised joints also?
Thanks and Regards,
So much depends upon;
duty cycle, tonnage, ore or waste moved meaning abrasiveness, trough side carcass thickness, steel cordage if any.
The splices I have seen in my previous job were 24 hour hot vulcanized using water cooled compression heat clamps for a man made fabric corded 36 inch belt installed upon 21 degree incline 450-500 tons per hour of minus one inch rock salt.
If my memory is right the entire splice was a foot long with all the layering as that belt was .5 inches thick prior to splicing the conveyor belt.
I do not remember if a sacrificial section of belt was spliced on both ends of the belt and then heat vulcanized.
Mr. Nordell and Mr, George Baker will will be better able to answer it than I can for you.
I am unsure what is available on the web from Goodyear, Dunlop, Bridgestone Krupp Robins and others regarding vulcanized splices.
lzaharis ■
Re: Hot Splice Lengths Determination
The step length given by the international standards is over dimensioned with regard to the surface area needed to transmit the nominal breaking strength of the fabric from one splice side to the other side. This means, that a step length should be sufficient in a static test to arrive at breaking a fabric ply instead of the step sliding apart.
The steps in practice are made longer for the following reasons:
1. To allow for possible errors in manual work such as cutting too deep when preparing steps.
2. When buffing the rubber left on the steps, touching the textile fibers resulting in loss of strength in the textile plies.
3. The dynamic fatigue in a splice during the lifetime of the belt. Due to the bending and reversed bending around pulleys and the impact on the belt at the loading point the strength of the splice is reduced. This process follows an a-asymptotic curve and stabilizes on approximately 28% of the original strength after 200.000 cycles.
In short: the used type of fabric determines the length of the step. Heavier fabrics need longer steps, not (just) a heavier belt. A type 800/4 used a 200 type fabric and would require the same step length as a type 630/3 or 1000/5, which also use the same fabric. A 1000/4 uses a type 250 fabric, which would need a longer step length etc.
In principle, cold joints can result in the same static strength and the same step lengths normally apply, however in the long run, cold joints tend to loose on durability due to belt flexing and load changes, however this is not likely solved by just increasing step lengths. ■
Hot And Cold Vulcanised Splices
I had forgotten about the overlap steps
lzaharis ■
Re: Hot Splice Lengths Determination
Thanks a lot for your participations. I understand that same type of fabric will have identical splice lengths. Could you still explain me what will be the standard step length in case of fabric 200 and 250. How are they arrived?
Thanks & regards, ■
Re: Hot Splice Lengths Determination
This is what we use:
TS of fabrictypeStep length mm
63 minimal 120
80 minimal 120
100 minimal 160
125 minimal 160
160 minimal 200
200 minimal 250
250 minimal 250
315 minimal 315
400 minimal 315
500 minimal 350
630 minimal 350
It is derived from practical testing, done for the creation of international standards, and the step lengths are now fixed in these standards.
The dynamical reduction of strength ends at around 28% as stated before, so when static test are done to determing how much surface will transfer the force from step to step so the joint breaks instead of sliding apart, this step is roughly multiplied by 3.6 to get to the values. As you can see the values are rounded to the same values as used for the belting/fabric types (200/250/315 etc) so the actual step lengths for the type you requested , 200 and 250, are the same, although theoretically the overdimension-rate (or how do you call it) on the 250 type shall be lower. That is just about what I can tell you about it. ■
Fabric Splice Ply Overlap Length
Adding a few notes:
The necessary ply-to-ply overlap requires more insight than knowing it is a fabric or its fabric strength. It also requires knowledge of how the splice strain field will respond to the fabric elastic modulus, and weave type ( straight or crimp), as well as the interply gum properties and splice geometry.
A straight warp polyester verses a crimped nylon fabric will likely have very different allowable overlap lengths. The belts could have the same overall rating but not carry the same load due to the complexity of splice strain and failure behavior.
All splices fail due to the rubber's strain cycling. You must understand what each type of fabric does to rubber's strain cycling. What the outer plies do verses the inner plies. The degree of overlap has often been found by trial and error, although there are analytic procedures that can predict, with reasonable accuracy, the failure location and mode.
Today there are also other procedures such as finger and hybrid-finger splices that can increase the splice fatigue rating to breaking strength greater than 24-28%. This value is derived from some common design principles as given in DIN 22101. The standard notes that when you add:
a) operating tension (1.00)
b) starting tension (0.40)
c) elongation, age, construction errors, idler transition strain, vertical curves and misalignment (1.00)
d) a+b+c = 2.40 force or tension multiple of the running load as the necessary temporal strength to design for, then this must also be designed for the fatigue reduction that occurs with time such as the 24-28% value, or in the case of steel cord belt 36% to achieve long life. These equate to the belts Safety Factors:
Fabric 2.4 / .24 = 10.0:1
Steel 2.4 / .36 = 6.7:1
These values should be taken with some reservation, unless you know and understand the fabric and shrinkage control properties, core gum fatigue properties, adhesion properties and special adhesion enhancers, and changes that occur with cyclic loading ( oxidation damage). ■
Re: Hot Splice Lengths Determination
[QUOTE=sganesh;55956]Conveyors Hot splice lengths - How are they derived?
Dear Experts,
How the lengths of Hot vulcanised joints in fabric belts are derived? For example, what will be the splice length of 500/3 and 1250/4 fabric belts? How are they derived? Do the derivations hold good for the cold vulcanised joints also?
Thanks and Regards,
splice lengths on a 500/3 will be 500mm & a 1250/4 will be a 1200mm splice but
don't get me wrong it falls in a sertan bel class
ex. 400/3 & 500/3 falls in the same belt class &
1000/5,1250/3,1250/4,1250/5 & 1600/4 would be in the same class ■
Re: Hot Splice Lengths Determination
[QUOTE=sganesh;55985]Thanks a lot for your participations. I understand that same type of fabric will have identical splice lengths. Could you still explain me what will be the standard step length in case of fabric 200 and 250. How are they arrived?
Thanks & regards,
a fabric 200/3 would have two steps of 150mm each
and the 250/3 & 315/3 would have two steps of 200mm each ■
Re: Hot Splice Lengths Determination
Splice lengths are derived based on several factors:
1) PIW reqiurement
2) Saftey factors involved.
3) Minimum pulley diameters / flexure.
4) Fabric/carcass styles (crimped/plain weave or straight warp) or steel
'
200 piw or 250 piw plied belts require 15" steps. Thats off the top pf my head. I could be off a little.
Buddy Wilson
Application Engineer / TSM-Southeast
Fenner Dunlop Americas ■
Re: Hot Splice Lengths Determination
Originally Posted by rvoijenTS of fabrictypeStep length mm
63 minimal 120
80 minimal 120
100 minimal 160
125 minimal 160
160 minimal 200
200 minimal 250
250 minimal 250
315 minimal 315
400 minimal 315
500 minimal 350
630 minimal 350
It is derived from practical testing, done for the creation of international standards, and the step lengths are now fixed in these standards.
The dynamical reduction of strength ends at around 28% as stated before, so when static test are done to determing how much surface will transfer the force from step to step so the joint breaks instead of sliding apart, this step is roughly multiplied by 3.6 to get to the values. As you can see the values are rounded to the same values as used for the belting/fabric types (200/250/315 etc) so the actual step lengths for the type you requested , 200 and 250, are the same, although theoretically the overdimension-rate (or how do you call it) on the 250 type shall be lower. That is just about what I can tell you about it.
Dear Experts,
We are using 1000/6 and 1000/4 belts.
1000/6 will be of 166.67 , say 200 . Step length will be 250 .
Minimum splice overlap length = 250*5=1250 mm
1000/4 will use ply 250. Minimum splice Overlap will be 250x3 = 750mm.
Could there be a huge differences of 500 mm , though belt rating is same for both the belts 1000 N/mm ?.
Request to clear my above doubt.
Regards, ■
Gap Between The Leading & Trailing Plies In Hot Vulcanizing Joi…
Dear Experts,
Many years ago , I was seeing that there was no visible gap between the leading & trailing plies in the hot vulcanizing splicing. But now it is recommended. One supplier said to have 2 mm and another said 20 mm.
I find it difficult as there is no standard is existing in the procedure of the splicing and also in the thicknesses of the vulcanizing compounds.
Having standardized procedure and materials will be great help for the end users like me.
Thanks & regards, ■
Hot Splice Lengths Determination
Conveyors Hot splice lengths - How are they derived?
Dear Experts,
How the lengths of Hot vulcanised joints in fabric belts are derived? For example, what will be the splice length of 500/3 and 1250/4 fabric belts? How are they derived? Do the derivations hold good for the cold vulcanised joints also?
Thanks and Regards, ■