Re: Longitudinal Cracking At Trough Line
Dale
There was a contractor at Appin Colliery NSW who was spraying in situ a polyurethane (or similar) coating onto their drift belt. There were FRAS issues but the product might be more applicable to your situation.
Give me a call if you want a name. ■
Re: Longitudinal Cracking At Trough Line
Dale,
Pls see some of the post by Larry Nordell on this topic......
Cheers
James ■
Repairing Longitudinal Cracks
Hi Dale,
Eli-Flex conveyor belt and rubber repair resin is the quick and easy way to repair longitudinal cracks extending over large distances.
Eli-Flex requires no patches, no adhesives, no vulcanising. You merely mix it up and paste it in.
For downloadable .pdf case studies and more info, please visit :
www.elichem.co.uk/eliflex.htm
In particular I draw your attention to a case study of a repair we completed successfully with Eli-Flex at Apasco Cement in Mexico. A belt had 460 feet of continuous longitudinal gouging. Short of replacing the belt, there was no other way to repair it.
This was done 2 1/2 years ago and is still running. you can view this at the website listed above.
Best Regards,
Aram Friedrich
aram@elichem.co.uk ■
Re: Longitudinal Cracking At Trough Line
Dale hello again,
Your crack at the trough junction is not new. Unfortunately their is no published details on want limits the belt selection, and idler configuration. Note the many interdepent details:
1. trough angle
2. belt bending sectional modulus at the junction
3. fatigue stress criteria at the junction - BELTSTAT has a critiera
4. variations in belt compound and ageing
5. idler spacing
6. idler roll in-line or offset and overlap
7. belt width
8. belt speed
9. mass per meter
10. rock size
11. steel cord configuration, diameter, and pitch - related to pt. 2
12. transverse fabric reinforcements - related to pt. 2
13 belt conver thicknesses - related to pt. 2
14. belt exposure to sunlight or belt cover - ageing
15. heat cycling in Australia outback - ageing
There are many 45 trough roll configurations operating for many years.
BELTSTAT does a idler junction stress analysis and has a critieria that should not be exceeded. Publish your details and I will submit our junction analysis result. We also observe if there is unusual added flex fatigue. We were asked to determine the parting of an 1800mm long belt in OZ about two years ago. Everybody was blaming the belt turnovers. In my opinion, it was cause by a VEE junction of the carry roll configuration. You can see it at the point of failure around the cable.
Lawrence Nordell
www.conveyor-dynamics.com ■
Re: Longitudinal Cracking At Trough Line
Hi Dale
Are there any successful repairs which can economically be done in-situ for long lengths of such cracks (e.g. spray coating)??
Without seeing the damage I’d say you have several options available, couple have been mentioned here.
The others that you could try would be Repair Band, fabric reinforced, there are several manufacturer and suppliers and the other is the T2 repair system, it’s a Rema Product utilising an extruder type heat gun and uncured rubber, it quick and very effective in most situations.
Be careful when asking about repairs from Service companies, if they are not familiar or don’t have the equipment for the T2 they won’t recommend, visa versa on the Repair Band, Eliflex etc.
A solution to this would be to do a 10 mtr section trial using the different methods on the same belt.
Run this for a month or so, you should get a fairly good idea on the wear, price, ease of use etc. ■
Longitudinal Cracking
Thanks guys for your responses. I will act on them. Further contributions from others welcome. As you all appreciated there is a 4-fold problem -
- how to repair the cracks occuring
- anything that can be done to reduce the likelihood/severity of cracking with the existing configurations
- anything (relatively minor) which can be done to change the existing configurations to reduce the likelihood/severity of the cracking
- what can be done for the future with changes to belt spec and/or idler configuration to prevent this happening (we are about to start a major plant expansion).
Please keep the responses coming in. ■
Re: Longitudinal Cracking At Trough Line
■
Longitudinal Crack Repair
Bruce has pointed out some excellent advice.
A side-by-side trial of Eli-Flex and Rema T2 will give you good data as to cost vs ease-of-application vs results.
Perhaps I can point out one salient difference :
Eli-Flex is the only repair method which does not involve having to purchase expensive application equipment.
Last I heard a T2 gun costs ( in the U.K ) over £ 4000,00 ( Pounds Sterling ). This is before you factor the costs of the repair material.
Once this gun is purchased, the user becomes bound to use it indefinitely so as to amortise the costs over time.
Eli-flex requires no extra equipment ( even the spatula comes free with the resin packs ), it is a stand-alone repair technique.
Hope this helps.
Aram Friedrich
www.elichem.co.uk ■
Causes Of Longitudinal Cracking
Gents,
I am trying to keep this thread alive because there are still unanswered questions.
It has been suggested to me that the cover grade can have a significant effect on the longitudinal cracking. We run almost exclusively A grade covers (changed from M grade & FRAS many years ago - I suspect on the recommendation of reputable belt manufacturers). It has now been suggested that the cracking problem will probably be eliminated if we use M grade covers. The wear rates on most belts are very low - so changing to M grade should not be a problem (unless there are other issues).
Any comments or experiences ?
Also (Larry & others) - do the belt fatigue life calculations you mentioned take into account the rubber grade and/or different rubber compound properties ? ■
Re: Longitudinal Cracking At Trough Line
Dale,
The better rubber compound (grade?) will alter the outcome.
Rubber fatigue life rating is dependent on the strain history, which will vary with compounds.
CDI has developed a simple strain (stress) level analysis and criteria, incorporated in the BELTSTAT Professional version and is based on:
1. belt construction -cover gauges and steel cord diameter
2. trough shape
3. idler spacing
4. material cross-sectional loading
This is based on known successful systems where we have exceeded the known design limits.
We do not claim this to be as appropriate as a full FEA and comphrehensive compound analysis, but is does keep us out of trouble.
Proper rubber compound fatigue sensitivity testing is the only way to get to the quantitative values.
FRAS and like compounds are notorious for poor longevity.
Lawrence Nordell
www.conveyor-dynamics.com ■
Re: Longitudinal Cracking At Trough Line
Dale,
I assume you are refering to the suspended idlers in a coal handling port in your home town. I was there two weeks ago on route to Heron Island for some R&R, a very pleasant experience.
From what I remember of the 45 degree idlers used at the port, the idlers are mounted from cantilevered brackets and are impossible to maintain. If the centre distance between the two mounting points was increased, you would obtain a lower troughing angle and this could reduce the severity of the cracking problem. Is that worth considering? I have heard on the grape vine that all the brackets are being replaced to make maintenance easier so why not change the width.
Regards,
Dave Beckley
Conveyor Design Consultants of WA
Perth Australia. ■
Trough Angle
Dale...
Matey with regards to the eliflex.. we use it here and well when your belts flatten out for delivery i would think your dirt trackers will pick it up and pull it out bit by bit...
Plus the cost to do the lengths your talking of would be pretty exxy.
we had a mob come in a few years back with a product called CONCUR .. which involved a copper disk buff of the effected areas and application of the resin.. which in affect was quite good yet bend pullies and snubs etc just buggered it...if the belt starts to part I would go for the reinforced bandaid black and green as we have repaired up to 120metre tears with great success. Even on EPT belts( ALUMINA) it seems to hold together well and you can still run your scrapers provided your air bag pressure remains at about 5psi..hope that helps
Catchya ■
Repairs To Longitudinal Cracking
Dale, I read these reply with great amazement, my experience with conveyor belting repairs is from recommendments from Belt Slicing/Supply Companys, it thier recommendations that one relies on.
These longitudal cracks that are being discussed, how long are they, how deep are they (have cracks starting from gouges), what is the hardness of belt beside cracks or accross belt, have the cracks carried through the thickness of belt, I presume your local Splicing company or yourself would have the equipment to carry out hardness test.
Inquired into Eli-flex & T2 repairs, these repairs are for gouges etc (so I am told), not for longitudinal splits through belt, one repair rep said, Eli-flex & T2 repairs are like putting putty on a nail head before painting.
If Eli-flex is so good why or where are thier plastic steel cord belt available on the market ?.
Repair band has been the only tempory solution we found correctly applied will enable production to continue, then change out or replace damaged section, and cold bonding repair band, does require 6hrs curing after application, know from experience.
Unable to comment on 45 deg idlers.
Lee Johns ■
Longitudinal Cracking
Dale, back again, what product are you handling, forgot to ask, your talking about A grade rubber, sounds like a rock quarry to me, there is a large quarry up that way somewhere, strange they are running steel cord belts.
Lee ■
Re: Repairs To Longitudinal Cracking
Hi Lee Johns, you wrote
I read these reply with great amazement, my experience with conveyor belting repairs is from recommendments from Belt Slicing/Supply Companys, it thier recommendations that one relies on.
Inquired into Eli-flex & T2 repairs, these repairs are for gouges etc (so I am told), not for longitudinal splits through belt, one repair rep said, Eli-flex & T2 repairs are like putting putty on a nail head before painting.
If Eli-flex is so good why or where are thier plastic steel cord belt available on the market ?
and this is from an earlier post in this thread.
Be careful when asking about repairs from Service companies, if they are not familiar or don’t have the equipment for the T2 they won’t recommend, visa versa on the Repair Band, Eliflex etc.
Again, you do have to be careful about service companies, like most business's they will only sell you what they distribute or manufacture, regardless of whether it is the best solution.
These forums allow for input from many and varied sources to hopefully educate the end-user as well as suppliers to the different products and methods available.
I personally have used T2, Eliflex and Repair Band.
All these products are excellent in the correct application.
The post actual stated "They are now getting longitudinal cracking" not splits. ■
Re: Longitudinal Cracking At Trough Line
Dale,
Your comments regarding the cover grade are correct. Grade A covers will generally “harden” quicker than say an M grade cover. This in turn can result in cover cracking.
As the belt is not wearing out then abrasion may not be an issue. What is the remaining cover thickness on the belts that fail?
In addition when specifying the cover grade you need to ensure that you correctly specify the ozone resistant properties of the covers. AS1333 does refer to the “Resistance of covers to ageing” however it does not adequately cover this issue of ozone & UV damage.
When you say the utilization is quite low, does this mean that the belt stands stationary for long periods of time (weeks or months)? If so you should consider a practice of running the belts on a regular basis to avoid developing a “set” in the belt.
Chris ■
Longitudinal Cracking at Trough Line
I considered continuing on the thread started by Kinder on 45 degree idlers but decided this subject warranted its own thread.
I have a client who has over 10,000 x 45 degree suspended 3-roll trough idlers with a 1800mm 19mm x ST1250 belt installed on 41 different conveyors. The utilisation of many of the conveyors is quite low, so the belts become 'old' before they wear out. They are now getting longitudinal cracking at the 45 degree trough line with belts 10+ years old. I presume this is fatigue cracking. They are not about to change the 10,000 idler sets to lower trough angle.
What can be done to prevent/reduce this cracking (now and for future new belts ??
What are the main influences on such cracking ?? (belt design (e.g. cord diameter, cord spacing, cover thicknesses, cover grades), number of cycles, weather exposure etc. etc.
Can fatigue cracking in a rubber belt be calculated ??
Are there any successful repairs which can economically be done in-situ for long lengths of such cracks (e.g. spray coating)?? ■