Re: Conveyor Tensile Strength Reduced
Not an expert, though have a look at this, particuarly figure 10 in the ckit link.
https://forum.bulk-online.com/showthread.php?t=13561
Regards,
Lyle ■
Re: Conveyor Tensile Strength Reduced
Thanks a lot Mr.Lyle,
That was one of the excellent thread which the forum members should not miss.
This thread was dealing with the steel cord belts. The problem faced in my conveyor is EP fabric.
Usually I allowed to operate the conveyors at least until the top ply becomes visible after the top cover is worn out.
But here though the top and bottom cover is good, the strength is found less.
Regards, ■
Re: Conveyor Tensile Strength Reduced
Similar issues regarding fatigue of the load carrying element be it steel cord or not.
Have you ever measured the strength of the belts with the "top cover worn out"?
Suspect it would be reduced due to mechanical damage (due to minimal cover) if nothing else.
Regards,
Lyle ■
Re: Conveyor Tensile Strength Reduced
Fabric polymers lose strength as does rubber (being a polymer) when strain cycles are applied. This is part of the oxidation ageing process.
Steel cord belt does also lose strength with time and repeated loading cycles. This is part of DIN 22101 when applying the "r1" factor. I am not sure of the recent rewrite by DIN. This factor may be omitted in the more recent DIN reissue. ■
Re: Conveyor Tensile Strength Reduced
I forgot:
Your approximate 15% is considered normal, when taken over 10 years for an overland and shorter time period. Its the total load strain cycles ( amplitude and frequency of each amplitude) that will reduce the apparent strength in a predictabel fashion. ■
Re: Conveyor Tensile Strength Reduced
Dear Shri S Ganesh,
As stated by earlier respondents, gradual loss of belt strength is not abnormal. The loss of strength will be influenced by the pulley diameters being used, material feeding arrangement and repetitive impact, lump size, conveyor length, exposure to sunlight, etc. If all these are on adverse side, the loss of strength will be comparatively faster. But you are already using the belt since 4 years. The 15% loss means limited reduction in safety factor.
After all, everything suffers from ageing and use.
Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyors.
Author of Book : Belt Feeder Design and Hopper Bin Silo
Advisor / Consultant for Bulk Material Handling System & Issues.
Pune, India.
Tel.: 0091 (0)20 25871916
Email: parimul@pn2.vsnl.net.in ■
Re: Conveyor Tensile Strength Reduced
Originally Posted by I G Mulani
...............
After all, everything suffers from ageing and use. .......................................
Dear experts,
Which has the more ill effect on the belt ?
Ageing without installing the conveyor or usage of conveyor within design parameters ?
Time duration is four years for both the cases.
Regards, ■
Re: Conveyor Tensile Strength Reduced
Dear Experts,
Is the reduction of conveyor strength continuous as long as it being operated?
So far I was replacing the conveyor till the top cover is worn out.
Should I switch over to a strategy on time based replacement ? ( I am not getting convinced ).
If I test the conveyor piece for it's belt rating , till what minimum value can I operate?
i.e, initial it was 1000 N/mm, now it is 860 N/mm, upto what minimum value it would be safe?
Is there any thumb rule relation between the designed rating and the minimum value at
which the belt need to be replaced - in terms of percentage ? Should I need any other detail?
Thanks a lot & Regards, ■
Belt Life & Performance -- Rubber Dependencies
The unfortunate part of conveyor belt design is the splice. Today we see further reduction in belt Safety Factor (SF), in particular, steel cord construction, to SF=4.0:1 levels for longer conveyors. Many more design attributes need to be studied to validate long life at reduced SF.
As I stated before, if we look at the splice for a measure of life, we know the rubber oxidation process is the cultprit. Rubber strength deteriorates with time and flexure (strain). However, splices can be rebuilt and thereby increasing the life expectancy while operating at reduced Safety Factors.
The remaider of the belt does not need the SF = 4:1. A belt could operate down to the limit of the steel cord fatigue strength. Steel cord strength is also cyclic loading dependent, but, it does not molecularly break down with oxidation (non-rust), that does not involve moisture.
Some words of wisdom. Most engineers do not know the specifics of power and tension that are needed to assess the true operating loading histogram of the belt. All fatigue models require knowledge of the loading histogram. Since this is highly rubber depended on the two essential properties of:
1. roll resistance - low rubber hysteresis or high hysteresis = high or low belt tension.
2. core gum performance in the splice as a function of loading and time in service
We will not go further into this realm, due to IP protection. ■
Conveyor Tensile Strength Reduced
Conveyor tensile strength reduced after 04 years though covers are good
Dear experts,
We had installed a conveyor having belt rating 1000 N/mm. This belt strength was checked at the manufacturer's lab prior to receiving the belt. It was above 1000 N/mm.
After four years, a piece from this belt was tested again. Now it is showing 860 N/mm.
How this could be possible? The top and bottom rubbers are in good condition.
Fabric is EP.
Requesting your expert's comments please.
Regards,
S.Ganesh ■