There is already a discussion on that. https://forum.bulk-online.com/showth...-Conveyor-Belt

The longer the belt the more savings that can be realized. But this would not be justifiable on short conveyors - you would need to take a hard look at the cost saving verses the premium cost for LRR belting.

Our software Belt Analyst™ by Overland Conveyor takes this calculation into consideration for calculating HP with LRR belting vs non LRR belting.

Also here is a great article on the subject.

Attachments

viscoelastic indentation and resistance (PDF)

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Thanks to Gary and of course the authors for a very fine paper. It would be interesting to learn if the major software suppliers have all taken the Indentation Resistance into account. I am particularly addressing the belt manufacturers with this question. From an EPC reviewers perspective the Clients willingness to invest in lower indentation resistance could influence the spares holding for the more mundane equipment i.e. use LRR belt on all, long or short belts of the same width. Power for shorter belts could therefore reduce. Later on Gary's observation predominates and Operations will use a more suitable, cheaper for them, belt. Belt will be OK but power will be inadequate. Operations can rightly blame the EPC/FEED.

Incidentally, I didn't see a significance in sag in figure 1 and no correction for sag in figure 2. Is there any significance for sag in this brave new world: or have we been wasting our time this past century? Perhaps it was addressed in the loading but I couldn't trace it and I am ageing rapidly according to those nearest and dearest. ■

Hello,

Belt conveyor total resistance R is made up of following resistances:

R = Main resistance + Lift resistance + Skirt board resistance + Material acceleration resistance + Scraper resistance + Idler tilt (forward tilt, etc.) resistance + Pulleys wrap resistance + Pulleys turning resistance + Discharge plough resistance (where applicable).

The energy saving belt reduces the main resistance only. All other resistances remain unchanged. The name main resistance does not imply that it is ‘main’ or dominant resistance all the time. For conveyor of medium length, say 250 to 750 m, it has respectable value, and its value can become more respectable for conveyor above say 750 m, if there is no sufficient lift. It becomes a prominent value when conveyor length is in kilometers. The main resistance is synonymous to rolling resistance of railway engineering terminology.

The main resistance (FH) formula is FH = (Conveying friction coefficient f) x (Belt line total moving mass) x g.

The multiplier g is to get force value in Newton (N) or poundal.

For commercial belt conveyors equipped with usual belt (grade M, N, etc.), the friction coefficient basic value is 0.02 i.e. f = 0.02.

Again f is total of four constituents as below:

f = Belt denting flexure resistance coefficient + Belt bending flexure resistance coefficient + Idler resistance coefficient + Material flexure resistance coefficient.

f = Belt denting flexure resistance coefficient + (Belt bending flexure resistance coefficient + Idler resistance coefficient + Material flexure resistance coefficient).

In above composition, belt denting flexure coefficient is around 55% of total value 0.02. The range is 50% to 60%, specific to the conveyor. Thus,

f = Denting flexure coefficient + Other three coefficients.

f = (0.02 x 0.55) + (0.02 x 0.45) = 0.011 + 0.009 = 0.02.

Now, broadly speaking energy saving belt has denting flexure resistance about half of usual belt .

Therefore, for energy saving belt, f = (0.011 x 0.5) + 0.009 = 0.0055 + 0.009 = 0.0145, as against 0.02 for usual belt. In case the designer is designing conveyor for higher value of f, then reduction in it will be also as above, with respect to magnitude, presuming that higher value is due to more value of material flexure and other reasons.

So, for primary investigation, the designer can consider f = 0.0145 or say 0.014 in conveyor design formula being used by him and see the result, to judge whether the particular conveyor is worth for energy saving belt or not.

The designer will observe that:

-For usual in-plant conveyor of low and medium capacity, the result will not be impressive for energy saving belt.

-For high capacity and adequately long conveyor, the result can be somewhat impressive.

-For long conveyors having length in kilometers, one will find the result is impressive in favour of energy saving belt .

There are also following other points to be taken into consideration:

1) For energy saving belt (superior visco-elastic property belt) the magnitude of indentation resistance is sensitive to temperature. If the yearly temperature range is say 5 degree C to 40 degree C, the belt indentation resistance will be high during winter and adequately low during summer. So conveyor design and components on the basis of winter temperature, may become as if near to usual belt. However, such conveyor will consume less power during major portion of a year (if cold spell during winter is of short duration).

2) Belt manufacturers may give effective belt for particular temperature range for case to case.

3) The rubber is easily manipulative material like steel. However, when one tries to make it excellent for less power, it becomes less favourable on other counts. So a compromise is made to suit specific application for optimum benefits (reference German publication ‘Bulk Solids Handling’ articles by specialists and researchers, on conveyor belt rubber).

4) The belt characteristics degrade as the time passes. So, it would be also necessary to know the implication on energy saving characteristics during later portion of the life of the belt.

5) Energy saving equipment / conveyors are very good for society and industry. However, for the buyer the cost-economy will be also of primary concern. He will examine the extra cost to him for conveyor versus saving in electricity bill (and its equivalent evaluated capital cost).

6) The conveyor designer might also have to consider belt future replacement. If it happens to be of different make with somewhat different energy saving value, then the conveyor designer has to keep some contingency in the conveyor original design.

7) The belt gets indented when moving on roller, but belt does not get fully un-indented instantly while leaving the roller. There is minute (very small) time lag. This causes the indentation resistance. Contrarily for energy saving belt, its rubber cover will recover faster from depression, and thereby less indentation resistance. In simple word it ‘Bounce-back’ more quickly.

8) Belt will have energy saving rubber cover on bottom side (pulley side face). It can have energy saving rubber cover or usual rubber cover on belt top face.

9) The information is for general awareness among conveyor users and designers about the available variant of belt and to give consideration to its use. The given figures, etc. are primarily for understanding. Refer manufacturer of belts for specific data.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

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: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Perhaps we might see some manufacturers' comments about this topic: given time. So far we seem to be lauding the low resistance belts on behalf of the makers who are apparently reluctant to share their knowledge.

Simplistically, as ever, I understand that there can be a power saving by using harder belts for long conveyors but no binding evidence is publically available throughout the business. As Ishwar mentioned, the power saving throughout the life of the belt is fraught with some uncertainty.

So the designer is obliged to carry out power calculations according to accepted and established literature anyway. There ends the case for the designer!

End of story: although waiting for a future thrilling instalment by belt manufacturers who might also be disposed to explain why the addition of sulphur and a few other modifiers raises the price of these fancy belts such that their use even becomes a topic for debate. As I read it, there is only the belt price difference separating the installed cost of a new conveyor. From the CAPEX perspective it is a done deal: reinforced by the fact that many owners 'free issue' belting. OPEX is pie in the sky in a volatile world. ■

Hello,

Referring to my earlier reply to this topic; following is the additional information for more clarity:

The conveyor total resistance and thereby its power; is to be calculated by summing up the calculated individual resistances as listed, and not by using alternative abbreviated formula having 'C' factor (as mentioned in DIN / ISO). In case of energy saving belt, the 'C' factor values will be different from commonly used values.

Ishwar G. Mulani

Author of Book : Engineering Science And Application Design For Belt Conveyors (new print November, 2012)

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: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Seems like the many thread bearers wish to dimissed the advantages of LRR or as some call Energy Optimized Belt (EOB). Ever since CDI published the advantages on 1989 20 km Channar Overland Conveyor (OLC), there are many who wish this technology would go away. Why? Because they cannot take advantage of beneficial rubber properties with their in-house technology.

Witness the complex mathematical treatment of Prof. Rudolphi & Mr. Reicks, Prof. Lodewijks, Prof. Wheeler, or Dr. Qiu's multiple publications. Not usable by the typical engineer who wishes to take advantage of the method.

Few engineers/researchers have the capacity to measure a piece of rubber and predict the drag loss from the rubber rolling indention properties. Fewer can do so with high accuracy. It takes an investment in rheology Dynamic Mechanical Analyzer (DMA) testing machines, testing techniques, in-house software to convert the test information into a Rubber Master Curve and finally into a constitutive mathematical model of the interactions between rubber and idler roll surface dynamics. This is also true for idler drag based on superior lubricants. See References: http://www.conveyor-dynamics.com/about/power.htm. Read the research of Professor Craig Wheeler at University of Newcastle in Australia. Prof. Gabriel Lodewijks Delft University published his Doctoral discertation on the subject.

There is no one value for DIN f drag. It changes with: temperature, tonnage, speed, indention cover thickness, rubber viscoelastic properties, idler roll diameter, idler spacing, idler trough angle, crossectional loading, belt construction (steel cord diameter, cord spacing, cord construction, fabric layers, top cover thickness, ....).

CDI has often published results of our OLC installations and derived benefits as have many belt suppliers. See our website for some insite to wit:

1. 1989 20 km Channar published in Bulk Solids Handling - DIN f = 0.0105, later near end of top cover life, DIN f = 0.085. Most rubbers become more efficient with time.

2. 1995 5 km German Creek showed performance using SBR rubber. Many coal operators use FR compounds. FR will increase indention drag by 25-50% depending the LRR or Super Low Rubber Rolling loss (SLRR). See above ref.

3. 1998 14 km Muja/Collie showed performance using NR rubber, again DIN f was about 40% higher than was possible with best LRR. See above ref.

4. 1998 7 km Southern Ohio Coal showing performance change between NR and LRR belt at 26% savings in power

6. 1999 (?) 10 km Crinum OLC measured power with NR vs. theory

7. 1998 16 km Zisco rolling loss published in Beltcon (South Africa)

8. 1998 14 km CRU-II published in Beltcon (South Africa)

9. 2007 20 km Curragh North using SLRR published by Goodyear in BSH

10. 2008 12 km (?) Sasol Twistdale (sic) LRR gain published by Goodyear at +20% gain between original belt and LRR

11. ContiTech, Phoenix, Bridgestone, Yokohama, Goodyear - all leading providers of belts with best practices endorse the use of LRR and SLRR rubber compounds and extole their benefits. A good LLR or SLRR belt can save a client the Net Present Value cost of the same belt over a 10 year, 6000 hr/yr. operating cycle vs. typical SBR, NR or FR belts. FR, and to a lesser extent SBR belts are high consumers of power. We call them "Power Hogs".

It seems some here do not read available literature, which clearly shows the gains. Why not read the literature before engaging in rheotoric. ■

Sorry for the misprint:

Channar DIN f - 0.0085 after 15 years of service.

Also, Prof. Manfred Hagar has many publications on the virtues of LRR rubber which span many years. Prof. Spaan, Prof. Lodewijks adviser, also published some of the watershed documents and led Prof. Yonkers to publish the first applicable treatment of rubber viscoelastic properties for belt conveyors. ■

Dear John,

"Hard" belts by themselves do not provide benefit on power reduction. This has been repeatedly dispelled in publications. Typically, Hard Belts signify a high loading of carbon black. If the carbon black is inert, as is often the case, it is used as a low cost filler to bulk the rubber, like Kayolin clays, ash, etc. These filler damp the resilience of rubber's relaxation recovery on the idler surface and therefore lead to higher power requirement. ■

Hi,

You are right dear, when I was using the same steel cord conveyor the power saving reached up to 15-20%. And also thanks to Gary for sharing such useful information. Power saving is very important for conveyor, when we are going to purchase a conveyor we always demand for good and power saving conveyor. So whenever we manufacture any conveyor we should always remember all important things like material that we used. ■

Belt characteristic behaviour is just one consideration for selection.

On a SATORP overland conveyor the Sub-contractor initially claimed that belt selection was a long process and there was additional confusion due to a grossly inadequate FEED. A few days later I was copied an email which informed that the belt had been selected and would be delivered over a year in advance of the splicing operation. In the interim the belting would be stored outdoors, ground standing and under canvass (maybe) in an Arabian coastal location. Belt design was far from finalised. It was only a couple of weeks before that the Sub-contractor advised that there was insufficient information for a proper FEED based design.

Why the sudden change of plan? Cash flow. SATORP was awash with cash and the priority was to show project progress by heavy spending. So the Sub-contractor agreed to embellish the progress by finalising a belt specification for a conveyor that was not yet designed. Main-contractor could then raise the PO for the belting and the project would steam ahead. Of course the down payment would also ensure survival of the hard pressed, elsewhere, Sub-contractor. All this was accomplished without my agreement and I was able to wash my hands and proceed to the next phase of the fiasco.

So what is my point? Well, if the Sub-contractor had shown enough nouse and nerve he could have ordered 58km of more expensive LRR belting and embellished the project progress even further. Some practitioners are seriously divorced from the realities of conveyor hardware procurement. The recent involvement of completely inexperienced US & French oil and gas contractors in the bulk solids business suggests the situation will only get worse: and why not? Some of us need the amusement. ■