Originally Posted by Bulk-offline

While we have heard often about LRR (Low Rolling Resistance) compounds - including at this forum, there seems to be a new variant : Super LRR (SLRR) doing the rounds these days.

The concept of LRR, when it was explained was interesting and certainly admissible in practice but when a superior variant is promoted, one wonders just how superior is this SLRR vis-a-vis the LRR rubber compound. This gives rise to certain questions in my mind which, I hope, experts in this forum could clarify - I suggest Better than 15%

1. Are there any documented studies of SLRR vs LRR ? YES. A number of studies have been published. By example: Curragh North by Dr. Robin Steven.

2. How much ADDITIONAL power consumption is expected from a SLRR belt w.r.t. a LRR belt under identical circumstances ? LRR=25% Reduction; SLRR another 20% beyond LRR

3. If there are power savings (due to reduced resistance from the rolling components) , Te would also be lower and hence T1 and hence there should be a reduction in the belt rating employed ? Has this acid test been carried out anywhere ? YES. See below story

4. What are the TEST PARAMETERS that distinguish a SLRR compound from a LRR compound ? Is there any documented comparitive study report ? A gain of 20% is significant.

5. Does a SLRR rubber conform to ALL the physical characteristics of a LRR rubber or are compromises made in that respect ? There are always compromises.

Somehow, the sceptic in me feels that the SLRR may just be a nice marketing gimmick that will work well amongst gullible users for the simple fact that no company is likely to actually test the comparitive power consumption between a SLRR belt and a LRR belt in actual working conditions.

Again, theoretical design computations usually bild in so many factors of safety that the ACTUAL power consumption in ANY long conveyor is always significantly less that the theoretical consumption calculated at the project approval stage. I BEG TO DIFFER - read below

This is one instance where I would love to be proved wrong with hard facts, data & answers since the potential of such a compound would be immense in dictating project economy for material handling systems. THERE ARE MANY PUBLICATIONS TO THE FACTS GIVEN BELOW. We claim the industry can reduce old replacement belts and new projects with a guaranteed savings in power, and belt strength reductions that exceed the old installation by more than 20%-40% depending on all design facts.

Thanks

WHO ARE YOU? WHY HIDE YOUR IDENTITY?

LRR (Low Rolling Resistance) is a term Conveyor Dynamics, Inc. (CDI) coined to describe the belt performance supplied by then Goodyear and now Veyance Technology on a project for Southern Ohio Coal Company in early 1990's. It was a 5 km overland, originally installed in the 1970's that required a new belt. The original belt used a NR (natural rubber) based compound. The new rubber was laboratory tested and demonstrated the potential for a +25% reduction in power. Field records were taken of the old belt and the new LRR. LRR did reduce the power consumption by about 26% according to our data acquisition. The only change was the rubber compound of the bottom cover. Veyance published the results in various papers. CDI have given many lectures on the performance of LRR.

ContiTech supplied a similar LRR belt for the 20 km Channar overland in Western Australia in 1989, designed by CDI. In fact, the ContiTech belt had a slightly better power reduction index, when compared to NR based rubbers. Power measurements were made and published in Bulk Solids about Channar's success 1991.

In 2007, Curragh North 20 km overland was commissioned, by LORA and CDI with a new Veyance compound designated SLRR, that better LRR by about another 20% at the nominal operating temperature of 25 C. It is important to note that the ambient temperature is extremely important in recognizing the potential benefit. At 5 C, the noted LRR, SLRR and NR compounds draw about the same power. Below - 5 C temperature, NR draws less power. These finding have been corroborated by Newcastle University (NU) belt-loop-to-idler indention testing machine. NU has been studying these belt indention loss behaviors for the last 2 years. Prof. Craig Wheeler has offered publications on some features. The work is proprietary to Veyance, CDI and LOR. CDI and Laing O'Rourke (LOR) partnered with NU and Veyance to study NR, LRR, SLRR and a new concept named Super Elastic Layer (SEL). Its constructions are patented. The study scope was to achieve validation and guidance on the next generation of power savings.

The test machine can measure power differences from actual belt constructions, different rubber compounds that undergo idler-to-belt indention at various speeds, temperatures, and synthesized loads together with differing idler diameters.

In our opinion, the test rig is superior to all previous test apparatus built to date.

Our theory is in excellent agreement with the test work on the noted belt constructions. Further test programs are being conducted on new rubber compounds to demonstrate to clients the benefits of evaluating TOTAL LIFE CYCLE COST BENEFITS.

Interested parties can contact the undersigned for a more in depth discussion. ■

The thread starter had something in mind with the question about belt rubber and its influence on Overland Conveyor (OLC) power and other performance indicators.

I have published many conversations on the "Power of Rubber" in Conveyor Design. In summary, for a long overland the difference in belt bottom cover formulation can mean:

1. Capital Cost Savings > 30% - belt tension and cover specs, motor sizes, pulleys, idlers and structural specifications can be more than 30% of the OLC system capital expenditure when fully optimized. Unfortunately, there are too many non-believers to encourage the advancement wholesale.

2. Operating Cost Savings > 100 % of belt captial cost: Power savings, in NPV belt life terms, can be greater than the cost of a new belt. Thus, by applying NPV analysis to an optimized belt design will yield a "no brainer" selection. Unfortunately, this is not easy for a less informed manager to do the due diligence and make the call for the mine owner benefit. Super Low Rolling Resistance (SLRR) belt does have a cost premium. In order to justify its purchase, the owner must do the Capex and Opex analysis. Too often, some unversed scribe will nominate excessive belt covers, which does not allow optimization.

There are many optimization techniques including these few:

A. Rubber compound & cover selections - geometry, formulation, temperature sensitivity,.....

B. Steel cord design

C. Idler optimization - roll diameter, bearing size, lubricant, trough shape and anlges, off-set rollers vs. in-line, idler spacing, .....

D. Power (motor) distribution - head, head & tail, booster stations, ratios, ......

E. Take-up design and control

F. Pulley arrangements

G. Chute Loading onto OLC

H. Terrain geometry - vertical and horizontal curves

The savings can be staggering and beyond belief to many. However, there now are a number of world class installations that demonstrate the truth. ■

We write a lot about the subject. Very few understand the concept and apply it.

Most belt conveyors today, if fitted with proper belt rubber properties, would lower the world's consumption of power by more than 1%. The mine duty power may drop by more than 15%.

Why is the industry so backward? I have seen a client specify a POWER HOG belt just to be able to say he did not want an efficient rolling resistant belt. So few apply what is now a 24 year old technology. There were many studies on the subject in the 1980's. Then the 20 km Channar OLC, in 1989, showed a power reduction from DIN f =0.015 to 0.010 or a 50% drop. Still no one took notice, only unprofessional comments that showed a bias for the status quo.

Today we see occassionally DIN f = 0.008 or lower. These values cannot be achieved on all belts. We can lower the average power consumption that is nearly equivalent to a 50% reduction. Who cares?

Rubber properties can be formulated to give much better TOTAL COST OF OWNERSHIP, if the client would ask for it. If more clients would ask for it, it would become a standard, and it would foster better rubber compounding for all the belt suppliers or those that did not would perish.

What does the industry have to do to support this better belt friendly environmental proposition. ■

Rubber properties can be formulated to give much better TOTAL COST OF OWNERSHIP, if the client would ask for it. If more clients would ask for it, it would become a standard, and it would foster better rubber compounding for all the belt suppliers or those that did not would perish.

What does the industry have to do to support this better belt friendly environmental proposition.[/QUOTE]

Dear Mr. Nordell:

Great question above and I am sure that you deal with this everyday on CAPEX projects. We try to have this discussion with all of our clients. However, with mining companies becoming larger in scale, there is a great disconnect between the Purchasing Departments and the actual mine users. The TCO concept should be used not only for belting; but, for all components. However, short sightedness by getting the lowest price today usually wins at the Purchasing Department. This would be a great topic for another thread. ■

The Purchasing Officer (PO) is endowed with making the best selection for the company's bottom line. Unfortunately, he is most often not an engineeer that can evaluate the difference. Therefore, if he is empowered to make the best selection, he should find a source of information that will lead to a fit-for-purpose choice.

What are the position criterion for the PO? If the PO is in charge of dollars, make him informed by providing evidence of the differences during the bid phase. Eventually, responsible PO's will read and make the prudent selection.

On this point, we also see too often, a consulting engineer in charge of specifying the belt conveyor design criteria, requiring extreme belt cover thicknesses. When we see top covers above 20 mm, without high impact loads or very sharp rock edges with large lumps, we see ignorance and irresponsible action. Top cover should be selected for belt life. Belt like is highly driven by the feed chute design. Yet, the dots do not connect for too many in charge of this design. The same can be said for bottom cover selections.

Bottom cover selection should be driven by wear and power. Wear can be somewhat complex. When we observe bottom covers of 8 mm or more for steel cord belts with less than 10 mm cord diameter (ST-5000 N/mm), this again shows ignorance of good belt design. The we have prudent viscoelastic properties. It can make a difference between an ST-5000 N/mm and ST-3000 N/mm design with commenserate reduction in belt bottom cover thickness. Its only $$$$$.

Since belt conveyors make up a goodly portion of many mine operations, maybe POs should be required to take a course in belting economics. ■