Dear Mr. Singh,

Selection of cover grade is given in IS:1891(Part-2 for HR) & also in a belt manufacturer catalouge.For calculating power you take weight of belt as per HR grade. As regards cover grade, we take M24 for heavy,sharp abrasive material & N17 for moderate abrasive material & less severe application, HR-T1- for temp. less 80 deg cel.& so on...

Regards.

A.Banerjee ■

Dear MR. Singh,

I used many HR grade belt for transporting hot lime & I did not have experiance of increase in power due to the same.You calculate power & rationalise & you will get same result.

Regards.

A.Banerjee ■

Dear Mr. Singh,

I discussed the issue with more senior people & find no answar. From where you got this idea I do not know but please do not waste time on it.

Regards.

A.Banerjee ■

Dear Mr. Singh,

We consider f=0.03 which is the max. & select standard motor power . So the percentage of increase with variour grade is insignificant.It is no matter in Raw materials handling system.

Have a good day.

Regards.

A.Banerjee ■

Mr. Singh is correct. Up till 1989, belts were purchased on price and not performance.

Rubber compounds can cause >50% difference in conveyor power between manufacturers and for the type of compounds used within a manufacturer's recipes.

I suggest Mr. Banerjee do some reading on the subject before offering further advice. Try our website to see comparisons of compound changes within one manufacturer one belt. He will find a 26% difference in power for a measured overland. If the belt could have been optimized to take advantage of the compound, the difference would have been closer to 35%. These facts are now beginning to be understood by the mining communitee.

CDI has been practicing this technology for over 15 years. We do well in competition with leading turnkey and engineering firms. By example, in partnership with Barcal Mowlem in Australia, we were recently awarded a single flight 20 km overland. The leading factors included cost of ownership.

Mr. Banerjee offers advice that will cost the owner unnecessary penalties. Mr. Banerjee advises that a DIN rolling resistance friction factor f= 0.030 is acceptable makes the point. In most cases, this is a very poor design factor.

Today, with better compounds, at a nominal tonnage up to 2000 t/h and belt speeds to 5 m/s, the DIN f should be less than 0.015.

We cannot give specific values for HR and FR. There are many dependencies that must be qualified to render an opinion. ■

Dear Mr Nordell,

You & Mr. Singh both are very much correct that I have not much exposure on power effect due to various cover grade.

But here f =0.03 ,I refered as artificial coeff. of friction of conveying not the rolling resistance offered by idler.Mr.Nordell, you have mentioned that as per DIN f can be .015 with better compound.Also you are refering f as rolling friction. I know that rolling friction of idler is about 0.0004. Please can you give me DIN particularly that page where the same is written. I do not have latest version as we normally use ISO 5048&IS 11592.

Have a good day.

Regards.

A.Banerjee ■

Mr Banerjee:

The factor I refered to is the rubber rolling resistance, not the idler rolling resistance. Please read the available literature to understand the facts.

You often remark about published works in your responses. To offer useful explanations to interested parties, you should be knowledgable beyond the uninformed. I beg you to please read the modern literature on rubber rolling resistance. I did note many I have published on my website. Mr. Staples has posted a number on his CKIT site. Dr. Wolhbier has included many from Bulk Solids Handling, including Professor Hager, and myself. They all deal with rubber rolling reisistance. Usually, most speak of the rubber indention resistance, but we must also include flexure and trampling losses. ■

Dear MR. Khalid,

Yes, I work in Dasturco, Kokata & you are correct that I should not write any thing on subject which I do not know.In my reply I expressed the same.

But considering individual, one cannot conclude about the company. This wrong statement.

A.Banerjee ■

Participants are in a very serious discussion. I was thinking whether I should get involved in this matter.

I would only like to point out that when HR grade belt is used, it implies that the material being conveyed would be hot and some times quite hot. So, the rubber condition during this actual conveying is to be considered for various implications like hardness of rubber, higher temp of rubber, and so on. In certain installations, I have seen rubber covers developing cracks during use for hot application. So all this effect to be counted according to the best of judgement and available data.

So, while making specific calculation for particular application, personally I consider somewhat higher value for artificial coefficient of friction. This depends upon temperature, etc. My reply is not the direct answer to the question. This reply / information is addressed to general readers.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Dear Mr. Singh,

I have been hesitate to answer your question regarding power draw with HR (high temp rubber compound ) verses FR (flame retardant rubber) because it leads to lengthy expalanations which I do not want to elaborate upon. However, I will generalize the answer and give warning not to generalize this to a design.

HR rubber, as previously noted has a number of additives and base polymer to protect against cure reversion, burning and checking which markedly differ from FR.

Usually, HR compounds CDI has tested for viscoeleastic properties, to apply to power consumption formulae, exhibit a very high hysteresis. This hysteresis increases (ie power goes up, with increasing temperature). We have measured the power increase up to 120C. We do understand HR belt can operate to over 200C. HR is unusual. Power can increase dramatically above 0 C. Compounds different substantially between manufacturers and according to the degree of heat resistance. As a course rule HR belt power can approximately double from zero and +100 C.

I say the above, noting that CDI have tested only 6 HR belts from different manufacturers.

FR rubber is usually compounded from cloroprene polymers. The rolling resistance can be reasonable and certainly far superior to HR. FR behaves as do most NR and SBR compounds where the rolling resistance generally improves from below zero up to +60C. Beyond +60-65 C the power consumption can again begin to rise exponentially with increasing temperature.

As temperature is elevated beyond 65C the FR rubber begins to breakdown or acts as though it is ageing and loses its life properties. Often FR belts have a life of about 8-12 years while a good NR or SBR belt can be rated over 20 years, not including wear. ■

Dear Author,

I have written to Mr. Nordell of CDI to withdraw the term BEG. Some body has deleted the same.Now I understand that we have Mr. S nordell & Mr. Nordell of CDI.

Regards.

A.Banerjee ■

TO Banerjee & AR Singh,

Banerjee: S Nordell is my wife's computer which I use late at night. Her first name is Sarah.

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AR Singh: Please drop the idler reference when refering to rubber rolling resistance. Idler friction factor addresses bearing and seal drag of the idler. THus, idler friction factor does not vary with manufacturers.

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Belt manufacturers do not have any incentive to build test rigs to measure idler rolling resistance. Some academics have and belt manufactueres are developing such systems now that there is an awareness that rubber can make a substantial difference to the design and operation of belt conveyors.

Some belt manufacturers are motivated, but, who do they sell to?

Why impose a standard and rolling resistance when it is a technological moving target?

I guess about 1-2% of the industry acknowledges this science.

If owners required performance guarantees the level of awareness would immediately change.

CDI has spent clsoe the 1.5 million dollars on this technology without $$ contributions from others, but on successful bidding against other design firms. When the client allows the science we both win. When the client does not allow the science we all loose.

Some belt manufacturers and engineers despise the science, give it a bad name, protect their domain, resist change, and see it as a threat to their survival by making them redundant.

It shouyld be an economic and environmental imperative to use our resources wisely. Who do we need to educate? ■

errata:

NOW YOU HAVE ME DOING IT1

THe above third paragragh has a reference to belt manufacturers and "idler" rolling resistance that should read "rubber" rolling resistance. ■