Hello Emerson...

Indeed Krupp had a whole set of measurements they did many moons ago on different types of installations, using load cell measurements if my memory serves me.

I lost my set of course which was a blow, but since then I have gathered alot of f factor information by extrapolating back from the power absorbed on numerous conveyors against weightometer throughput loads, as well as measuring actual coasting times, and extrapolating back from that.

The difference between f factors for operating and coasting is quite vast, and also varies with the conveyor configuration.

So in other words you need alot of measurements if you don't want to be misled.

Regards

LSL Tekpro ■

Dear Mr. Emerson,

The value of f is one of the very important input in conveyor design. The f value is suggested by reputed standards like DIN, ISO, BS and many. The value appearing in such standards and publications cannot be without extensive testing, observations, and so on. However, such standard and publications do not mention the name of people in general. So, I am not in a position to say particularly who did this field trials and testing. It is obvious that extensive testing, observation, inference from field data etc. have been done in Europe, USA and Japan also. The f value and its related guidelines appearing in standard / publications of repute, are the aggregate sum effect of many participants, often across the nations, debates amongst them and so on.

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.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Maybe getting a bit off the meat of the question here.

Emerson..basically you are asking how to measure f ?

Well don't waste your time measuring the rolling resistance of a spare idler roll and calculating it from that.

In practice the simplest way is to read off the Amps from the drives for a known set of load conditions.

This will give you the power:

Power = Amps x 1.732 x Volts x % efficiency of motor x power factor / 100

Then you calculate the total belt driving force Te from

Te = .97 x .97 x Power / belt speed.

This assumes 97% efficiency for the gearbox and again for the fluid coupling

Remove the portion of Te to lift the load, to accellerate the material plus a bit more for pulleys scraper etc, and you are left with the actual frictional component of Te

Remove the return belt frictional component ( normally reasonably low) using f = .013 for well aligned hot weather installations to .017 for colder climates (but not freezing)

This leaves you with the carry friction from which you calculate f

I have done this many times and it is surprising how f varies from installation to installation. So it takes a while to get good at selecting realistic values.

Regards

LSL Tekpro ■

Dear Mr. Bulk-Offline,

CEMA method uses the f in different form viz. Kx, Ky and 0.015. The f is sum effect of Kx, Ky and 0.015 of CEMA. The f of DIN / ISO is applied to total moving mass whereas the Kx, Ky and 0.015 of CEMA are applied to sub-values of total moving mass. In detail analysis, f is also sub-divided into various kinds of resistances to derive its overall value.

The basic concept is the same i.e. moving mass x coefficient = Resistance. But, both the methods calculate this by different procedures. There is no single factor of CEMA which can be compared with f value of DIN / ISO. Only end result (resistance total value) can be compared. The information about this subject is very lengthy inclusive of many calculations, derivations, etc., and is not suitable / feasible to put here. One should refer and study the relevant literature to know about this subject.

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.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

If you are looking for the belt line resistance of top and bottom strand, then be cognizant of two points:

1. The above must remove the rotating mass and losses of the drive assembly including pulleys.

2. As Graham noted the net gravity forces must not be included.

Be aware of reading meters: a) are they calibrated against know operating factors, b) do they include all three legs of the 3-phase circuit, c) are they corrected for the power factor cos(phi). We often find their are very inaccurate when compared against properly applied drive shaft strain gauges. ■