SELECTION METHOD
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rollers to be protected or manufactured from the appropriate materials that are time resistant to the corrosive substance. The rollers may be in steel, covered with several layers of a particular specification of paint, or covered in rubber or in other anti corrosive materials. Otherwise the rollers may be entirely manufactured from plastic materials that are resistant to corrosion (see PL rollers). Environmental conditions where, in particular, dusty conditions prevail (cement, limestone, ash) rollers with the very best sealing systems that offer the highest possible protection are required (PSV).

2.3.1 - Choice of diameter in relation to speed It has already been stated that one of the important factors to consider in the project design of a conveyor is the speed of the belt, in relation to the required conditions of transport. From the speed of the belt and the roller diameter one is able to establish the number of revolutions of the roller from the formula: v x1000 x 60 n = - [revs/min] D x n where: D = roller diameter [mm] v = belt speed [m/s] Tab. 15 shows the relationship between the maximum belt speed, the roller diameter and its relative numbers of revolutions. It is...

2.3.2 - Choice of the type in relation to load The type and size of rollers to use in a belt conveyor depends essentially on the belt width, the pitch of troughing sets, and above all the maximum load on the roller under the greatest forces, notwithstanding other corrective factors. The calculation of this load is normally made by the plant project designer. Nevertheless, as a check or as in the case of straightforward conveyors, we would like to give you the following helpful fundamental concepts. The first value to define is the load on the troughing set transom. Following this, according...

Working life | Fs Less than 6 hours per day 0.8 From 10 to 16 hours per day 1.1 Over 16 hours per day 1.2 Tab. 19 - Environmental factors Conditions i Fm Lump size with layers of fine material 150 e 300 mm without layers of fine material Clean and with regular 0.9 maintenance Presence of abrasive or 1.0 corrosive materials Presence of very abrasive or 1.1 very corrosive materials Tab. 22 - Coefficient of theoretical bearing life Project theoretical working life of bearings 10'000 20'000 30'000 40'000 50'000

Load determination Having defined the diameter of the roller in relation to the speed and therefore the number of revolutions, one may now proceed to determine the static load Ca on the carrying troughing set, using the following formula: The dynamic load on the return set will be: Cr1 = Cr x Fs x Fm x Fv Multiplying them using the operating factors we have the dynamic load Ca1 on the transom: Ca1 = Ca x Fd x Fs x Fm Multiplying them by the participation factors one obtains the load ca on the highest stressed roller (central roller in the case of troughing set with rollers of equal length)....

Example: One wishes to select a troughing set and rollers for a belt conveyor to convey crushed limestone, with a load requirement Q = 2000 t/h at a speed v = 2 m/s and with the following additional data: therefore the roller load will be: lump size working function belt width belt weight carrying transom pitch return set pitch roller diameter Choosing a transom at 30° satisfies the load requirements on the 1200 mm belt. The static load on the carrying trough set is given by: Iv Ca = ao x ( qb + _ ) 0,981 [daN] The dynamic load will be: Ca1 = Ca x Fs x Fd x Fm [daN] Ca1 = 288 x 1 x 1.02 x 1...