RUBBER TECHNOLOGIES

SELECTION OF THE TYPE OF BELT

Once the maximum tension that the belt shall support is known, the type and resistance of the carcass to support it can be selected.

SAFETY FACTOR

On the conveyor belts, high safety factors are considered as they shall take into account the additional efforts on duty, such as the bending on both drums, the irregularities of the sharing of tensions on the carcass, the irregularities on the load, starting overtensions, resistance loss at splices, load impacts, aging of the belt, etc. The DIN 22101 standard recommends the following factors for textile carcass belts:

TABLE XI - SAFETY FACTOR FOR TEXTILE BELTS NUMBER OF LAYERS (Z) from 3 to 5 from 6 to 9 greather than 9SAFETY FACTOR (S) 11 12 13

The usual is that the number of layers shall not exceed 5, so in general, factors around 11 or 12 shall be taken. It is also preferable that the number of layers shall be as little as possible, as a greater flexibility of the belt is obtained and a better coupling of the layers during the work.

The safety factor depends on the time that the belt completes its run, as the number of bendings on the drums depend on this factor as well as the load impacts. In general, if there are not other factors able to affect it, it can be diminished down to two units, if the time of run is over 5 minutes.

For the belts with metallic carcass, the safety factor recommended shall be equal or greater than 8. In this case, if the time of run is greater than 10 minutes, this factor can be diminished in one unit.

RUBBER TECHNOLOGIES

So, the number of textile layers of reinforcement on one belt, shall be given by:

In the case of belt of metallic carcass, the nominal resistance of the belt shall be given by:

Where:

z.- Number of textile layers

S.- Safety factor

Tm.- Maximum working tension of the belt, in kilos

B.- Width of the belt, in meters

Rl.- Nominal resistance of each textile layer

Rn.- Nominal resistance of the metallic carcass of the belt