Dear Mr. Mahmud,

The belt safety factors as per German practice are as below :

Continuous operation condition (steady state, favourable application) : 6.7

Continuous operation condition (steady state, normal application) : 8.0

Continuous operation condition (steady state, unfavourable application) : 9.5

Momentary condition (starting / braking state, favourable application) : 4.8

Momentary condition (starting / braking state, normal application) : 5.4

Momentary condition (starting / braking state, unfavourable application) : 6.0

All the above safety factors are minimum at vulcanised joint. For an average conveyor you can consider it as a normal application, accordingly, steady state safety factor 8.0 and starting state safety factor 5.4, at joint.

In general the above are as per DIN 22101 (Feb 1982) standard.

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 ■

Morning Mahmud

Generally the basic safety factors are

Steelcord 6.7

Fabric 10

The above relate to maximum running tensions

The reason for the difference being that the steelcord splice does not suffer the same de-rating as the fabric one. This is for example due to a three ply belt having two overlapping plies only at the splice thus giving 2/3 x the strength.

2/3 x 10 = 6.7

The question is normally asked why do belts fail if they are working at such safety factors.

The answer is that if a belt were flat and pulled at the ends it could still have a safety factor of 3 to 4 and would not break.

If you put the same belt on a conveyor with the transitions, radii, and especially pulleys and dynamics, the belts normally fail at a this range of "safety factor"

I use a minimum safety factor of 3.8 with absolutely everything taken into account. (And I mean everything)

Regards

LSL Tekpro ■