However, if lower elongations are required, we suggest to increase the safety factor up to the double.
Rubber covers for elevator belts have two main functions: protection of the carcass against material and moisture aggression, assurance of the perfect bucket holding up without bolt loosening in course of time. In order to guarantee safety and longer life, under hard working conditions too, all type of rubber covers are antistatic and ozone protected.
- SX – Medium temperature resistance
- SX is a rubber compound assuring resistance against abrasion; it is formulated for maximum temperature of 100°C. It is not oil resistant.
- BX – Superior temperature resistance
- BX is the rubber cover that assures the maximum heat resistance for a rubber compound. It is designed to work at maximum temperature of 180°C. It is not oil resistant.
Metal clamps for ELEMET
There is not a general purpose clamp suitable for all steel elevator belts as it must be designed in accordance with the tensile strength of the belt, the diameter and the construction of the steel cables, the pulleys diameter, the holes pattern for bucket fixation.
Although ELEMET are realized with very thin and elastic steel cables in order to minimize the effort in the joint bending area, two particulars of these clamps are fundamental for the right performances without breaking of the cords or tearing of the belt:
- Sufficient radius of curvature in order to distribute the tensions along the cords reducing the possibility of cord breaking due to steel fatigue;
- Suitable bolts distribution, steel plates robustness and clamp surface with high friction coefficient to assure perfect clamping with a minimum number of cord breaking.
Elevator belts is described. Various tensions T [daN] in the belt must be taken into consideration:
- T1=P1·H due to belt weight P1
- T2=P2H/p due to bucket weight P2
- T3=P3H/p due to material weight P3
Capacity Q and weight of the handled material for each bucket P3 are connected by.
If there are inconsistency between P3 and P3calc use in the calculation of T3 the greatest value between the data P3 and the value P3calc coming from the capacity calculation. An investigation on this conflict is suggested.
- T4=DJT3/H due to friction at the loading point.
- T5=MAX(K(T3+T4)-(T1+T2),Fv/2) to guarantee motion transmission.
The therm K(T3+T4)-(T1+T2) represents half of the minimum take-up value that must be applied. Negative values mean that buckets and belt weigth are sufficient to assure the minimum required pretension.
The maximum tension in the belt is the sum of these a.m. values T=T1+T2+t3+t4+t5. For the calculation of the minimum tensile strenght a usefull belt width Bu=B-dfnf lower than the real belt width must be considered because of the presence of the hole necessary for the bucket holding.
If at least one of these datas are unknown, we suggest to use a safety factor fs ≥ 15 in the calculation of minimum tensile strength instead of the standard safety factor (fs=12 for Eletex and fs=10 for Elemet).
So, the minimum tensile strength is CRmin= fs. Chosen a tensile strenght CR greater or equal to the here above calculated value CRm, it is possible to verify the effective safety factor fs’= .
The motor power necessary to move the belt loaded with the material must balance T3+T4 because the tensions T1 + T2 produces autocompensative effects along the whole lenght of the conveyor: .
Introducing the mechanical efficiency of the transmission and a power surplus of 20%, the minimum motor to apply to the conveyor belt must be Pm=1,2Pa/h.
- P1 [kg/m] = Belt weight
- P2 [kg/each] = Bucket weight
- P3 [kg/each] = Material weight for each bucket
- P3calc [kg/each] = Material weight of each bucket necessary to guarantee the capacity Q
- Q [Ton/h] = Elevator capacity
- v [m/sec] = belt speed
- H [m] = Elevation
- p [m] = Buckets pitch
- D [m] = Lower pulley diameter
- J = friction factor on the carter: generally 8, for big lump size 12
- K = Friction factor on drive pulley (tipically 0,5)
- Fv [kg] = Applied counterweight (including the lower pulley weigth)
- T [kN/m] = Maximum belt tension
- CRmin [kN/m] = Minimum tensile strength
- B [mm] = Belt width
- Bu [mm] = Usefull belt width
- df [mm] = hole diameter
- nf [mm] = hole number for each bucket
- fs = Safety factor
- fs’ = Effective safety factor
- Pa [kW] = Theorical motor power
- Pm [kW] = Minimum required motor power
- h = Drive efficiency
- P3calc=Q p