HOW TO CHOOSE THE PROPER FASTENER
First of all it is necessary to ascertain the chemical compatibility of the fastener with the product to carry and with the environment.
It is also important to consider the mechanical actions on the belt and on the fasteners (direction and system of loading, presence of deflectors, stacking and positioning of the product).
There are normally three basic aspects to consider in order to choose the proper fastener:
- Thickness of the belt to join
- Diameter of the pulleys on which the belt winds up
- Maximum tensile strength applied to the belt.
The first two aspects are usually known, and can be easily obtained by the Belt Fastener Selection Chart.
The tensile stress applied to the full-load working belt can certainly be calculated, but it is hardly ever known by the operator who has to choose the fastener and make its choise according to his experience.
For this reason it seems appropriate to determine the breaking tensile strength for belts with standard characteristics and a thickness from 2 up to 5 mm joined with VAT fasteners; the results of the test have been indicated in the technical data sheets.
This information can be scarcely meaningful if the belt workload is not a known value.
As the only catalogue data that provides information about the resistance of the tensile insert is the Tensile Strength for Elongation 1%, we tried to determine a Factor of Safety by the ratio:
FoS = Breaking Tensile Stength/Tensile Strength for Elongation 1%
We perfectly know that this Factor can have a merely indicative value as the breaking load of the fastener depends mainly on the characteristics of the weft of the conveyor belt while the tensile strength for elongation 1% depends on the characteristics of the warp.
For 2 or 3 plies belts is recommended that FoS is higher than 3.
