CONVEYOR BELT TESTING
The abrasion resistance is measured by moving a test piece across the surface of an abrasive sheet mounted to a revolving drum. It is expressed as volume loss in cubic millimeters, for instance 150 mm³.
A smaller number indicates better abrasion resistance.
The total belt elongation consists of an elastic (which recovers) and a plastic (which remains) portion.
As per ISO 9856, a belt sample is subjected to a sinusoidal cyclic stress that varies from 2 to 10 % of the belt's nominal breaking strength. 2 - 10 %, because this is a typical operating range for textile conveyor belts. After 200 cycles, the amount of permanent elongation of the test piece and the amount of elastic elongation produced by the force differential are recorded from a force-elongation.
Typical permanent elongation values: Polyamide (P): 1,0-2,5%, Polyester (E): 0,5-1,5%, Aramide (D): 0,25-0,75%, Steel: 0,1-0,25%.
Other (static) tests, e.g. as per DIN 22102, require a reference tension of 10% of the nominal belt breaking strength. The maximum total elongation for EP belts is 1,5, 2,5 or 3,0 %, depending on belt class
A rheometer test identifies most of the problems in a rubber compound.
An uncured sample is placed between two dies. The lower die oscillates. The upper die is connected to a sensor to measure the torque response of the rubber at the deformation during the vulcanization process at a constant temperature.
STEEL-CORD PULLOUT STRENGTH
Steel-cord pull-out strength,
static (just pull) or dynamic (10.000 cycles),
without reheating or with reheating (to simulate splicing).
The cyclic load ranges from 3.6 percent to 36 percent of the nominal static pull-out strength for a given cord diameter (see DIN 22131 or AS 1333).
The test is carried out until the number of required cycles is achieved or till failure of the bond occurs.
STEEL CORD TENSILE/BREAKING STRENGTH
The actual steel cord breaking strength is ascertained by tearing the entire rope until it breaks. Result stated in kN.
RUBBER STRENGTH AND ELONGATION
The tear resistance is the quotient of the force required for a test piece of specified shape and size with a defined cut to resist tear propagation.
The force is acting in the direction perpendicular to the plane of the cut and of the test piece thickness.
SEPARATION STRENGTH / ADHESION
Test as per ISO 252.
Normal minimum requirements are 6 N/mm between plies and 4,5 N/mm between cover and ply.
It is not common to determine a hardness requirement.
Usually a belt cover will have a hardness between 55 to 70 °ShA.
A test mainly for steel cord conveyor belts with different combinations of additional reinforcements ("breakers").
There are a few different methods on the market, but no standard yet.