Cost-efficient and Application-oriented Design of Steel Cord Conveyor Belts for the Mining Industry
Conveyor belts in the mining industry are facing ever higher demands as regards conveying capacity, conveyor length, service life and energy efficiency. In addition to designs according to various general standards manufacturers further develop their products for better economy.
Dr. Andrey Minkin
(ed. WoMaMarcel - 23/4/2015)
While German or Australian standards allow low “freedom” in the design of a steel cord conveyor belt, the International Standard EN ISO 15236 (and DIN EN ISO 15236, resp.) is more flexible in this regard. In addition to the recommended belt designs conforming to EN ISO 15236-A1 and -A2, the following applies in the selection of the number of cords:
“Based on the minimum breaking strength of the cord Fbs in kN, the minimum breaking strength of the belt (kN) in N/mm, and the width of the belt B in mm, the minimum number of cords (nmin) is calculated according to the following equation:“
“The actual number of cords, n, must be greater than or equal to nmin. The number of cords in the tables should be regarded as a recommendation only. It results from the equation Eq. (1) and from the requirement that the edge width cannot be greater than 40 mm and cannot be less than 15 mm”, i.e.:
“A higher number of cords as well as a lower number can be selected if the conditions are met with regard to the minimum breaking strength as defined in EN ISO 15236-1 and EN ISO 15236-4.”
Table 1 shows the comparison between designs according to three standards for an example belt 2200 St2500 12:6 X: From this table, it is evident that the design conforming to International Standard EN ISO 15236 compared to Australian Standard AS1333 makes for a belt that is not just approx. 11% lighter and approx. 11% less expensive, but also makes it possible for the drive pulley diameter of a belt conveyor system to be reduced by 36%. (Compare design conforming to AS1333 and “Based on EN ISO 15236 A2”). A slight increase of the cord pitch by 0.5 mm has a positive effect on the belt splice.
From this a general recommendation can be formulated for economical belt design: “In the case of belt design, a large number of thin cords should be preferred.” However, this rule only applies if the dynamic splice efficiency of the belt splices of at least 45%, which is required according to DIN 22101, is ensured. Often with long-distance conveyors having a center distance exceeding 1000 m, customers require a higher dynamic splice efficiency of the belt splice than 45%. This is especially applicable for long-distance conveyors having a center distance extending over several kilometers (often 10 km or more), where service lifes for a belt of 10 to 15 years are expected.
Steel Cord Conveyor Belts with and without Extra Low Loss Bottom Cover
In the design of a steel cord conveyor belt for horizontal long-distance conveyors (center distance exceeding 1000 m), the selection of the rubber compound for the bottom cover is of great significance. With the bottom cover made of a proper rubber compound, the indentation rolling resistance (IRR) can be significantly reduced. With long-distance conveyors, the IRR is responsible for 50% to 70% of the total resistance  (Fig. 2). This effect is strengthened with increasing center distance of a long-distance conveyor.