Cost Reduction in Belt Conveying

Conveying & Transportation

Cost Reduction in Belt Conveying

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.
(ed. WoMaMarcel - 23/4/2015)
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Various Standards influence the Design of Steel Cord Conveyor Belts.

Steel cord belts are in widespread use in the mining industry. They are used primarily for long-distance conveyors, heavy mining machinery (bucket wheel excavators, overburden conveyor gantries, tractor shovels, bucket-chain excavators, stackers, spreaders, loaders, etc.), short- and middle-distance belt conveyors in surface mining and in general wherever high conveying capacities and small takeups are required. In this connection, two important properties of a steel cord conveyor belt compared to a fabric ply conveyor belt are critical: high nominal breaking strengths with low reference elongations. Today, conveyor belt designers have at their disposal a broad range of design standards and modern materials, meaning that belt manufacturers are able to design conveyor belts in a cost-efficient and application-oriented way – corresponding exactly to the customer’s needs. This article provides an overview of the opportunities relating to how belt manufacturers and end customers can jointly achieve these goals. Furthermore, the new product Stahlcord Barrier from the Contitech Conveyor Belt Group is presented here as an example for this approach.

Various Standards influence the Design of Steel Cord Conveyor Belts

The selection of the cord breaking strength or the cord diameter and the cord pitch of a steel cord conveyor belt has a strong influence not just on its manufacturing costs and the degree of difficulty of the splicing, but also on elements of the belt conveyor system. For example, in the selection of a pulley diameter conforming to DIN 22101 [1], a cord diameter is multiplied by a numerical factor. This value is used in combination with the pulley load factor in the determination of the system’s pulley diameter. Fig. 1 shows a typical steel cord conveyor belt along with its components and important parameters.


Fig. 1: Steel cord conveyor belt with two fabric reinforcements. (Picture: ©Contitech)

Depending on the application, the parameters and components of a conveyor belt are determined by the belt manufacturer in consultation with the customer. In terms of design, it is often not just internationally known standards that are taken into account, but also the internal company standards of the customer. In addition to many national standards (AS, CEMA, GOST, DIN, NF, etc.), the following standards are most frequently used in the design of a steel cord conveyor belt and its splice.

  • German Industrial Standard DIN 22131 parts 1 to 4 [2]
  • International Standard EN ISO 15236 parts 1 to 4 [3]
  • Australian Standard AS1333 [4]
     

In spite of the fact that DIN 22131 has been withdrawn and replaced by EN ISO 15236 (DIN EN ISO 15236), DIN 22131 is still used worldwide because of the many years of good experience of OEMs and end customers.

In all three standards, the recommendations for selecting the parameters for a steel cord conveyor belt are summarized in the form of a table. This table with preferred belt types contains information about minimum breaking strength of a belt (N/mm), maximum cord diameter, minimum breaking strength of the cord, cord pitch, minimum thickness of the cover plates, and the number of cords as a function of the belt width. Therefore, the design of belt types of St500 to St5400 or St6300 that are used most often is predetermined. The recommended belt designs always include strength reserves that are achieved by higher cord breaking strength and number of cords. Depending on the application, the strength reserves should be critically analyzed because they can result in increased costs of a steel cord conveyor belt and the system components (e.g. pulley).

The German Industrial Standard DIN 22131 part 1 specifies that the breaking strength of a steel cord vulcanized into the conveyor belt must be at least as great as the product of minimum breaking strength of the conveyor belt and the cord pitch according to the table with recommended belt designs, with an allowance of approx. 10%. The Australian Standard AS1333 determines for each belt strength class and belt width the number of cords, cord pitch, and minimum cord breaking strength. Therefore, the strength reserves are pre-programmed in both standards.

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