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High Angle Conveying, the Vital (missing) Link to IPCC Systems – 2017

Belt Conveyor Technology

High Angle Conveying, the Vital (missing) Link to IPCC Systems – 2017

Installations and recent studies have demonstrated the technical and economical advantages of high angle conveying for optimization of any IPCC system, yet that industry continues to struggle with the use of conventional solutions to achieve the high angle function.
(ed. WoMaMarcel - 07/4/2017)
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Sandwich Belt Conveyor – the Vital Link for IPCC Systems

Suitability for IPCC systems has been demonstrated at all Dos Santos Sandwich Belt high angle conveyors with a number of units handling very large ore and rock at very high rates. We will approach the suitability issue methodically and then demonstrate the suitability of actual installations.

The most common concerns regarding sandwich belt high angle conveyor suitability for IPCC applications:

  • Can they handle very high tonnage rates?
  • Are they suitable for continuous operation 24/7?
  • Can they handle large, heavy, primary crushed ore and waste rock?
     

The various installations answer these concerns.

Of these, the most important concern is third on the list. The answer is: “large belts can handle large lumps, small belts can handle small lumps”. Fig. 14 shows a to-scale comparison of sandwich belt cross-sections for widely varying belt widths. Clearly, “large” lump size is relative. 350 mm lumps are too large to handle at a sandwich belt of 1000 mm width, but not at a sandwich belt of 2600 mm width. Indeed, to have compatibility of belt width and material size we limit the material size with regard to the trough depth. For predominantly lumpy material, we limit the lump size to the depth of the trough. For occasionally lumpy material (less than 10% large lumps), we increase the size criteria to 125% of the trough depth. This is to limit the separation of the belts, preserving a good covering over the bulk material and positive belt to belt contact at the edges of the sandwich.


Fig. 14: To-scale sandwich belt cross-sections of various belt widths.

Table 1 lists select sandwich belt high angle conveyor installations, along with the lump size handled, against the Dos Santos lump size criteria. A severity light provides a relative measure of the lump size for the belt width. A green light indicates that the lump size does not exceed the depth of the trough. A yellow light indicates that the lumps handled exceed the trough depth but not by more than 25%. A red light indicates that the lumps handled are in violation of the lump size criteria even for occasionally lumpy material. Nevertheless, the units of Table 1 operated successfully even with the large violating lumps. In such cases, the design, belt speed, components, belt construction and covers were selected to handle the coarse material. Along the convex curves, rubber disc center rolls are typically used to soften the ride when handling large lump materials.


Table 1: Various sandwich belt high angle conveyor installations with design lump size against the lump size criteria.

Due to radius of curvature constraints, closely spaced 20° troughing idlers are typical along the sandwich carrying curves. Thus the trough depth that serves as the lump size criteria is that of a 20° trough.

It is interesting to compare this with the similar criteria for the conventional conveyors at the same site, subject to the same duties. Generally, for conventional troughed belt conveyors, the maximum lump size criterion is related to the belt width. For predominantly lumpy material, the maximum lump size is BW/5, while for occasionally lumpy material (less than 10% lumps) maximum lump size is BW/3. This compares with the corresponding sandwich belt criteria, of BW/9 and BW/7, listed on Table 1. Recognizing that the sandwich belt high angle conveyor at the same site, subject to the same duty, will always use wider belts than the conventional conveyor, lump size criteria tends to be close to compatible.

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