Overland Pipe Conveyor Conveyor Belts: Save Energy by Minimising Belt Rolling Resistance

Author / Editor: Yijun Zhang * / Marcel Dröttboom

For long overland pipe conveyors the costs from increased power consumption are significant. The low rolling resistance trough belt is well studied in theory, tested in lab, and proven in applications. This article describes a methodology that analyses the low rolling resistance pipe belts and introduces recent applications on overland pipe conveyors.

(Picture: Conveyor Dynamics)

Overland tubular pipe conveyors can overcome difficult terrains and protect the environment. But a pipe conveyor’ power consumption typically doubles to a comparable trough conveyor, due to the additional rolling resistance from the pipe belt. For overland pipe conveyors with longer than 3 km, the capital and operating costs from the increased power consumption are significant. The Low Rolling Resistance (LRR) trough belt is well studied in theory, tested in lab, and proven in conveyor applications. This paper describes a methodology that analyses the LRR pipe belts and introduces recent applications of LRR pipe belts on overland pipe conveyors that reduce power consumption and improve performances.

From Steele Belts to Continuous Production

Belt conveyors have been widely used to as an efficient way of transporting bulk materials. The ubiquitous trough belt conveyors have the benefits of high degree of reliability and availability, and low operating and maintenance cost. However, trough belt conveyors have limited capability to negotiate difficult terrains, mainly due to limited horizontal curves the trough belt can withstand. Typical curve radii are around thousands of meters. The tubular pipe conveyors solve this problem by folding the belt into a smaller pipe cross section, and allowing the belt to rotate within idler frames. The allowable horizontal curve radii are around hundreds of meters.

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This conveniently falls in the range of horizontal curve radii of typical paved roads. As a result, pipe conveyors can be constructed alongside of existing roads. Being more versatile in conveyor routing also avoids some of the property rights and land permitting issues, which are becoming more important in an increasingly crowded world. The open trough belt could raise concerns about materials spillage into the environment. Folding the belt into the enclosed pipe shape separates the material from the environment. This protects both the material and the environment, especially for dusty materials with fine particles. In certain cases, this also protects the material from being stolen.

Besides the benefits, pipe conveyors are more expensive than trough conveyors in terms of capital cost (excluding civil cost) and operating cost. The folded pipe belt, depending on its cross sectional belt stiffness, exerts additional contact pressure on idler rolls. The additional contact pressure, when coupled with the belt bottom cover, translates into additional indentation rolling resistance, belt tension, and power consumption. To accommodate the increased belt tension and power consumption, bigger drive size and more expensive belt are required, in addition to more idlers, which all increase the capital cost. The engineering of pipe conveyor is more complex. The lack of open design standard limits the engineering proprietary to a few practitioners with good understanding and experience. Pipe conveyor system with improper engineering or a belt unfit for the system can lead to problems that are difficult and costly to solve.

During recent years, more overland pipe conveyors longer than 3 km have been commissioned, with some conveyor lengths exceeding 6 km [1]. Now pipe conveyors longer than 10 km long are being planned. As a general trend, it can be expected the conveyor lengths will keep increasing, as is true for overland trough conveyors, whose single-flight lengths have exceeded 20 km [2] and now approaching 30 km. With intrinsically higher friction, the increase in power requirement and belt tension with conveyor lengths for long pipe conveyors can quickly escalate to a very expensive level. Making the long pipe conveyors more efficient thus has significant implications for system suppliers and end users.