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Frank J.Loeffler, Jr. PE


INTRODUCTION

For more than 100 years the troughed belt conveyor has been used to transport bulk materials. Its success has been attributed to its relatively low capital cost, high degree of reliability and availability, and low operating and maintenance costs. The only significant problems with conventional conveyors have occurred at transfer points when the transported materials were sticky, dusty or there was a need to provide a totally enclosed system to protect the product from the environment or contain dribble from the return belt.

The pipe or tube conveyor solves these problems by transporting the product in a circular cross section formed by overlapping the belt edges and using idlers arranged in a hexagonal pattern to form a tubular shape (see figure #1).

FIGURE No. 1 - Cross Section

The belt encloses the product being conveyed and protects the product from the elements and the environment from the product. The return belt is also formed into a circular cross section, rolled with the carrying side of the belt inward to prevent material clinging to the belt from dislodging at the return idlers.

The only area where the belt is open is at the head and tail end area=s. This limits the possible clean up to the relatively short transition section=s where the belt changes from flat to the circular shape. The most critical area is at the head discharge. This problem can be easily solved by a short Adribble@ collection belt to convey collected material to the discharge chute.

The pipe / tube conveyor also eliminates the need for transfer points to change direction. The pipe / tube conveyor has the ability to form horizontal curves over a much smaller radii than conventional trough belt conveyors, since the belt is constrained on all sides by the idler rolls. This eliminates all the environmental problems and expense of belt cleaners, pulleys, drives, chutes, dust collectors, power distribution and the cost of maintenance associated with transfer points.

For the reasons stated above, the pipe conveyor is an obvious excellent choice for the handling of dusty fly ash, limestone, lime and wet sticky coal, lignite or petroleum coke. What we hope to accomplish in the following pages is to provide sufficient data to allow designers of conventional conveyors familiar with the CEMA method of conveyor belt calculation a method to modify the CEMA equations so they can be used for pipe conveyor preliminary design. The methods outlined in this paper are not meant to influence the pipe/tube conveyor manufacturer=s design and standards but to provide a guideline for preparing a specification.

DESIGN CONSIDERATIONS

Pipe conveyors= have several specialized requirements regarding capacity, lump size and idler spacing. These are included in tables 1 and 2 to assist in developing a proper layout and specification for a pipe / tube conveyor.

The power industry has accepted the CEMA handbook (Conveyor Equipment Manufacturers Association) as the standard to use for designing trough belt conveyors. Since pipe conveyors are relatively new and there is no recognized standard, this paper suggests modifications to the CEMA standards for idler selection and horsepower / tension calculations that could be used to specify the minimum requirements for equipment selection.

CONVEYOR CAPACITY

Table No. 1 shows the pipe/tube conveyor capacity and recommended belt speeds.

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Frank Loeffler, Jr., PE:

  • Over forty years of diversified engineering and management experience associated with the design and construction of bulk materials handling systems. Experience includes: Power, Co-Generation, Mining, Aggregates, Coal, Grain, Steel, Aluminum, Minerals Processing, Pulp & Paper, Ports, Fertilizer, Waste Handling, Recycling, Sulfur, Petroleum Coke, Cement, etc.
  • Typical Equipment includes: Belt Conveyors, Steep Angle Conveyors, Bucket Elevators, Screw Conveyors, Drag Conveyors, Dust Collection, Fire Protection Systems, Sampling Systems, Stacking & Reclaim Machines, Rotary Rail Car Dumpers, Shiploaders, Barge Loaders, Ship Unloaders, Barge Unloaders.
  • Twelve years of this experience has included Forensic Engineering for cases involving: Personal Injury, Conveyor Fires, Guarding, Product Liability, Restraint of Trade, Product Design Evaluation, Code Compliance & Real Estate Asset Appraisal.

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