Engineering Guide

Screw Conveyor Engineering Guide

Material Characteristics

The Material Tables on the following pages contain information regarding materials which may be effectively conveyed, using KWS Manufacturing Company's screw conveyor systems. For information on unlisted materials, refer to the Engineering Department of KWS Manufacturing Company, Inc.

"Convey-ability" data for unlisted materials can, when necessary, be complied by making a comparison of listed materials which have similar physical characteristics, such as weight and particle size. The following is a brief description of the information presented in the Materials Table.

Maximum Particle Size

Conveyor size, speed, and horsepower requirements, are directly affected by bulk density and internal friction, which are relative to the particle size of conveyed material,

Average Weight per Cubic Foot

This section of the Materials Table is supplied to enable you to convert the required capacity in pounds or tons per hour to volume in cubic feet per hour.

Note: Since most typical applications of screw conveyors receive slightly aerated, gravity fed products, the weights listed in this table are averages and when possible, actual bulk densities should be used.

Conveyor Loading

The recommended percentages of conveyor loading is a prime factor in determining the size of conveyor, and is based on the maximum depth at which materials will flow through the conveyor without causing undue wear. Considerations should be made, for example, for materials with a high abrasiveness because wear indexes would normally be higher due to a larger contact area with component parts.

Horsepower Factor

The horsepower factor, representing the relative mobility of the material, is necessary for horsepower calculation.

Recommended Component Series

This information is presented to assist in the selection of the proper materials of construction, component weights and other specifications best suited for the material to be conveyed. The alphabetical code refers to general component series, and the numerical code gives bearing and shaft type recommendations. See component series tables

Abrasiveness, Corrosiveness And "Flow-ability"

In addition to the above information, the Materials Table also presents graphically the relative abrasiveness, corrosiveness and "flow-ability" of the materials listed. These characteristics, as well as other special aspects of materials, are given further treatment in the Component Selection Section. The values of the graphic presentation used in the Materials Table are listed below.

Note: Some materials, while they are not corrosive under "normal" conditions; may become corrosive under certain other conditions, such as when heated or in the presence of moisture.

Special Characteristics Notes

Notable unusual material characteristics are fisted by numerical codes in the last column of the table where applicable. An explanation of these numerical codes is given below.

1. Contains explosive dust
2. Fluidizes easily
3. Absorbs moisture.
4. Usage or value affected by contamination.
5. Emits toxic fumes or dust.
6. Usage or value affected by material degradation.
7. Exceptionally light or fluffy.
8. Tends to pack under pressure.
9. Fibrous material which tends to mat.