A capacity table is provided on the next section to aid you in calculation of proper conveyor size. To use this table, find the capacity at maximum RPM, opposite the recommended percentage of conveyor loading, which equals or exceeds the capacity of material required per hour. The recommended conveyor diameter will then be found in the appropriate column on the same line, as will the maximum particle size recommended for the screw diameter.
If the maximum particle size you plan to convey is larger than the maximum recommended particle size for the conveyor you’ve chosen from the table, you must then select a larger conveyor, adequate to handle the maximum particle size you intend to use.
Calculation of Conveyor Speed
Conveyor Speed can be most conveniently calculated, by use of the nomographs supplied on pages. To use this nomograph – first locate the two known values (screw diameter, and required capacity, in cu. ft. per hour), then with a straight edge connect these two points. The appropriate conveyor speed will be the intersection point on the third value column marked “Speed”.
Maximum economical capacities will be listed for reference opposite their respective conveyor diameters, and should not be exceeded. Another method of calculating conveyor speed is:
Not Recommended Factors for Conveyors With Paddles*
| Factor |
Paddles Per Pitch |
| 1 |
2 |
3 |
4 |
| 1.08 |
1.16 |
1.24 |
1.32 |
* Std. paddles at 45° reverse pitch
Example:
A conveyor is required to transport 10 tons per hour of a material weighing 62 pounds per cubic foot and having a maximum particle size of 100 mesh. To further complicate the problem, we will require that the material be mixed in transit using cut and folded flights. Since the distance the material is to be conveyed is relatively short, we want to use short pitch screws, to insure proper mixing of material. The materials table recommends a loading percentage of 30% A.
Actual calculated volume:
For proper calculation of size and speed, this volume must be corrected, by use of capacity factors, to compensate for cut and folded, and short (2/3) pitch flights.
These capacity factors, taken from the preceding charts are:
Cut and folded flights 30% loading = 3.75
Short pitch flights (2/3 pitch) = 1.50
With capacity factors included, capacity will now be calculated:
SC = 3.75 * 1.50 * 323
SC = 1817cu.ft.
This selection capacity value will be used in the capacity table, for calculating correct size and speed. In the appropriate column, under 30% A loading, we find that a 14″ conveyor, at the maximum recommended speed will convey 2194 cu. ft. per hr. or 21.1 cu. ft. per revolution.
To calculate actual conveyor speed, the following formula should be used:
This is the correct speed at which the 14″ conveyor with cut and folded, and short pitch flights will convey the actual capacity of 323 cu. ft. per hour.
Graphic selection of this conveyor could also be accomplished by use of the 30% A nomograph on page 22 and the selection capacity of 1817 cu. ft. per hour.
