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How to use it
Enter the geometry of the screw, the speed and the conveying length, then describe the material with the bulk density, the degree of filling and the resistance coefficient. You get the capacity and the power, split into the three parts of the standard: material conveying, no-load running and lifting.
Formulas used
Q in t/h, L and H in metres, D in metres, powers in kW. The factor k reduces the capacity by about 2% for each degree of inclination.
What remains to be checked
Degree of filling and resistance coefficient depend on the real product: moisture, particle size and tendency to pack change the result more than the geometry. Then there are shaft deflection and intermediate bearings, starting torque with the screw full and, for food products, cleanability. The dedicated service is sizing of a conveying or feeder screw.
FAQ
Which degree of filling should I choose?
45% for light, free-flowing materials such as grain and flour, 30% for medium materials, 15% for heavy or abrasive ones such as sand, cement and ores. A higher filling increases wear and the risk of clogging at the bearings.
Which pitch should I use?
Normally the pitch equals the diameter. It is reduced to 0.5–0.8 times the diameter for inclined screws, for feeders and for materials that flow too easily.
Does the formula apply to feeder screws?
It gives the order of magnitude. In a feeder the screw runs full under the hopper: the capacity depends on the real filling and on the density of the compacted product, and must be calibrated with a test.