Question 1

How is a screw conveyor sized for a given throughput?

Accepted Answer

Screw conveyor sizing is based on: the required volumetric or mass throughput (kg/hour or m³/hour); the material bulk density (kg/m³ — determines the screw diameter and speed needed for the required mass throughput); the conveyor length and inclination (inclined screw conveyors have lower throughput than horizontal ones at the same speed, due to material falling back against the screw rotation); and the material properties (cohesive or free-flowing; abrasive; sticky). The screw diameter and rotational speed (rpm) determine the volumetric throughput. Higher speed increases throughput but increases wear on the screw and trough and can cause product degradation in sensitive materials. Screw conveyor manufacturers can calculate the required screw diameter and speed for a specified throughput and material if provided with the material bulk density, flowability, and abrasiveness data.

Question 2

What cleaning procedure is required for a food screw conveyor?

Accepted Answer

Cleaning requirements for food screw conveyors depend on the product and application. For dry non-hygroscopic products (flour, grain, dry spice), cleaning may be performed by: dry brush-out or air blow-down of the trough and screw; followed by visual inspection for residue; and periodic wet cleaning with hot water and approved food-grade detergent, followed by drying. For wet, sticky, or hygroscopic products, more frequent and thorough cleaning is required — the screw and trough must be accessible for cleaning; enclosed tube screw conveyors are more difficult to clean than open trough types. For allergen-containing ingredients (wheat flour, nut powders, etc.), the cleaning procedure must be validated to demonstrate effective allergen removal, and allergen swab testing should be carried out at the cleaning validation frequency. The conveyor design must allow disassembly for inspection and cleaning of the screw, trough, and bearings.

Food Grade Screw Conveyor Manufacturers

Food grade screw conveyors — types and applications

Food Grade Screw Conveyor Manufacturers

Food grade screw conveyors — types and applications

Frequently asked questions

How is a screw conveyor sized for a given throughput?

What cleaning procedure is required for a food screw conveyor?

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