Screw Conveyor

The screw conveyor is a fundamental piece of equipment used in industrial production for transporting powdery and granular materials. As it operates continuously in dusty environments, the quality of its operation and maintenance directly impacts its service life, operational safety, and the continuous, stable functioning of the production line. Given that the operation of a screw conveyor involves multiple systems—including mechanical transmission, electrical control, and material transport—establishing a scientific and standardized system for operation and maintenance is essential to ensuring its long-term, efficient, and stable performance.

Structural composition of the equipment

From the perspective of operation and maintenance, the screw conveyor can be divided into the following functional modules:

(I) Screw assembly module: Includes the screw shaft and screw flights. This is the core working component that comes into direct contact with the material and is also the part most prone to wear. Screw flights come in various types, such as solid, ribbon, and paddle configurations.

(II) Drive and transmission module: Includes the electric motor, gear reducer, coupling, etc. This serves as the power source for the equipment. The gear reducer must be lubricated and maintained in accordance with its instruction manual.

(III) Bearing support module: Includes head bearings, tail bearings, and intermediate hanger bearings. These are critical components for supporting the screw shaft and ensuring its proper rotation; they require periodic greasing.

(IV) Casing and sealing module: Includes the U-shaped trough or tubular casing, cover plate, and sealing devices. This module acts as the material containment vessel and sealing structure; the seals must be checked regularly for leakage.

(V) Inlet and outlet module: Includes the material inlet and outlet ports. These must be kept clear to prevent blockages.

Application scope of the equipment

Screw conveyors are widely used in industries such as organic fertilizer, compound fertilizer, BB fertilizer, chemicals, grain, animal feed, pharmaceuticals, and environmental protection. They are suitable for the enclosed conveying of powdery or small-lump materials.

Types of usable raw materials

Screw conveyors are suitable for transporting non-sticky, granular, or small-lump materials, such as fertilizers, grains, cement, fly ash, and chemical raw materials. Shaftless screw conveyors are suitable for sticky or easily entangled materials.

The working principle of the equipment

The working principle of a screw conveyor is as follows: rotating screw flights push the material along the interior of a stationary casing. The material's own weight and the frictional resistance of the casing prevent it from rotating with the screw, causing it instead to move in an axial direction.

Equipment operating instructions

(I) Pre-start Checks: Operators must undergo training and be certified qualified before commencing operation. Before starting, check the screw conveyor for any loose fastening bolts. Ensure the inlet and outlet are unobstructed. Verify that the gearbox oil level meets specifications and check the lubrication status of all bearings.

(II) No-load Start-up: The screw conveyor must be started without a load—that is, with the casing empty of material. Material feeding should only begin after the machine has started. Starting the machine while loaded is strictly prohibited to prevent motor burnout due to overload or bending of the screw shaft.

(III) Operational Monitoring: Gradually increase the feed rate until the rated conveying capacity is reached. Ensure the feed is uniform; uneven feeding can easily lead to material blockages and overload the drive unit. Monitor the equipment for normal operation and check for any abnormal noise. Observe bearing temperatures to ensure the rise remains within normal limits.

(IV) Shutdown Procedure: Stop the material feed first, and cut off the power supply only after all material has been completely discharged from the casing.

Equipment maintenance methods

(I) Daily Inspection System: Equipment inspections are to be conducted according to standard routine procedures. Inspect machine operation daily, paying attention to any abnormal noise. Check seals for leaks. Inspect fasteners for looseness; if any are loose, shut down the machine immediately and retighten them. Check the wear on the spiral blades; if wear is severe, perform repair welding promptly.

(II) Periodic Maintenance System: Lubricate the drive unit's gearbox in accordance with the manufacturer's manual. Use No. 30 mechanical lubricating oil for the gearbox in winter and No. 45 oil in summer. Change the oil after 2,000 hours of operation. Inspect the nylon liner (for shaftless screw conveyors) after 6,000 hours of operation; replace it promptly if wear is excessive.

(III) Lubrication Management: Use lithium-based grease for the bearing housings at both ends; inject approximately 5 grams every two weeks. Regularly inject grease into the screw conveyor's hanger bearings. Periodically apply lubricating oil to all transmission components.

(IV) Precautions: Do not overload the conveyor; failure to discharge material can cause the screw shaft to bend and the casing to rupture due to pressure buildup. When conveying high-temperature materials, monitor the casing for thermal expansion and contraction.

Common issues with the equipment

(I) Material blockage: Material accumulates inside the casing, preventing normal conveyance. Causes include uneven or excessive feeding, high moisture content increasing material stickiness, and discharge outlet clogs.

(II) Difficulty starting: The motor lacks power and produces abnormal noise upon startup. Causes include a missing power phase and uncleared material accumulation inside the casing.

(III) Abnormal noise: Harsh noise occurs during operation. Causes include the screw flight rubbing against the casing, wear on the hanger bearing, and bearing damage.

(IV) Material leakage: Material leaks from the shaft end or flange connections. Causes include damaged sealing components and loose flange bolts.

Application of the equipment in the production line

Screw conveyors perform the critical task of enclosed material transport in production lines across sectors such as fertilizers, chemicals, grain processing, and environmental protection. In organic and compound fertilizer production lines, they serve as "micro-circulation" units, linking crushers, screening machines, and granulators. In quantitative packaging systems, they are used to feed material at controlled rates to packaging scales.

Types of usable raw materials

Screw conveyors are suitable for transporting non-sticky, granular, or small-lump materials, such as fertilizers, grains, cement, fly ash, and chemical raw materials. Shaftless screw conveyors are suitable for sticky or easily entangled materials.