Equipment Introduction

Screw conveyors are one of the oldest and simplest methods for conveying bulk materials, mainly consisting of a rotating conveying screw within a fixed trough.

1. Core Classifications:
2. Shafted Screw Conveyors: Composed of an auger, U-shaped or O-shaped material trough, cover plate, inlet/outlet, and drive unit; suitable for powdery and granular materials.
3. Shaftless Screw Conveyors: Eliminates the central shaft design, offering strong anti-winding capabilities; suitable for easily entangled materials such as sludge and straw.
4. Tubular/Fully Sealed Type: Suitable for applications with high dust control requirements, such as cement and chemical powder conveying.
5. Core Advantages: Compact structure, fully enclosed dustproof design, can be arranged horizontally/inclined/vertically, controllable conveying capacity, and small footprint.

Structural Composition

A complete screw conveyor typically consists of three main parts: the screw conveyor body, the inlet/outlet device, and the drive unit. The screw conveyor body is the core component, composed of a head section, an intermediate section, and a tail section.

Specifically, its main components include:

Screw (Auger): The main component for material conveying, consisting of screw blades and a screw shaft. Screw blades come in various types depending on the material, such as solid (full-surface) and ribbon-face. The screw shaft is usually made of hollow steel tubing with a diameter of 30–70 mm.

Bearings: Used to support the screw, and are classified into three types according to their location:

Head Bearing: Installed at the discharge end, bearing radial and axial forces, using a radial thrust bearing.

Tail Bearing: Installed at the inlet end, bearing only radial forces, using a radial spherical bearing.

Intermediate Hanger Bearing: When the screw shaft length exceeds 3 meters, it needs to be installed in the middle to prevent bending.

Material trough (casing): Usually made of thin steel plate, with a semi-circular bottom cross-section, used to hold the conveyed material.

Drive unit: Consists of an electric motor, reducer, and transmission components, providing power to the equipment.

Working Principle

The working principle of a screw conveyor can be summarized as “screw rotation—friction constraint—axial displacement”:

1. Power Input: The drive unit drives the screw shaft to rotate within a fixed trough.
2. Friction Constraint: Due to its own weight and the external friction between the material and the trough wall, the material does not rotate with the screw shaft.
3. Axial Displacement: The rotating screw blades generate axial thrust on the material, causing it to move along the trough towards the discharge port, much like a “non-rotating nut moving along the screw.”

Key Design Principles: The drive unit and discharge port are usually located at the same end, while the feed port is placed near the tail end of the other end. This ensures that the screw shaft primarily bears tensile force rather than compressive force during conveying, preventing buckling and instability of the shaft.

Applicable Raw Materials (Fertilizer Industry)

Stable Conveying Capabilities:

1. Powdered Materials: Fermented manure powder, humic acid, bentonite, talc coating powder, urea/compound fertilizer powder;
2. Granular Materials: Granulated organic fertilizer, compound fertilizer, BB fertilizer finished granules;
3. Slightly Moist Materials (Moisture content ≤30%): Semi-dry fermented compost, crushed cake fertilizer;
4. WLS Shaftless Dedicated: High-moisture livestock and poultry manure, sludge, bacterial residue (moisture content 30%~45%).

Prohibited Conveying: Moisture content >45%; Strongly sticky mud, large hard stones, long-fiber straw (easily entangled in shafted hanger bearings), high-temperature molten fertilizer.

Production Line Applications

Screw conveyors are used in almost all industrial sectors involving the handling of bulk materials:

Standard Operation and Full-Cycle Maintenance

1. Start-up and Shutdown Procedures

Start-up: Run the machine unloaded for 3 minutes. If there are no abnormal noises or overloads, then feed material evenly. Do not start under heavy load.

Shutdown: Stop upstream feeding first, run the machine unloaded for 3-5 minutes to empty the material inside, then disconnect the power to prevent material from clumping and sticking to the blades.

2. Daily Graded Maintenance
3. Daily: Clean clumping at the feed inlet, check for powder leakage at the shaft end seal, and observe that the motor current does not exceed the rated value.
4. Weekly: Add lubricating grease to the head, tail, and hanger bearings; tighten the flange bolts on the machine casing.
5. Quarterly: Check the reducer oil level and change the gear oil every 4 months; check for blade wear and repair by welding.
6. Annual Overhaul: Disassemble and clean the entire machine of accumulated fertilizer, replace aged seals and worn hanger bearings.
7. Safety Regulations

Do not open the sealing cover or put your hands inside the machine during operation. Power must be disconnected and a sign must be posted before maintenance. For wet, sticky fertilizer, use a shaftless model to reduce the risk of material blockage.

4. List of vulnerable parts: Spiral blades, hanger bearings, shaft end seal packing, gearbox oil seal, cover plate sealing strip.

Common Faults and Troubleshooting

Screw conveyors may experience various faults during operation. The following are common problems, their causes, and solutions:

Summary of Equipment’s Comprehensive Technical Features:

1. Enclosed and environmentally friendly, zero dust generation during powder conveying, suitable for environmental control measures in organic fertilizer plants;
2. Multi-functional, capable of conveying, batching, and light mixing, simplifying production line equipment configuration;
3. Minimal footprint, multi-point inlet and outlet design suitable for small batching workshops;
4. Precise quantitative control, variable frequency speed regulation achieves accurate fertilizer proportioning, improving the stability of nutrient content in the finished product;
5. Different models are available to handle dry and wet materials. The LS shafted model is suitable for dry powder materials, while the WLS shaftless model is suitable for high-moisture, sticky manure materials, covering the conveying needs of all fertilizer categories.