Screw conveyors are widely used in bulk material handling across many industries. During long-term operation, however, they may develop problems such as material blockage, reduced conveying capacity, material leakage, motor overload, abnormal vibration, and bearing failure. These issues are often related to material properties, feeding conditions, component wear, installation accuracy, or insufficient maintenance.
When a fault occurs, inspect the feed inlet, trough, screw flight, bearings, transmission components, and drive system according to the actual symptoms. Identify the cause before taking corrective action. Increasing motor power or repeatedly restarting the equipment without investigating the problem may cause further damage.
Material Blockage
Material blockage is one of the most common problems during screw conveyor operation. It may occur at the feed inlet, inside the conveying section, or at the discharge outlet. Severe blockage can prevent the screw shaft from rotating freely and may cause the motor overload protection to trip.
Common Causes
Excessive moisture or material adhesiveness: Wet or sticky materials may adhere to the screw flights and inner surface of the trough. The buildup gradually reduces the available conveying space.
Feed rate exceeding the conveyor capacity: Continuous feeding at an excessive rate or sudden increases in feed volume can cause material to accumulate inside the trough and increase the load on the screw shaft.
Foreign objects mixed with the material: Metal fragments, stones, pieces of wood, fibers, and other foreign objects may become trapped between the screw flight and trough, preventing the screw from rotating.
Blocked discharge outlet or downstream equipment: When material cannot discharge properly, it accumulates inside the conveyor and increases the resistance acting on the screw flights.
Worn screw flights or damaged bearings: Severely worn flights, a bent shaft, or damaged bearings may reduce conveying efficiency and cause material to remain inside the trough.
Incorrect startup or shutdown sequence: If upstream feeding continues after downstream equipment stops, or if material is left inside the conveyor after shutdown, internal buildup may occur.
Corrective Actions
Check the material's moisture content, adhesiveness, and tendency to form lumps. Pre-treat the material where necessary and prevent oversized material and foreign objects from entering the conveyor.
Adjust the feed rate according to the conveyor's rated capacity. Maintain a steady material supply and avoid sudden overloading.
Inspect the feed inlet, discharge outlet, and downstream equipment. Remove blockages and ensure that the material flow path is clear.
Check the screw flights, shaft, and bearings for wear or damage. Repair or replace components as required.
Follow the operating procedures for equipment startup and shutdown. In an interconnected conveying line, downstream equipment is generally started before upstream feeding equipment. During shutdown, stop the material feed first and allow the conveyor to discharge the remaining material before stopping it. The actual sequence must follow the system control logic and manufacturer's instructions.
For severe blockages, stop the equipment, isolate the relevant power sources, and apply lockout/tagout before clearing the material through the designated inspection openings. Never reach into the trough or use tools to remove blockages while the conveyor is running. Do not force the equipment to restart before identifying the cause.
Reduced Conveying Capacity
When the conveyor continues to run but its actual throughput is significantly lower than the designed capacity, check the material supply, screw flights, drive system, and conveying passage.
Common Causes
Irregular material feeding: Insufficient material supply, unstable operation of the feeding equipment, or a partially blocked inlet may prevent the screw flights from receiving enough material.
Screw flight wear: Wear along the outer edges of the flights or flight deformation reduces their ability to move material. This is especially common when handling abrasive materials.
Changes in material properties: Variations in moisture content, adhesiveness, or bulk density may affect material filling and movement inside the trough.
Insufficient screw speed: A motor, gearbox, or transmission fault may cause the screw shaft to rotate below its designed speed.
Material buildup inside the trough: Material adhering to the screw flights or trough walls reduces the available conveying space and interferes with material flow.
Corrective Actions
Check the feeding equipment and material supply. Adjust the feed rate to maintain a continuous and uniform supply.
Inspect screw flight wear. Repair or replace flights that have worn beyond the allowable limit.
Check the motor, gearbox, coupling, and other transmission components. Confirm that the actual screw speed meets the design requirements.
Remove material buildup inside the trough and check the discharge outlet for partial blockage.
If the material properties or required throughput have changed, reassess the conveyor's capacity and operating parameters.
Material Leakage
Material leakage usually results from damaged seals, improperly connected trough sections, or problems at the inlet and discharge connections. When handling powders, inadequate sealing may also allow dust to escape.
Common Causes
Worn shaft-end seals: Packing seals, lip seals, or other sealing arrangements at the shaft ends may wear or deteriorate over time, allowing material or dust to escape through the clearance around the shaft.
Loose flange connections: Loose bolts or damaged gaskets at the trough flanges may create gaps through which material can leak.
Loose inlet or discharge connections: Leakage may occur when the flanges, flexible connections, or other fittings at the feed inlet and discharge outlet are not properly sealed.
Inspection cover or end cover sealing problems: Incorrectly installed covers, deteriorated seals, or loose fasteners may allow material or dust to escape during operation.
Abnormal internal pressure: In enclosed or dust-controlled screw conveyor systems, pressure conditions or problems in the dust collection ductwork may increase the risk of leakage at sealing points.
Corrective Actions
Inspect the shaft-end seals and packing glands. Replace seals that are worn or deteriorated.
Check the trough flanges and end cover connections. Retighten loose bolts and replace damaged gaskets where necessary.
Inspect the feed inlet, discharge outlet, and flexible connections. Confirm that the connections are correctly positioned and sealed.
For enclosed conveying systems, check the dust collection ductwork and internal pressure to ensure that the system operates within the specified conditions.
For fine powders that are prone to leakage, select sealing arrangements suitable for the material and operating conditions. Inspect these components regularly.
Sticky materials may cause buildup or restricted discharge, but they are not necessarily the direct cause of leakage at a sealing point. When leakage occurs, first locate the exact leakage position and inspect the corresponding seals and connections.
Motor Overload or Failure to Start
Motor problems may appear as failure to start, excessive operating current, overload trips shortly after startup, or abnormal motor temperature. Both the electrical system and mechanical load should be checked rather than assuming that the motor itself is defective.
Common Causes
Excessive feed rate: Material accumulation inside the trough increases the operating load on the screw shaft beyond the design range.
Mechanical blockage inside the conveyor: Foreign objects or contact between the screw flights and trough may increase the resistance of the drive system.
Bearing or gearbox faults: Seized bearings, damaged gears, or insufficient lubrication can increase mechanical resistance.
Power supply abnormalities: Low voltage, phase loss, or electrical wiring faults may cause starting difficulties or abnormal motor current.
Incorrect motor selection: The motor's rated power or starting torque may be insufficient for the actual material load and startup conditions.
Corrective Actions
Reduce the feed rate and check for material buildup or foreign objects inside the trough.
Check whether the screw shaft can rotate freely. Inspect the flights for contact with the trough, and check the bearings and gearbox for abnormal resistance.
Check the supply voltage, three-phase current, electrical terminals, and motor protection devices.
Verify that the motor's rated power, gearbox output torque, and actual operating load are compatible.
If the motor windings are damaged or the bearings have failed, arrange for repair or replacement by qualified personnel.
If the motor trips immediately after startup, do not repeatedly reset the overload protection device. First check for mechanical blockage, power supply abnormalities, and excessive load. Restart the equipment only after the cause has been identified and corrected.
Abnormal Vibration and Noise
Noticeable vibration, impact noise, or continuous friction noise during operation usually indicates a problem with the screw assembly, bearings, support structure, or transmission components.
Common Causes
Bent screw shaft or installation misalignment: A shaft that does not meet straightness requirements, or poor alignment between the trough sections and screw shaft, may cause periodic vibration.
Worn hanger bearings: Worn or damaged intermediate hanger bearings may fail to support the screw shaft properly, resulting in abnormal noise.
Contact between the screw flights and trough: Deformed flights, shaft misalignment, or uneven clearance may cause metal-to-metal contact.
Loose fasteners: Loose bolts on hanger bearing housings, trough flanges, foundation anchors, or drive connections may cause vibration.
Uneven material feeding: Uneven material distribution inside the trough may create unbalanced loads on the screw shaft.
Bearing or gearbox damage: Worn rolling bearings, abnormal gear meshing, or insufficient lubrication may produce continuous noise.
Corrective Actions
Stop the equipment and inspect the screw shaft for straightness and correct positioning. Straighten or replace a deformed shaft as required.
Inspect hanger bearings, end bearings, and couplings. Replace worn or damaged components.
Check the clearance between the screw flights and trough. Correct flight deformation and eliminate areas of unwanted contact.
Tighten loose bolts and inspect the equipment supports and foundation for stability.
Adjust the feeding equipment to reduce localized material buildup and intermittent impact loads.
Check gearbox lubrication and gear meshing. Repair the gearbox if necessary.
If vibration or metal impact noise suddenly becomes more severe, stop the equipment and inspect it before further operation. Continued operation may cause additional damage to the screw shaft, flights, or support structure.
Bearing Overheating or Abnormal Wear
Bearings are important support components in a screw conveyor. End bearings and intermediate hanger bearings carry rotational loads and are affected by lubrication conditions, installation accuracy, and exposure to material dust.
Common Causes
Insufficient lubrication: Inadequate grease or oil, or lubrication intervals that do not meet the equipment requirements, may increase internal bearing friction.
Unsuitable lubricant: The lubricant type, viscosity, or operating temperature range may not be suitable for the actual bearing and working conditions.
Seal failure: Dust, particles, or moisture entering the bearing can accelerate wear on the raceways and rolling elements.
Installation misalignment: Incorrect bearing installation, shaft misalignment, or an improperly secured bearing housing may cause additional loads.
Prolonged equipment overloading: Excessive resistance during screw shaft operation increases the load carried by the bearings.
Corrective Actions
Check lubrication according to the equipment manual. Use lubricants compatible with the bearing type and operating conditions.
Inspect the bearing seals to prevent dust, moisture, or material from entering the bearing.
Check bearing position, shaft alignment, and bearing housing fasteners.
Replace bearings that show abnormal noise, excessive clearance, or visible damage.
Determine whether the equipment has been operating under excessive load and eliminate the cause of the additional bearing load.
Bearing temperature should be evaluated according to the bearing type, rotational speed, lubrication method, ambient temperature, and manufacturer's specifications. A single temperature-rise limit should not be applied to every screw conveyor.
Screw Shaft or Transmission Component Failure
During prolonged overloading, foreign object jamming, or operation with installation misalignment, the screw shaft, connecting shafts, couplings, and connecting pins may become deformed or break.
Common Causes
Excessive instantaneous torque: When material blocks the conveyor or a hard foreign object becomes trapped in the flights, the drive system may experience a sudden increase in torque.
Prolonged overloading: Continuous operation above the designed feed capacity may accelerate fatigue damage to the shaft, flights, and connecting components.
Poor shaft alignment: Misalignment between the trough, bearing housings, and drive assembly may subject connecting shafts to additional bending loads.
Materials or structural design unsuitable for the application: The shaft material, connection design, or component dimensions may not withstand the actual torque and operating conditions.
Continued operation after bearing failure: A failed support may allow the screw shaft to shift position and vibrate abnormally, causing further damage to connecting components.
Corrective Actions
Check for foreign objects and material blockage inside the conveyor. Remove the cause of excessive torque before repairing damaged parts.
Inspect the screw shaft, connecting shafts, couplings, and connecting pins. Replace components showing cracks, significant deformation, or fractures.
Recheck the positions of the trough, bearing housings, and drive assembly to ensure that shaft alignment meets the design requirements.
Verify that the screw shaft and transmission components have sufficient torque capacity for the actual material load.
For applications with a high risk of overload, consider protection devices such as torque limiters, shear pins, or motor current monitoring, where compatible with the equipment design.
After replacing a failed component, investigate why it broke. Replacing the damaged part without resolving material blockage, foreign object jamming, or prolonged overloading may result in repeated failures.
Screw Conveyor Troubleshooting and Routine Maintenance
When a fault occurs, the initial inspection can be guided by the equipment symptoms and the components most likely to be involved.
| Equipment symptom | Areas to check first | Corrective action |
|---|---|---|
| Material cannot be conveyed and accumulates inside the trough | Feed inlet, discharge outlet, screw flights, and material condition | Clear the blockage, adjust the feed rate, and inspect flight wear |
| Conveying capacity drops significantly | Feeding equipment, screw speed, flight edges, and trough | Check the material supply, drive system, and flight wear |
| Material leaks from shaft ends or flange connections | Shaft-end seals, flange gaskets, and fasteners | Replace seals and repair the connections |
| Motor trips on overload after startup | Power supply, feed load, bearings, gearbox, and screw assembly | Check electrical faults and mechanical blockage |
| Vibration or noise increases during operation | Screw shaft, hanger bearings, bearing housings, and coupling | Check shaft alignment and support conditions |
| Bearing temperature rises abnormally | Lubrication system, bearing seals, and installation position | Inspect lubrication, seals, and bearing condition |
| Screw shaft or connecting components break | Foreign objects, material blockage, drive torque, and installation misalignment | Identify the cause of overload and repair or replace damaged components |
Routine maintenance should also include equipment operating records. Pay particular attention to motor current, bearing temperature, gearbox condition, abnormal vibration, and screw flight wear. For conveyors handling abrasive materials, inspections of the flights and trough liners should be carried out more frequently as required.
For interconnected production lines, check the startup and shutdown sequence and the interlock logic between upstream and downstream equipment. This helps prevent upstream feeding from continuing after downstream equipment has stopped.
Before maintenance, stop the equipment, isolate the power supply, apply lockout/tagout, and confirm that the machine cannot start unexpectedly. Clearing blockages, inspecting screw flights, and replacing bearings must be carried out by personnel with the appropriate skills and in accordance with the equipment manual and site safety procedures.
Conclusion
Common screw conveyor problems include material blockage, reduced conveying capacity, material leakage, motor overload, abnormal vibration, bearing failure, and breakage of the screw shaft or transmission components. These problems may result from material properties, incorrect feeding, component wear, installation misalignment, or inadequate lubrication and maintenance.
When troubleshooting, first identify the affected area based on the equipment symptoms. Then check the material, mechanical components, and electrical system in a systematic way. Problems such as blockage, overload, and abnormal vibration should not be addressed simply by changing the screw speed or replacing the motor. The screw flights, bearings, transmission system, and material flow passages also need to be inspected.
A regular inspection and maintenance program helps detect flight wear, seal failure, and bearing problems before they cause unexpected downtime. This supports more stable screw conveyor operation and reduces unplanned maintenance.
Hansheng Automation provides CNC precision machining of non-standard metal components according to customer-supplied engineering drawings. Our machining work covers components for yacht equipment, RC racing cars, tobacco and packaging machinery, and filling machinery.
