A change in current, a new sound, dust around a shaft seal or declining delivery can help locate a developing screw conveyor fault. None is a diagnosis by itself, and not every failure gives a long warning. Overload may result from compacted powder, a restricted outlet, a dragging bearing, misalignment or an electrical or drive problem. Increasing motor size before finding the cause can expose other components to greater loads.
Use this guide to separate observable symptoms from checks that require isolation or specialist assistance. For a cement and powder screw conveyor, examine the silo, screw, drive and receiver together. Record the operating state and recent changes before replacing parts.
Safe shutdown before intrusive diagnosis
Follow the site’s equipment-specific hazardous-energy procedure before opening hatches, removing guards or clearing material. The following sequence identifies the required functions; it is not a replacement for that procedure:
- Notify affected personnel and stop the conveyor and associated feed using the defined shutdown sequence.
- Isolate and lock the relevant energy sources, including electrical drive, automatic upstream feed and pneumatic or other auxiliary equipment.
- Relieve or restrain stored energy, pressure, gravity-fed material and possible shaft rollback. A motor disconnect does not secure a silo full of powder.
- Verify effective isolation and absence of hazardous movement using the approved method. An attempted start alone does not prove all energy is controlled; electrical verification belongs to qualified personnel. Return controls to the safe position after checks.
- Only then permit the planned inspection or clearing work. Before restoration, account for people and tools, refit guards and follow the authorized release and restart process.
Settled material can move suddenly when a plug is removed. Stop buttons and emergency stops do not replace isolation. Do not reach into a connected conveyor, force repeated restarts or assume a brake controls every source of stored energy.
A diagnostic approach: from symptom to component group
Where? A mid-tube sound suggests checking the hanger bearings, alignment and local rubbing. Drive-end sound calls for checks of the reducer, motor and coupling; tail-end sound calls for checks of the end bearing and seal. Sound can travel through the structure, so location is a lead, not proof.
When? A symptom during empty running points toward mechanical or electrical causes, residual buildup or incorrect settings. A loaded-only symptom suggests load-dependent resistance, feed or discharge problems, but may still arise from a bearing or shaft that deflects under load. A problem after a full shutdown raises the question of consolidation and breakaway torque.
What changed? Recent maintenance suggests checking assembly and settings. Higher production may exceed the verified duty. A trend over weeks may indicate wear or buildup. Record speed, material, temperature and load so comparisons are meaningful; do not create an unsafe test simply to reproduce the fault.
Motor overload and repeated tripping
An overload device reports a condition, not its cause. Read the actual trip code and event history. Current alone is not shaft torque or mechanical power, especially under VFD operation. Check voltage, phase condition, motor data and protection settings through qualified personnel, alongside the mechanical load path. Do not raise a protection setting simply to suppress repeated trips.
If safe controlled testing is authorized after the initial inspection, compare empty and loaded behavior at the same intended speed. High empty current can accompany bearing drag, rubbing, misalignment or reducer resistance, but can also have electrical causes. A rise only with material calls for checks of inlet rate, moisture, consolidation and discharge restriction. Catalog capacity remains a reference dependent on actual material, fill and incline.
Control feed to the verified capacity. A VFD on the screw does not necessarily control a gravity-fed inlet. Stop feed first and run out material during normal shutdown when the process allows; where loaded starts are unavoidable, verify that duty explicitly. Use the motor power guide and loaded-start torque guide for the separate calculations, and the blockage guide for restriction checks.
Abnormal noise and vibration
Compare a new sound with the established baseline at comparable speed and load. Mid-tube noise may indicate hanger wear, but also deposits, a foreign object, loose parts or shaft-to-shell contact. Do not diagnose one bearing from sound alone. A loaded shaft may deflect differently from an empty one.
At the drive, check the reducer’s oil condition and level against its instructions, mounting, coupling condition and motor bearings. Knocking at startup or load changes can involve joint looseness or backlash. At the tail, examine the bearing, seal and contamination path. Leakage and heat may accompany damage, but require inspection rather than a guess about the failed part.
Load-dependent vibration can involve uneven feed, buildup, supports or alignment. Check structure and fasteners as well as rotating parts, particularly after repositioning an inclined conveyor. Stop and investigate metal scraping, severe or rapidly increasing vibration, abnormal heating, visible deformation or repeated trips. Judge temperature against the approved limits and trend; a housing being warm to the touch is not a universal failure threshold.
Reduced throughput without complete blockage
First verify delivered mass over a known interval, actual screw speed and available inlet supply. An apparent loss may arise from changed density, silo starvation, a slipping connection or an incorrect weighing indication. Compare like operating conditions before concluding the flights are worn.
During isolated inspection, measure flight outside diameter and thickness at defined stations, and check deposits, clearances and supports. There is no universal replacement threshold of 10–15% of radial flight height. Use the approved wear limits, remaining strength, clearance and measured performance. Hardfacing requires an approved repair method and a check of distortion and final dimensions.
A worn hanger can allow sag and local rubbing or disrupt the flow area; sag does not inherently change the manufactured helix pitch. A steeper layout may increase fallback. Clean deposits by the approved method and correct moisture or feeding causes. The capacity calculation guide helps distinguish geometry from actual delivered flow.
Seal leakage and dust emission
Trace dust around shaft seals, covers, flanges and flexible connections. Check operating pressure, venting, shaft runout and seal condition rather than treating every leak as a worn seal. Powder tracks can reveal the route, but a hot or noisy end bearing does not prove dust ingress without inspection.
Replacing a seal may be necessary, yet will not cure excess pressure or misalignment. Inspect an affected bearing and replace it if damaged under the approved procedure. Verify the repaired assembly for containment and operating condition. For the relationship between seal choice, purge and shaft motion, use the shaft seal guide.
Material fallback and poor discharge
Check actual valve opening, receiver level, chute blockage and pressure conditions before changing speed. Material can return on an incline or accumulate behind a restricted outlet. Net delivery depends on material, pitch, housing and speed as well as angle; more power alone does not add geometric capacity.
If the layout cannot be made less steep, verify the proposed geometry and speed with capacity, torque, thermal and mechanical limits, including the settled load after stopping. Do not assume that increasing rpm always reduces fallback. The inclination guide sets out the checks for the complete duty.
When to contact the engineer
Repeated coupling-bolt failure calls for a joint, alignment and load-path review; it is not proof that a stronger bolt alone is needed. A bent or cracked shaft requires an engineering disposition, not improvised straightening or welding. A process change affecting throughput, material or start frequency requires reassessing the complete drive and conveyor together.
Escalate a failed loaded restart, recurrent symptoms after repair, uncertain structural damage or disagreement between observed load and the original selection. Provide dated fault records, trip codes, speed and current trends, material condition, photographs and details of recent work. The quotation input checklist adds layout, throughput and supply information needed for a project review.
Conclusion
Troubleshooting starts with location, timing and operating changes, followed by safe verification and a correction matched to the cause. Confirm the result under approved conditions and record the new baseline. Do not use a larger motor, a higher trip setting or repeated reset as a substitute for diagnosis.
VOGO offers catalog selection diameters Ø89–Ø407 mm with project-specific drive and component arrangements. Use the conveyor datasheet with the fault record to request a review of the actual duty.
