An RCA and Action Plan to achieve smooth Kiln Feed

Problem Statement:

The belt bucket elevator (BBE) feeding the kiln is getting swayed during operation, leading to operational instability, potential mechanical damage, and interlock tripping.

Objective:

To achieve stable, variation-free kiln feed, ensuring the belt bucket elevator runs smoothly without sway, and preventing unnecessary shutdowns and mechanical failures.

Action Plan:

Step 1: Immediate Running Condition -> Controlled Operation

  • Bypass the tripping interlocks temporarily, but keep the elevator under strict manual supervision.
  • Continuously monitor the elevator's operation during this period.
  • Manually adjust the elevator through tensioning device until relative stability is achieved.
  • Restore interlocks once the system behavior is stable and predictable.

Step 2: Inspection of Material Discharge to Elevator

  • Check material discharge from the final air-slide to the bucket elevator inlet.
  • Ensure centralized discharge into the elevator boot to avoid lateral force on the belt, which leads to swaying.
  • If the material is falling off-center, modify the air-slide chute or install flow guides.

Step 3: Venting System Assessment and Correction

  • Check and ensure proper venting at both:
    • Boot section (inlet)
    • Discharge hood (outlet) of the elevator
  • Bucket elevator should not experience excessive positive or negative pressure.
  • Install pressure transmitters at both boot and head sections to continuously monitor pressures.
  • Provide a bleed-off valve or adjust venting system (by bag filter or vent pipe) if required to maintain neutral pressure.

Step 4: Shutdown/Planned Stoppage - Mechanical Inspection

During plant shutdown or bucket elevator stoppage:

  • Conduct thorough mechanical inspection including:
    • Belt Alignment: Must run true without side pulling.
    • Drum Condition: Check drum face for wear, tapering, or buildup.
    • Joint Condition: Inspect all belt joints (mechanical or vulcanized) for alignment and straightness.
    • Pulley Lagging: Inspect pulley surface for slippage signs.
    • Tensioning Mechanism: Check for correct tension. Too tight or too loose will cause instability.
    • Elevator Buckets: Uniform mounting of buckets. Check for loose or broken buckets.
    • Casing Inspection: Check inner walls for abnormal material buildup or distortion.
    • Boot Pulley Cleaning Arrangement: Ensure scraper/cleaners are functional to avoid material accumulation.

Step 5: Stable Kiln Feed Management

5.1 Continuous Mode Kiln Feed Bin Filling

  • Check if kiln feed bin filling is continuous.
  • If NO:
    • Implement gate control with PID loops at the air-slide discharge.
    • Install a dummy bin or small buffer bin just before the main kiln feed bin for material buffering. [CONFIRM]
  • If YES:
    • Proceed to the next checks.

5.2 Bin Level Management

  • Analyze bin level variation:
    • Target a narrow filling range (preferably ±5-10% variation).
    • Refine the PID control loops for better material flow stability.
  • Manually monitor bin level at different times and under different operating conditions to validate performance.

5.3 Bin Pressure Monitoring

  • Check if kiln feed bin has pressure sensors installed.
  • If NOT available:
    • Plan to install bin pressure transmitter for real-time monitoring.
    • Meanwhile, manually record pressure trends using available methods (magnahelic gauges, U-tube manometers).

Step 6: Bag Filter Operation

  • Ensure kiln feed bin venting bag filter operates properly.
  • Bag filter health is critical to:
    • Maintain proper bin pressure.
    • Prevent material back-flow.
    • Avoid dust accumulation inside the system.
  • Check Bag Filter Points:
    • Differential pressure across filter bags.
    • Cleaning mechanism (pulse jet / shaking mechanism).
    • Timer settings for bag cleaning.
    • Leakage or bypass paths in ducting.

Step 7: Interlocks Review and Strengthening

  • Review existing interlocks:
    • Bin aeration must stop if bag filter is not operating or if bin pressure is higher than safe limits.
    • Material feeding should interlock with stable venting.
    • Consider additional interlocks based on venting and pressure alarms to protect the elevator operation.

Conclusion and Summary

The swaying of the kiln feed bucket elevator is not just a mechanical issue. It is linked closely to upstream material flow variation, venting system health, and overall feed system dynamics.

A systematic approach, combining running checks, mechanical inspections, feed stabilization, and control system improvements, will permanently solve the problem and ensure stable kiln feeding.

Continuous monitoring and preventive maintenance actions post-correction are necessary to sustain the results.


[Components of Kiln Feed System]

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