More Related Content
What's hot (20)
Similar to Kiln 5 Drive System Preliminary Root Cause Analysis_rev2 (20)
Kiln 5 Drive System Preliminary Root Cause Analysis_rev2
- 1. Kiln 5 Drive System Failure Root Cause Analysis October 2013 By Thebe Setshedi
- 2. Introduction - Background Mar 23, 2015 Thebe Setshedi 2
- 3. Introduction - Background Mar 23, 2015 Thebe Setshedi 3 1. Main motor 2. Main gearbox 3. Auxiliary motor 4. Auxiliary gearbox clutch unit 5. Pinion gear 6. Pinion coupling 7. Girth gear
- 4. Introduction Failure Background Mar 23, 2015 Thebe Setshedi 4 1. Main motor 2. Main gearbox 3. Auxiliary motor 4. Auxiliary gearbox clutch unit (SOUTH) 5. Pinion gear 6. Pinion coupling (NORTH) 7. Girth gear
- 5. Problem Description Mar 23, 2015 Thebe Setshedi 5 What Kiln drive system failed When On the 26th September 2013 around 23:00 Where Kiln 5 main coupling & auxiliary clutch Who Kiln field operators and maintenance team Why The was an overload on the system How Coupling fracture and auxiliary seizing
- 6. System Operation Mar 23, 2015 Thebe Setshedi 6 Parameter Operating value Maximum Value Kiln operation speed-main motor 0.33 rpm 0.9 rpm Kiln speed - Auxiliary motor (1000rpm) 0.024 rpm 0.024 rpm Kiln feed rate (Ore) 32 tons/hr. 34tons/hr. Kiln feed rate (coal + dolomite) 16 tons/hr 17 tons/hr Kiln Motor current output 2850 kW 3050 kW Main motor operation speed 350 rpm/ 36.7 rad/s 1000 rpm Main motor torque 1700 N.m 1900 N.m Environment Temperatures 45 deg. Cel. 65 deg. Cel.
- 7. Investigation Failed Components Mar 23, 2015 Thebe Setshedi 7
- 8. Investigation Failed Components Mar 23, 2015 Thebe Setshedi 8
- 9. Investigation Failed Components Mar 23, 2015 Thebe Setshedi 9 Inner ring webs of the South coupling fractured
- 10. Investigation Failed Components Mar 23, 2015 Thebe Setshedi 10 Auxiliary gearbox seizes
- 11. Investigation Failed Components Mar 23, 2015 Thebe Setshedi 11 Broken auxiliary south brakes brake pads shoe broken Auxiliary south brake actuators not functioning
- 12. Investigation - Aspen Results Evidence that the motor is not responding to the drive, feedback is not approaching reference speed for hours 14/09/2013 from 12:00 16:00 Signs of a kiln slipping back more often Mar 23, 2015 Thebe Setshedi 12
- 13. System Operation Mar 23, 2015 Thebe Setshedi 13 Brakes Motor Fluxing Drive Program
- 14. System Operation Mar 23, 2015 Thebe Setshedi 14 Auxiliary motor Main Motor Overruns Helps in braking the kiln
- 15. System Operation Truths & Myths Mar 23, 2015 Thebe Setshedi 15 Myth : Brakes are designed to prevent the kiln from slipping back Truth : The electric drive should be programmed such that it slows down the kiln to a stop, the brakes are just there to hold the kiln in a stationary position isolation. Myth : Auxiliary drive/brakes are to act as anti-run system to prevent the kiln from running back. Truth : The auxiliary brakes are just there to isolate the auxiliary drive system. Myth : The drive system is initially designed such that the auxiliary drive is to be a start up for the main drive. Truth : The primary function of the auxiliary drive is to be able to empty the kiln or slowly rotate the kiln in a case of main drive failure to prevent the kiln shell from permanently deforming.
- 16. Why is the Kiln Slipping back Mar 23, 2015 Thebe Setshedi 12 months Appraisal 16 3000 N.m 3000 N.m Braking torque needed by brakes to stop the kiln from running back Assuming 20 deg. burden angle Neglecting roller friction Running back inertia Current braking torque on each main brake = 1000.Nm Braking torque from each auxiliary brake = 1000 N.m Electric drives not fluxed enough to stop the kiln by slowing it down.
- 17. Mode of Failure Analysis - Coupling Mar 23, 2015 Thebe Setshedi 17 Function : Transmit Torque Transmit energy Failure : Inner ring webs fracture FACT : for fracture to happen there must have been a resultant force beyond what the coupling can withstand FACT : This unwanted force can only come from the difference in torque output of the motors or change in the weight of the kiln Deductions : The inner ring was receiving torque from the motor but the outer ring was completely stationary indicating breaking effect. Coupling Kiln
- 18. Mode of Failure Mar 23, 2015 Thebe Setshedi 18 Obstruction on the 2 pinion 1. Auxiliary motor turning in the opposite direction 2. Auxiliary clutch failure Gearbox Failure Brakes failure Motor Failure Stationary No energy flow Energized but not necessary in motion
- 19. Mode of Failure Mar 23, 2015 Thebe Setshedi 19
- 20. Mode of Failure Analysis Overrunning clutch/gearbox Mar 23, 2015 Thebe Setshedi 20 Function : Transmit Torque in one direction and overruns in another. Failure : Clutch not overrunning, completely seized, not even transmitting torque in any direction FACT : This clutch is NOT designed to run backwards by the main motor, it is NOT an anti-run back clutch. FACT : The anti-run back properties of the clutch is provided by the auxiliary brakes, if the brakes fails, then the clutch fails.
- 21. Aspen Results Mar 23, 2015 Thebe Setshedi 21 Main drive speed Auxiliary brakes Main brakes
- 22. Final Root Cause Mar 23, 2015 Thebe Setshedi 22 Coupling fracture Base bolts fracture Girth gear cover lifts up One side (South) of the drive is stationary while the north side is trying to turn Auxiliary gearbox is damaged bearing seize Kiln runs/slips backward when stopped Programming on the drive Programming on the drive WHY WHY WHY WHY
- 23. Actions Action Objective Responsible Person - Date Put back the auxiliary drive, For more effective braking effect half Done Danie van der merwe Draft a standard for brakes inspection and also an inspection plan. Strength the brakes to counteract enertia. To make sure that the brakes are forever in good condition, this will prevent the kiln from running back. Thebe 30 Nov 2013 Determine the allowable torque that the entire system can withstand without interrupting kiln normal operation. Help in understanding why certain components fail and how we can protect them. Thebe 30 Nov 2013 Program the drives such that they dont allow a torque output high enough to damage any component in a system, and make sure that drives are fluxed to slow a kiln to a stop. This will trip the kiln before the motor produce enough torque to damage any component in the system Solly Moroosele - Design a mechanical fail safe mechanism This mechanism will minimize damages by failing first in a case of system torque overload. Thebe 15 Dec 2013 Mar 23, 2015 Thebe Setshedi 23
- 24. Conclusion and recommendations - speed Copyright 息 ArcelorMittal Mar 23, 2015 Thebe Setshedi 24 Root Cause : Brakes failure brake pads/ brakes calibration
- 25. Conclusion and recommendations - Torque Copyright 息 ArcelorMittal Mar 23, 2015 Thebe Setshedi 25 Root Cause : Brakes failure brake pads/ brakes calibration
- 26. Conclusion and recommendations Copyright 息 ArcelorMittal Mar 23, 2015 Thebe Setshedi 26 Root Cause : Programming on electric drives. Recommendation : it is also necessary that the auxiliary system be put back - if we lose the main drive, the kiln will be forced to wait longer in one position and permanently deform the kiln and induce extra torque and eccentricity on the rotation.
- 27. Copyright 息 ArcelorMittal Mar 23, 2015 Thebe Setshedi 27 Question & Answers
- 28. Mar 23, 2015 Thebe Setshedi 28
- 29. Seconds From Disaster Mar 23, 2015 Thebe Setshedi 29