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Failure Modes of
Steel Transfer Car at LD1
Ambarish AmbujMT(Technical) ’11
Guide: Kumar VarunSr Manager, LD1
Scheme of the Presentation
• Project Objectives and Achievements• About Steel Transfer Car• Failure Data• Failure Modes
– Mode 1: Wheel Assembly Damaged– Mode 2: Spring Assembly Damaged– Mode 3: Tie Rod Assembly Damaged– Mode 4: Derailment (Breakdown on 16th April ’12)– Mode 5: Brass Bush Failure– Mode 6: Axle Cracked
• Road Ahead
Project Objectives & Achievements
Objectives
1. To understand the steel transfer car
2. To collect the failure data and analyse it
3. To study different failure modes
4. To suggest measures to prevent failure
Achievements
1. Design and working of steel car understood
2. Failure data collected and analysed
3. Different failure modes studied and analysed
4. Preventive measures suggested for significant failure modes
About Steel Transfer Car
Function: Transfers Ladle containing Liquid Steel from Vessel
Area to Ladle Furnace AreaCapacity: 260t Weight: 100tNumber: 2Equipment Owner: MHS MechanicalDesigner: Design CellManufacturer: TGSDrive Mechanism: Motor Driven with Gear
Transmission
About Steel Transfer Car
• Components:– Car Frame– Ladle Stool– Cable Mast– Wheel-Axle
Assembly– Spring Assembly– Motor– Gearbox
About Steel Transfer Car
Wheel-Axle Assembly
Spring Assembly
Motor & Gearbox Assembly
Track Stopper
Failure Data
Date Problem Correction
04-05-2000East side Wheel collar got
deformed and its width became 258mm
Wheel assembly changed
27-07-2000West Side frame got damaged and wheel got jam as ladle got
through in the car
wheel assembly changed & frame repaired
09-02-2001West side frame got damaged as ladle punctured in the car
Frame repaired
North-east Spring assembly damaged
changed the spring assembly
Track stopper damaged Welding doneSouth-west Spring Assembly
damagedchanged the spring
assemblyTrack stopper damaged Welding done
All 4 spring assemblies brokenchanged the spring
assemblyWest side both top half bush
worn outchanged top half bush and
lubricated
Planned ShutdownWest side wheel assembly changed and housing slot
increased to 120 from 100
Fixed guide block found 7mm thinner (88 instead of 95mm)
All four fixed guide blocks changed
Maintenance Log: Steel Transfer Car #1
07-08-2009
04-06-2003
21-09-2002
28-06-2001
S No Component Failures % Occurrence1 tie rod assembly 13 28.262 wheel assembly 10 21.743 spring assembly 10 21.744 Brass Bush 5 10.875 gearbox 4 8.706 coupling 2 4.357 Axle 2 4.35
46
Failure Summary
tie rod assembly
28%
wheel assembly
22%
spring assembly
22%
Brass Bush11%
gearbox9%
coupling4%
Axle4%
Failure Data
020406080
100120140160180
Risk
Prio
rity
No
Failure Mode RPNwheel assembly 175spring assembly 150tie rod assembly 120
Derailment 72Axle 48
Brass Bush 45gearbox 32coupling 24
Show Calculation
SOD Analysis
*Basis
Failure Mode Sever Occurr Detect RPNtie rod assembly 4 6 5 120wheel assembly 7 5 5 175spring assembly 6 5 5 150
Brass Bush 3 3 5 45gearbox 2 2 8 32coupling 3 1 8 24
Axle 6 1 8 48Derailment 9 1 8 72
SOD Basis
Rating occurrence Severity Detection10 45% and above breakdown >24hrs can not be detected9 40-45% breakdown >16hrs8 35-40% breakdown >8hrs can be detected in proper inspection7 30-35% shutdown, very high cost6 25-30% shutdown, high cost5 20-25% shutdown, medium cost observable trends in inspection4 15-20% shutdown, low cost3 10-15% shutdown, very low cost2 5-10% shutdown, major repair easily visible 1 0-5% shutdown, minor repair
Mode 1: Wheel Assembly Damaged
Wheel Collar Cracked
Foreign Particle (steel lump) on/near track strikes already flared wheel
Why Steel Lump Why Wheel flared
Liquid steel splash during
tapping, solidifies near
track
Wheel Pressing Against Track
Wheel Rubbing Against Frame
Adequate Track Cleaning
Misalignment Wheel-frame Clearance
15mm
Change Spring Design
Why
Why
Improper Wheel AssemblyFrame SkewedUnbalanced
force on wheels
Track Stopper Inadequate Improve Wheel Assembling SOP
Use sensor to stop car at right time and pneumatic stopper to absorb shock
Why
False Flange Contact
When the centre of the track and that of wheel do not match, car has tendency to turn
This causes collar to touch the track
Reaction force, causing flare in the wheel
wheel
track
Wheel Rubbing with Frame
• Marks on the frame, indicating the rubbing of wheel with frame
Wheel-Frame Clearance Inadequate
Clearance between the wheel and the plate supporting the car-support-spring is just 15mm
Spring Design Change required to increase the clearance
Increasing Wheel-Frame Clearance
Spring 1 Spring 2
Spring 3 Spring 4
Increase the gap between spring 3 & 4 so that the gap between spring 1 & 2 can be decreased, consequently increasing the clearance between wheel and spring
The Wheel Assembly
Critical dimension
Improper Assembly
Track Stopper is Problematic!
– If there is mass imbalance in the frame, axle will deviate from the position normal to track length to nullify the imbalance created by frame.
– If the track stopper is damaged, as the car approaches the stopper, one wheel strikes stopper before the other one, creating unbalanced force on wheels, deflecting the axle.
Consequently, wheels will not be aligned properly, touching the outer frame and rubbing against it
Changing the track stopper
• Existing track stopper welded at the end of the track• The car strikes stopper at significant speed• This can be avoided by stopping motor at right moment• Sensor can be used to trip the motor at exact time• Also, pneumatic stopper can be used in place of traditional stopper to
stop the car smoothly and absorb the shock
Rail Adhesion
• While starting the car, tangential force on the track-wheel contact greatly increases shear force.
• Fine sand provides some ‘lift’ which assists starting the car
Mode 2: Spring Assembly Damaged
Spring Assembly Damaged
Material Defect
Shock Load on Spring
Steel Lump on Track
Track Cleaning not Adequate
Install Track Cleaners
Car Strikes Track Stopper
Motor not Stopped at Right Time
Install Sensor & PLC to Stop
Motor at Right Time
Spring Under-designed
why
why
why
why
why
X
X
Mode 3: Tie Rod Assembly Damaged
Tie Rod Assembly Damaged
Material Defect
Shock Load on Spring
Car Strikes Track Stopper
Motor not Stopped at Right Time
Install Sensor & PLC to Stop
Motor at Right Time
Eliminate Tie Rod Assembly (Attach Drive
unit Base Rigidly to Frame)
Spring Under-designed
X
X
why why why
X
Mode 4: Derailment
As it Happened:• On 16th April ’12, around 7am, Steel Transfer Car #1 derailed from track. • Upon inspection of the site, track was found damaged.• Caterpillar, used to clean the track, uprooted the clamp and displaced track• Track was repaired and the Car was placed back on the track.• Vessel was down for 16hrs Reasons:• The person at job can’t see the shovel properly while track cleaning• The shovel of new caterpillar is long and sharp, increasing the chances of
damage to track.Preventive Measures:• Careful cleaning of the track. One person to assist (give directions) during
cleaning• Inspection of track after cleaning• Change in shovel design to minimise the chances of clamp uprooting
Mode 5: Brass Bush Failure
• Was a significant problem• The axle rubbed with top-
half bush resulting in wearing out
• Back in 2007, design changed. Two greasing points in top-half bush
• No failures after that
Mode 6: Axle cracked
• Occurred twice in 2003• Information not available on the causes• Defective Material or unbalanced forces might have been the
culprit• NDT has been installed • No failure in last 8 years
Road Ahead
• Change spring design to increase wheel-frame clearance• Install sensor and PLC to stop car at right time• Installation of pneumatic/hydraulic stopper• Change in shovel design of caterpillar• Create SOP for wheel assembly so as to avoid any imbalance• Create revised SOP for track cleaning and assign one helper
References
• Railway Track Engineering by JS Mundrey• Interface, The Journal of Wheel/Rail Interaction
– What Kind of Rail Materials Will Survive in Heavy-Haul Service? By James R. Hornaday, Jr.
– Understanding Stresses in Rails By Jude Igwemezie
Acknowledgements
• Mr. Kalyan Prasad, HOMM, LD1• Kumar Varun, Sr. Manager, LD1• S. Samantha, Foreman, MHS, LD1
Thank You