cindy liu - bureau veritas
TRANSCRIPT
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A Review of Longwall Chain Reliability
25 October 2016
Cindy Liu
BEng, MSc, CPEng
Senior Consultant Metallurgist
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Longwall Chain Reliability
Affects productivity and production continuity of Longwall coal mining
operations.
Life expectation relies on conventional warranted tonnes production
BSL Chain – half to one block or 2-5mt
AFC Chain – one to two blocks or 4-10mt
Shearer haulage chain – Two to three blocks
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Chain breakage -
One off failure can lead to 7-24hrs of unplanned downtime
Chronic problem can cause extensive production loss for weeks
Third most significant cause of downtime
Up to 27% of equipment downtime
Reliability of chain normally affected by the following factors
• Chain quality
• Operational environment
• Maintenance practices
Longwall Chain Reliability
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Chain Quality
Major manufacturers
JDT, Thiele, KBP, RUD – Germany
Parsons – UK/China
Chain link designs
Round links chains DIN22252
Flat link chains DIN22255
Broadband chains (JOY)
Power chain (CAT)
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Standard
DIN22252 and DIN22255
Material
23MnNiMoCr54
JDT OH grade– Tungsten addition improve loading capacity, wearability by forming complex carbides in the matrix
Parsons Cor-X – Vanadium addition improves CVN values hence improving the resistance to Hydrogen induced SCC
Mechanical Properties
Chain Quality
Material Hardness CVN
DIN Standard 360-380 HB 50J min
JDT OH/Plus 390-400 HB Typically 80J plus
Parsons Cor-X 350-380 HB Typically 90-110J
KBP Super/Plus >380HB 50J min
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V H
H V
H
V H H V
H
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Service Induced Chain link Failure
Chain Failure
Tensile Overloading Cracking
Stress corrosion cracking
Corrosion fatigue cracking
Chain tension Sprocket wear Corrosion Mechanical
Frictional inducted cracks
Pre-exsisting defect
Welding flaw
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Welding Defect 1
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Welding Defect 2
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Stress Corrosion Cracking
Susceptible Material –High strength low alloy steel with low notch toughness has the highest susceptibility to stress corrosion cracking
Corrosive Environment –Underground mining high level of sulphate and chlorine, acidity of mine water further exacerbate the corrosion issue
Stress – Residual tensile stress + operational stress
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Case Studies – Stress Corrosion Cracking
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Case Studies – Stress Corrosion Cracking
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Case Studies – Stress Corrosion Cracking
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Case Studies – Corrosion Assisted Fatigue Cracking
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Case Studies – Corrosion Assisted Fatigue Cracking
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Case Studies – Corrosion Assisted Fatigue Cracking
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Case Studies – Corrosion Assisted Fatigue Cracking
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Chain Reliability
►Pre-commission Chain Assessment
- Dimension Check
- Metallurgical soundness
- Chemical Composition
- Free of welding defect
- Heat treatment condition
- Mechanical properties
- Hardness test
- Charpy V-notch
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Chain Reliability
►Remnant life assessment
- Dimension check determine 5t pitch extension
- Magnetic particle examination
- Sprocket lug wear condition
- Interlink contact wear
- Galling related cracks
- Corrosion Grooves
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Condition Assessment Chart
Link IDInterlink contact wear Sprocket wear
Corrosion conditionLeading Trailing Leading Trailing
FH1 (FB) Minor Moderate 1.0mm 1.6mm
Extensive pitting under
flight bar anchoring site,
measuring up to 2.3mm
FV2 MinorMinor to
ModerateN/A N/A
Extensive pitting on the
bottom rail up to 0.5mm
FH3 Minor Minor to
Moderate0.6mm 1.6mm
Isolated pits up to 0.8mm
on trailing crown
Link IDInterlink contact wear Sprocket wear
Corrosion conditionLeading Trailing Leading Trailing
GH1 (FB)Minor to
Moderate
Moderate -
severe0.4mm 1.6mm
Extensive pitting under
flight bar anchoring site,
measuring up to 1.8mm
GV2 MinorMinor to
ModerateN/A N/A
Minor corrosion damage
on the trailing crown
adjacent to the flight bar
GH3 Minor to
ModerateModerate 0.4mm 1.3mm
Isolated pits up to 0.8mm
on trailing crown
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Future Project
• Application of ACARP funding – Validation of galvanized chain
►Validate the suitability of galvanized chain in the extremely corrosive mining environment.
►Quantify the cost-effectiveness of the investment, between chain life extension and cost.
►Determine the functionality of galvanized chain, by ways of periodic condition assessment.
►Provide a manufacturing guide line in terms of coating thickness, surface finish, chemical composition requirements.
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