cindy liu - bureau veritas

© - Copyright Bureau Veritas

A Review of Longwall Chain Reliability

25 October 2016

Cindy Liu

BEng, MSc, CPEng

Senior Consultant Metallurgist

2Bureau Veritas Presentation _ Date© - Copyright Bureau Veritas

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


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


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)


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


V H

H V

H

V H H V

H


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


Welding Defect 1


Welding Defect 2


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


Case Studies – Stress Corrosion Cracking


Case Studies – Corrosion Assisted Fatigue Cracking


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


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


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


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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