Post on 26-Jul-2015
DYNAMICS OFKETTLE CORROSION IN THEHOT DIP GALVANIZING
INDUSTRY
Mario Ubiali
Intergalva, 8‐12 June 2009
Madrid, Spain
Background
• Zinco Service introduced the KID technologyat Intergalva 2006, in Naples
• Since then, over 220 ke?les have beeninspected in Europe, Canada and USA
• Enough data to start looking for meaningfulconnecGons and trends
FUNDAMENTALS: WHAT TOEXAMINE?
• Thickness readings: a set of numerical values
• Corrosion maps: a graphic representaGon ofcorrosion distribuGon on the wall of the ke?le
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STEP 1: ANALYZINGNUMERICAL DATA
• KETTLES ARE CATEGORIZED AS FOLLOWS:
• By furnace type: Flat Flame VS. High Velocity• By ke?le size: Three Lenght Categories
» 4‐8 meters long» 9‐12 meters long» 13 and more
• By age in service: From 2 to 10 years of service life
STEP 1: ANALYZINGNUMERICAL DATA
• WHAT FIGURES DO WE USE FOR ANALYSIS ?
• AVERAGE THICKNESS: Calculated according to normalstaGsGcal rules
• MINIMUM THICKNESS READING: A significant index !
STEP 1: ANALYZINGNUMERICAL DATA
LET’S TAKE A LOOK AT RESULTS…..
Kettle Age (years in service)
Kettle
Size (mt)
2 3 4 5 6 7 8 9 10
4-8 NA 46 42,3 46,4 42,2 42,5 36,5 NA NA
9-12 NA 44,1 NA NA NA 34,5 32,9 NA NA
13 and up NA 45,7 41,8 45,1 NA 41,7 39,4 34,6 34,5
Kettle Age (years in service)
Kettle
Size (mt)
2 3 4 5 6 7 8 9 10
4-8 46 NA 45,4 44,2 44,1 43,2 43,1 NA NA
9-12 NA 42,6 46,3 45,5 43,9 NA NA NA NA
13 and up NA NA NA 45,2 44,5 NA 42,5 41,4 NA
FLATFLAME
ENDFIRED
AVERAGE THICKNESSCOMPARISON
FLATFLAME
ENDFIRED
MINIMUM THICKNESSCOMPARISON
Kettle Age (years in service)
Kettle
Size (mt)
2 3 4 5 6 7 8 9 10
4-8 NA 40,9 38,7 42,3 37,9 32,2 30 NA NA
9-12 NA 39,9 NA NA NA 30,6 28,9 NA NA
13 and up NA 42,2 36,5 41,4 NA 31,2 30,2 30 26,2
Kettle Age (years in service)
Kettle
Size (mt)
2 3 4 5 6 7 8 9 10
4-8 41,1 NA 26,2 37,8 40,1 41,7 38,8 NA NA
9-12 NA 39,9 41,1 41,9 36,7 NA NA NA NA
13 and up NA NA NA 41,9 35,7 NA 31,5 24,5 NA
STEP 1: CONCLUSIONS
• WHAT INDICATIONS FROM DATA ANALYSIS?• KETTLE SIZE INFLUENCE• LOSS OF THICKNESS IN TIME• AVERAGE CORROSION IN COMPARISON• LOWEST READINGS IN COMPARISON• END FIRED OR FLAT FLAME?• INFLUENCE OF PRODUCTION THROUGHPUT
STEP 1: CONCLUSIONS
• BY LOOKING AT AVAILABLE DATA, THERE IS NOEVIDENCE OF A DIRECT INFLUENCE OF KETTLE SIZEON CORROSION BEHAVIOUR.
• LACK OF CORRELATION BETWEEN KETTLE SIZE ANDCORROSION BEHAVIOUR MIGHT HELP IN ANALYSISOF CORRELATION BETWEEN PRODUCTIONTHROUGHPUT AND CORROSION (SEE NEXT SLIDES!)
STEP 1: CONCLUSIONS
• COLLECTED DATA SHOWS THAT IN BOTH FLAT FLAME AND ENDFIRED SYSTEMS THERE IS A DIRECT RELATIONSHIP BETWEENAGE AND THICKNESS LOSS.
• COLLECTED DATA ALSO SHOWS THAT THICKNESS DROPSFASTER AFTER AN AGE OF FIVE YEARS, CONFIRMING KNOWNTHEORIES ON HEAT EXCHANGE AS A FUNCTION ON THICKNESS.
STEP 1: CONCLUSIONS
• AVERAGE CORROSION APPEARS, ACCORDING TO AVAILABLEDATA, BETTER IN HIGH VELOCITY SETTINGS THAN IN FLATFLAME ONES.
• ALTHOUGH THIS INDICATION MIGHT LEAD TO DRAW SOMECONCLUSIONS, FURTHER INVESTIGATION MUST BEPERFORMED ON A WIDER STATISTICAL BASE.
• ALSO, BEFORE JUMPING TO CONCLUSIONS, ONE MIGHT TAKEA LOOK AT LOWEST READINGS!
STEP 1: CONCLUSIONS
• LOWEST READINGS SHOW THAT IT IS VERY HARD TOCOMPARE ALTERNATIVE HEATING SYSTEMS
• IT SEEMS BY LOOKING AT HARD DATA THAT END FIREDSYSTEMS ARE PRODUCING HIGHER LOWER VALUES THAN FLATFLAMES ONLY IN SHORT KETTLES.
• WE MUST THINK OF A MODEL TO EXPLAIN THIS DIFFERENCE. ITCOULD BE RELATED TO HEAT EFFICIENCY AS KETTLES BECOMEBIGGER.
STEP 2: ANALYZINGCORROSION MAPS
• HOW DO WE READ THEM ?
• CORROSION DISTRIBUTION: Corrosion Maps provide asnapshot view of how corrosion is distributed in ke?lesand help performing comparisons.
• CORROSION PROGRESSION: Repeated inspecGons onke?les have allowed some consideraGon for corrosionprogression.
STEP 2: ANALYZINGCORROSION MAPS
• Corrosion is a funcGon of heat distribuGon andexhaust velocity.
(please
, don’t
laugh!)
STEP 2: ANALYZINGCORROSION MAPS
• ProducGve age of the ke?le is important, but focus must be ontotal usage of furnace heat potenGal.
STEP 2: ANALYZINGCORROSION MAPS
• Moving parts and regular flows inside the ke?le can seriouslyaffect corrosion.
WHAT’S NEXT?
• A SERIOUS INTEGRATED STUDY ON HEAT DYNAMICS OFFURNACE/KETTLE SYSTEMS, IN RELATION TO EXISTING CORROSIONDATA
• MORE KID INSPECTIONS, TO BUILD A LARGER STATISTICAL BASE TO BEPERIODICALLY ANALYZED TO CONFIRM OR CHANGE CONCLUSIONS
• POSSIBLE INTERACTION WITH FURNACE MANUFACTURERS ANDGALVANIZERS TO PUT KID INSPECTION DATA ON THE COMPLETEBACKGROUND OF FURNACE HISTORY, STRUCTURE AND TECH DATA