aga tech forum 2009: trends in kettle corrosion

Trends in Kettle Corrosion: Three Years of Data Collection and Its Meaning for the Hot-Dip

Galvanizing Industry

Mario Ubiali

AGA Tech Forum,Omaha, NE - 7-9 Oct 2009

Background

• Zinco Service introduced the KID technology at Intergalva 2006, in Naples

• Since then, over 220 kettles have been inspected in Europe, Canada and USA by the Zinco Global Network

• Enough data to start looking for meaningful connections and trends

FUNDAMENTALS: WHAT TO EXAMINE?

• Thickness readings: a set of numerical values

• Corrosion maps: a graphic representation of corrosion distribution on the wall of the kettle

1300 1200 1100 1000 900 800 700 600 500 400 300 200 150 140 120 110 50

40 45.9 46.9 47 48.5 47.6 48.2 46.6 48.2 46.8 47.4 47.2 43.7 46.5 48.1 46.6 45.7 46.8

70 45.3 47.4 48.3 46.8 48 47.5 48.1 48.9 46.7 48.7 47.8 47.1 45.9 46.5 45 45.5 46

120 46.3 47.3 48 47.6 47.3 47.2 47.4 48.8 48 47.4 48 46.9 45.7 46.2 45.8 45.2 45.4

160 47.9 47.9 47.9 47.2 47.9 46.7 47.8 47.8 47.8 48.2 48.2 47.4 47.5 47.6 47.2 47.1 45.2

200 48.1 48.2 48.9 48.9 47.7 48.2 48.5 48.5 48.4 48.9 48.9 47.6 48.4 48.1 48.1 47.5 47.8

250 48.9 48.7 45 48.2 48.1 48.5 48.4 48 47.2 48 48.3 47.8 47.9 46.6 47.8 48.4 48

STEP 1: ANALYZING NUMERICAL DATA

• KETTLES ARE CATEGORIZED AS FOLLOWS:

• By furnace type: Flat Flame VS. High Velocity• By kettle size: Three Lenght Categories

» 10 to 24 feet long» 25 to 40 feet long» 41 feet and more

• By age in service: From 2 to 10 years of service life


• WHAT FIGURES DO WE USE FOR ANALYSIS ?• AVERAGE THICKNESS: Calculated according to normal

statistical rules• MINIMUM THICKNESS READING: A significant index !


LET’S TAKE A LOOK AT RESULTS…..

FLATFLAME

ENDFIRED

AVERAGE THICKNESSCOMPARISON

Kettle Age (years in service) Kettle

Size (ft) 2 3 4 5 6 7 8 9 10

10-24 NA 1.81 1.66 1.82 1.66 1.67 1.43 NA NA 25-40 NA 1.73 NA NA NA 1.35 1.29 NA NA 41up NA 1.79 1.64 1.77 NA 1.64 1.55 1.36 1.35


Size (ft) 2 3 4 5 6 7 8 9 10

10-24 1.81 NA 1.78 1.74 1.73 1.70 1.69 NA NA 25-40 NA 1.67 1.82 1.79 1.72 NA NA NA NA 41up NA NA NA 1.77 1.75 NA 1.67 1.62 NA

FLATFLAME

ENDFIRED

MINIMUM THICKNESSCOMPARISON


Size (ft) 2 3 4 5 6 7 8 9 10

10-24 NA 1.61 1.52 1.66 1.49 1.26 1.18 NA NA 25-40 NA 1.57 NA NA NA 1.20 1.13 NA NA 41up NA 1.66 1.43 1.62 NA 1.22 1.18 1.18 1.03


Size (ft) 2 3 4 5 6 7 8 9 10

10-24 1.61 NA 1.03 1.48 1.57 1.64 1.52 NA NA 25-40 NA 1.57 1.61 1.64 1.44 NA NA NA NA 41up NA NA NA 1.64 1.40 NA 1.24 0.96 NA

Average Thickness - 4 to 8 Meters

42,3

46,4

42,2 42,5

36,5

45,444,2 44,1 43,143,2

25

30

35

40

45

50

4 5 6 7 8

Age (YRS)

Thickness (mm)

Flat Flame High Velocity

STEP 1 : DATA COMPARISON

AVERAGE THICKNESS - 10 TO 24 FEET

lklklklklklklklklklklklklklklklklkl

1,66

1,78 1,82 1,74

1,68 1,73

1,66 1,78

1,43

1,69

Average Thickness - Longer than 13 Meters

45,1

41,7

39,4

34,6

45,244,5

NA

41,442,5

NA

25

30

35

40

45

50

5 6 7 8 9

Age (YRS)

Thickness (mm)



1,77 1,77 1,74 1,64

1,55

1,67 1,62

1,36


AVERAGE THICKNESS - 41 FEET AND MORE

Lowest Thickness - 4 to 8 Meters

38,737,9

32,2

30

26,2

37,8

42,3

38,8

41,7

40,1

20

25

30

35

40

45

4 5 6 7 8

Age (YRS)

Thickness (mm)



LOWEST THICKNESS - 10 TO 24 FEET lklklklklklklklklklklklklklklklklkl

1,52

1,03

1,66

1,48 1,471,57

1,26

1,64

1,18

1,52

Lowest Thickness - Longer than 13 Meters

41,4

31,230,2 30

41,9

35,7

NA

31,5

24,5

20

25

30

35

40

45

4 5 6 7 8

Age (YRS)

Thickness (mm)


STEP 1 : DATA COMPARISONLOWEST THICKNESS - 41 FEET AND MORE


1,62 1,64

1,40

1,22 1,181,24

1,18

0,96

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 NO EVIDENCE OF A DIRECT INFLUENCE OF KETTLE SIZE ON CORROSION BEHAVIOUR.

• LACK OF CORRELATION BETWEEN KETTLE SIZE AND CORROSION BEHAVIOUR MIGHT HELP IN ANALYSIS OF CORRELATION BETWEEN PRODUCTION THROUGHPUT AND CORROSION (SEE NEXT SLIDES!)

STEP 1: CONCLUSIONS

• COLLECTED DATA SHOWS THAT IN BOTH FLAT FLAME AND END FIRED SYSTEMS THERE IS A DIRECT RELATIONSHIP BETWEEN AGE AND THICKNESS LOSS.

• COLLECTED DATA ALSO SHOWS THAT THICKNESS DROPS FASTER AFTER AN AGE OF FIVE YEARS, CONFIRMING KNOWN THEORIES ON HEAT EXCHANGE AS A FUNCTION OFTHICKNESS LOSS.

STEP 1: CONCLUSIONS

• AVERAGE CORROSION APPEARS, ACCORDING TO AVAILABLE DATA, BETTER IN HIGH VELOCITY SETTINGS THAN IN FLAT FLAME ONES.

• ALTHOUGH THIS INDICATION MIGHT LEAD TO DRAW SOME CONCLUSIONS, FURTHER INVESTIGATION MUST BE PERFORMED ON A WIDER STATISTICAL BASE.

• ALSO, BEFORE JUMPING TO CONCLUSIONS, ONE MIGHT TAKE A LOOK AT LOWEST READINGS!

STEP 1: CONCLUSIONS

• LOWEST READINGS SHOW THAT IT IS VERY HARD TO COMPARE ALTERNATIVE HEATING SYSTEMS

• IT SEEMS BY LOOKING AT HARD DATA THAT END FIRED SYSTEMS ARE PRODUCING BETTER LOWER VALUES THAN FLAT FLAMES ONLY IN SHORT KETTLES.

• WE MUST THINK OF A MODEL TO EXPLAIN THIS DIFFERENCE. IT COULD BE RELATED TO HEAT EFFICIENCY AS KETTLES BECOME BIGGER.

STEP 2: ANALYZING CORROSION MAPS

• HOW DO WE READ THEM ?• CORROSION DISTRIBUTION: Corrosion Maps provide a

snapshot view of how corrosion is distributed in kettles and help performing comparisons.

• CORROSION PROGRESSION: Repeated inspections on kettles have allowed some consideration for corrosion progression.


• Corrosion is a function of heat distribution and exhaust velocity.


• Productive age of the kettle is important, but focus must be on total usage of furnace heat potential.

• TWO KETTLES: SAME SIZE, SAME KIND OF FURNACE - DIFFERENT PRODUCTION THROUGHPUT

KETTLE 1 KETTLE 2


• Moving parts and regular flows inside the kettle can seriously affect corrosion.

QuickTime™ e undecompressore TIFF (Non compresso)

sono necessari per visualizzare quest'immagine.

WHAT’S NEXT?

• A SERIOUS INTEGRATED STUDY ON HEAT DYNAMICS OF FURNACE/KETTLE SYSTEMS, IN RELATION TO EXISTING CORROSION DATA

• MORE KID INSPECTIONS, TO BUILD A LARGER STATISTICAL BASE TO BE PERIODICALLY ANALYZED TO CONFIRM OR CHANGE CONCLUSIONS

• POSSIBLE INTERACTION WITH FURNACE MANUFACTURERS AND GALVANIZERS TO PUT KID INSPECTION DATA ON THE COMPLETE BACKGROUND OF FURNACE HISTORY, STRUCTURE AND TECH DATA

aga tech forum 2009: trends in kettle corrosion

Technology

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na na1

na nafired25

na naflame25

thickness mm3025

moreaverage thickness

thickness readings

feetlowest thickness