Two Case Studies on Metallurgical Failures
Author: Dr Janet Cotton
Date: 27th August 2011
Fractured Bollard
Fracture site
Bollard Failure
What caused the catastrophic
fracture of the bollard?
What does the fracture surface say about the failure
What was the load requirements for bollard
What was the bollard made from, what are its properties
Fracture Surface
Fracture site
Bollard Material
Grey Cast Iron
Sample Rupture Strength (UTS) MPa Strain to Failure (Elastic)
1 116MPa 2.05%
2 117MPa 1.73%
3 118MPa 0.60%
4 132MPa 0.37%
Grey Cast Iron
Grey Cast Iron
Sample Rupture Strength (UTS) MPa Strain to Failure (Elastic)
1 116MPa 2.05%
2 117MPa 1.73%
3 118MPa 0.60%
4 132MPa 0.37%
Grey Cast Iron
KIC = applied stress x SQRT (flaw size x PI)
Bollard Materials
BS Marine Structures BS 6349
Fenders, bollards, fairlead etc
First published in 1985 Revised 1994
Recommendations for Bollard Materials
BS 1452 – Cast Iron BS 2789 – Ductile Iron BS 3100 – Cast Steel
Bollard Installed 1961
Bollard Materials
Manufacturer Material Description Relevant Standard
Trelleborg Ductile Cast Iron ASTM A 536, 65-45-12 or 80-55-6
BS EN 1563
Trelleborg Grey Cast Iron None given
Trelleborg Cast Steel None given
Fendercare Grey Cast Iron EN GJL 250
BS EN 1561
Fendercare Spheriodal Graphite
Cast Iron
EN GJS 450-10
BS EN 1563 – 1997
Fendercare Cast Steel GE 300
EN 10293-1991
Bollard Materials
Standard Material Value
BS 1452 1961 grade 10 Grey Cast Iron 170MPa
BS 1452 1961 grade 12 Grey Cast Iron 205MPa
BS 1452 1990 grade 180 Grey Cast Iron
BS 1561 Grey Cast Iron 250-300MPa
ASTM 48 A class 150 Grey Cast Iron 150MPa
BS 1563 1997 Spheroid Cast Iron 450MP
Tested Bollard Strength Grey Cast Iron 116MPa -132MPa
Standard Mooring Arrangement – BS 6349-4 1985
Mooring Rope
Standard Mooring Arrangement – BS 6349-4 1985
Finite Element Analysis
Finite Element Analysis
Standard Mooring Arrangement – BS 6349-4 1985
Bollard Material
Fracture site
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Heat Exchanger
Hot Dip Galvanising
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• Brown Deposit • Iron / Si Rich – rust from pipes (hematite)
• Light Brown Deposit •Iron / Si Rich with Cl – rust from pipes contaminated with Cl
• Black Deposit •Iron rich – rust from pipes (magnetite)
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DETERMINANDS METHOD Baltimore Specification CTO623 CTO624 No 7 Condenser
pH at 25°C SANS 5011:2005 6.5-9.0 7,0 5,9 7.07
Conductivity at 25°C in mS/m SANS 7888:2005 132 18,3 185
Dissolved solids at 180 °C in mg/L SANS 5213:2005 1200ppm max TO FOLLOW TO FOLLOW 1060
Calcium as Ca in mg/L SANS 11885:2008 30-500ppm 26,65 3,964 31.85
Magnesium as Mg in mg/L SANS 11885:2008 35,13 4,857 43.29
Sodium as Na in mg/L SANS 11885:2008 162,2 23,68 200
Chloride as Cl in mg/L SANS 9297:2007 274 44 337
Sulphate as SO4 in mg/L SANS 6310:2005 250ppm max 84 6 270
Total alkalinity as CaCO3 in mg/L SM 2320:1995 250ppm max 41 5 38
Iron as Fe in mg/L SANS 11885:2008 500ppm 0,107 <0,01 1.39
Selenium (recoverable) as Se in mg/L SANS 11885:2008 <0,01 <0,01 <10
Zinc as Zn in mg/L SANS 11885:2008 18,85 0,049 2.15
Total hardness as CaCO3 in mg/L Calculation 211,2 29,90 78.63
Sulphur mg/L 20
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steel pipe
zinc coating steel pipe
zinc coating
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Corr
osio
n R
ate
pH of water
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• Mass of Zinc = 372 kg
• Volume of Zinc when new – 85 micron x 312 m3 = 2.6 x10-2 m3
• Life cycle of condenser – 15 years – accepted corrosion rate 5 micron / year
• pH 14 (maximum) – corrosion rate of 5 times that of pH of 8/9
•25 microns per year – 0.48 microns per week
• At pH 14 it would take more than 1 year to remove the volume of Zinc on condensers
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pH
Ammonia (kg)
Ammonia (kg) Vs Condenser pH
pH ~ 12.5 @ ~ 2800 kg
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steel pipe zinc coating
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Position Fe wt% Zn wt% Si wt%
1 15.14 84.50 0.36 2 97.71 2.02 0.28 3 8.05 91.61 0.34 4 7.06 92.59 0.35 5 32.00 50.03 17.96
2 3 4 5
1
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• Poor water treatment • The effect of ammonia on feed water • “Poor Sample Preparation” • Sand in the Feedwater • Galvanic effect of the box on pipe array
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