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by the strain rate induced by the wave loading as the vessel exited the ice field. The reanalysis
indicates that a marginally higher rate than the low strain rate would have been just sufficient to
reduce the toughness below a CTOD of 0.1 mm, and would have caused a brittle initiation under
the prevailing loading conditions.
Like many other brittle failures, however, the Kurdistun illustrates that catastrophic failure occurs
only when the circumstances for brittle fracture propagation occur. In this case, if the vessel had
not cooled down due to its passage through the ice, the port bilge keel initiation event may not have
propagated beyond the ground bar. This failure illustrates, as do many other cases, the influence
welded attachments can have on the integrity of structures.

4. CONCLUSIONS

(1) The MV Kurdistun suffered a catastrophic brittle fracture initiating in the port bilge keel weld,
which propagated into the ship’s structure, causing the vessel to break in two just forward of
the wash bulkhead in the No. 3 tanks.
(2) All materials tested met the required standards. However, the weld in the ground bar of the
port bilge keel was incorrectly made, inducing a large weld defect, and reducing the local
toughness.
(3) The weld defect experienced some fatigue damage, increasing the local notch acuity, and, as the
vessel encountered “head on” seas on emerging from an ice field, a brittle fracture was initiated.
(4) The combination of still-water bending moment, thermal stresses, wave loading, residual stresses
from welding, defect size, and low toughness meant that brittle fracture initiation was inevitable.
(5) The combination of events leading to the Kurdistun encountering the ice field, and the charac-
teristics of its bunker oil cargo, meant that the temperature of the ship’s plate was reduced to
the external water temperature (- 1 “C) despite carrying a hot cargo. This resulted in the
catastrophic propagation of the brittle fracture from the bilge keel initiation site as the vessel
emerged from the ice field, resulting in the eventual complete fracture of the vessel.

AcknowledgementsThe failure investigation described in this article was performed by a team of engineers, metallurgists
and technical support staff at TWI. The author would like to thank the DOT, who sponsored the work, and all the colleagues
at TWI who assisted in the investigation. In particular, the efforts of Dr Phil Threadgill, who performed the metallurgical
investigation and appeared with the author at the public enquiry, and Miss Alison Wood, who documented all the samples
and assisted with the mechanical test programme, were invaluable.

REFERENCES

1. Ganvood, S. J., Threadgill, P. L. and Wood, A. M., Failure investigation concerning the “M V Kurdistan” casualty-
final report. Welding Institute Contract Report 3642/1/80, April 1980.
2. M V Kurdistan-Formal Investigation Report of Court No. 8069. HMSO, London, 1982.
3. Corlett, E. C. B., Colman, J. C. and Hendy, N. R., Kurdistan-the anatomy of a marine disaster. Royal Institution of
Naval Architects Spring Meetings, Paper No. 8, 1987.
4. Ganvood, S. J. and Harrison, J. D., in Pressure Vessel and Piping Technology-l985. A Decade of Progress. ASME, pp.
1043-1054.
5. Challenger, N. V., Phaal, R. and Garwood, S. J., Appraisal of PD 6493:1991. Fracture assessment procedures Part 111:
assessment of actual failures. TWI Research Members Report 512/1995, June 1995.