Page 132 - Failure Analysis Case Studies II

Failure Analysis Case Studies If
D.R.H. Jones (Editor)
0 2001 Elsevier Science Ltd. All rights reserved 117

INVESTIGATION OF THE MV KURDZSTAN CASUALTY

S. J. GARWOOD
Rolls Royce and Associates, Po Box 31, Derby DE24 8BJ, U.K

(Received 30 October 1996)
Abstract-The failure of the MV Kurdistun demonstrates the classic combination of high stress, low toughness
and defect which are required to cause initiation of a brittle failure. This paper describes the failure investigation.
The casualty illustratcs the importance that secondary stresses and thermal stresses can have on the conditions
which lead to failure. The formal investigation into the Kurdistan involved the use of elastic-plastic fracture
mechanics (for the first time in a U.K. court) to help ascertain the circumstances leading to the failure. 0 1997
Elsevier Science Ltd. All rights reserved.

1. BACKGROUND

The “MV Kurdistan” (originally named “Frank D Moores”) was completed in June 1973 by Swan
Hunter (Shipbuilders) Ltd at the Hebburn Shipyard, Tyne and Wear. In common with her three
sister ships, the Kurdistan was designed with a dead-weight of - 32,000 t, and was strengthened for
ice over the front third of the ship using Grade A steel plate -22mm (0.86in.) thick rather than
the normal 15mm (0.57in.). The ship was classed with Lloyds, as + IOOAl Oil Tanker Ice class
1 + LMC. The owners were Common Bros of Newcastle.
On 15 March 1979, the Kurdistan was carrying 30,000 tons of bunker C6 fuel oil, which was
heated to 140 “F (- 60 “C). This was the first occasion this ship had carried this cargo, although its
sister ships had apparently been carrying similar cargoes for a number of years with no problems.
The ship had only recently (October 1978) come out of dock, where the heater coils required for the
transportation of the bunker fuel had been fitted.
The ship was steaming off the east coast of Canada in deep water, a voyage from Point Tupper,
Nova Scotia to Baie des Sept-Iles, Quebec. There was a south-south-easterly gale to storm passing
over the area, causing rough seas and a heavy swell when, in circumstances fully described in [I, 21,
the vessel encountered a field of pack ice (Fig. 1). The ice field was apparently entered at full speed
(- 15 kn) at 12.35 Atlantic Standard Time on 15 March 1979, and, due to the combination of wind
and swell, the ice pressure was sufficient to halt the progress of the ship completely within 1.5 miles.
At 12.53, the captain ordered the ship to reverse out of the ice field. This manoeuvre was completed
at 13.05, and the ship turned to proceed to steam (at - 7-8 kn) into the swell along the edge of the
ice field, the wind conditions causing the loose ice to close into the ice edge.
The vessel had apparently travelled just two ship’s lengths after leaving the ice field (1305.5 h)
when, heading into the swell, the bow lifted, and the ship was felt to “shudder”. This “shuddering”
was also described by various members of the ship’s complement as pounding and vibration.
Following this incident, two cracks were reported in the side shell in the vicinity of the No. 3 tank
(Fig. 2). On the starboard side, a 6 in. (I50 mm) crack was visible approximately 12 ft (- 4 m) below
the level of the deck, and 23 ft abaft of the bulkhead. On the port side, a vertical crack, starting
- 12 ft, and ending - 18 ft (- 5 m), below deck level, 37 ft (- 11 m) abaft of the bulkhead, was
apparent. Oil was seen to leak from both cracks, particularly the port side, which appeared to have
opened up by -0.5 in. (12mm) in the centre. At this time, ullages (measurements of the tank levels)
were taken of the No. 3 wing tanks, indicating a large drop in oil level. At 14.30, air was reported
to be heard entering the No. 3 centre tank, and an ullage of 8ft was recorded (the ullage should
have been 4 ft). At this time, the wing tanks had an ullage of 10 ft. It was assumed that a longitudinal
bulkhead had also cracked, and that oil was entering the wing tanks from the centre tank. To
prevent further spillage, oil was pumped from the No. 3 to the No. 4 wing tank.

Reprinted from Engineering Fuilure Analysis 4 (l), 3-24 (1997)