Lesson Learned

Contract Number:
Design Number:
Library File Number: Submitted Date: 03/23/2011

SR/Terminal/Vessel: M/V Kitsap

Region: WSF
Contract Title: Hull Crack in the Vicintiy of Frame-60 - Discovered March 9, 2010

EXPERIENCE: Describe the particular situation or event.
During routine compartment inspections following the daily operations of Monday, March 8, 2010, the engineering department crew members aboard the M/V Kitsap (ON630023) discovered a weeping crack in the hull of the vessel in the vicinity of Frame 60, starboard side, number-2 end. The approximately 5-inch long crack ran across Frame 60 and a very small amount of sea water was weeping into two compartments, the Steering Gear Room #2 and Void #2. The hull crack was located on the number two end (Seattle facing) approximately 4-feet beneath the waterline. Commercial divers were dispatched and a sealant was externally applied to the hull crack to stop the weep. The Kitsap was taken out of operational service and with USCG permission, sailed to Seattle, Pier-52 awaiting emergency drydocking at Todd's Pacific Shipyard on Friday, March 12, 2010. Repairs were completed to the satisfaction of the WSF and USCG inspectors and the Kitsap was refloated on Sunday, March 14. The Kitsap resumed operational service that evening on the Bremerton/Seattle route. The cost of drydocking and repairing the hull crack was approximately $85,000.

LESSON: Describe what knowledge was gained from the experience.
The investigation ruled out any causal effects due to reported landings at Bremerton earlier on Monday, any failure or inefficiency of the vessel's cathodic protection system or CAPAC system, or steel plate imperfections. The conclusion of the investigation is that this crack resulted from a release of a number of stresses and forces common to this area of the Issaquah class vessel hulls. It is an area highly susceptible to cracking and high residual stress due to the proximity of the vertical butt seams in the steel plates, differing plate thickness in this area, the location of a transverse bulkhead leading to additional steel stresses, the angular discontinuity of hull plates meeting at this location, as well as the proximity to the primary support for the propulsion shaft and propeller with its inherent vibrations.

RECOMMENDATION: Describe how the knowledge gained can be used.
1. The type and sequence of any hull repair, including insert repairs, on the Issaquah Class vessels should be considered carefully and a weld sequence developed. 2. That the WSF Hull Inspection Guidance Plan be continued and drydock maintenance periods continue to include an aggressive inspection of known hull areas of stress and wear.

Project Delivery Method:
Design-Build

Design-Build Phase:

Operations

Categories:
Hull

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