Tuesday, May 31, 2011

Top 10 Towing Vessel Material Failures—Part I

The U.S. Coast Guard Office of Investigations and Analysis recently conducted an analysis of all material failures on towing vessels after a reportable marine casualty in 2004-2008.

This study analyzes material failures that are the “first events” of marine casualties for towboats on rivers and other inland waters; tugs engaged in harbor operations, ship dockings, and lightering barges; and tugs towing offshore barges on coastal routes.
Excerpted from “Top Ten Deficiencies Found on Vessels.” Full text available on http://homeport.uscg.mil/. Navigate to missions/investigations/safety reports.

In many instances “towline” refers to a facing wire or to an inter-barge connection wire. Failure of these wires is at times attributed to operator error in the handling of the boat or error of the deck crew who might have fastened it incorrectly. In some instances the wire was either too small or too worn to be safe.

Fuel Filter
As a material failure, a fuel filter becoming clogged with dirt, water, or both is more common on towing vessels than it is on other commercial vessels.

Steering Gear
Although the term “linkage” does not precisely identify a component in a steering system, we cannot overemphasize the number of different mechanical connecting components that exist in a vessel’s steering system.
Hose. Most hose failures are a burst along its length. Crimped-on end fittings also fail, occasionally without warning.Rudder. Less than half of all rudder casualties are the direct result of groundings or flotsam strikes, and the exact causes of most of these casualties are never attributed to one particular event. In more than 20 percent of these casualties the rudder has been lost.
Ram. Casualties related to this major component are both hydraulic and mechanical. Hydraulic failures are commonly stuck pistons and blown seals. Half of all mechanical ram-related failures involve the attachment of the ram to the rudder.
Pump. The same mounting and connecting failures noted with rams occur with steering pumps, accounting for approximately 40 percent of failures. Sixty percent of pump failures are with the pump internals—seals and bearings.

The list continues in part 2.