Safety alert: Vibration abrasion an electrical risk
The U.S. Coast Guard has issued a safety alert warning of possible issues from vibration abrasion and chafing in electrical wires.
The alert was issued after a towboat with barges in tow temporarily lost power when its main generator apparently sustained a short circuit due to wire abrasion. In that incident, described in the April 4 alert, the vessel regained power from a standby generator and retained control of its tow.
“The casualty involved a diesel-driven generator, which grounded out and tripped off line when one of the primary leads exiting the generator housing chafed against its steel enclosure,” the alert said.
“Investigators determined that other vessels operated by the same company had similar generators and wiring arrangements. Inspection of those generators showed similar signs of chafing and abrasion, but the wiring had not yet reached the point of failure,” the alert continued.
The generator brand was not named in the alert. On vessels with similar equipment, electrical taping was wrapped around areas that were visibly frayed. Rubber protectors secured with tie-wraps provided extra protection.
The electrical failures from abrasion and chafing found by investigators are reminiscent of vibrational loosening that can occur with diesel engine components and has caused fuel oil spray fires.
“While this situation is different than a failed fuel line,” the alert said, “the unsafe condition leading to the failure is similar. Both circumstances serve as a reminder for personnel to consider what could occur as a result of vibration.”
The Coast Guard urges operators to inspect piping systems connected to the engine, engine mounts, pipe clamps, wire bundles, brackets and places where components run through decks or overhead openings. Other places aboard a vessel that house generators’ larger leads also should be inspected.
“As a result of this casualty the Coast Guard strongly recommends that vessel operators with similar generators on board consider having a qualified individual inspect the casing area where the winding leads exit the generator frame for similar wear,” the alert said.
To read the alert, visit www.uscg.mil/hq/cg5/cg545/alerts/0216.pdf.
30 barges break away after tow hits Mississippi River bridge
Thirty barges loaded with grain broke away and two later sank after the towboat Michael G. Morris struck a railroad bridge over the Mississippi River near Thebes, Ill.
The accident occurred at about 0500 on April 6 when the 8,000-hp towboat operated by AEP River Operations ran into the Thebes Railroad Bridge linking Missouri and Illinois. One of the barges partially sank alongside the bridge and another sank in the middle of the channel downriver at mile marker 42.
Authorities closed the river from mile 44 to mile 20 after the accident, and travel restrictions remained in effect for more than a week. Vessels with reduced tow sizes were allowed to transit the safety zone starting on April 8 after junction buoys were placed to mark the sunken barge.
Salvage efforts to raise and remove the barges began on April 9, and crews were able to move the barge next to the bridge outside the channel, the Coast Guard said in a news release. The sunken barge at mile 42 was moved outside the channel on April 14.
The Coast Guard is investigating the accident and did not specify a cause.
The accident capped a relatively quiet period on the Mississippi River following a string of bridge strikes and breakaways this winter during a period of unusually high water.
Bulker damaged after grounding in Columbia River
A loaded bulk carrier sustained “significant hull damage” after running aground in the Columbia River near Cathlamet, Wash.
The 623-foot Panama-flagged Sparna was outbound carrying a full load of grain when it grounded at about 0015 on March 21 with a river pilot still on board. The vessel sustained multiple hull fractures, including a 5-by-25-foot gash that left a boulder lodged inside, the Coast Guard said in a news release.
Sparna remained at anchor until March 23, when it traveled back upriver to a repair facility in Kalama, Wash., with support from two tugboats. The Coast Guard established a safety zone around the vessel during transit.
The ship was carrying 218,380 gallons of high-sulfur fuel and 39,380 gallons of marine diesel when it grounded. Authorities said Sparna’s fuel tanks remained intact during the incident.
The Coast Guard is investigating the cause of the grounding.
Casualty flashback: April 1963
The USS Thresher nuclear-powered submarine was undergoing deep-dive sea tests some 200 miles off Cape Cod when the crew stopped responding to communications from a nearby military ship on the surface.
The submarine, which disappeared at about 0915 on April 23, 1963, was never heard from again. U.S. military investigators believe the vessel sustained an engine room problem, lost propulsion and imploded more than 1,300 feet below the surface.
Thresher was the first-ever nuclear-powered submarine to sink, and 129 sailors and technicians from Portsmouth Naval Shipyard went down with the sub.
The accident led to a massive underwater search for the wreckage and probe into the cause. Investigators believe the vessel experienced a failure of a saltwater piping joint that used silver brazing rather than traditional welding, according to published reports. Water from the failed joint could have sprayed electrical components, causing a short circuit that affected the reactor, leading to the loss of propulsion.
The sub was unable to blow its ballast tanks, a maneuver used to rapidly bring the vessel to the surface, likely due to moisture buildup in high-pressure air flasks that subsequently froze, according to reports.
An alternate theory of the incident suggests an electrical failure occurred, affecting the main coolant pumps, which in turn caused the reactor plant to shut down. The theory offered by Bruce Rule and Norman Polmar, said the vessel likely imploded at a depth of 2,400 feet — some 400 feet deeper than its projected “collapse death.”
The authors argued the collapse would have occurred in one-tenth of a second, which is faster than the human body can perceive such an event.
Following the accident, the U.S. Navy established the SUBSAFE program aimed at preventing catastrophic losses to the nation’s nuclear subs. The program focused on ensuring the watertight integrity of vessel hulls and the ability to respond to onboard flooding.