Clutch Slippage Resulted in Tanker Running Aground


The Transportation Safety Board of Canada (TSB) investigated this occurrence for the purpose of advancing transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.


On 08 January 2017, at 0820 Atlantic Standard Time, the bunkering tanker Arca 1 went aground while under reduced propulsion due to a failure of the port propulsion clutch. There were 6 people on board. The vessel sustained major damage to the hull and propulsion machinery. There were no injuries and there was no pollution. The vessel was refloated and towed to Sydney, Nova Scotia.


During the occurrence, the friction plate on the port propulsion clutch arrangement slipped, which caused overheating and led to the failure of the clutch.

The starboard Z-drive separated from the mounting arrangement when the vessel contacted the bottom, causing the destruction of the starboard transmission. The outer hull was indented, and several transverse members sustained damage.

Port Z-drive


  1. The tension on the main propulsion clutch was not checked and adjusted before or during the voyage as per the original equipment manufacturer’s recommendation. As a result, clutch slippage occurred and caused the loss of port propulsion.
  2. When the port propulsion clutch failed and port propulsion was lost, the available propulsion power was reduced by 50%.
  3. Following the reduction of speed, the increased time required to complete the passage prevented the vessel from arriving at Sydney, Nova Scotia, before the weather deteriorated.
  4. In the severe weather, the vessel gradually lost headway and ultimately drifted to the west.
  5. The anchor was deployed twice, but could not hold and was dragged. The vessel drifted west toward the shore until it ultimately ran aground.
  6. The master was not qualified to act as master of the vessel and the motorman was not qualified to act as chief engineer.
  7. The voyage planning was carried out in a manner that was inconsistent with best practices, as contingencies and limitations were not taken into account.
  8. The decision to sail was not consistent with the limitations imposed on the vessel in its Single Voyage for Delivery Authorization, given that seas in excess of 4 m were forecast to develop within 24 hours.
  9. If crew members are not qualified for the positions to which they are assigned, they may not carry out these duties effectively, increasing the risk of accident or injury.
  10. If vessel maintenance is not carried out as per the original equipment manufacturer’s recommendations, the equipment may fail, increasing the risk of accident or injury.

Action taken

Following the occurrence, the company informed the TSB that it had taken the following measures to address safety concerns and avoid occurrences in the future:

  • The owner brought the vessel to its final destination in Mazatlán, Mexico, on board a heavy-lift transport.
  • An agreement has been signed with Lloyd’s Register to certify the vessel and the company’s management processes under international safety management rules.
  • The company has contracted Lloyd’s Register to certify the vessel, limited to operations in ports and short-distance coastal navigation.
  • The company has contracted Mexican (flag) maritime authorities to certify the vessel, limited to operations in ports and short-distance coastal navigation.

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Source: Transportation Safety Board of Canada


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