What is STS Mooring Operation ? |

What is STS Mooring Operation ?

STS mooring operations during the hours of darkness, and during reduced visibility are not recommended and strongly discouraged for safety reasons.

Unberthing operations are permitted during darkness, subject to the Master’s discretion, and in consultation with the head office, whenever in doubt.

For vessels carrying out STS operations in the Gulf of Mexico, the STS mooring and unmooring operation is permitted to be carried out at any time of the day, without tugs, weather permitting, and in consultation with the office whenever in doubt.

If the length overall of a vessel or barge coming alongside own vessel exceeds 100m, it should be considered an STS operation.

During an STS operation, no other activity is to be permitted for e.g., bunkering, de-slopping etc.

The vessel must carry out a STS drill at least 24 hrs prior arrival at the trans-shipment location and record this in the deck log books.

For vessels carrying out STS whilst underway, the speed of own vessel must not be greater than 5 knots, keeping in line with the recommendations in the STS guide.

For vessels carrying out STS operations with the mother vessel at anchor:

  1. A tug should be used to hold the anchored ship on a steady heading. If no tug is available, postponement of this operation should be considered.
  2. For both berthing and unberthing operations, tugs are to be used at all times.

In accordance with the OCIMF STS transfer guide, it should be agreed by the masters of both ships, before the operation starts, which individual will have overall advisory control of the STS operation. However, this does not relieve either master from his responsibility to ensure the safety of his own vessel.

If the master, on receiving instructions to engage in a STS operation has any concerns regarding the ability of the ship, (design and equipment) the experience of the officers and the crew or the number of people on board, to safely conduct the operation, the office must be advised immediately. 

Purpose of meeting shall be to establish, amongst others:

  • Communication procedures.
  • Emergency signals to be used.
  • Emergency stop procedures.
  • Product identification.
  • Routine stop procedures. 
  • Starting rate/Maximum loading rate/Topping off rates.

There shall be direct contact via agreed VHF channel between the transfer vessel/barge and own vessel’s Cargo Control Room.

Radio checks shall be carried out every 15 minutes. If communication is lost, cargo transfer shall be stopped immediately. Operations shall not be resumed until communications have been re-established.

Communications during STS operations involving cargo transfer shall be logged in the Port Log book.

The emergency signal established during the pre-transfer meeting shall be demonstrated prior commencing cargo operations.

These should include at least a 15, 10 and 5 minutes‘ warning.

At 15 minutes’ warning:

  • Transfer rate shall be reduced.
  • Chief Officer shall assume control in Cargo Control Room.
  • Deck OOW and personnel shall be stationed at the manifold to operate the valves.


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