[Answer] How To Carry Out STS Transfers Safely?


Ship to ship (STS) transfer is the transfer of crude oil, petroleum products, liquid bulk chemicals and liquefied gas between sea-going tankers. However, in order for this procedure to be carried out safely, certain measures must be taken.  Let us have a look at the measures that should be followed efficiently for the Ship to ship transfer of crude oil.

Careful assessment of risks

According to Skuld Club, the STS transfer area should be carefully assessed for risks and chosen for a safe operation, in co-ordination with the appropriate authorities.

In selecting the area, the following considerations should be taken into account:

  • Sea room;
  • Traffic density;
  • water depth;
  • Availability of a safe anchorage.

Equipment for STS transfer

Before the beginning of the STS operation, the masters of the two tankers should exchange information regarding the availability, readiness and compatibility of the equipment to be used in the operation. This should include the two ships themselves, having regard to their design and characteristics.

Tankers with fenders 

The tanker(s) should be provided with fenders, both primary and secondary. The former should ideally be floating pneumatic type complying with ISO 17357.

The secondary can be foam filled type, light in weight and more easily hauled well above the water in positions with limited access to lifting gear.

The fenders can be secured to either vessel, although landing on an unprotected section of the hull is less likely if the fenders are appropriately secured to the manoeuvring ship.

How about smaller vessels?

When smaller vessels of similar size are carrying out the transfer, the accommodation superstructures will likely extend to the ships’ sides.

Fenders may need to be considered to protect the superstructures from contact during the operation as a result of rolling and listing of one or both of the vessels.

Contingency plans

However –  and most importantly – the organisers of an STS operation are required to develop contingency plans for dealing with emergencies.

Before committing to an STS operation, the parties involved should carry out a risk assessment covering operational hazards and the means by which they are managed.

Tankers will have in place their generic risk assessment through their Safety Management Systems (SMS) to cover STS operations. However, a specific risk assessment and contingency plan, which are local to the area of the scheduled STS operation, should be made or requested from the STS service provider” says Skuld.

Of course relevant training for STR transfers and drills are important for the crew to be familiar with the procedure.

STS operation preparation

Before the start of any STS operation, a joint plan of operation (JPO) should be developed to make sure that all parties involved, including the STS service provider, are on the same page with regard to how the operation is to be conducted.

Communications with the master of the other oil tanker should be established at an early stage to co-ordinate the meeting point and the method and system of approach.

When the preparation of either oil tanker has been completed, the other vessel should be so informed. The operation may proceed only when both oil tankers have confirmed their readiness.

Bunkering operation

MARPOL, Annex I, Chapter 8 do not recognize bunkering operations, and are not considered as STS cargo transfer operations.

However, as Skuld notes, most of the above factors can be applied to bunkering operations, particularly when the receiving vessel is at anchor.

Finally, further consideration should be given to bunkering Outside Port Limits (OPL). Bunkering OPL can be more hazardous than at a designated anchorage as the waters are typically less sheltered. In addition, in case of an incident, it would be likely to take significantly longer to mobilise an emergency response.

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Source: Safety4Sea


  1. Great article. We (John W. Stone Oil Distributor) have been engaged in offshore bunkering in the US Gulf of Mexico for some time now. When we are not in Dynamic Positioning mode with one of our vessels, we generally adhere to the recommendations of SKULD, and several other organizations (OCIMF, USCG …). Over the years we have taken a very conservative approach, which in some instances has cost us business, but in the long run, bunkering with a safe, reliable, and consistent operator saves everyone time and money.

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