Ship-to-ship Cargo Transfer

A ship-to-ship (STS) transfer operation is the transfer of cargo between seagoing ships positioned alongside each other, either while stationary or underway. Cargoes typically transferred via STS methods include crude oil, liquefied gas (LPG or LNG), bulk cargo, and petroleum products. The nomenclature STS transfer should be used in reference to techniques used by civilian merchant vessels, as differentiated from underway replenishment which is the term used by the US Navy for similar, but usually far more complicated, operations between naval vessels while underway.

Most of cargo operations are taking place between a ship and a land-based terminal. Nevertheless it sometime can be useful to transfer cargo from one ship to another in open sea and this is called a ship-to-ship operation. At that moment, one of them will act as the terminal where the other one will moor. The receiving ship is called the mother vessel.

Problems

It is not easy to close two moving objects smoothly. Therefore seafarers established a few procedures which will be used regarding the sizes and manoeuvrability’s of the vessels involved. We can consider three configurations

1.Vessels making way, fast approach (1)

2.Mother vessel stopped (2)

3.Vessels making way, tactful approach (3)

The table below show the required manoeuvre regarding the operation for a few vessels

Vessels making way, fast approach