2b_Moorings,

A Swivel is a device that allows an incoming fixed orientation Product/Process line to connect to a Floater that rotates around the same axis. The first two Diagrams illustrate the impact of Swivels on the remaining deck area in which to place modules or pancakes. The first shows the typical positions for a Swivel Stack. The third and forth are two styles of stack. The third is a through deck variation the forth in hull with cone connection. Do we need swivels the answer is not necessarily, the fith diagram shows one where the connections between incoming lines and to the process deck are through flexibles. It is also the case that where a vessel is large enough to not have to weathervane or completely cicrculate presenting an equal aspect in all positions, then it can be fixed moored without a swivel. Fixed platforms have an advantage in not needing a swivel.

Various Swivel Applications
The first two Diagrams illustrate conventional applications using a ship shape Floater, the first is a through Deck the second a cone. The third and forth show other applications where swivels may be used. The third is a CALM usually used in Offloading, the forth is a SALM where in a simple form it uses a knuckle joint but again som versions use a table top requiring Swivels

Through Deck Swivel Applications
* The first Diagrams illustrate a through Deck Application particularly styled for an inshore ap[plication.
* The second Diagram shows where such a swivel can be positioned. Position A) allows the ship to face bow or stern into the weather, this is a least rotation case. B) is the point nearer the Bow it allows a space of use between bow and swivel for such things as accomodation, control Room, helipad etc. C) is in the bow probably more favoured for hull conversions where accomodation and control; is alrady in place in the stern. D) and E) are other alternates in feront of the bow allowing a better style of connection to the shipconventional applications using a ship shape Floater, the first is a through Deck the second a cone.
* The third and forth show other applications where swivels may be used. The third is a CALM usually used in Offloading, the forth is a SALM where in a simple form it uses a knuckle joint but again som versions use a table top requiring Swivels. Diagram three elaborates these positioned. The Forth Diagram shows an applications to Stern offloadid to a shuttle tanker connected inseries with the FPSO. The impact from such arrangements means that the FPSO weather vanes around the Swivel Column, the shuttle tanker acts like a dog and can wag for its tail to come around and end in an unwelcome position.
*The last diagram shows this series connection for Offloading. The FPSO starts unloading from a fully loaded condition ie Low in the Water, the shuttle can be in a light ship case with minimal balast ie high in the water. Both react to wind, wave and current and because of size and conition react differenly as loading progresses.