A critical component in the design of any weathervaning buoy, FSOs or FPSOs is the swivel stack.

The swivel stack transfers fluids, electricity and fibre optics between the fixed geostationary part and the rotating, weathervaning part of the system.

Swivel stacks can vary in complexity. On a simple buoy the swivel stack can comprise a single low pressure swivel for the crude oil, whereas on a complicated FPSO there can be many multi-path toroidal swivels transferring high pressure crude oil, gas, water injection fluids as well as electrical, hydraulic and pneumatic power plus electrical, hydraulic, pneumatic and fibre optic control signals.

Here at Monobuoy, we have design and build swivel stacks using our own design for the fluid swivel elements and proprietary electrical and fibre optic swivel elements.

We have designed and built crude oil, gas, pneumatic and high pressure toroidal hydraulic swivels.


12 Crude oil swivel for FSO,
with hydraulic swivel and
electrical swivel on top

3, 300 bar toroidal swivel for a disconnectable FPSO

The swivel was specially designed to be extremely low profile to enable it to fit between the existing product swivel and hydraulic signal swivels

The innovative engineers at Monobuoy used a helicopter main rotor bearing to keep the overall height of the swivel to less than 200mm
The low profile 300 bar swivel on dynamic rotation test at 390 bar

Designing and Building Single Point Mooring Systems

Our track-records include the following:

2002 - two 18" inline swivels, 15 bar for Vietsovpetro, Vietnam

2007 - 10" and 6" double product oil and gas swivel, Gabon
2009 - 12" single path crude oil swivel for FSO, Vietnam

2010 - 3", 300 bar toroidal swivel for a disconnectable FPSO, Australia

2014 - 2 x 24" single path crude oil swivel for WAHA Oil Company, Libya

Monobuoy also performed numerous swivel overhauls
Double product oil and gas swivel

1st path 10'' crude oil, 15 bar working pressure

2nd path is 6'' LPG, 15 bar working pressure
2 x 24" Single path crude oil swivel