Buoyancy for bundled offset risers

Offshore staff

ABERDEEN, UK --Balmoral Engineering has introduced a new buoyancy system to support bundle hybrid offset risers (BHORs).

Supatherm, launched last week at Offshore Europe in Aberdeen, is claimed to be a 'pure' – i.e. macrosphere-free – syntactic material that can tolerate temperatures of over 90º C without syntactic buoyancy loss. According to Balmoral, it also exhibits numerous mechanical advantages over competing materials, notably in compressive strength.

With standard BHOR designs, the company says, buoyancy forces react against a tower top bulkhead rather than being transferred to the central core pipe every 15-25 m (49-82 ft), as is the case with drilling riser systems. This creates the need for tolerance of very large uniaxial compressive forces simultaneous with triaxial stresses arising from hydrostatic pressure.

BHOR buoyancy also differs from drilling riser buoyancy in performance requirements, Balmoral adds. It must provide a much longer service life, as it cannot be maintained, replaced, or have any performance loss compensated for by tensioners or other devices.

Supatherm is available in three standard grades at operating temperatures of up to 90º C, and can be cast into large, complex modules.

09/13/2007