Slipstream (fairings)
Our VIV suppression systems now include the patented 'Slipstream' fairing system. As with VIV suppression strakes, fairings can be used where it is necessary to minimise VIV on subsea risers (mainly SCRs). Fairings reduce vibration without incurring an increased drag penalty. However the specific environmental conditions need careful consideration by engineering houses, operators and installers as fairings will not always provide the desired effect.
Each rotomoulded fairing module consists of a 'teardrop' shaped polyethylene moulding fixed onto the riser by a system of hinged clamps. The whole system relies on its ability to rotate around the riser in reaction to the prevailing current, i.e. the fairings rotate freely around the riser. To simplify installation and reduced deployment time frames, axial restraint is provided by the use of a single clamp located every 3 to 4 fairing modules.
The system is designed using materials that have a long subsea track record and have been selected to provide a lightweight solution reducing loads and stresses in the bearing surfaces. Our fairings are particularly suited for larger diameter risers (up to 36" OD). They are easily and quickly installed onto risers either during pipe lay or onshore prior to mobilisations, with stinger installable systems available. These systems are backed up by a rigorous testing programme.
As with VIV suppression strakes, fairings are used where it is necessary to minimise vortex induced vibration on subsea risers (mainly SCRs). Unlike VIV suppression strakes, fairings will reduce vibration without incurring an increased drag penalty. However, the specific environmental conditions do need to be considered as fairings will not always provide the desired effect. These systems will normally be considered and specified by engineering houses, operators and installers.
Advantages:
- We have a great deal of technical understanding of fairing geometries and effectiveness
- The system has been verified and optimised through CFD analysis and full scale tank testing
- Slipstream is manufactured from lightweight, neutrally buoyant materials and modules are therefore man-handleable and easy to install
- As the system does not cover the whole riser, ROV inspections of the pipeline can be easily carried out.
- Alternative fairing solutions tend to encapsulate the whole riser and can be difficult to install and ROV inspections cannot be carried out.
Slipstream can be manufactured to suit risers from small diameters up to large drill riser strings (circa 36" OD). In reality, the larger diameters tend to be better suited to fairings than VIV suppression strakes.