Hybrid suppression systems consist of a combination of one or more VIV suppression devices. Perhaps the most common hybrid suppression system consists of a mix of standard helical strakes and fairings. Other hybrid suppression combinations are also possible such as short-chord fairings and long-chord fairings. Hybrid suppression systems are becoming more popular as engineers strive to maximize the benefits of each type of suppression device and to optimize the overall suppression system performance while minimizing overall project costs. Installation considerations may also determine the selection of hybrid suppression systems and their components.
Like the fairing example above, within a class of VIV suppression devices there are many combinations that could also be considered “hybrid” in the sense that all of the devices on a tubular are not identical. Examples include:
- Helical strakes at the top of a tubular coated with anti-fouling inhibitor, helical strakes in the middle of the tubular without anti-fouling and made of one material, and helical strakes near the bottom of the tubular made of an alternate material that provides superior abrasion resistance (for example, for a steel catenary riser);
- Fairings at the top of a tubular having a copper protection system to maintain weathervaning in areas of high marine growth (and fairings on the rest of the tubular without copper protection); and
- Standard helical strakes (or fairings) at the top of the riser without hydrostatic pressure compensation and helical strakes below a certain depth with hydrostatic pressure compensation.
While this article has focused on helical strakes and fairings, there are also other classes of VIV suppression devices besides these two classes. While most of these classes have been used only in the laboratory, some alternative devices have been used in the field. VIV Solutions continues to develop alternative devices and may introduce one or more of these into the market during the next few years.