Standards and Practices - Structural Integrity of Offshore Wind Turbines - page 45

standards facilitate international trade by enabling production companies
to design to a single set of codes, rather than attempting to satisfy multiple
national codes. A single standard also decreases the likelihood of design
errors often introduced when designers use unfamiliar codes for projects
in different regions.

CLASSIFICATION SOCIETY GUIDELINES 1

Provided in this section is an overview of the guidelines for offshore wind
turbines offered by independent classification societies. It should be
noted that no set of guidelines evaluated during this study and described
below can stand alone as a guideline for offshore wind turbines, espe-
cially with respect to site-specific environmental conditions prevalent in
U.S. waters. As examples, only the American Bureau of Shipping (ABS)
guidelines address tropical storms, none of the guidelines addresses the
ice loading that may be a controlling factor in the Great Lakes region, and
none addresses the seismic loading prevalent offshore the West Coast
and Alaska. Finally, all depend on other references to address some spe-
cific design parameters, such as the IEC standards for turbine load cases.

DET NORSKE VERITAS

DNV is a leading contributor to research on offshore oil and gas design
requirements, plays a leading role in development of standards for off-
shore wind, and provides certification services worldwide. DNV worked
with RISØ Danish National Laboratory researchers to develop national
standards for wind turbines. DNV also customized these national stan-
dards to suit its own internal practices, and it has been a key participant
in developing the IEC standards. Although the IEC standards do not
reflect DNV guidelines completely, there are significant similarities. The
major differences are the lack of prescriptive material, welding, and com-
ponent specifications in the IEC standard relative to DNV.

1

This text is modified compared with the version of the report released April 28, 2011, to more
clearly convey the completeness of coverage of offshore wind turbine standards and guidelines
prepared by classification societies and to correct errors in the dates and numbers of two DNV
standards cited in the text.