Det Norske Veritas - Germanischer Lloyd

RISER INTERFERENCE
 N DNV-RP-F203

Annotation

Scope and Application

The scope of work is first of all to propose a framework for feasible analysis strategy and practical design procedures with focus on how to assess if the risers collide or not. Whenever the terminology "risers" is used in this document it generally also applies for all types of riser systems e.g. umbilicals, flexible risers, Steel Catenary Risers (SCRs) and Top-Tensioned-Risers (TTRs).

In order to derive a complete framework for feasibility and practical design procedures, the following topics need to be considered:

— overall framework and design approach

— safety philosophy

— environmental conditions and loads

— analysis strategies and hydrodynamic interaction models

— acceptance criteria and fundamental requirements.

The safety philosophy and design principles adopted in DNVOS- F201 /5/ apply. However, any recognised code considering the set of limit states discussed herein is in principle acceptable. The basic principles are in agreement with recognised codes and reflect state-of-the-art industry practice and latest research.

In view of high uncertainties in interference predictions, no calibration of safety factors is applied. Instead, conservative environmental modelling and analysis are applied; reference is made to DNV-OS-F201 /5/ and API RP 2RD /1/. A formal calibration is neither feasible nor optimal with the present level of experience.