American Petroleum Institute

Recommended Practice for the Analysis of Spread Mooring Systems for Floating Drilling Units
 N RP 2P

Annotation

Foreword

The purpose of this document is to present a rational method for analyzing, designing or evaluating spread mooring systems used with floating drilling units. This method provides a uniform analysis tool which, when combined with an understanding of the environment at a particular location, the season of the year, the characteristics of the unit being moored, the type of hole being drilled, and other factors, can be used to determine the adequacy and safety of the mooring system. Although portions of the method may be useful in analyzing other types of mooring systems, its application to the design of mooring systems for lay barges, tankers, derrick barges, dredges, etc., is left to the discretion of the user.

The technology of mooring floating drilling units is continually evolving. This procedure is a compilation of those factors which are best understood and can be quantified at this time. It is felt that the method encompasses most of the major considerations known at this time. Conversely, designers or analysts should not construe that the omission of any particular phenomenon, calculation or other consideration from this document implies that it may not be significant for a particular situation. It is recognized that data can be, and is, appropriately developed from model tests. Wind, wave, and current tank data are routinely used in design and analysis. The utilization of data from model tests is encouraged when it clearly represents accurate information describing a phenomenon more precisely than the analytic method herein presented. It is further recognized that in special circumstances where precise environmental conditions, mooring loads, or mooring component design data are understood, the methodology and/or safety factors implied in this recommended design practice may not be appropriate.