_RP_2P-1987_scan.pdf

Analysis of Spread Mooring Systems for Floating Drilling Units API RECOMMENDED PRACTICE 2P(RP 2P)SECOND EDITION,MAY 1,1987 American Petroleum Institute 1220 L Street,NorthwestI)Washington,DC 20005 Issued by AMERICAN PETROLEUM INSTITUTE Production Department FOR INFORMATION CONCERNING TECHNICAL CONTENTS OF THIS PUBLICATION CONTACT THE API PRODUCTION DEPARTMENT,211 N.ERVAY,SUITE 1700,DALLAS,TX 75201(214 220-9111.SEE BACK SIDE FOR INFORMATION CONCERNING HOW TO OBTAIN ADDITIONAL COPIES OF THIS PUBLICATION.Users of this publication should become familiar with Its scope and content.This publication is intended to supplement rather than replace individual engineering judgment.OFFICIAL PUBLICATION l?REG.U.S.PATENT OFFICE Copyright 1987 American Petroleum Institute RP 2P:Analysis of Spread Mooring Systems for Floating Drilling Units 3 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.Additionally,sophisticated computer analysis methods are being developed and employed in the industry.These are also recognized as valuable contributions to the understanding of mooring systems.But it is further the purpose of this document to present an analysis method which can be used by properly qua!-NOTE:This recotnmended practice is under the jurisdiction of the API Cotnmittee on Standardization of Offshore Structures.This is the second edition of this recotmnended practice and s-upersedes the first edition dated Jan.1,1984.It was mtthorized for publication at the 1986 Standardization Conference and later ratified by letter ballot.ified people who may not have access to proprietary model tests or computer programs.Policy Attention Users:Portions of this publication have been changed from the previous edition.The location of changes have been marked with a bar in the margin as shown to right of this paragraph.In some cases the changes are significant,while in other cases the changes reflect minor editorial adjustments.The bar notations in the margins are provided as an aid to users as to those parts of this publication that have been changed from the previous edition,but API makes no warranty as to the accuracy of such bar notations.American Petroleum Institute(API)Recommended Practices are published to facilitate the broad availability of proven,sound,engineering and operating practices.These Recommended Practices are not intended to obviate the need for applying sound judgment as to when and where these Recommended Practices should be utilized.The formulation and publication of API Recommended Practices is not intended to,in any way,inhibit anyone from using any other practices.Nothing contained in any API Recommended Practice is to be construed as granting any right,by implication or otherwise,for the manufacture,sale,or use in connection with any method,apparatus,or product covered by letters patent,nor as insuring anyone against liability for infringement of letters patent.This Recommended Practice may be used by anyone desiring to do so,and a diligent effort has been made by API to assure the accuracy and reliability of the data contained herein.However,the Institute makes no representation,warranty or guarantee in connection with the publication of this Recommended Practice and hereby expressly discla