In-service Inspection of Mooring Hardware for Floating Structures

API RECOMMENDED PRACTICE 2I THIRD EDITION, APRIL 2008

REAFFIRMED, SEPTEMBER 2020

In-service Inspection of Mooring Hardware for Floating Structures

Upstream Segment

API RECOMMENDED PRACTICE 2I THIRD EDITION, APRIL 2008

REAFFIRMED, SEPTEMBER 2020

Special Notes

API publications necessarily address problems of a general nature. With respect to particular circumstances, local, state, and federal laws and regulations should be reviewed.

Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make any warranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of the information contained herein, or assume any liability or responsibility for any use, or the results of such use, of any information or process disclosed in this publication. Neither API nor any of API's employees, subcontractors, consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.

API publications may be used by anyone desiring to do so. Every effort has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use or for the violation of any authorities having jurisdiction with which this publication may conflict.

API publications are published to facilitate the broad availability of proven, sound engineering and operating practices. These publications are not intended to obviate the need for applying sound engineering judgment regarding when and where these publications should be utilized. The formulation and publication of API publications is not intended in any way to inhibit anyone from using any other practices.

Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard is solely responsible for complying with all the applicable requirements of that standard. API does not represent, warrant, or guarantee that such products do in fact conform to the applicable API standard.

All rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher. Contact the Publisher, API Publishing Services, 200 Massachusetts Avenue, NW, Suite 1100, Washington, DC 20001.

Copyright © 2008 American Petroleum Institute

Foreword

This recommended practice is under the jurisdiction of the API Subcommittee on Offshore Structures.

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for the manufacture, sale, or use of any method, apparatus, or product covered by letters patent. Neither should anything contained in the publication be construed as insuring anyone against liability for infringement of letters patent.

This document was produced under API standardization procedures that ensure appropriate notification and participation in the developmental process and is designated as an API standard. Questions concerning the interpretation of the content of this publication or comments and questions concerning the procedures under which this publication was developed should be directed in writing to the Director of Standards, American Petroleum Institute, 200 Massachusetts Avenue, NW, Suite 1100, Washington, DC 20001. Requests for permission to reproduce or translate all or any part of the material published herein should also be addressed to the director.

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years. A one-time extension of up to two years may be added to this review cycle. Status of the publication can be ascertained from the API Standards Department, telephone (202) 682-8000. A catalog of API publications and materials is published annually and updated quarterly by API, 200 Massachusetts Avenue, NW, Suite 1100, Washington, DC 20001.

Suggested revisions are invited and should be submitted to the Standards Department, API, 200 Massachusetts Avenue, NW, Suite 1100, Washington, DC 20001, standards@api.org.

iii

Contents

Page

1. Scope 1

   1. General 1

   2. Purpose 1

   3. Inspection Philosophy and Exception to This Document 1

   4. Mooring Component Traceability and Inspection Documentation 2

2. Guidelines for In-service Inspection of MODU Mooring Chain and Anchor Jewelry 2

   1. Common Problems with MODU Chain 2

   2. Recommended Inspection Method 3

   3. Recommended Inspection Procedure 7

   4. Guidelines for Rejecting Chain Components 12

   5. Guidelines for Chain Repair, Removal, and Replacement 14

   6. Recommended Inspection Schedule 15

   7. Special Event Inspection 16

3. Guidelines for In-service Inspection of MODU Mooring-wire Rope and Anchor Handling Equipment . 16 3.1 Common Problems with MODU Mooring-wire Rope 16

1. Recommended Inspection Method 23

2. Recommended Inspection Procedure 26

3. Guidelines for Rejecting Wire Rope 30

4. Recommended Inspection Schedule 32

5. Special Event Inspection 33

6. Recommendations for Proper Use and Maintenance of MODU Mooring-wire Rope 33

7. Inspection of Anchor-handling Equipment and Termination of Pendant Wire Rope 33

1. Inspection of Steel Components for Permanent Moorings 35

   1. General 35

   2. Difference Between MODU and Permanent Mooring Inspection 35

   3. Typical Components in Permanent Moorings 35

   4. Mooring Component Information 36

   5. Inspection Objective, Type, and Schedule 37

   6. Detailed Component Inspection and Discard Criteria 39

2. Inspection of Fiber Ropes for MODU and Permanent Moorings 48

   1. General 48

   2. Inspection and Testing Techniques 49

   3. Damage Assessment and Discard Criteria 50

   4. Repair Procedures 57

   5. Inspection and Maintenance Procedures 58

Annex A (normative) Mooring Component Traceability, Inspection, and Retirement Documentation 61

Annex B (informative) MODU Mooring Inspection for Areas of Tropical Cyclone 67

Annex C (informative) Summary of JIP Test Data and Fiber Area Reduction Criteria 71

Bibliography 73

Figures

1. Typical Chain Stud Problems 4

2. Chain Diameter Measurement 5

3. Dockside Inspection Method 6

   v

   Page

4. Offshore Inspection Method 7

5. Chain Length Measurement 9

6. Inspection of Anchor Jewelry 11

7. Discard Criterion for Bent Links 12

8. Examples of Severely Loose Studs 13

9. Examples of Distributed Crown Wire Breaks 17

10. Typical Wire Fractures 17

11. Locally Grouped Broken Wires 18

12. Local Decrease in Rope Diameter 18

13. Progression of Wear in Wire Rope 20

14. Wire Rope with Heavy External Corrosion 21

15. Progression of External Corrosion 22

16. Wear of Internal Wires Caused by Lack of Lubrication Between Wires 23

17. Effect of Internal Lubrication on Wire Rope 24

18. Kink and Bend of Wire Rope 24

19. Deformation Caused by Improper Drum Winding 25

20. Wire Rope Inspection with Assistance of a Workboat 25

21. Lay Length and Diameter Measurement 27

22. Internal Inspection of Wire Rope 29

23. Common Rope Constructions for Mooring Applications 31

24. Acceptable Terminations for Pendant Wire Rope 34

25. Examples of Subsea Connectors 36

26. Chain Details Recorded by Work Class and Micro-ROV 40

27. Example of Chain Wear from Sitting in a Fairlead Pocket 40

28. Example of Chain Wear at Hawse Pipe 42

29. Example of Heavy Marine Growth and Chain Corrosion at Splash Zone 42

30. Example of Detached Clump Weight on the Seabed 43

31. Chain Diameter Reduction Due to Excessive Interlink Wear 43

32. Example of Chain Link Subjected to Out-of-Plane Bending 44

33. Example of Bird Caging and Kinking of Spiral Strand During Installation 46

34. Example of Disconnected Anodes for Spiral Strand 47

35. Wire Rope Socket Disconnected Due to Detachment of Retaining Pin 48

36. Fiber Rope Test Insert for Rope Inspection 49

37. Example of Concentrated Damage 51

38. Example of Distributed Damage 53

39. Example of Damage to Splice 54

40. Example of Minor Jacket Damage 54

41. Examples of Severe Jacket Damage 55

42. Marine Growth Detected Between the Jacket and Load Carrying Fiber 56

43. Examples of Potentially Harmful Marine Growths 56

44. Marine Growths at 200 ft Below Water Surface in DeepStar TLM 57

45. Rope Twisting During Installation 57

A.1 Measurements for Chain Manufacturing Record 62

C.1 JIP Full Rope Test Results 72

Tables

1. Upper Limit of Length Over Five Links and Length of Individual Link for Used Chain 14

2. Chain Inspection Intervals 16

3. Criteria for Crown Broken Wires 31

4. Wire Rope Inspection Intervals 32

vi

Introduction

The third edition of API RP 2I is an extension of the second edition, which addresses in-service inspection of mooring components for MODUs only. Major changes of this edition include:

• inspection guidelines for steel permanent moorings on permanent floating installations are added;

  
  

• inspection guidelines for fiber ropes used for permanent and MODU moorings are included;

  
  

• special guidance for MODU mooring inspection in the areas of tropical cyclones is provided.

The third edition was developed in response to the need for inspection guidelines of permanent and fiber rope moorings in addition to MODU moorings. The additional guidelines are based on study results of joint industry projects (JIPs) and industry experience accumulated in the last 15 years operating a large number of MODUs and permanent floating installations. This document compiles factors that are best understood and can be quantified at this time. The information in this document will be updated after further experience and knowledge are gained. Accordingly, comments and suggestions toward broadening and refining these guidelines are encouraged.

In-service Inspection of Mooring Hardware for Floating Structures

1. Scope

   1. General

      This recommended practice provides guidelines for inspecting mooring components of mobile offshore drilling units (MODUs) and permanent floating installations. Although this document was primarily developed for the moorings of MODUs and permanent floating installations, some of the guidelines may be applicable to moorings of other floating vessels such as pipe-laying barges and construction vessels. Furthermore, some of the guidelines may be applicable to secondary or emergency moorings such as moorings for jack-up units, shuttle tanker moorings, and dynamic positioning (DP) vessel harbor mooring.

      
      

      The applicability of this document to the moorings of other floating vessels is left to the discretion of the user.

      
      

   2. Purpose

      The need for rigorous, effective inspection of mooring hardware is apparent because most of the mooring failures involved faulty mooring components including corroded or physically damaged wire-rope or chain, defective connecting links, or mooring hardware of inferior quality. This document should be useful to engineers and operating personnel concerned with the following:

      
      

      1. planning a mooring inspection;

         
         

      2. conducting or supervising a mooring inspection;

         
         

      3. deciding whether to reject, repair, or replace mooring hardware;

         
         

      4. communicating with others concerning acceptable mooring hardware.

      
      

   3. Inspection Philosophy and Exception to This Document

      1. Inspection Philosophy

         
         

         The inspection philosophy of this document is to remove a mooring component with excessive deterioration from service. Based on this philosophy, a criterion of limiting the strength reduction to 10 % minimum breaking strength (MBS) was established in the first edition of this document. This criterion has been used by the industry for more than 20 years with generally satisfactory results, and it has become a long standing and widely accepted criterion.

         
         

      2. Inspection and Design Check

It should be emphasized that this document does not address the critical design issues such as tension factor of safety and fatigue, although some discussion is given to the design issue of corrosion allowance. Any attempt to link inspection with these critical design issues will make discard criteria a moving target, depending on design assumptions, analysis software used, margin of safety, and location of the operation, etc. Setting an industry inspection standard in this case is impossible. The design check should be conducted separately. If the design check indicates that the reliability of the mooring system can be overly compromised, the acceptance of a mooring component that passes the discard criteria should be carefully re-evaluated. On the other hand, if the design check indicates that the mooring component is significantly over-designed, and it can tolerate much more damage than allowed by this document, design calculations should be submitted to the appropriate authority asking for permission

1