Structural Integrity Management of Fixed Offshore Structures

API RECOMMENDED PRACTICE 2SIM FIRST EDITION, NOVEMBER 2014

REAFFIRMED, SEPTEMBER 2020

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Copyright © 2014 American Petroleum Institute

Foreword

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• the term “shall” denotes a minimum requirement in order to conform to the specification,

  
  

• the term “should” denotes a recommendation or that which is advised but not required in order to conform to the specification,

  
  

• the term “may” is used to express permission or a provision that is optional,

  
  

• the term “can” is used to express possibility or capability.

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Contents

Page

1. Scope 1

2. Normative References 1

3. Terms, Definitions, Acronyms, and Abbreviations 1

   1. Terms and Definitions 1

   2. Acronyms and Abbreviations 5

4. Structural Integrity Management Overview 6

   1. General 6

   2. Competency 7

   3. Risk 7

   4. Limitations 7

5. Structural Integrity Management Process 8

   1. General 8

   2. Data 8

   3. Evaluation 10

   4. Strategy 16

   5. Program 17

   6. Decommissioning 17

6. Surveys 18

   1. Inspection Strategy 18

   2. Personnel Qualifications 18

   3. Level I Surveys—Routine Above-water Inspection 18

   4. Baseline Underwater Inspection 20

   5. Level II, III, and IV Surveys—Routine Underwater Inspection 21

   6. Special Inspections 24

   7. Survey Work Scope 26

   8. Inspection Specification 26

   9. Data Records 27

7. Damage Evaluation 27

   1. General 27

   2. Degradation Mechanisms 27

   3. Component Evaluation 29

   4. System Evaluation 30

8. Structural Assessment Process 30

   1. General 30

   2. Assessment Category 31

   3. Assessment Initiators 31

   4. Assessment Information 33

   5. Assessment Method 34

   6. Performance Criteria 38

   7. Risk Reduction. 38

      v

      Contents

      Page

9. Assessment for Metocean Loading 38

   1. General 38

   2. Assessment Criteria 39

   3. Assessment Loading 40

   4. Design Level Method 43

   5. Ultimate Strength Method 44

   6. Risk Reduction. 46

10. Assessment for Fatigue Loading 46

11. Assessment for Seismic Loading 46

    1. General 46

    2. Simplified Analysis 47

    3. Design Basis Check 47

    4. Extreme Level Earthquake 47

    5. Abnormal Level Earthquake 47

    6. Risk Reduction. 47

12. Assessment for Ice Loading 48

    1. General 48

    2. Design Basis Check 48

    3. Simplified Analysis 48

    4. Design Level Method 48

    5. Ultimate Strength Method 48

    6. Risk Reduction. 48

13. Risk Reduction 49

    1. General 49

    2. Exposure Reduction 49

    3. Likelihood Reduction 50

14. Platform Decommissioning 56

    1. General 56

    2. Decommissioning Process 57

Annex A (informative) Commentary on Structural Integrity Management 59

Bibliography 95

Figures

1. SIM Process 6

2. SIM Process and Document Organization 9

3. Risk Categorization Matrix Example 12

4. Assessment Within the SIM Process 15

5. Fitness-for-Purpose Assessment Process 32

6. Deck Silhouette Definition 42

7. Wave Heading and Direction Convention 43

8. SMR Techniques 51

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Contents

Page

1. Schematic Load vs Deformation Diagram of an X-braced Platform 67

2. Schematic Load vs Deformation Diagram of a Diagonally Braced Platform 68

Tables

1. Exposure Category Matrix 13

2. Risk-based Inspection Program Intervals 21

3. Default Inspection Program 23

4. Drag Coefficient, Cd, for Wave/Current Platform Deck Forces 43

5. Design Level Metocean Criteria, U.S. Gulf of Mexico 44

6. Ultimate Strength Metocean Criteria, U.S. Gulf of Mexico 45

A.1 Decommissioning Activities 89

Introduction

The purpose of this recommended practice is to provide guidance to owner/operators and engineers in the implementation and delivery of a process to manage the structural integrity of existing fixed offshore platforms. This process is called structural integrity management (SIM).

The SIM process described in this recommended practice is based on internationally recognized industry standards, including API 2A-WSD, 22nd Edition and ISO 19902:2007, and on global industry best practices. This recommended practice details engineering practices for the evaluation, assessment, and inspection of existing fixed offshore structures to demonstrate their fitness-for-purpose. This recommended practice incorporates and expands on the recommendations of Section 14, “Surveys” and Section 17, “Assessment of Existing Platforms” as previously provided in API 2A, 21st Edition.

The principal section describing the recommended SIM process is Section 5. It contains details of each aspect of the SIM process and provides a roadmap for using the recommended practice. Each of the remaining sections provides self-contained detailed guidance on performing the relevant SIM task.

Section 6 contains guidance on underwater surveys of fixed platforms. Two approaches are provided: a risk-based underwater survey (6.5.2) and an exposure-based underwater survey (6.5.3). When the owner/operator has not adopted a risk-based SIM strategy, an exposure-based (default) inspection program should be used.

In particular, Section 9 contains guidance on the selection of calibrated metocean criteria used for the fitness-for- purpose assessment of platforms designed and constructed to API 2A-WSD, 19th Edition and earlier editions that are located in the U.S. waters of the Gulf of Mexico or West Coast. In addition, Section 9 contains guidance on the selection of appropriate metocean criteria used for the fitness-for-purpose assessment of platforms designed and constructed to API 2A-WSD, 20th Edition and later for platforms located in the waters of the U.S. Gulf of Mexico or

U.S. West Coast.

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Structural Integrity Management of Fixed Offshore Structures

1. Scope

   This recommended practice provides guidance for the structural integrity management (SIM) of existing fixed offshore structures used for the drilling, development, production, and storage of hydrocarbons in offshore areas. However, the general principles of SIM apply to any structure.

   
   

   Specific guidance is provided for the evaluation of structural damage, above- and below-water structural inspection, fitness-for-purpose assessment, risk reduction, mitigation planning, and the process of decommissioning. This recommended practice incorporates and expands on the recommendations of Section 14, “Surveys” and Section 17, “Assessment of Existing Platforms” as previously provided in API 2A-WSD, 21st Edition. See Annex A for additional information and guidelines on the provisions stated in the numbered sections of this document.

   
   

   The SIM process provided in this recommended practice is applicable to existing platforms installed at any location worldwide. However, the recommended practice provides specific metocean criteria, which are only applicable for use in fitness-for-purpose assessments of platforms located in the U.S. Gulf of Mexico and the U.S. West Coast.

   
   

   For guidelines, recommended practices, and other requirements relating to planning, designing, and constructing new fixed offshore platforms, including reuse and change-in-use of existing platforms, reference should be made to the latest edition of API 2A-WSD.

   
   

   For guidelines, recommended practices, and other requirements relating to planning, designing, and constructing new offshore floating production systems, including reuse and change-in-use of existing floating production systems, reference should be made to the latest edition of API 2FPS.

   
   

2. Normative References

   The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

   
   

   API Recommended Practice 2A-WSD, Planning, Designing, and Constructing Fixed Offshore Platforms—Working Stress Design, 22nd Edition

   
   

   API Recommended Practice 2EQ, Recommended Practice for Seismic Design Procedures and Criteria for Offshore Structures

   
   

   API Recommended Practice 2MET, Recommended Practice for Derivation of Metocean Design and Operation Conditions

   
   

   API Recommended Practice 2N, Planning, Designing, and Constructing Structures and Pipelines for Arctic Conditions

   
   

3. Terms, Definitions, Acronyms, and Abbreviations

3.1 Terms and Definitions

For the purposes of this document, the following definitions apply.

3.1.1

air gap

The clearance between the highest water surface that occurs during the extreme metocean conditions and the underside of the cellar deck.

1