Risk-based Inspection

API RECOMMENDED PRACTICE 580 FIRST EDITION, MAY 2002

Risk-based Inspection

Downstream Segment

API RECOMMENDED PRACTICE 580 FIRST EDITION, MAY 2002

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Copyright © 2002 American Petroleum Institute

FOREWORD

This recommended practice is intended to provide guidance on developing a risk-based inspection (RBI) program on fixed equipment and piping in the hydrocarbon and chemical process industries. It includes:

• What is RBI

• What are the key elements of RBI

• How to implement a RBI program

  It is based on knowledge and experience of engineers, inspectors, risk analysts and other personnel in the hydrocarbon and chemical industry.

  RP 580 is intended to supplement API 510 Pressure Vessel Inspection Code, API 570 Pip- ing Inspection Code and API 653 Tank Inspection, Repair, Alteration and Reconstruction. These API inspection codes and standards allow an owner/user latitude to plan an inspection strategy and increase or decrease the code designated inspection frequencies based on the results of a RBI assessment. The assessment must systematically evaluate both the probabil- ity of failure and the associated consequence of failure. The probability of failure assessment must be based on all forms of deterioration that could reasonably be expected to affect the piece of equipment in the particular service. Refer to the appropriate code for other RBI assessment requirements. RP 580 is intended to serve as a guide for users in properly per- forming such a RBI assessment.

  The information in this recommended practice does not constitute and should not be con- strued as a code of rules, regulations, or minimum safe practices. The practices described in this publication are not intended to supplant other practices that have proven satisfactory, nor is this publication intended to discourage innovation and originality in the inspection of hydrocarbon and chemical facilities. Users of this recommended practice are reminded that no book or manual is a substitute for the judgment of a responsible, qualified inspector or engineer.

  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 federal, state, or municipal regulation with which this Publication may conflict.

  Suggested revisions are invited and should be submitted to the director, Standards Depart- ment, American Petroleum Institute, 1220 L Street, N.W., Washington D.C. 20005, stan- dards@api.org.

  
  

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  	CONTENTS	Page
  1	INTRODUCTION, PURPOSE AND SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 1
  	1.1 Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 1
  	1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 2
  	1.3 Target Audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 2
  2	REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 3
  	2.1 Referenced Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 3
  	2.2 Other References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 3
  3	DEFINITIONS AND ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 4
  	3.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 4
  	3.2 Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 6
  4	BASIC CONCEPTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 7
  	4.1 What is Risk? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 7
  	4.2 Risk Management and Risk Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 7
  	4.3 The Evolution of Inspection Intervals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 7
  	4.4 Inspection Optimization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 8
  	4.5 Relative Risk vs. Absolute Risk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 8
  5	INTRODUCTION TO RISK-BASED INSPECTION. . . . . . . . . . . . . . . . . . . . . . . . .	. 8
  	5.1 Consequence and Probability for Risk-Based Inspection. . . . . . . . . . . . . . . . . .	. 8
  	5.2 Types of RBI Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 9
  	5.3 Precision vs. Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	11
  	5.4 Understanding How RBI Can Help to Manage Operating Risks . . . . . . . . . . . .	11
  	5.5 Management of Risks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
  	5.6 Relationship Between RBI and Other Risk-Based and Safety Initiatives . . . . .	12
  	5.7 Relationship with Jurisdictional Requirements. . . . . . . . . . . . . . . . . . . . . . . . . .	13
  6	PLANNING THE RBI ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	13
  	6.1 Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	13
  	6.2 Establishing Objectives and Goals of a RBI Assessment . . . . . . . . . . . . . . . . . .	13
  	6.3 Initial Screening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	14
  	6.4 Establish Operating Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	16
  	6.5 Selecting a Type of RBI Assessment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	16
  	6.6 Estimating Resources and Time Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
  7	DATA AND INFORMATION COLLECTION FOR RBI ASSESSMENT . . . . . . .	17
  	7.1 RBI Data Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
  	7.2 Data Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	18
  	7.3 Codes and Standards—National and International . . . . . . . . . . . . . . . . . . . . . . .	18
  	7.4 Sources of Site Specific Data and Information . . . . . . . . . . . . . . . . . . . . . . . . . .	18
  8	IDENTIFYING DETERIORATION MECHANISMS AND FAILURE MODES . .	19
  	8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	19
  	8.2 Failure and Failure Modes for Risk-Based Inspection . . . . . . . . . . . . . . . . . . . .	19
  	8.3 Deterioration Mechanisms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	19
  	8.4 Other Failures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	20

  
  

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  1. ASSESSING PROBABILITY OF FAILURE 20

     1. Introduction to Probability Analysis 20

     2. Units of Measure in the Probability of Failure Analysis 20

     3. Types of Probability Analysis 21

     4. Determination of Probability of Failure 21

  2. ASSESSING CONSEQUENCES OF FAILURE 23

     1. Introduction to Consequence Analysis 23

     2. Types of Consequence Analysis 23

     3. Units of Measure in Consequence Analysis 24

     4. Volume of Fluid Released 24

     5. Consequence Effect Categories 25

  3. RISK DETERMINATION, ASSESSMENT AND MANAGEMENT 26

     1. Purpose 26

     2. Determination of Risk 26

     3. Risk Management Decisions and Acceptable Levels of Risk 28

     4. Sensitivity Analysis 28

     5. Assumptions 28

     6. Risk Presentation 29

     7. Establishing Acceptable Risk Thresholds 29

     8. Risk Management 30

  4. RISK MANAGEMENT WITH INSPECTION ACTIVITIES 30

     1. Managing Risk by Reducing Uncertainty Through Inspection 30

     2. Identifying Risk Management Opportunities from RBI

        and Probability of Failure Results 30

     3. Establishing an Inspection Strategy Based on Risk Assessment 31

     4. Managing Risk with Inspection Activities 31

     5. Managing Inspection Costs with RBI 32

     6. Assessing Inspection Results and Determining Corrective Action 32

     7. Achieving Lowest Life Cycle Costs with RBI 32

  5. OTHER RISK MITIGATION ACTIVITIES 32

     1. General 32

     2. Equipment Replacement and Repair 33

     3. Evaluating Flaws for Fitness-for- Service 33

     4. Equipment Modification, Redesign and Rerating 33

     5. Emergency Isolation 33

     6. Emergency Depressurizing/De-inventory 33

     7. Modify Process 33

     8. Reduce Inventory 33

     9. Water Spray/Deluge 33

     10. Water Curtain 33

     11. Blast-Resistant Construction 33

     12. Others 34

         
         

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  6. REASSESSMENT AND UPDATING RBI ASSESSMENTS 34

     1. RBI Reassessments 34

     2. Why Conduct a RBI Reassessment? 34

     3. When to Conduct a RBI Reassessment 35

  7. ROLES, RESPONSIBILITIES, TRAINING AND QUALIFICATIONS 35

     1. Team Approach 35

     2. Team Members, Roles & Responsibilities 35

     3. Training and Qualifications For RBI Application 36

APPENDIX A DETERIORATION MECHANISMS 39

Figures

1. Management of Risk Using RBI 8

2. Risk Plot 9

3. Continuum of RBI Approaches 10

4. Risk-based Inspection Planning Process 11

5. Example Event Tree 28

6. Example Risk Matrix Using Probability and Consequence Categories

   to Display Risk Rankings 29

7. Risk Plot when Using Quantitative or Numeric Risk Values 30

Tables

1. Thinning 39

2. Stress Corrosion Cracking 41

3. Metallurgical and Environmental Failures 43

4. Mechanical Failures 45

vii

Risk-based Inspection

1 Introduction, Purpose and Scope

1.1 PURPOSE

The purpose of this document is to provide users with the basic elements for developing and implementing a risk-based inspection (RBI) program. The methodology is presented in a step-by-step manner to the maximum extent practicable. Items covered are:

1. An introduction to the concepts and principles of risk- based inspection for risk management; and

2. Individual sections that describe the steps in applying these principles within the framework of the RBI process:

   1. Planning the RBI Assessment.

   2. Data and Information Collection.

   3. Identifying Deterioration Mechanisms and Failure Modes.

   4. Assessing Probability of Failure.

   5. Assessing Consequence of Failure.

   6. Risk Determination, Assessment and Management.

   7. Risk Management with Inspection Activities.

   8. Other Risk Mitigation Activities.

   9. Reassessment and Updating.

   10. Roles, Responsibilities, Training and Qualifications.

   11. Documentation and record-keeping.

The expected outcome from the application of the RBI pro- cess should be the linkage of risks with appropriate inspec- tion or other risk mitigation activities to manage the risks. The RBI process is capable of generating:

1. A ranking by risk of all equipment evaluated.

2. A detailed description of the inspection plan to be employed for each equipment item, including:

   1. Inspection method(s) that should be used (e.g., visual, UT, Radiography, WFMT).

   2. Extent of application of the inspection method(s) (e.g., percent of total area examined or specific locations).

   3. Timing of inspections/examinations.

   4. Risk management achieved through implementation of the inspection plan.

3. A description of any other risk mitigation activities (such as repairs, replacements or safety equipment upgrades).

4. The expected risk levels of all equipment after the inspec- tion plan and other risk mitigation activities have been implemented.

1. Key Elements of a RBI Program

   Key elements that should exist in any RBI program are:

   1. Management systems for maintaining documentation, per- sonnel qualifications, data requirements and analysis updates.

   2. Documented method for probability of failure determination.

   3. Documented method for consequence of failure determination.

   4. Documented methodology for managing risk through inspection and other mitigation activities.

   However, all the elements outlined in 1.1 should be ade- quately addressed in RBI applications, in accordance with the recommended practices in this document.

   
   

2. RBI Benefits and Limitations

The primary work products of the RBI assessment and management approach are plans that address ways to manage risks on an equipment level. These equipment plans highlight risks from a safety/health/environment perspective and/or from an economic standpoint. In these plans, cost-effective actions for risk mitigation are recommended along with the resulting level of risk mitigation expected.

Implementation of these plans provides one of the follow- ing:

1. An overall reduction in risk for the facilities and equip- ment assessed.

2. An acceptance/understanding of the current risk.

The RBI plans also identify equipment that does not require inspection or some other form of mitigation because of the acceptable level of risk associated with the equipment’s current operation. In this way, inspection and maintenance activities can be focused and more cost effective. This often results in a significant reduction in the amount of inspection data that is collected. This focus on a smaller set of data should result in more accurate information. In some cases, in addition to risk reductions and process safety improvements, RBI plans may result in cost reductions.

RBI is based on sound, proven risk assessment and manage- ment principles. Nonetheless, RBI will not compensate for:

1. Inaccurate or missing information.

2. Inadequate designs or faulty equipment installation.

3. Operating outside the acceptable design envelope.

4. Not effectively executing the plans.

5. Lack of qualified personnel or teamwork.

6. Lack of sound engineering or operational judgment.

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