SABIC RBI Methodology Training Final Rev5

Table of Contents Risk Based Inspection Methodology Training Chapter 1 - Introduction to RBI 1.1 RBI Overview 1.2 API 580 Risk Based Inspection 1.3 API 581 RBI Base Resource Document 1.4 Risk Measurement 1.5 Risk Management 1.6 Meridium RBI Methodology Chapter 2 - Degradation Mechanism Evaluations 2.1 Introduction 2.2 Internal Corrosion Degradation Mechanism Evaluation 2.3 External Corrosion Degradation Mechanism Evaluation 2.4 Environmental Cracking Degradation Mechanism Evaluation 2.5 Other Degradation Mechanisms Chapter 3 - Consequence Evaluations 3.1 Introduction 3.2 Flammable & Toxic Consequence Evaluation 3.3 Flammable Consequence Evaluation 3.4 Toxic Consequence Evaluation 3.5 Economic Impact Consequence Evaluation 3.6 Environmental Consequences 3.7 Exchanger Bundle Consequences 3.8 Tank Bottom Consequences 3.9 Safety/Health Consequences Chapter 4 - Risk Ranking 4.1 Risk Ranking Chapter 5 - Inspection Strategy Management 5.1 Strategy Management Chapter 6 - Overview of Integrated Evergreen RBI Workflow 6.1 Integrated Evergreen RBI Workflow 6.2 Block A – RBI System Identification & Collecting and Loading Design and Process Data 6.3 Block B – Risk Assessment 6.4 Block C – Developing Inspection Strategies 6.5 Block D – Executing Inspection Strategies 6.6 Overall RBI Workflow Diagram Glossary

© Copyright Meridium, Inc. 2002-2011. All rights reserved. Confidential and proprietary information of Meridium. Published Sep. 2011.

1 2 7 10 11 13 15 17 18 18 22 25 29 32 33 33 38 42 45 46 48 52 54 55 56 60 61 62 63 66 71 74 78 82 83

Table of Contents Appendices

86

Appendix A – Risk Matrix Graphic

86

Appendix B – Simplified RBI Steps

87

Appendix C – Representative Hole Sizes per RBI Component

88

Appendix D – Structural Tmin per RBI Component

89


Table of Contents Revision History Version

Date

Author

Description

0

30-Ago-2007

V. Nihalani

Initial draft

1

15-Sep-2007

M. Gurley

General Edits based on client review

2

16-Feb-2008

M. Gurley

Changes to section 2.3, and added appendix A,B.

3

16-Mar-2008

M. Gurley

Added Appendix C,D

4

10-Ago-2008

D. Rodas, M. Gurley

General Review Edits per Client Comments , Added Safety Consequence section, Updated TOC

5

13-Sep-2011

D. Rodas, F. Perillo

General Review Edits after version upgrade from 321 to 342


Ch.1 - Introduction to RBI

Chapter 1 Introduction to RBI


Page 1


1.1 RBI Overview Risk Based Inspection (RBI) involves prioritizing and managing an Inspection program, where the equipment items to be inspected are ranked according to “risk”.

“80% of the risk is associated with less than 20% of the equipment.”

It is often said that, “80% of the risk is associated with less than 20% of the Equipment”. Thus, in order to optimize the utilization of finite Inspection resources, companies deploy their Inspection resources on their most critical equipment.

1.1.1 Goals of an RBI Program The goal of RBI is to effectively manage risk through optimal utilization of resources. RBI typically involves the deployment of maintenance and inspection resources to work on high-risk items, so that the overall cumulative risk is reduced. In some cases, RBI may involve performing inspections more often than would be required per conventional inspection practices. In other cases, certain low risk items may not be inspected as frequently.

1.1.2 RBI vs. Traditional Inspection Methodologies The most important distinction between RBI and other FMEA methodologies is that RBI systematically accounts for both the Probability of Failure and Consequence of Failure when determining Risk. HAZOP (Hazard and Operability Analysis) accounts for Consequence of Failure, but not Probability of Failure. API 510/570 accounts for Probability of Failure, but does not adequately account for Consequence of Failure.


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Ch.1 - Introduction to RBI 1.1.3 Levels of RBI Analysis There are three levels of RBI Analysis, each of which corresponds to an approach. Many approaches fall somewhere on a continuum, between the three defined levels. • Level One – Qualitative • Level Two – Semi-Quantitative • Level Three – Quantitative The Qualitative approach is based upon a questionnaire, while the quantitative approach is based upon detailed calculations. Each approach has its advantages and disadvantages. The Qualitative approach is more subjective and has minimal data requirements, but input from a knowledgeable Subject Matter Expert is essential. The Quantitative Approach is more objective, but data requirements are extensive.

1.1.4 RBI Benefits Adopting the RBI methodology to direct the course of an inspection program can yield many benefits such as: • Improve safety and reliability • Reduce overall inspection costs by spending budgets more efficiently • Assess plant risks using qualitative, semi-quantitative or quantitative analysis • Identify critical contributors to risk • Optimize inspection intervals and methods

1.1.5 Outcomes of the RBI Process Expected outcomes of the RBI process include: • A detailed Inspection Strategy, including inspection methods, scope, and frequency • An equipment ranking by risk • Other risk mitigation activities • An expected risk level after the Inspection Plan and risk mitigation activities have been implemented • An understanding/ acceptance of current risk • A more efficient risk control and management system for the assessed Equipment


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Ch.1 - Introduction to RBI 1.1.6 RBI Limitations The effectiveness of RBI may be limited by the following: - Human error - Natural disasters - External events - Secondary events - Deliberate acts (i.e. sabotage) - Inherent risk in handling hazardous materials - Inspection method detectability - Design errors - Previously unknown mechanism of deterioration - RBI was developed to address the function of Pressure Boundary Containment (i.e. RBI is not typically used in evaluating damage mechanisms that don’t affect the pressure boundary) - Inaccurate or missing information - Inadequate design or faulty equipment installation - Operating outside the acceptable design envelope - Ineffective execution of the plan - Lack of qualified personnel and teamwork - Lack of sound engineering and operational judgment - Should not be used as a substitute for RCM, RCA, or PHA’s Adopters of RBI should be mindful of these pitfalls and associated impact on risk and effective RBI implementation.

1.1.7 Evergreening It is important that the RBI Process be an “evergreen” process. Most often, companies invest a lot of time and resources performing an RBI study for an upcoming Turnaround, but then fail to update the study on a regular basis. Since RBI is essentially a condition-based inspection program and equipment conditions change over the life of the equipment, RBI studies should be updated as the equipment or process conditions change. As equipment conditions change, an RBI assessment should be re-evaluated. Companies often define Trigger Points that necessitate an RBI re-analysis. These trigger points may be either new Inspection data or changes in the process or process excursions. The RBI process should be integrated with other processes such as the MOC, PHA and CPP (Critical Process Parameter) processes. This methodology can be particularly useful when optimizing the scope of work for a turnaround/Shutdown.


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1.1.8 Industrial Applications of RBI Industrial applications of Risk Based Inspection include: • Petrochemicals • Specialty chemicals • Offshore platforms • Pipelines • Pharmaceuticals • Pulp and paper • Cement • Other process industries

1.1.9 RBI Acceptance by Other Industries The following industries have also recognized RBI as an acceptable practice: • Fossil fuel power • Nuclear power

1.1.10 U.S. Regulatory Acceptance Latest editions of the following codes recognize RBI as an acceptable practice: • API 510 Pressure Vessel Code • API 570 Piping Code • API 653 Aboveground Storage Tank


Page 5

Ch.1 - Introduction to RBI 1.1.11 RBI Resource Documents The American Petroleum Institute has published two documents in regards to risk based inspection. These documents are discussed later in this document. • API 580 – Risk Based Inspection This document describes the fundamental elements of an RBI Program • API 581 – RBI Base Resource Document This document describes the tools and methods used to accomplish the requirements entailed in the RBI Program (i.e. inspection methods)

1.1.12 The Future of RBI Risk Based Inspection will no doubt evolve as a methodology. Likely changes to RBI include: • Integration with API 750 Management of Process Hazards • Integration with PSM (OSHA 29 CFR 1910.119) • Integration with EPA’s Risk Management Program (RMP) regulations

1.1.13 Conclusion The RBI method of comparative risk ranking provides a useful tool to deploy resources more efficiently and make better manpower staffing decisions.


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1.2 API 580 Risk Based Inspection 1.2.1 API 580 The API 580 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 API 580 brings to light the various issues that should be considered in an RBI program. It does not specify an exact methodology, but recognizes that different methodologies can be used to accomplish the intended objectives of an RBI program.

1.2.2 API RP Development Group The API RP Development Group consists of representatives from over twenty international refining, chemical, and exploration companies. Among the representatives are experts in Mechanical Design, Corrosion Engineering, NDE, and Inspection Compliance. Whenever necessary, the group consults others with specialized expertise.

1.2.3 Regulatory Acceptance Countries that recognize API 580 to some extent include: • USA • Germany • Brazil • Netherlands • United Kingdom • Malaysia • Japan • Mexico • Kingdom of Saudi Arabia


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Ch.1 - Introduction to RBI 1.2.4 API 580 – RBI Intersection with PHA, RCM…etc RBI alone cannot adequately cover all aspects of risk management. It should complement existing processes like PHA and RCM, but not serve as a substitute for them. For instance, an RBI assessment could define how inspection activities could mitigate the risk associated with loss of containment for a piece of equipment. However, when the same equipment neared the end of its life, an RCM strategy could define an “end of life” strategy involving equipment replacement or repair. RCM Analysis is applied at a system level. Whenever a Loss of Containment function is subjected to an RCM Analysis and inspection activities are planned to mitigate the risk associated with the loss of containment, RBI Analysis results could be used to complement the Equipment Plan.

1.2.5 API 580 - Topics Covered API 580 covers all the following topics: • Planning the RBI assessment • Collecting data and information • Identifying deterioration mechanisms and Failure analysis • Assessing Probability of Failure • Assessing Consequence of Failure • Risk determination, assessment, and management • Risk management with Inspection activities • Other risk mitigation activities • Reassessing and updating • Roles, responsibilities, training and qualifications • Documentation and record keeping Note – A good RBI program facilitates all the above items. The amount of data collection required for a full-blown quantitative RBI analysis can be extensive. However, if a systematic corrosion study is carried out and different Damage Mechanisms are accurately identified, then data gathering and collection efforts will be almost parallel activities.


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Ch.1 - Introduction to RBI 1.2.6 API 580 – Equipment Covered API 580 applies to all the following equipment: • Pressure Vessels • Process Piping • Storage Tanks • Rotating Equipment (Pressure-containing components) • Boilers and Heaters • Heat Exchangers (Shells and Bundles) • Pressure Relief Devices

1.2.7 API 580 – Equipment Not Covered API 580 does not apply to the following equipment: • Instrument and Control Systems • Electrical Systems • Structural Systems • Machinery components However, companies have started investigating the adoption of RBI methodologies for these types of equipment if their failure could lead to loss of containment from connected “static” equipment.


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1.3 API 581 RBI Base Resource Document The API 581 Base Resource Document (BRD) describes the basic technology and methods adopted within the API RBI methodology. Whereas API 580 describes the basics of an RBI program, this document describes in greater detail the different tools and methods that allow a user to meet the requirements of API 580. Some of these would include things like: • Explanation of performing Risk Analysis • Explanation of performing Consequence Analysis • Explanations of Probability of Failure Evaluations • Development of Inspection Strategies • Damage Mechanism Evaluations • Etc…

1.3.1 Summary API 580 lays the groundwork for a well rounded successful RBI program. Using this document as a base resource will help to understand the fundamental parts that make up the overall RBI program. Once these principles are applied, API 581 can be used as a tool to help determine which specific methods to use. At the end of the RBI assessment, the company has a better understanding of the process, the associated damage mechanisms, and the risk associated with it. Good documentation not only helps companies during audits but also helps keep the analysis alive.


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1.4 Risk Measurement Figure 1-2 shows the risk matrix used throughout Meridium RBI. By using this matrix, you can see that the product of likelihood and consequence determines the risk associated with a piece of equipment.

Inspection Priority Categories

Probability Categories

1

11

7

4

2

1

High Medium-High

2

16

13

8

6

3

Risk Ranking

Medium Low

3

20

17

14

9

5

4

23

21

18

15

10

5

25

24

22

19

12

E D C B A Consequence Categories

Figure 1-2: RBI Risk Matrix

•

•

•

Probability is the combined probability of occurrence for all of the types of damage that could take place to a given piece of equipment, such as internal corrosion, cracking, fatigue, etc. Consequence is often the worst-case scenario if there are multiple consequence effects, such as loss of containment and production loss. Inspection Priority is the combination of consequence and probability which will be used to generate RBI recommendations.

It is important to understand that RBI will not totally eliminate risk but will expose the high risk equipment, and then allow users the © Copyright Meridium, Inc. 2002-2011. All rights reserved. Confidential and proprietary information of Meridium. Published Sep. 2011.

Page 11

Ch.1 - Introduction to RBI opportunity to mitigate it. However, studies have shown that given the same level of Inspection activity, RBI Inspection programs provide more risk reduction than conventional Inspection Programs. This can be seen in figure 1-3 which can also be found in the API 581 document.

Figure 1-3: RBI vs. Conventional Inspection program Risk

1.4.1 Relative vs. Absolute Risk When using an absolute risk value, it pertains to the piece of equipment being assessed and doesn’t consider any other equipment in the area. By using a relative risk value, the user is comparing all equipment in a group against each other to determine relative risk. Although companies have developed their own formulas to quantify risk, RBI essentially focuses on calculating relative risk, as opposed to absolute risk. Companies in different parts of the world may place different levels of emphasis on various things when they try to quantify risk. In any case, it is very important that a consistent method be used, in order for this relative ranking to be effective. Consistency in performing the risk assessment is more important than accuracy. © Copyright Meridium, Inc. 2002-2011. All rights reserved. Confidential and proprietary information of Meridium. Published Sep. 2011.

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1.5 Risk Management 1.5.1 Basis of Risk Management Programs Risk Management Programs generally involve the following four-phase process: •

Phase One: Identify Specific Failure Modes or Deterioration Mechanisms - Different Failure Modes that apply to individual equipment or components are identified. Failure modes are defined as the different mechanisms that may cause the equipment or component to deteriorate over time and eventually lead to failure. Failure Modes are sometimes referred to as Damage Types.

•

Phase Two: Assess Risk - The deterioration rate and equipment tolerance to each deterioration mechanism is ascertained. This assessment results in a Damage Factor for each deterioration mechanism. The Cumulative Damage Factor is obtained by adding the individual Damage Factors and is used to assess risk.

•

Phase Three: Identify Risk Mitigation Alternatives - Highrisk equipment is examined and different risk mitigation alternatives are investigated. These alternatives might include a more sensitive Inspection Plan, Equipment Re-design, Equipment replacement, Equipment repair, or in some extreme cases a Change in Process.

•

Phase Four: Develop an Action Plan - An action plan is established to carry out the recommended actions that have been identified in Phase Three.

1.5.2 Using RBI to Manage Operating Risks To manage operating risks, you should define the susceptibility of each Equipment item and consider the following factors: • Process fluid or contaminants and aggressive components • Unit throughput • Desired unit run length between scheduled shutdowns • Operating conditions, including upset conditions


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Ch.1 - Introduction to RBI 1.5.3 Risk Management using Probability of Failure The probability of failure is a function of four factors: • Deterioration mechanism • Rate of deterioration • Probability of detecting deterioration and predicting future deterioration states using inspection techniques (i.e. inspection confidence rating) • Tolerance of equipment to the type of deterioration (i.e. material of construction) Since RBI is fundamentally based upon the assessment of equipment risk with respect to different damage types, it is critical that all these factors be considered. Note that this analysis should be performed for both normal and upset conditions.

1.5.4 Establishing Inspection Plans & Priorities Following are the key deliverables needed to establish an Inspection Plan and priorities: • Inspection Plan with unmitigated risk for current operation • Ranking of equipment by unmitigated risk • Mitigation plan for unacceptable risks

1.5.5 Inspection may not adequately manage risk… In some cases, it may not be possible to adequately manage risk through inspection. Consider the following cases: • Equipment nearing retirement • Failure mechanisms dictated by operating conditions, i.e. low temperature brittle fracture which can’t be predicted by inspection • Consequence-dominated risks Therefore, RBI should be used in conjunction with other processes like HAZOP and RCM.


Page 14


1.6 Meridium RBI Methodology To meet the intent of the RBI Methodology within the Meridium software the following components are used: • Degradation Mechanism Evaluations • Consequence Evaluations • Risk Ranking • Inspection Strategy Management These separate components of the Meridium RBI Methodology are discussed in greater detail throughout the sections that follow. Figure 1-1 depicts a high level overview of the Meridium RBI Workflow. In this graphic, you can see the different aspects of the integrated workflow and how they relate to one another. For more detailed information, refer to the official STRP4 RBI Workflow document.

Figure 1-1: RBI Workflow


Page 15

Ch.1 - Introduction to RBI 1.6.1 Degradation Mechanism Evaluations used in Meridium • • • •

Internal Corrosion (quantitative) External Corrosion (quantitative) Environmental Cracking (quantitative) Other Damage Mechanisms (qualitative)

1.6.2 Consequence Evaluations used in Meridium • • • • •

Flammable Consequence (quantitative) Toxic Consequence (quantitative) Economic Impact Consequence (quantitative) Product Leak Consequence – Tube Bundles (quantitative) Environmental Consequence (qualitative)

1.6.3 Risk Ranking Meridium determines the overall risk ranking by taking into account all of the individual rankings from all of the Potential Degradation Mechanisms in the following manner: • Rolling up Probability of Failure (POF) - from individual Degradation Mechanism Evaluations the worst case scenario for POF is used for the overall POF. • Rolling up Consequence of Failure (COF) - from individual Consequence Evaluations the worst case scenario for COF is used for the overall COF. • Performing Risk Ranking based on a 5 X 5 Risk Matrix – The overall risk ranking is determined by plotting the rolled up POF and COF on the standard 5 X 5 matrix as seen in figure 1-2.

1.6.4 Inspection Strategy Management Using the Risk Ranking and subsequent inspection priority, Meridium uses Strategy Rule Sets to create a System Generated RBI Recommendation (SGRR) from a reference table that has been populated by subject matter experts. These recommendations are then reviewed by an Analyst and reconciled into executable inspection plans.


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Ch.2 - Degradation Mechanism Evaluations

Chapter 2 Degradation Mechanism Evaluations


Page 17


2.1 Introduction During the Risk Assessment of an RBI Component, one of the main tasks is to perform Degradation Mechanism Evaluations. These evaluations take into account a host of different information depending on the specific mechanism being evaluated and run that data through stored calculations within the Meridium software. The objective of these evaluations is a Probability Category for each Potential Degradation Mechanism (PDM). These Probability Categories are then used in conjunction with the Consequence Categories to determine the overall Inspection Priority. Consequence Evaluations are covered in Chapter 3. This section will discuss the methods that are used to evaluate each damage mechanism. The calculations and decision sequences that are shown in this chapter are automatically computed by the Meridium software. They are displayed here to explain how the data input is being used in these evaluations.

2.2 Internal Corrosion Degradation Mechanism Evaluation The required sequence of calculations for internal corrosion is depicted in figure 2-1 and explained in greater detail throughout this section.

Figure 2-1: Calculation Sequence for Internal Corrosion


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Ch.2 - Degradation Mechanism Evaluations 2.2.1 Calculating or Estimating Intermediate Variables In order to perform Internal Corrosion Degradation Mechanism Evaluation, it is necessary to calculate or estimate the following intermediate variables: o

Corrosion Rate (Long Term & Short Term) =

CRLT

CRST

o o o o

Vbase - Vlast =

=

Where

Dbase - Dlast

Vnear – Vlast Dnear - Dlast

Where

CRLT – Long Term Corrosion Rate Vbase – Base Measurement Vlast – Last Measurement Value Dbase – Base Measurement Date Dlast – Last Measurement Date CRST – Short Term Corrosion Rate Vnear – Near Measurement Value Vlast – Last Measurement Value Dnear – Near Measurement Date Dlast – Last Measurement Date

Estimated Wall Loss = Nominal Wall Thickness – Estimated Wall Thickness Estimated Wall Remaining = Nominal Wall Thickness – Estimated Wall Loss Fractional Wall Loss = Estimated Wall Loss / Nominal Wall Thickness Over Design Factor (Wall Ratio) = Estimated Wall Remaining / Tmin

The Corrosion Rate can be based on any of the following: o Expected (Design) Corrosion Rate – A user-entered value that represents the best estimate or intended Design Corrosion Rate o Short-term Corrosion Rate – Calculated based on the Near and Last Thickness Measurements for the associated RBI component o Long-term Corrosion Rate - Calculated based on the Base and Last Thickness Measurements for the associated RBI component The Corrosion Rate and the time between inspections allow one to establish the Estimated Wall Loss and in turn, calculate the Fractional Wall Loss. The calculation of Pressure Minimum Thickness involves the following steps, as depicted in figure 2-2: o Select Design Code o Select Material Specification o Select Material Grade o Look Up Allowable Stress o Select Joint Efficiency o Calculate Pressure Minimum Thickness


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Figure 2-2: Pressure Minimum Thickness Calculation Sequence

Fundamentally, the Design Code choice determines what Allowable Stress tables are applicable. The Material Specification is a pick list of the materials listed in the Allowable Stress table for the chosen Design Code. The Material Grade is a pick list that is based on the choice of Material Specification. First, the user selects what Design Code applies: o ASME VIII Div 1 o ASME B31.3 o API 650 o Null If “Null” is chosen for Design Code, then the user can enter the Allowable Stress, Material Specification, and Material Grade manually. If the Design Code is not “Null”, then the Material Specification and Material Grade must be selected from the pick-lists. The Allowable Stress is a “look-up” based on the choices of Design Code, Material Specification, Material Grade and Design Temperature. The determination of Allowable Stress for Storage Tank Bottoms, however, is based on Material Specification and Material Grade selections, but not Design Temperature. In addition, there is an Override option that will permit manual entry of Allowable Stress. Joint Efficiency is also selected from a pick-list. The default value is 1.00.


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Ch.2 - Degradation Mechanism Evaluations Based on these values, Pressure Minimum Thickness can be calculated: Pmin = f (E, PDesign, OD, AS) where:

Pmin = Minimum Pressure Thickness E = Joint Efficiency PDesign = Design Pressure OD = Outside Diameter AS = Allowable Stress The Structural Minimum Thickness is looked up from standard tables using industry best practices and based on the RBI Component type. - The higher of the Structural Minimum Thickness and Pressure Minimum Thickness is used to calculate the Estimated Minimum Thickness. It is also possible to override this value by entering the value manually. - The Number of Years in Service and Corrosion Rate are used to calculate Wall Loss. - Wall Loss divided by the Initial Wall Thickness results in Fractional Wall Loss. - Wall Remaining is obtained by Subtracting Wall Loss from Initial Wall Thickness. - Wall Remaining divided by Estimated Minimum Thickness results in a Wall Ratio. The Corrosion Factor (CF) is determined based upon: - Number of inspections - Inspection Confidence (Very High, High, Medium, Low) – Based on inspection history - Fractional Wall Loss The Internal Corrosion Probability Category (ICPC) is determined based on the value of the corrosion factor (CF) that was determined in the previous table: Corrosion Factor (CF)

Internal Corrosion Probability Category (ICPC)

1 <= CF < 10

4

10 <= CF < 100

3

100 <= CF < 1000

2

CF >=1000

1

In order to account for over design, the final Internal Corrosion Probability Category (ICPC) is lowered by one category (the numeric ICPC goes down one Rank) if: - The Corrosion Rate is less than 0.127mm/year and - The wall ratio is greater than 1.5


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2.3 External Corrosion Degradation Mechanism Evaluation 2.3.1 Introduction External Corrosion Degradation Mechanism Evaluations involve the following calculations/assessments: An assessment of the Corrosion Rate can be based on any of the following: o Expected Corrosion Rate – A user-entered value that represents the best estimate of the Local Corrosion Rate. o Calculated Corrosion Rate – This Corrosion Rate is calculated for Corrosion Under Insulation (CUI) and is a function of Operating Temperature. o Average Corrosion Rate – This represents the Average Corrosion rate as measured by determining pit depths.

2.3.2 Adjustments to External Age and Corrosion Rates Adjustments to External Age and Corrosion Rates are made based on the factors outlined below: External coatings/paint is visually inspected and graded with a Coating Quality rating. These ratings can influence an Age Adjustment based on the following values: Coating Quality

Coating Factor

Age Adjustment

Best

2

-10

Average

1

-5

None

.2

-1

Insulation is visually inspected and graded with an Insulation Condition. The resulting Insulation Condition is used to apply a Corrosion Rate Adjustment, as follows: Insulation Condition

Corrosion Rate Adjustment

Good (G)

x 0.5

Fair (F)

No adjustment

Poor (P)

x 1.5


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Ch.2 - Degradation Mechanism Evaluations The Insulation Type is used to apply a Corrosion Rate Adjustment, as follows: Insulation Type

Corrosion Rate Adjustment

Asbestos

x 1.5

Calcium Silicate (not Chlorine free)

No adjustment

Calcium Silicate (Chlorine free)

x 0.75

Mineral Wool / Fiberglass

x 0.75

Foam / Cellular glass

x 0.50

A Corrosion Rate Adjustment is applied to account for Local Humidity. Local Humidity may be either atmospheric or resulting from the proximity of equipment to a cooling tower. • If atmospheric humidity is High, then the corrosion rate is adjusted higher by a factor of 50%. • If the equipment is located within 50 yards of a cooling tower, then the user-selected humidity factor should be raised by one category.

2.3.3 After Adjustments Have Been Made After adjustments have been made to External Age and Corrosion Rates: -

The External Age and Corrosion Rate are used to calculate Wall Loss.

-

Wall Loss divided by the Initial Wall Thickness results in Fractional Wall Loss.

-

Wall Remaining is obtained by Estimated Wall Loss from Initial Wall Thickness.

-

Wall Remaining divided by Estimated Minimum Thickness results in a Wall Ratio.

The Corrosion Factor (CF) is determined based upon: -

Number of inspections

-

Inspection Confidence (Very High, High, Medium, Low) – Based on inspection history

-

Fractional Wall Loss


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Ch.2 - Degradation Mechanism Evaluations External Corrosion Probability Category (ECPC) is then determined based on Corrosion Factor using the Table below: Corrosion Factor (CF)

External Corrosion Probability Category (ECPC)

1 <= CF < 10

4

10 <= CF < 100

3

100 <= CF < 1000

2

CF >= 1000

1

In order to account for over design, the final External Corrosion Probability Category (ECPC) is lowered by one category (the numeric ECPC goes up one Rank) if: - The Corrosion Rate is less than 0.127mm/year and - The wall ratio is greater than 1.5


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2.4 Environmental Cracking Degradation Mechanism Evaluation 2.4.1 Introduction Environmental Cracking Degradation Mechanisms can be performed for the following degradation mechanisms: o Wet H2S o Chloride Stress Corrosion Cracking o Caustic Cracking o Amine Cracking o Polythionic Acid SCC o Sulfide Stress Cracking o Carbonate Cracking o Hydrogen Stress Cracking – Hydrofluoric Acid

2.4.2 Environmental Probability Category An Environmental Probability Category is determined for each environmental cracking mechanism by calculating an Environmental Cracking Corrosion Factor. This factor is based on the Initial Potential for environmental cracking, any damage found during previous inspections, the number of previous inspections, and inspection confidence. Initial Potential is determined based on the material properties and contaminant levels. Table 2-1 shows these Initial Potential criteria.


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Table 2-1 Initial Potential Criteria for Environmental Cracking Degradation Initial Mechanism Potential Wet H2S H (Blistering, M SOHIC, HIC, SSC) L Chloride H Stress Corrosion Cracking (C1 M SCC)

Caustic Cracking

Amine Cracking (ASCC)

Polythionic Acid SCC (PTA)

Material / Environmental Criteria H2S > 50 ppm, free H2O, not PWHT, HCN > 20 ppm OR pH < 5.5 H2S > 50 ppm, free H2O, PWHT, HCN > 20 ppm OR pH < 5.5 OR Cracking Agent > 50 ppm, free H2O, Not PWHT, HCN < 20 ppm, no erosion (i.e., stable scale) H2S >= 20 ppm and < 50 ppm, free H2O, PWHT, HCN > 20 ppm OR Complies with MR-0175, HCN , 20 ppm Chloride (Cl-) concentration >= 50 ppm, temperature > 140°F plus residual stress and dissolved O2 >= 10 ppm OR all austenitic stainless steels (304, 316, 321, 347) Chloride (Cl-) concentration 25 - 50 ppm, dissolved O2 < 10 ppm, temperature > 140°F plus residual stress

L

Chloride (Cl-) concentration 5 - 25 ppm, dissolved O2 < 0.1 ppm, pH >= 9.0, temperature > 120°F

H

Carbon steel or 300 SS at temperatures > 200°F and all concentrations of caustic. Steaming out caustic systems, and operation upsets, Not PWHT

M

Carbon steel at temperatures > 200°F and < 30% caustic concentration, PWHT of CS welds and bends.

L

Operating temperatures < 100°F and up to 50% caustic concentration, or temperatures < 150°F and caustic concentration < 20%

H

Carbon steel not PWHT and MEA all concentrations and temperatures or DEA/MDEA > 140°F

M

Carbon steel not PWHT and MEA and operating temperatures of 125 - 150°F for all types of amines

L

Carbon steel PWHT regardless of operating temperature and concentration

H

Sensitized austentic SS are likely when: surface has iron sulfide scale, operating temperature > 800°F process upsets with air and water ingress, poor caustic wash procedures

M

Sensitized austentic SS and non-thermally stabilized 321 and 347 are possible when: likely when: surface has iron sulfide scale, higher upset temperatures, some process upsets with air and water ingress, good caustic wash procedures

L

A chance for sensitized austentic SS and thermally stabilized 321 and 347 when: surface has iron sulfide scale, stable operation (no process upsets), good caustic wash procedures


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Ch.2 - Degradation Mechanism Evaluations The Current Potential for Environmental Cracking and Adjusted Years Since Last Inspection are calculated based on the following things and can be found in Table 2-2: • Initial Potential for environmental cracking • Number of Prior Environmental Cracking Inspections • Inspection Confidence • Whether there was Damage Found during the last inspection Table 2-2 Current Potential and Adjusted Years in Service Reference Table # Prior Damage Current Potential for Environmental Inspection Found Environmental Cracking Confidence (Last Cracking Inspections Inspection)

0 >0

N/A Low

N/A No

Initial Potential Initial Potential

>0

Low

Yes

1

Very High

Yes

>1

Very High

Yes

1

High

Yes

One Category Higher than Initial Potential, up to High One Category Higher than Initial Potential, up to High Two Categories Higher than Initial Potential, up to High One Category Higher than Initial Potential, up to High

>1

High

Yes

Two Categories Higher than Initial Potential, up to High

1

Medium

Yes

One Category Higher than Initial Potential, up to High

>1

Medium

Yes

Two Categories Higher than Initial Potential, up to High

1

Very High

No

One Category Lower than Initial Potential (If Initial Potential = Low, Current Potential = Low)


Adjusted Years Since Last Inspection

Years in Environmental Cracking Service Years in Environmental Cracking Service

Years since Last Environmental Cracking Inspection + (Years in Environmental Cracking Service – Years Since Last Environmental Inspection) / 4 Years since Last Environmental Cracking Inspection + (Years in Environmental Cracking Service – Years Since Last Environmental Inspection) / 4 Years since Last Environmental Cracking Inspection + (Years in Environmental Cracking Service – Years Since Last Environmental Inspection) / 2 Years since Last Environmental Cracking Inspection + (Years in Environmental Cracking Service – Years Since Last Environmental Inspection) / 2 Years Since Last Environmental Cracking Service

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# Prior Environmental Cracking Inspections

Damage Current Potential for Inspection Found Environmental Confidence (Last Cracking Inspection)

>1

Very High

No

1

High

No

>1

High

No

1

Medium

No

>1

Medium

No

Adjusted Years Since Last Inspection

Low

Years Since Last Environmental Cracking Service Initial Potential Years since Last Environmental Cracking Inspection + 5 (with a maximum = (Years in Environmental Cracking Service)) One Category Lower Years since Last Environmental Cracking than Initial Potential ( Inspection + 5 (with a maximum = (Years in If Initial Potential = Environmental Cracking Service)) Low, Current Potential = Low) Initial Potential Years since Last Environmental Cracking Inspection + 10 (with a maximum = (Years in Environmental Cracking Service)) One Category Lower Years since Last Environmental Cracking than Initial Potential ( Inspection + 10 (with a maximum = (Years If Initial Potential = in Environmental Cracking Service)) Low, Current Potential = Low)

The corrosion factor for environmental cracking is then calculated by using the current potential for environmental cracking and the adjusted years since the last inspection. Based on these values, Pressure Minimum Thickness can be calculated: ECCF = f (POTcurrent, , Yadjusted)) where:

ECCF = Environmental Corrosion Cracking Factor POTcurrent = Current Potential for Environmental Cracking Yadjusted = Adjusted Years The Environmental Cracking Probability Category is based on the Environmental Cracking Corrosion Factor, as follows: Environmental Cracking Corrosion Factor

Environmental Cracking Probability Category

1-9

4

10 - 99

3

100 - 999

2

1000+

1


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2.5 Other (Qualitative) Damage Mechanism Evaluation 2.5.1 Introduction In addition to the quantitative degradation mechanism evaluation methodologies described earlier, Meridium System also includes a list of qualitative degradation mechanism evaluation. When these qualitative degradation mechanisms are evaluated, a user can manually specify a POF Category of 1-5. No calculations are performed by the system. Meridium provides the following qualitative Degradation Mechanisms as a starting point: • • • • • • • • • • • • •

Mechanical Fatigue Temper Embrittlement Liquid Metal Embrittlement Graphitization Brittle Fracture Carburization Creep Erosion Hot Hydrogen Attack Hydrogen Embrittlement Phase Change Embrittlement Stress Corrosion Cracking Thermal Fatigue

Clients have the ability to add additional degradation mechanisms that can be evaluated in a similar qualitative manner.


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Ch.2 - Degradation Mechanism Evaluations 2.5.2 Achieving Consistency Since these degradation mechanisms are qualitative, it is desirable that some guidelines be set as a corporation so that these degradation mechanisms are evaluated consistently across sites and by different people. In order to facilitate this, Meridium allows the client to maintain a Reference Table at a Corporate Level that can be used to document these guidelines. Shown in figure 2-4 is an example for Brittle Fracture (which is an ODM). The entered guidelines can be seen beside each POF ranking, describing what those ratings should be equivalent to.

Figure 2-4: Other Degradation Mechanism Reference Table


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Ch.2 - Degradation Mechanism Evaluations If the above mentioned reference tables are populated, then when a user selects a POF Ranking for an ODM, the system automatically looks up the description from the Reference Table and Populates it on the ODM Evaluation Datasheet as shown in Figure 2-5.

Figure 2-5: Other Degradation Mechanism (Brittle Fracture) Data Sheet

Having such guidelines available provides the RBI Analyst with the necessary information that facilitates ranking POF categories in a consistent manner.


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Ch.3 - Consequence Evaluations

Chapter 3 Consequence Evaluation


Page 32


3.1 Introduction As discussed in Chapter 2, the two main parts of an RBI Risk Assessment are Degradation Mechanism Evaluations (covered in Chapter 2) and Consequence Evaluations. When evaluating Consequences of failure for an RBI component we are not concerned with the mechanism (i.e. internal corrosion, CUI, cracking…etc) but the overall consequence of the failure. Because of this, once all of the consequences have been evaluated the worst case consequence scenario (in conjunction with the Probability Category) is used as a basis for determining the Inspection Priority/Risk Ranking. The following sections explain in more detail the different Consequence Evaluations performed within Meridium.

3.2 Flammable & Toxic Consequence Evaluation 3.2.1 Flammable and Toxic Consequence Overview When you perform a Loss of Containment Consequence Analysis, you estimate what might happen if the selected equipment item were to experience a loss of containment. Loss of Containment consequences might include fire, toxicity, environmental contamination, production leak, and/or production loss, based on the particular equipment type.

Loss of Containment Consequence Analysis Steps Following are the basic steps used in Flammable and Toxic Consequence Evaluations: 1)

Characterize the Fluid • Determine if the fluid is hazardous (flammable, toxic, or reactive) o If toxic, then what is the amount? • Determine the Initial Fluid State (liquid or gas) • Select a Representative Fluid (the chemical species that most closely resembles the fluid in terms of properties) Note - For mixtures, use the closest match, based first on boiling point, and then on molecular weight

2)

Estimate the amount of fluid that could be released • For liquids, also specify whether the area has a dike that could contain a leak Estimate the leak size • Based on the RBI Component Type

3)


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Ch.3 - Consequence Evaluations 4)

5)

Criticality Calculator calculates the duration of the leak • Based on leak size, pressure differential, fluid thermodynamic properties, and time necessary to detect and isolate the leak Calculate separate flammable and toxic consequences • Based on fluid properties, amount of fluid releases, and other miscellaneous factors.

These basic concepts will be covered in subsequent sections. Some additional factors will also be considered for heat exchanger bundles and storage tank bottoms.

3.2.2 Characterizing the Fluid The analysis process begins by characterizing the fluid that resides in the pipe or vessel. First, you must determine whether the fluid is hazardous, and in particular: • Flammable • Toxic • Reactive (Capable of causing a chemical or thermal burn) You must correctly identify the fluid’s initial state (gas or liquid). Finally, you must select a Representative Fluid, i.e. the chemical species that most closely resembles the fluid in terms of properties. If the stream is relatively pure, then it is easy to select a Representative Fluid. However, a stream may contain a mixture of flammable and toxic fluids, such as a natural gas with a high H2S content. Frequently, refinery and chemical distillation streams are mixtures of flammable materials. In the case of hydrocarbons, the representative material should match the molecular weight and volatility of the stream as closely as possible. Flammable consequence results are not highly dependent on the exact material selected, provided the molecular weights are similar, because air dispersion properties and heats of combustion are similar for all hydrocarbons with similar molecular weights. Sometimes flammable fluids, such as amines or alcohols, are mixed with water. If a mixture will burn, then it should be treated as a flammable component, and its Heat of Combustion and Pool Fire Factor should be calculated for the mixture. Properties of fluids can be found in standard reference books, but it may be necessary to consult with someone familiar with the process operation in order to properly select the representative fluid, initial state, and fluid properties.

To summarize, the following information is required for a Loss of Containment


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Ch.3 - Consequence Evaluations Consequence Analysis: • Is the fluid flammable, toxic, or reactive? • Is the Initial Fluid State gas or liquid? • What is the Representative Fluid? • If the Representative Fluid is Toxic: What amount of toxic material is present? Is there a toxic end point, i.e. a dike to contain the toxic material? • If the Representative Fluid is Flammable: What is its Heat of Combustion? What is its Pool Fire Factor? • If the Representative Fluid is Reactive, then use the following values to model: Final State = Liquid Pool Fire Factor = 1

3.2.3 Estimating the Amount of Fluid that could be released Once a representative fluid’s properties have been selected, the next step is to estimate the maximum amount of material that could be released if a Loss of Containment event were to occur. Theoretically, this would be the amount of material contained in a particular section of the plant. However, the amount of material released is often reduced because operators can close manual valves, de-inventory sections, or otherwise stop a leak once they become aware that a release is in progress. In addition, piping restrictions and differences in elevation can serve to effectively slow or stop a leak.

3.2.4 Estimating the Leak Size In order to estimate the amount of material that would be released, it is necessary to assume that a pre-defined set of leak sizes exist based on the particular equipment type. These predefined leak sizes represent small, medium, large, and rupture cases for the particular equipment type.

3.2.5 Estimating the Release Rate This analysis approach models all releases as continuous, or occurring over a measurable period of time, and allowing a liquid to form a pool on the ground or a gas to disperse into the atmosphere. Release rates depend upon the physical properties of the material, the initial phase, and the process conditions. Release rate equations are based on whether the fluid is a liquid or gas in the equipment, and if it is a gas, whether it will experience sonic or subsonic flow. Two-phase flow is usually modeled as a liquid.


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3.2.6 Calculating Liquid Release Rate The Liquid Release Rate is a function of the following variables and is based on Bernoulli equations:

Ql = f (ρ , A, ΔP ) where: Ql = Liquid mass flow

ρ = Liquid density

A = Cross-sectional area of hole ΔP = Pressure differential •

Calculating Gas Release Rate with Sonic Flows

The Gas Release Rate with Sonic Flows is a function of the following variables:

Qv = f (T, A, Cp/Cv)

where: Qv = Gas Mass Flow T = Upstream Temperature A = Cross-sectional Area of hole Cp/Cv = Ratio of Heat Capacities •

Calculating Gas Release Rate with Subsonic Flows Qv = f (P, T, A, Cp/Cv)

where: Qv = Gas Mass Flow P = Upstream Pressure T = Upstream Temperature A = Cross-sectional Area of hole Cp/Cv = Ratio of Heat Capacities


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Ch.3 - Consequence Evaluations 3.2.7 Estimating the Duration of the Release Once the release rate is calculated, the next step is to estimate the Release Duration. Release duration is the lesser of the time required to detect and isolate the leak or the time required to de-inventory the entire system. The time required to detect and isolate the leak is based on the physical location of the plant, the location and type of isolation valves, and the leak size and location. Detection and isolation are considered separate events. The sum of these two events represents the time that material escaped from the piping or vessel. If these times are not known, then default values of 5 minutes can be used for both detection and isolation time. On the other hand, the length of time to de-inventory the entire system is calculated by simply dividing the system inventory by the release rate.

3.2.8 Calculating Leak Quantity The amount of fluid released as a result of a leak is calculated by multiplying the release rate, which is assumed to be constant, by the release duration. A constant release rate is a conservative assumption, since the release rate generally decreases over time as the system pressure declines.

3.2.9 Determining the Final Fluid Phase The dispersion characteristics of a fluid after release are highly dependent on the final phase of the fluid (gas or liquid). If the fluid changes state upon release, the final material phase may be difficult to assess. Therefore, the following table has been provided to offer simple guidelines for determining the final fluid phase. Fluid Phase at Steadystate Operating Conditions

Fluid Phase at Steady-state Ambient Conditions

Determination of Final Phase for Consequence Calculation

Liquid

Liquid

Model as liquid

Gas

Gas

Model as gas

Gas

Liquid

Model as liquid

Gas

Model as gas unless fluid boiling point at ambient conditions is greater than 80º F, in which case you should model as liquid

Liquid


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3.3 Flammable Consequence Details Flammable consequence calculations are based on methods developed by the US EPA (Environmental Protection Agency) and are calculated based on the area affected by a possible ignition release. Releases involving fluids with a final gas phase are modeled as vapor cloud explosions, and those involving fluids with a final liquid phase are modeled as pool fires. Figure 3-1 depicts the decision tree used for evaluating the flammable consequence for a risk assessment.

Figure 3-1: Flammable Consequence Evaluation Decision Tree


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Ch.3 - Consequence Evaluations 3.3.1 Calculating Flammable Consequence for Fluids in Final Gas Phase The following assumptions are made regarding the release of fluids with a final Gas Phase, in order to model the release as a vapor cloud explosion: • A release of flammable gases or a volatile flammable liquid will form a vapor cloud with a quantity equal to the total quantity of material released. • The entire contents of the vapor cloud are within the flammability limits, and will explode. • 10% of the flammable vapor in the cloud will participate in the explosion. The following equation is used:

D = f (Wf, HCf, HCTNT) D = Distance to flammable effect Wf = Flammable material mass HCf = Flammable material heat of combustion HCTNT = TNT heat of combustion where:

3.3.2 Calculating Flammable Consequence for Fluids in Final Liquid Phase The following assumptions are made regarding the release of fluids with a final Liquid Phase: • When a flammable vapor or condensing flammable vapor is released, the total quantity of the flammable substance forms a liquid pool. • The liquid leak area is not diked, and the liquid instantaneously forms a pool 0.39 inch (1.0 cm.) deep. • The liquid pool will ignite. • Consequence distances are calculated based on a heat radiation level that could cause second-degree burns from a 40-second exposure. • Those exposed would be able to escape the heat in 40 seconds. • The heat radiation level is 5,000 Watts per square meter. • Ambient temperature is 25º C (77º F).


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Ch.3 - Consequence Evaluations A Pool Fire Factor (PFF) has been calculated for flammable substances with boiling points below the assumed ambient temperature (25º C or 77º F). This factor is used to estimate the distance from the center of a pool fire from which second degree burns would result after a 40-second exposure. The PPF for liquids with boiling points above the assumed ambient temperature (25º C or 77º F) is a function of the following variables:

PFF = Pool Fire Factor Hc = Heat of Combustion Hv = Heat of Vaporization Cp = Heat Capacity Tb = Boiling Temperature PFF = f (Hc, Hv, Cp, Tb)

where:

3.3.3 Flammable Release Probability The flammable release consequence is a strong function of the probability that the release will ignite. The probability of ignition is a function of the representative fluid and associated operating temperature. In general, as the temperature of the released fluid increases, the probability of ignition increases. The probability of ignition is a function of the following variables:

Pig = f (Top, Tfp, Tauto, Pigfp) where:

Pig = Probability of Ignition Top = Operating Temperature Tfp = Flash Point Temperature Tauto = Auto Ignition Temperature *Pigfp = Probability of Ignition at Flash Point Temperature * If near ignition source Pigfp = 100%


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Ch.3 - Consequence Evaluations 3.3.4 Determining Consequence Category for a Flammable Release For flammable materials, the consequence of a release is based on the area affected by the ignition event. For a vapor release, the effect is modeled as a vapor cloud with an endpoint (distance from the release) determined by a 1 psig over-pressure from the blast. This threshold is considered the pressure that might cause broken windows and result in injuries to those in the affected area. For a liquid release, the effect area is determined as the distance from the ignited liquid pool where the thermal radiation would potentially cause second degree burns to a human with a 40 second exposure. The effects of the two thresholds (1 psig over-pressure and 5 KW per m2) are considered sufficiently equivalent from a safety perspective to compare directly. Consequence Category is based on the flammable affect area, as follows: Flammable Effect Area (m²)

Consequence Category

> 464,515.2

A

46,451.5 – 464,515.2

B

4,645.2 – 46,451.5

C

464.5 – 4,645.2

D

< 464.5

E


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3.4 Toxic Consequence Details Toxic consequences are determined based on the area affected by the release. Toxic materials with a final gas phase are modeled using dispersion modeling software based on a standard set of atmospheric and topographical conditions. Toxic materials with a final liquid phase are modeled as a liquid pool with a release rate from the pool to atmosphere estimated as the rate of evaporation from the pool. Figure 3-3 summarizes the steps associated with calculating a toxic consequence.

Figure 3-3: Toxic Consequence Evaluation Decision Tree


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Ch.3 - Consequence Evaluations 3.4.1 Calculating Toxic Gas Release Rate into the Atmosphere The following assumptions are made regarding the release rate of toxic gas: • Toxic gases include all regulated toxic substances that are gases at ambient temperature (25ºC or 77ºF). • Meteorological conditions for the worst-case scenarios are defined as atmospheric stability class F (stable atmosphere), wind speed of 1.5 meters per second (3.4 miles per hour), and ambient temperature of 25ºC or 77ºF. • Topography is classified as urban since a plant generally contains many obstructions.

3.4.2 Calculating Toxic Liquid Release Rate into the Atmosphere The following assumptions are made regarding the release rate of toxic liquids into air: • The release rate to air for toxic liquids is the rate of evaporation from the pool formed by the released liquid. • The total release quantity spills onto a flat, non-absorbing surface. • The total quantity spilled spreads instantaneously to a depth of 0.39 inch (one centimeter) in an undiked area or to cover a diked area instantaneously. • At ambient temperature, the pool liquid then evaporates at a rate determined by the following equation:

Qr = f (ρ , LFA, Qt ) where:

Qr = Liquid Mass Evaporation Rate

ρ

= Liquid Density

LFA = Liquid Factor Ambient Qt = Total Liquid Mass Released •

At temperatures sufficiently above ambient temperature, the following equation is used to determine the evaporation rate:

Qr = f (ρ , LFB, Qt ) where:

Qr = Liquid Mass Evaporation Rate

ρ

= Liquid Density

LFB = Liquid Factor Boiling Qt = Total Liquid Mass Released


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Ch.3 - Consequence Evaluations 3.4.3 Estimating the Distance to Toxic Endpoint Toxic endpoint is assumed to be the distance from the release where a serious injury from exposure to a toxic substance in the air would occur. Determination of the appropriate toxic endpoint depends on whether the gas or vapor is neutrally buoyant or dense. Reference tables for both 10 minute and 60 minute releases provide consequence distances for both neutrally buoyant and dense gases and vapors under urban (congested) conditions. Tables for 10 minute releases are used if the duration of the release is 10 minutes or less; tables for 60 minute releases are used if the duration of the release is more than 10 minutes.

3.4.4 Determining the Consequence Category of a Toxic Release The toxic consequence category is determined by the area affected by the toxic event. Toxic releases for both vapor and liquid releases are modeled as a dispersed elliptical cloud with a toxic endpoint determined by a published toxic concentration threshold which will cause serious injury upon exposure in the air. The toxic affect area (TAA) can be converted into a consequence category by using the following table: Toxic Effect Area (m²)

Consequence Category

> 464,515.2

A

46,451.5 – 464,515.2

B

4,645.2 – 46,451.5

C

464.5 – 4,645.2

D

< 464.5

E


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3.5 Economic Impact Consequence Evaluation 3.5.1 Determining the Economic Impact The economic impact of an RBI Component failure is the sum of: -

Maintenance Cost – Estimated cost of repairing the component to state of safe operation

-

Lost Production Cost – This is a calculated value based on: o Product Unit Price – This value is auto-populated from a reference table based on the product code selected by the RBI Analyst. o Amount of Downtime – The estimated amount of time that the production impact will last o Product Throughput Rate Impacted - This indicates the throughput rate that would be impacted because of equipment downtime (because of shutdown or slowdown). This field is calculated as (Rated Capacity X % Reduction of Rated Capacity/100)©

For example, if a product has a product unit price of 5000SAR and the downtime caused by a failure is 24 hours and the Product Throughput Rate Impacted is 5 metric tons per day and the overall estimated then the calculated result would be – (5000 X 24 X 5 = 600,000SAR)

The following ranking guidelines are recommended while Performing Economic Impact Consequence Evaluation: Consequence Category

Description

Economic Impact

A

Catastrophic

> 10,000,000 SAR

B

Very Serious

1,000,000 – 10,000,000 SAR

C

Serious

100,000 – 1,000,000 SAR

D

Significant

10,000 – 100,000 SAR

E

Minor

< 10,000 SAR


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3.6 Environmental Consequence Evaluation 3.6.1 Determining the Environmental Impact The environmental impact of failure is set by picking the definition of each consequence from the picklists located in Meridium. These picklists are populated with the definitions and consequence rankings from SABIC SHEM standards. They are as follows: Environment – Release/Spillage

Environment – Release/Spillage



Environment – Release/Spillage Environment – Off Spec Discharge

Environment – Off Spec Discharge

Environment – Off Spec Discharge

Event with a potential release/spillage < then 10 MT of hazardous chemicals/substance inside/outside the SABIC premises and/or resulting in fatality to personnel inside/outside the SABIC premises. Event with a potential release/spillage between 4 to 10 MT of hazardous chemicals/substance inside/outside the SABIC premises and/or resulting in injury to personnel inside/outside the SABIC premises. Event with a potential release/spillage between 1 to 4 MT of hazardous chemicals/substance inside/outside the SABIC premises and not resulting in injury to personnel outside the SABIC premises. Event with a potential release/spillage between < 1 MT of hazardous chemicals/substance inside/outside the SABIC premises and/or not resulting in injury to personnel inside/outside the SABIC premises. Event with no potential release/spillage of hazardous chemicals/substance inside/outside the SABIC premises. Event that potentially results in off spec discharge to sea water, canal, river, storm water causing mortality to aquatic life or off spec discharge causing failure of public/central waste water treatment plant. Event that potentially results in off spec discharge of greater then 500% of local regulations for sea water, canal, river, storm water at the point of discharge from the facility. Event that potentially results in off spec discharge of greater than local regulations for sea water, canal, river, storm water at the point of discharge from the facility.


A

B

C

D

E

A

B

C

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Ch.3 - Consequence Evaluations Environment – Off Spec Discharge Environment – Water Contamination Environment – Water Contamination Environment – Water Contamination Environment – Water Contamination Environment – Other

Environment – Other

Environment – Other

Environment – Other Environment – Other Environment – Other

Event that has no off spec discharge

E

Event that potentially results in contamination of deep / potable water aquifer or contamination requires remediation of greater then 70 metric tons of contaminated soil . Event that potentially results in contamination of deep / potable water aquifer or contamination requires remediation of 30 to 70 metric tons of contaminated soil. Event that potentially results in contamination of deep/potable water aquifer or contamination requires remediation of less than 30 metric tons of contaminated soil. Event does not result in contamination of deep / potable water aquifer.

A

Event with a potential release of Nonhazardous chemicals/ substance inside/outside the SABIC premises and release/spillage > 50 MT Event with a potential release of NonHazardous Chemicals/ Substance (including polymers, fertilizer etc) within or outside the SABIC Divisions, Affiliates and Subsidiaries premises and Release/spillage of 20-50 MT Event with an potential emission from vent/stack including dust (except steam) of contaminants greater than the local regulations or failure of Pollutant control device. Event that potentially results in 5 minutes of cumulative smoky flaring within any two hours during normal operations All other events with a potential release/spillage of non-hazardous chemicals/substance <20 MT. Event will not potentially result in a release/spillage of non-hazardous chemicals / substance.

B


B

C

E

C

C

C

D

E

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3.7 Exchanger Bundle Consequence Evaluation 3.7.1 Determining the Exchanger Bundle Consequence The consequences for exchanger bundles are calculated differently due to the fact that there are two processes at work (shell side and tube side). Depending on the effect of the two processes mixing, the flammable, toxic, and product loss consequence will be evaluate.

3.7.2 Determining the Leak Rate The initial leak size is modeled as being the same diameter as the nominal thickness of the tube wall and increasing in a linear fashion over time depending on the corrosion rate entered by the user. By using the corrosion rate for this calculation, the material of construction is taken into account. For the leak rate calculation, an average leak rate value is used. The delta pressure is calculated based on the operating pressure that has been entered for both the shell side and tube side processes. With these values (and the fluid characteristics), the system can calculate a leak rate over time. These leak rates can be then be classified as Major or Minor depending the amount of product being leaked Category

Flammable

Toxic

Major

Leak Rate > 45Kg/min

Leak Rate > 2.2Kg/min)

Minor

Leak Rate < 45Kg/min

Leak Rate < 2.2Kg/min)

3.7.3 Flammable Consequence Determination If the leaking fluid is flammable then the user first selects what effect a tube leak will have on the mixing of the products. There are three choices for the user to select: • Catastrophic (The leak could cause a catastrophic loss of containment or violent chemical reaction) • Flammable HC (hydrocarbon) leak into a utility system • Utility leak into a HC system


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Flammable Consequence Category Table If Flammable leak type is:

and Leak Rate Category is:

And final fluid phase is:

Then Flammable Consequence Category is:

Leak could cause a catastrophic loss of containment or violent chemical reaction

Major or Minor

Liquid or Gas

A

Major

Gas

B

Minor

Gas

C

Major

Liquid

C

Minor

Liquid

D

Major

Liquid or Gas

D

Minor

Liquid or Gas

E

Flammable HC leak into a utility system Flammable HC leak into a utility system Flammable HC leak into a utility system Flammable HC leak into a utility system Utility leak into a HC system Utility leak into a HC system

3.7.4 Toxic Consequence Determination If the leaking mixture is toxic then the leak type will have to be determined in a similar fashion as the flammable consequence. The following choices are available: • Catastrophic (The leak could cause a catastrophic loss of containment or violent chemical reaction) • Toxic leak into a utility system • Toxic leak into a process system • Leak into a toxic system


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Ch.3 - Consequence Evaluations Toxic Consequence Category Table If Toxic leak type is:

and Leak Rate Category is:

And final fluid phase is:

Then Toxic Consequence Category is:

Leak could cause a catastrophic loss of containment or violent chemical reaction

Major or Minor

Liquid or Gas

A

Major

Liquid or Gas

A

Minor

Liquid or Gas

B

Major

Liquid or Gas

B

Minor

Liquid or Gas

C

Major or Minor

Liquid or Gas

D

Toxic leak into a utility system Toxic leak into a utility system Toxic leak into a process system Toxic leak into a process system Leak into a toxic system

3.7.5 Product** Loss Consequence Determination One of the unique issues concerning tube bundle leaks is the possibility of a small leak occurring over a long period of time. For this reason an additional consequence is evaluated due to the economic impact of this lost product. As stated above an average leak rate is calculated by the system. It is also estimated that a leak starts at one half of the typical inspection interval* and lasts until the next inspection when it’s then discovered. This information coupled with a unit value price for the product can be used to determine an overall product loss amount using the following formula: Product Value Lost = Pv*Lr*Ld Where: Pv = Product value (SAR/Kg) Lr = Average Leak Rate (Kg/min) Ld = Leak Duration (Inspection interval / 2) When the overall value of the lost product is determined then the category is assigned based on the following table: Consequence Category

Description

Value of Lost Product

A

Catastrophic

> 10,000,000 SAR

B

Very Serious

1,000,000 – 10,000,000 SAR

C

Serious

100,000 – 1,000,000 SAR

D

Significant

10,000 – 100,000 SAR

E

Minor

< 10,000 SAR


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*Note – Inspection Interval refers to an estimated time that the equipment would be normally opened such as a re-occurring turnaround or cleaning cycle. This is an estimate, so there is no need to change this value based on precise inspection intervals that are calculated. **Product refers to whatever process fluid is currently contained within the piece of equipment.


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3.8 Tank Bottom Consequence Evaluation 3.8.1 Determining the Tank Bottom Consequence Tank bottom consequences will be evaluated depending on the type of foundation it is built on and the effect of the product leaking out of the bottom. If a leak is allowed to go on for a long period of time and it enters the ground then a significant expense can be incurred in cleaning up the spill.

3.8.2 Foundation Type The foundation type of the tank bottom has to be entered to determine the effect of a bottom leak. If the foundation is an impervious type (such as a concrete, or double bottom), then the leak will be modeled in much the same way as other components with regards to flammable and toxic consequences. If the foundation is non-impervious then the leak will be absorbed by the ground. The selection of foundation types are: • Double Floor • Concrete • Clay • Silt • Sand • Gravel

3.8.3 Determining the Leak Rate The initial leak size is modeled as being the same diameter as the nominal thickness of the bottom plate and increasing in a linear fashion over time depending on the corrosion rates (both internal and underside) entered by the user. By using the corrosion rate for this calculation, the material of construction is taken into account. For the leak rate calculation, an average leak rate value is used.

3.8.4 Leak Effect Depending on the environmental effects of the bottom leak (for a non-impervious foundation type, a significant economic impact can be assumed. The duration of the leak is estimated as one half of the typical inspection interval*. The following table shows the different Leak Effects and their relative clean-up costs. These rates are based on USA estimated costs and have been converted to KSA Riyals. Changing the values of these clean-up costs will not have an overall effect on the consequences as they will still remain relative to each other. Leak Effect Ground Public Surface Water Underground Water Table

Clean-up Cost (SAR/m3) 65 130 650


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Ch.3 - Consequence Evaluations *Note – Inspection Interval refers to an estimated time that the equipment would be normally opened such as a re-occurring turnaround or cleaning cycle. This is an estimate, so there is no need to change this value based on precise inspection intervals that are calculated.

3.8.5 Tank Bottom Consequence After the total economic impact of the unit clean-up efforts are calculated, the tank bottom consequence factor can be assigned based on the following table. Consequence Category

Environmental Clean up Cost

A

> 10,000,000 SAR

B

1,000,000 – 10,000,000 SAR

C

100,000 – 1,000,000 SAR

D

10,000 – 100,000 SAR

E

< 10,000 SAR


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3.9 Safety Consequence Evaluation 3.9.1 Determining Safety/Health Consequence The Safety Consequence evaluation is intended for those safety consequences not covered in the Flammable and Toxic consequence evaluations. Example of these type of consequences would be things such as steam burns, physical injuries, hot water burns…etc. The user manually selects the consequence definition based on the pick list found in the SABIC SHEM standards. The following table shows the definitions and their corresponding consequence categories.

Event potentially resulting in loss of life

A

Event potentially resulting in injury/illness that causes a lost workday

B

Event potentially resulting in injury/illness that requires medical treatment

C

Event potentially resulting in injury/illness that requires only first aid.

D

No safety/health impact

E


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Ch.4 - Risk Ranking

Chapter 4 Risk Ranking


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Ch.4 - Risk Ranking

4.1 Risk Ranking 4.1.1 Introduction In the Meridium RBI Workflow being implemented at SABIC, Risk Ranking is done on a 5 X 5 Matrix as shown in figure 4-1. Inspection Priority is the number indicated in each cell of the Risk matrix and is obtained by mapping the POF on the Y Axis and COF on the X Axis. POF is categorized on a scale of 1-5 with 1 representing the Highest Likelihood of failure and 5 the least COF is categorized on a scale of A-E with A representing the most severe Consequence of failure and E the least. Based on the Inspection Priority obtained, Risk is ranked as either High, Medium High, Medium or Low. The color legends corresponding to each Risk Rank have been illustrated in the Table above.

4.1.2 Inspection Priority As seen in the above Risk Matrix, Inspection Priority can have a value of 1-25. Inspection Priority indicates the priority that should be given to the RBI Component based on the Risk Assessment performed. Inspection Priority of 1 indicates the Highest Priority while 25 indicates the lowest. Inspection Priority is obtained for each Degradation Mechanism evaluated. This Inspection Priority for each Degradation Mechanism is obtained by mapping the POF Category for that Degradation Mechanism and the Combined Consequence on the Risk Matrix. A Combined Inspection Priority is also obtained which represents the Inspection priority after all Degradation Mechanisms have been considered and rolled up. This is obtained by mapping the Combined POF – Rolled Up Category and the Combined Consequence on the Risk Matrix.


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Ch.4 - Risk Ranking

Risk = POF x COF

POF = Probability of Failure COF = Consequence of Failure


Inspection Priority Categories 1

11

7

4

2

1

2

16

13

8

6

3

3

20

17

14

9

5

4

23

21

18

15

10

5

25

24

22

19

12


Figure 4-1: RBI Risk Matrix

Risk Ranking

Inspection Priority

High

1-5

Medium High

6 - 12

Medium

13 - 19

Low

20 - 25


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Ch.4 - Risk Ranking In the Risk Assessment illustrated in figure 4-2: • POF Category for Internal Corrosion is 2 and a Combined Consequence of B which results in an Inspection Priority of 6 for Internal Corrosion. • POF Category for External Corrosion is 2 and a Combined Consequence of B which results in an Inspection Priority of 6 for External Corrosion. • POF Category for Environmental Cracking is 4 and a Combined Consequence of B which results in an Inspection Priority of 15 for Environmental Cracking. • POF Category for Other Damage Mechanism is 2 and a Combined Consequence of B which results in an Inspection Priority of 6 for Other Damage Mechanism. • After all Degradation Mechanisms have been considered, the Probability of Failure of 1 and a Combined Consequence of B results in an Inspection Priority-Rolled Up of 2.

Figure 4-2: Sample Risk Assessment


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Ch.4 - Risk Ranking 4.1.3 Rolling up Consequence of Failure (COF) A consequence Category is obtained for each type of Consequence (Flammable, Toxic, Production Loss etc.) and then the worst case scenario is used as the Consequence of Failure- Rolled Up.

4.1.4 Rolling up Probability of Failure (POF) A POF Category is obtained for each Degradation Mechanism. The worst case is taken is used as the Probability of Failure – Rolled Up except when: There are two or more Degradation Mechanisms that have the same POF Category and that is the highest amongst all the Degradation Mechanisms evaluated. In this case the Probability of Failure – Rolled Up goes up by one (1) rank. This upward adjustment cannot be made if the POF for the individual Degradation Mechanisms is already the highest i.e. 1. In the example above, there are three Degradation Mechanisms (Internal Corrosion, External Corrosion and Other Damage Mechanism) that all have a POF of 2. This results in a Probability of Failure –Rolled up to 1.


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Ch.5 - Inspection Strategy Management

Chapter 5 Inspection Strategy Management


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5.1 Strategy Management Strategy Management involves using the Risk Assessment values and Strategy Rule Sets to determine an Inspection Scope. Strategies Rule Sets have been developed for each Degradation Mechanism that will be evaluated in an RBI Risk Assessment. These strategies follow a logic tree that will determine what type of inspection scope is needed for a specific Degradation Mechanism. For example, figure 5-1 depicts a portion of the logic tree for Internal Corrosion of pressure vessels.

Environmental Cracking

Environmental Cracking Inspection Priority

1-5

Y

LC19

1st Inspection?

6-12

N

Y

LC191

LC20

1st Inspection?

13-19

N

Y

LC201

LC21

1st Inspection?

20-22

N

Y

LC211

LC22

1st Inspection?

23-25

N

Y

LC221

LC23

1st Inspection?

N

LC231

Figure 5-1: Partial View of an Inspection Strategy Logic Tree

These logic trees have been entered as strategies within the Meridium software. After performing a risk assessment for an RBI Component the strategies are executed and the appropriate inspection scope is recommended based on the logic case that the decision making process ended on (i.e. for the tree above if the inspection priority is a 3 and the half life is less than 2 years then logic case (LC) 10 would be used to generate a recommended inspection scope). For a detailed explanation of these strategies refer to the SABIC_STRP4 RBI Strategy Management document. © Copyright Meridium, Inc. 2002-2011. All rights reserved. Confidential and proprietary information of Meridium. Published Sep. 2011.

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Chapter 6 RBI Workflow


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Ch.6 - RBI Workflow

6.1 Integrated Evergreen RBI Workflow As companies operate in today’s competitive environment, owner operators are continuously striving to improve process safety and environmental stewardship while accomplishing their business objectives of operating in a cost effective manner. While pursuing the above objectives one of the methodologies that has gained widespread acceptance is Risk Based Inspection (RBI). API 580 is one of the first RBI standards published that outlines the essential elements of an RBI program specifically as it pertains to secondary failures or failures associated with loss of containment and use of Inspection Activities to manage the risk associated with these type of failures. Some of the early adopters of RBI have successfully used the principles of RBI for reducing risk while optimizing their inspection activities.

6.1.1 RBI High Level Workflow The Meridium RBI Workflow that is illustrated in figure 6-1 has been developed to address the following essential elements: • Evergreen RBI Process: As the equipment condition is changing and new history is being obtained, RBI Assessment should be re-evaluated and Inspection Plan Updated. • Integrated RBI Process: For an effective RBI program, the RBI Analysis workflow is tightly integrated with the Inspection Management System as well as the data coming from the Maintenance and Process Historian Systems. • Consistent RBI Process: In order to drive consistency in the RBI program the RBI System Identification results provide valuable input and serve as the starting point for the RBI Analysis Process performed at the RBI Component Level.


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Ch.6 - RBI Workflow The different blocks of the RBI Workflow have been detailed in the figures and tables that follow. Each block is shown independently with a table that details the specific sections of that block.

Figure 6-1: RBI High Level Workflow


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Ch.6 - RBI Workflow

Block ID

Block Description

Purpose

RBI System Identification & Collecting and Loading Design and Process Data

This is the upfront engineering work that is required before beginning the RBI Analysis. Although only represented as one block, this is the most important step of the RBI Workflow. If done correctly, it will lay the foundation of an evergreen RBI process. This involves performing a Corrosion Study, where RBI System are identified, Potential Degradation Mechanisms are assigned to the RBI System, and RBI Components are identified for each RBI System. It also involves collecting and capturing related Design and Process Data at the RBI Component Level. This has been broken down into different steps as indicated in the Section 3.

B

Risk Assessment

Based on the Degradation Mechanisms identified in the Block ID A above and the data gathered, a systematic evaluation is performed on all of the degradation mechanisms and consequences. These evaluations result in a Risk Ranking associated with each Degradation Mechanism, as well as an Overall Risk Ranking. This has been broken down into different steps as indicated in the Section 4. As a part of this process, other Historical Data (Maintenance Event History and Process Excursions) is also reviewed and evaluated.

C

Developing Inspection Strategies

After the Risk Assessment Stage, the results of the Risk Assessment are used by Strategy Rule Sets to get preliminary RBI Recommendations that are then reviewed and reconciled by an RBI Analyst to generate final Inspection Strategies.

D

Executing Inspection Strategies

The Inspection Strategies are then tracked in Inspection Manager and when Inspections are due, they are performed in the field and the results are documented in Inspection Manager and/or Thickness Monitoring within Meridium.

A


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Ch.6 - RBI Workflow

6.2 Block A – RBI System Identification & Collecting and Loading Design and Process Data

Figure 6-2 RBI High Level Workflow – Block A


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Ch.6 - RBI Workflow

Figure 6-3 RBI Workflow - Block A Detail


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Ch.6 - RBI Workflow

Block ID

Block Description

Purpose Involves taking a Process Unit and breaking it into RBI Systems based on grouping of Equipment or Equipment Components that are exposed to similar Corrosion Mechanism Environments.

A1

Define RBI System

RBI System is defined by a team comprised of a Process Engineer, Inspector, Inspection Engineers, Corrosion Engineer and Operations Specialist. The team collectively examines the process and divides a process unit into several RBI Systems. As part of this step, a brief description is developed with regard to System Description, Process Description and Corrosion Mechanisms applicable for the RBI System.

A2

Assign CPPs (Critical Process Parameters) for the RBI System defined in A1

A3

Assign Potential Degradation Mechanisms for the RBI Systems

Identifying CPPs for the RBI System forms the basis of defining the Operating Window from a Reliability Standpoint. This also involves identifying the Process Parameters that need to be monitored and the associated thresholds.

Involves assigning the Potential Degradation Mechanisms applicable for the RBI System under consideration. Meridium provides a library of Potential Degradation Mechanisms; some of which are evaluated based on quantitative algorithms built into Meridium. Others are qualitative; the evaluation of which is done outside Meridium or based on company agreed guidelines.


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Ch.6 - RBI Workflow Block ID

A4

Block Description

Identify and Assign RBI Components for Respective RBI System

Purpose Define RBI Components - Since different components of the same Equipment may be subjected to different Degradation Mechanism Environments, an RBI Analysis is performed at the RBI Component level rather at an Equipment Level. This step involves identifying the RBI Components for the various Equipments. These RBI Components form the basis for performing the RBI Analysis in Step B4. For example, typical RBI Components for a Shell and Tube Exchanger could be Exchanger Channel, Exchanger Shell and Tube Bundle. Assign RBI Components to respective RBI System By assigning RBI Components to the RBI System, the Potential Degradation Mechanisms and CPPs assigned to the RBI System get passed down to the RBI Components that are a part of the RBI System. The individual Potential Degradation Mechanisms and CPPs can still be validated and modified at the RBI Component level.

A4a

Capture Design and Process Data on RBI Components

Additional Process and Design Data is captured for the RBI Components created in Step A4 with the objective for creating a repository of data that is used for RBI Analysis.

A4b

Review and Validate Potential Degradation Mechanisms obtained from RBI System

As there may be some specific considerations for part of the RBI system, the PDMs obtained from the RBI System need to be validated and modified (as necessary) at the RBI Component level. These PDMs are systematically evaluated during the RBI Analysis step.


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A5

A6

Block Description

Purpose

Create Inspection Profile Items

Involves setting up Inspection profile items that are conceptually similar to setting up TMLs for UT Inspections (this step can either be carried out when new Equipment is installed or during the process of Documenting an Inspection Report). Just as TMLs form the basis where Thickness Readings are captured during a UT/RT Inspection, Inspection profile Items form the basis where Inspection findings are captured during a Qualitative Inspection. An Inspector/SME creates the items and sets up an Inspection profile so that Inspections and related Findings can be documented in a consistent manner.

Create TML’s

Create TML Groups and Define Technical Characteristics Since technical design data for each TML Group will be different, TML Groups need to be defined for each equipment and technical data needs to be captured for these TML Groups. Some typical TML Groups for a Shell and Tube Exchanger would be Channel Inlet Nozzle (N1), Channel Outlet Nozzle (N2), Shell Inlet Nozzle (N3) and Shell Outlet Nozzle (N4), Channel Head, Shell Head, Tubes, Tubesheet etc. Please note that these TML Groups are different from the RBI Components defined in A4. Create TML’s for TML Groups - After the TML Groups have been defined and TML Group data captured; TMLs are defined for these TML Groups. Users also have an option of mapping TML Groups to the RBI Components created in Step A4.


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Ch.6 - RBI Workflow

6.3 Block B – Risk Assessment

Figure 6-4 RBI High Level Workflow – Block B


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Ch.6 - RBI Workflow

Figure 6-5 RBI Workflow - Block B Detail


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Ch.6 - RBI Workflow

Block ID

Block Description

Purpose

Review/Analyze Inspection Data

While performing RBI Analyses, an evaluation is done on each Degradation Mechanism. During these evaluations, Inspection History available for that Equipment is reviewed and analyzed to determine the Number of Inspections as well as the Inspection Confidence Rating applicable for each Degradation Mechanism being evaluated.

B2

Evaluate Captured Excursion data

In addition to Inspection Data, it is also important that Process Excursion Data is evaluated in order to get a more realistic understanding of the extent of degradation with regard to each Degradation Mechanism.

B3

Review Corrosion Analysis Data

A review of Corrosion Data is necessary for evaluation of Internal Corrosion Degradation Mechanism.

B1

B4

Risk Assessment

POF Evaluations are performed for each DM. These evaluations result in a POF Ranking on a scale of 1 -5 on the Risk Matrix for each DM. COF Evaluations are performed for the associated Consequences. The Consequence Evaluations result in a COF Ranking on a scale of A-E on the Risk Matrix for each Consequence Category. An Overall Risk Ranking (POF X COF) on the RBI Component is then obtained resulting in a Ranking of High, Medium High, Medium or Low on the Risk Matrix.


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Ch.6 - RBI Workflow

6.4 Block C – Developing Inspection Strategies

Figure 6-6 RBI High Level Workflow – Block C


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Ch.6 - RBI Workflow

Figure 6-7 RBI Workflow - Block C Detail


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Ch.6 - RBI Workflow

Block ID

Block Description

Purpose Generate RBI Inspection Recommendations RBI Recommendations are generated based on: RBI Risk Assessment Results (B4) and Strategy Logic configured in System RBI Strategy Rule Sets. The output from this step is RBI Recommendations which include Inspection Task, Plan and Scope. These RBI Recommendations need to be evaluated and consolidated by the RBI Analyst as outlined in the next step.

C1

Generating and Consolidating RBI Recommendations

C2

Task Management

Task Management has been broken down into steps C2a – C2c.

Creation/Update of Task

Inspection Tasks can originate from one of three sources: o RBI Strategies. o Traditional or Legacy Inspection Strategies: These would apply to Equipment that has not yet been transitioned from the traditional approach to the RBI Based Approach. o Non RBI Inspection Tasks for Equipment that are not covered under the RBI Scope (Cathodic Protection Systems, ERPs, etc) but still need to be managed from an Inspection Management Standpoint (based on Company Guidelines and Policies).

C2a

Finalize RBI Strategies The RBI Recommendations generated above are then consolidated where the following options are available for each RBI Recommendation: o Can be used as such for an Inspection Strategy. o Multiple Recommendations can be grouped and managed through a single Inspection Strategy. o Some RBI Recommendations can be cancelled after clearly documenting the justification for this action. An example illustrating these cases has been given in the RBI Functional Specification Document.


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Block Description

Purpose The Inspector reviews the list of upcoming tasks with ‘Recommended Inspection Dates’ as calculated by the System. The Inspector then aligns the Inspection Dates with Turnarounds or other Events to determine the ‘Scheduled Inspection Dates’ based on Company guidelines and Policies.

C2b

Inspector reviews and schedules Task

Implementation Related Details Although there will be instances when the Scheduled Inspection Dates are set past the Recommended Inspection Dates, it is necessary that appropriate mechanisms are put in place to minimize these occurrences. Thus, if the Scheduled Inspection Date goes past the Recommended Next Inspection Date, alerts will be provided and triggered to notify the responsible person. If SAP privileges are made available, the person in-charge has an option of creating a SAP Notification automatically, for performing the Inspection Task. If not, then an SAP notification can be created manually, and then the SAP Notification Number is entered manually in Meridium.

C2c

Inspector tracks Scheduled Inspection Task

The Inspector tracks Scheduled Inspection Tasks, reviews existing Inspection Profile Items and TMLs and makes modifications (as deemed appropriate) when ready to perform the Inspection.


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Ch.6 - RBI Workflow

6.5 Block D – Executing Inspection Strategies

Figure 6-8 RBI High Level Workflow – Block D


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Ch.6 - RBI Workflow

Figure 6-9 RBI Workflow - Block D Detail

Block ID

Block Description

Purpose

D1

Perform Inspections

Based on Existing Inspection Schedules from C2 the Inspector performs Inspections.

D2

Document Qualitative Inspections

This has been broken down in more detail as shown in Block D2 - Documenting Qualitative Inspections (See figure 5-10).

D3

Capture New Thickness Readings

UT/RT Thickness Readings are documented in TM. As New Thickness Readings are captured, new Corrosion Rates are calculated and are made available for RBI Analysis.

D4

Update Inspection Schedules

The Inspection Task Last Date is reset based on Inspection Completion Date and a new Next Inspection Date (NID) is calculated by the System.

D5

Manage Recommendations

This has been broken down in more detail in Block D5Manage Inspection Recommendations (See figure 5-11).


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Ch.6 - RBI Workflow

Figure 6-10 RBI Workflow - Block D2 Detail


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Ch.6 - RBI Workflow

Figure 6-11 RBI Workflow - Block D5 Detail


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Ch.6 - RBI Workflow

6.6 Overall RBI Workflow Diagram Figure 6-12 depicts all of the separate RBI Workflow blocks as one integrated workflow. Figure 6-12 Overall RBI Workflow


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Glossary

Glossary


Page 83

Glossary

Term/Acronym

Meaning

Absolute Risk

A risk value assigned to a piece of equipment without considering its relationship to other equipment in the area

APM

Asset Performance Management.

Asset

The physical aspect of a plant item that is relevant to the mechanical design, construction and maintenance of a process plant. Assets may sometimes be referred to in general terms as equipment items.

COF

Consequence of Failure.

RBI System

RBI System is grouping of Equipment or Equipment Components that are exposed to similar Corrosion Mechanism Environments.

Corrosion Mechanisms

These are the mechanisms identified by the Corrosion Engineer during the RBI System Identification Process. Examples are Amine Corrosion, HCL Corrosion, Galvanic Corrosion etc.

CPP

Critical Process Parameters.

ERPs

Electrical Resistance Probes. Used for real time corrosion monitoring.

Inspection Confidence Rating

Confidence Rating applied to Inspection History based on effectiveness of NDE Methods used for detecting a particular Damage Type (i.e. internal degradation, external degradation…etc).

Inspection Profile Items

Inspection Profile Items are created to characterize the Equipment and form the basis how the Equipment will be inspected and documented.

Inspection Strategies

Inspection Strategies outline the Plan, Task and Scope.

NDE

Non Destructive Examination.

NID

Next Inspection Date.

Operating Window

Aggregation of CPPs considered together comprises the Operating Window for the specific Process. Any excursions outside the Operating Window should be reviewed and evaluated for any potential impacts on existing RBI Analysis and subsequently Inspection Strategies.

Persistent Fluid

A fluid that will remain in a liquid form once it has been released from a storage tank. This is used in Tank Bottom consequence evaluations.

POF

Probability of Failure.

Potential Degradation

These are the Potential Damage Types, they are indicative on how Corrosion Mechanisms are evaluated as part of the RBI Analysis.


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Glossary Term/Acronym

Meaning

Mechanisms (PDM)

Examples are General Corrosion (Thinning), Localized Corrosion, Pitting etc. These represent the Effects of Corrosion Mechanisms.

Recommended Inspection Dates

Inspection Dates recommended by the System based on Strategy Rule Sets and results of the RBI Assessment.

Relative Risk

A risk value that is assigned by comparing all of the equipment in a similar manner to determine a risk value that is relative to the values of other equipment in the area.

Risk Assessment

Overall Assessment of Risk based on POF and COF. Sometimes referred to as an RBI Analysis

Risk Matrix

Risk Matrix used to depict Risk on a 5X5 Risk Matrix with POF Rankings on one scale and COF on another scale.

RT TML

RT TMLs are those TMLs where Thickness Measurements are obtained using the Radiography NDE method.

Scheduled Inspection Dates

Inspection Dates Scheduled by the inspector based on other activities like T/A Schedule.

Shell Side

A term referring to the process outside of the tubes of a shell and tube heat exchanger.

System RBI Strategy Rule Sets

Rule Sets that are used to recommend Plan, Scope and Task based on the Degradation Mechanism evaluated and associated Risk.

TMLs

Thickness Monitoring Locations.

Tube Side

A term referring to the process inside the tubes and channel of a shell and tube heat exchanger. Also sometimes referred to as Channel Side.

UT TML

UT TMLs are those TMLs where Thickness Measurements are obtained using the Ultrasonic NDE method.


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Appendices

Appendix A - Risk Matrix


Inspection Priority Categories 1

11

7

4

2

1

2

16

13

8

6

3

3

20

17

14

9

5

4

23

21

18

15

10

5

25

24

22

19

12



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Appendices

Appendix B – Simplified RBI Steps Upfront

1. 2. 3. 4. 5. 6. 7.

Create RBI Systems Engineering and Data Assign CPP’s to RBI System Gathering Assign PDM’s to RBI System Identify and Create RBI Components Assign RBI Components to RBI System Validate PDM’s and CPP’s for RBI Components Capture additional operating and design data for RBI Components 8. Create inspection profiles (if needed) 9. Create TML’s (if needed)

10. 11. 12. 13. 14. 15. 16. 17. 18.

Create RBI Analysis for RBI component Perform Damage Mechanism Evaluations Perform Consequence Evaluations Generate RBI Recommendations Review and reconcile RBI recommendations Create inspection tasks Execute inspection tasks Document inspections Go to step 10


Sustainable RBI Process

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Appendices

Appendix C – Representative Hole Sizes per RBI Component Types RBI Component

Equipment Type

Leak Size(Cm2)

Hole Diameter (mm)

1" Pipe 1.5" Pipe 10" Pipe 12" Pipe 14" Pipe 16" Pipe 18" Pipe 2" Pipe 2.5" Pipe 20" Pipe 24" Pipe 3" Pipe 3/4" Pipe 30" Pipe 36" Pipe 4" Pipe 48" Pipe 6" Pipe 60" Pipe 8" Pipe Column Bottom Column Top Filter Fin/Fan Cooler Heat Exchanger Chan Heat Exchanger Shell Pressure Vessel Reactor Storage Tank

Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel

0.710 0.968 9.548 11.419 12.387 13.355 13.355 1.245 1.652 14.452 15.548 2.052 0.316 20.258 25.613 2.852 31.677 6.413 45.613 7.935 53.548 53.548 20.258 0.645

3.007 3.511 11.029 12.061 12.562 13.043 13.043 3.983 4.587 13.568 14.074 5.112 2.007 16.064 18.063 6.027 20.088 9.038 24.105 10.054 26.118 26.118 16.064 2.867

Pressure Vessel

38.323

22.095

Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel

38.323 53.548 126.709 2027.093

22.095 26.118 40.176 160.695


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Appendices

Appendix D – Structural Tmin Values per RBI Component RBI Component

Equipment Type

1" Pipe 1.5" Pipe 10" Pipe 12" Pipe 14" Pipe 16" Pipe 18" Pipe 2" Pipe 2.5" Pipe 20" Pipe 24" Pipe 3" Pipe 3/4" Pipe 30" Pipe 36" Pipe 4" Pipe 48" Pipe 6" Pipe 60" Pipe 8" Pipe Column Bottom Column Top Filter Fin/Fan Header Heat Exchanger Tubes Heat Exchanger Chan Heat Exchanger Shell Pressure Vessel Reactor Storage Tank

Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Piping Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel Pressure Vessel


Structural Tmin (mm) 1.575 1.575 3.175 3.175 3.175 3.175 3.175 2.388 2.388 3.175 3.175 2.388 1.575 3.175 3.175 2.388 3.175 2.388 3.175 2.388 3.175 3.175 3.175 3.175 0.889 3.175 3.175 3.175 3.175 3.175

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SABIC RBI Methodology Training Final Rev5

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