Rp 581 Inspection Effectiveness

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DATE: 2-20-2012

API RP 581 Committee Meeting

API Ballot Proposal:

Removal of most of the language and all of the tables regarding inspection effectiveness from

the main body of Part 1 and Part 2 of API RP 581.

Reassembly of this information in a new annex of Part 2 that will discuss inspection

effectiveness and provide the tables per API RBI damage mechanism as examples for the user

to adapt and adopt to their specific knowledge and skills.

Technical Basis:

This will provide a good platform that emphasizes the user responsibility to understand and

apply RBI principles. In particular, it will consider:

a) Philosophy behind the new tables and how to use them;

b) Owner-User responsibility of adoption/adaptation;

c) Methodology to account for confidence in inspection

d) Application to PoF

Proposed By:

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PART 1

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PART CONTENTS

1 SCOPE ... 4

2 REFERENCES ... 4

3 DEFINITIONS ... 4

4 API RBI CONCEPTS ... 4

4.1 Probability of Failure ... 4

4.2 Consequence of Failure ... 4

4.3 Risk Analysis ... 4

4.4 Inspection Planning Based on Risk Analysis ... 4

4.4.1 Overview ... 4

4.4.2 Risk Target ... 4

4.4.3 Inspection Effectiveness – The Value of Inspection ... 4

4.4.4 Inspection Effectiveness – Example ... 5

4.4.5 Inspection Planning ... 5

4.5 Nomenclature ... 6

4.6 Tables... 6

4.7 Figures ... 7

5 PRESSURE VESSELS AND PIPING ... 8

5.3 Risk Analysis ... 8

6 ATMOSPHERIC STORAGE TANKS ... 9

6.3 Risk Analysis ... 9

7 PRESSURE RELIEF DEVICES ... 10

7.1 General... 10

7.2.1 Definition ... 10

7.2.2 Calculation of Probability of Failure to Open ... 10

7.2.3 PRD Demand Rate ... 10

7.2.4 PRD Probability of Failure on Demand ... 10

7.2.5 Protected Equipment Failure Frequency as a Function of Overpressure ... 11

7.2.6 Calculation Procedure ... 11

7.2.7 Overview ... 11

7.2.8 Calculation of Probability of Leakage... 11

7.2.9 Calculation Procedure ... 11

7.3 Consequence of PRD Failure to Open ... 11

7.4 Consequence of Leakage ... 11

7.5 Risk Analysis ... 11

7.7 Nomenclature ... 11

7.8 Tables... 12

7.9 Figures ... 12

8 HEAT EXCHANGER TUBE BUNDLES ... 13

8.1 General... 13

8.2 Methodology Overview ... 13

8.5 Risk Analysis ... 13

8.6.1 Use of Risk Target in Inspection Planning ... 13

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8.6.3 Inspection Planning Without Inspection History (First Inspection Date) ... 13

8.6.4 Inspection Planning with Inspection History ... 13

8.6.5 Effects of Bundle Life Extension Efforts ... 14

8.6.6 Future Inspection Recommendation ... 14

8.7 Bundle Inspect/Replacement Decisions using Cost Benefit Analysis ... 14

8.8 Nomenclature ... 14

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1 SCOPE

2 REFERENCES 3 DEFINITIONS

4 API RBI CONCEPTS 4.1 Probability of Failure 4.2 Consequence of Failure 4.3 Risk Analysis

4.4 Inspection Planning Based on Risk Analysis 4.4.1 Overview

4.4.2 Risk Target

4.4.3 Inspection Effectiveness – The Value of Inspection

An estimate of the probability of failure for a component is dependent on how well the independent variables of the limit state are known [10]. Using guidelines for inspection effectiveness given in API RBI, Part 2, Annex B.2 aIn the models used for calculating the probability of failure, the flaw size (e.g. metal loss for thinning or crack size for environmental cracking) may have significant uncertainty especially when these parameters need to be

projected into the future. An inspection program may be implemented in order to obtain a better estimate of the

damage rate and associated flaw size.

An inspection program is the combination of NDE methods (i.e. visual, ultrasonic, radiographic etc.), frequency of inspection, and the location and coverage of an inspection in order to find a specific or set of damage

mechanisms. Inspection programs vary in their effectiveness for locating and sizing damage, and thus for

determining damage rates. Once the likely damage mechanisms have been identified, the inspection program

should must be evaluated in order to determine the effectiveness in finding the identified mechanisms.

The effectiveness of an inspection program may be limited by:

a) Lack of coverage of an area subject to deterioration,

b) Inherent limitations of some inspection methods to detect and quantify certain types of deterioration,

c) Selection of inappropriate inspection methods and tools,

d) Application of methods and tools by inadequately trained inspection personnel,

e) Inadequate inspection procedures,

f) The damage rate under some conditions (e.g. start-up, shut-down, or process upsets) may increase the

likelihood or probability that failure may occur within a very short time; even if damage is not found during an inspection, failure may still occur as a result of a change or upset in conditions,

g) Inaccurate analysis of results leading to inaccurate trending of individual components, (problem with a

statistical approach to trending), and

h) Probability of detection of the applied NDE technique for a given component type, metallurgy,

temperature and geometry .

It is important to evaluate the benefits of multiple inspections and to also recognize that the most recent inspection may best reflect the current state of the component under the current operating conditions. If the operating conditions have changed, damage rates based on inspection data from the previous operating conditions may not be valid. Determination of inspection effectiveness should consider the following:

a) Equipment or component type,

Formatted: para, No bullets or numbering

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a) Active and credible damage mechanism(s),

b) Susceptibility to and rate of damage,

c) NDE methods, coverage and frequency, and

d) Accessibility to expected deterioration areas.

Inspection effectiveness may be introduced into the probability of failure calculation by using Bayesian analysis or more directly by modifying the model for the independent variables, the distribution function, and/or the distribution function parameters. For example, if the model for metal loss is determined to be a lognormal distribution, the distribution parameters, mean and coefficient of variation, may be changed based on the NDE method and coverage used during an inspection. Extending this concept further, a series of standard inspection categories may be defined, and the distribution parameters adjusted based on the NDE method and coverage defined for each standard category.

In API RBI, examples of the inspection effectiveness categories for various damage mechanisms and the associated inspectionsrecommended (i.e. NDE technique and coverage) for each damage mechanism are provided in Part 2, Annex 2.C. These are provided as examples to the user and represent minimally acceptable inspections per damage mechanism, corresponding to various inspection effectiveness ratings. The user should adopt and modify similar tables according to specific risk management plans and experience-based

inspection programs. In addition, the rules for combining the benefits of multiple inspections are also provided

in Part 2

By identifying credible damage mechanisms, determining the damage rate, and selecting an inspection effectiveness category based on a defined level of inspection, a probability of failure and associated risk may be determined using

.

Equations (1.8) or (1.9)

4.4.4 Inspection Effectiveness – Example

. The probability of failure and risk may be determined using these equations for future time periods or conditions as well as current conditions by projecting the damage rate and

associated flaw size into the futurean inspection program will become more effective.

In API RBI, the inspection effectiveness is graded A through E, with an A inspection providing the most effective inspection available (90% effective) and E representing no inspection. A description of the inspection effective levels for general thinning damage is provided in Part 2

To illustrate the method in which different inspection levels effect the damage factor and probability of failure, consider the example of the general thinning damage mechanism (procedures for modifying damage factors based on inspection effectiveness are provided in API 581 for all damage mechanisms). For general thinning, API RBI utilizes an approach based on a metal loss parameter,

, Table 5.5.

rt

A . The damage factor is calculated as a

function of this parameter and is based on the premise that as a pressure vessel or piping wall corrodes below the construction Code minimum wall thickness plus the specified corrosion allowance, the damage factor will increase. An inspection program for general thinning will result in a reduction of the damage factor based on the effectiveness of the inspection to quantify the corrosion rate. As an example, the general thinning damage

factor, Dthin_f , for a component with an A_rt equal to 0.5 is 1200 if there is no inspection (i.e. Inspection

Effectiveness is E) as shown in Part 2, Table 5.5. If a B level inspection is performed, the damage factor is reduced to 600. If two B level inspections have been completed, the damage factor is further reduced to 200. When these damage factors are substituted into Equation (1.1),

4.4.54.4.4 Inspection Planning

it becomes apparent that an effective inspection program can reduce the probability of failure of a component and the risk of loss of containment.

In planning inspections using API RBI, a plan date is typically chosen far enough out into the future to include a time period covering one or several future maintenance turnarounds. Within this period, three cases are possible based on predicted risk and the specified risk target.

a) Case 1 – Risk target is exceeded at a point in the future prior to the inspection plan date – This is the

classical case and is represented in Figure 4.3. In this case, the results of an inspection plan will be the number of inspections required, as well as the type or inspection effectiveness required, to reduce the risk at the future plan date down below the risk target. The target date is the date where the risk target is expected to be reached and is the date of the recommended inspection.

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b) Case 2 – Risk already exceeds the risk target at the time the RBI analysis is performed – This case is

shown in Figure 4.4 and indicates that the current risk at the time of the RBI analysis exceeds the risk target. An immediate inspection will be recommended at a level sufficient to reduce the risk at the future plan date down below the risk target.

c) Case 3 – Risk at the future plan date does not exceed the risk target – This case is shown in Figure 4.5

and indicates that the predicted future risk at the plan date will not exceed the risk target and therefore, no inspection is recommended during the plan period. In this case, the inspection due date for inspection scheduling purposes should be adjusted to the plan date indicating that an evaluation of the equipment for Inspection or re-analysis of risk should be performed by the plan end date.

The concept of how the different inspection techniques with different effectiveness levels can reduce risk is shown in Figure 4.3. In the example shown, a B Level inspection was recommended at the target date. This inspection level was sufficient since the risk predicted after the inspection was performed was determined to be below the risk target at the plan date. Note that in Figure 4.3, a D Level inspection at the target date would not have been sufficient to satisfy the risk target criteria. The projected risk at the plan date would have exceeded the risk target.

4.5 Nomenclature 4.6 Tables

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4.7 Figures

Figure 4.3 – Case 1: Inspection Planning When the Risk Target is Exceeded Between the RBI Date and the Plan Date and the Impact of Inspection at Various Levels of Effectiveness

time Risk Installation Date RBI Date Target Date, Inspection Performed Plan Date Risk Target

Total Risk with Inspection at the Risk Target Date Total Risk without

Inspection at the Risk Target Date

A B C D

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5 PRESSURE VESSELS AND PIPING 5.1 Probability of Failure

5.2 Consequence of Failure 5.3 Risk Analysis

5.4 Inspection Planning Based on Risk Analysis

The procedure to determine an inspection plan is provided in paragraph 4.4 and is supplemented by Annex 2.C. This procedure may be used to determine both the time and type of inspection to be performed based on the process fluid and design conditions, component type and materials of construction, and the active damage mechanisms.

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6 ATMOSPHERIC STORAGE TANKS 6.1 Probability of Failure

6.2 Consequence of Failure 6.3 Risk Analysis

6.4 Inspection Planning Based on Risk Analysis

The procedure to determine an inspection plan is provided in paragraph 4.4 and is supplemented by Annex 2.C. This procedure may be used to determine both the time and type of inspection to be performed based on the process fluid and design conditions, component type and materials of construction, and the active damage mechanisms.

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7 PRESSURE RELIEF DEVICES 7.1 General

7.2 Probability of Failure 7.2.1 Definition

7.2.2 Calculation of Probability of Failure to Open 7.2.3 PRD Demand Rate

7.2.4 PRD Probability of Failure on Demand

a) General

b) Categories of Service Severity

c) Default Probability of Failure on Demand vs Time in Service d) Default Data for Balanced Bellows Pressure Relief Valves

e) Default Weibull Parameters for Pilot-Operated Pressure Relief Valves f) Default Weibull Parameters for Rupture Disks

g) Adjustment for Conventional PRVs Discharging to Closed System h) Adjustment for Overpressures Higher than Set Pressure i) Adjustment for Environmental Factors

j) Presence of an Upstream Rupture Disk k) Use of Plant Specific Failure Data

l) Modification of Failure on Demand Based on PRD Specific Testing Data 1) Tracking Historical Inspection and Testing Data

2) Determine the Effectiveness of Inspection Programs in Confirming Failure Rates

Inspection programs vary in their effectiveness for determining failure rates. The definitions for inspection effectiveness used by API RBI are provided in Table 7.7

Aan inspection and testing program should track the effectiveness of the inspection and the testing performed for each pressure relief device. The concept of inspection effectiveness is similar to the concept that is described in

. The inspection’s effectiveness is based on the inspection’s ability to adequately predict the failure (or pass) state of the PRD being inspected. Limitations in the ability of a program to improve confidence in the failure rate result from the inability of some test methods to detect and quantify damage.For pressure relief devices,

paragraph 4.4.3

Default confidence values, based on expert opinion, are provided in

Annex 2.C of this document for fixed equipment. With For

inspection effectiveness for pressure relief devices, a measure of confidence in the Pass/Fail/Leak result of the inspection effort is obtainedutilized. For a full discussion of inspection effectiveness as related to pressure relief devices, refer to Annex 2.C.

Table 7.8, indicating the level of confidence each of the three levels of inspection effectiveness will accurately represent actual PRD performance in an overpressure demand case. For example, the 90% effectiveness associated with passing a “highly effective” bench test means that there is a 90% probability the valve would have opened upon demand in its installed service. Therefore, it also carries a 10% probability that the PRD would have failed upon demand during operation. The values shown in Table 7.8

The conditional probabilities listed reflect the confidence that an inspection result will predict the device’s performance upon demand. For passing PRDs, the highest confidence is assigned when the PRD is bench tested without any prior cleaning (i.e. as-received condition.) Bench testing where the devices are cleaned prior to testing, in-situ testing, and visual inspections provide some information about PRD performance, but are not considered as reliable as the as-received bench test.

are called conditional probabilities.

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The philosophy is different for PRDs that fail an inspection. In the case of a “highly effective” bench test failure, the 95% confidence translates to a 95% chance that the PRD would have failed upon demand in actual service. Unlike the passing test case, the “usually effective” in-situ test, or bench test where the valve has been steamed out prior to testing, is assumed to have the same 95% confidence for failure upon demand in actual service.

An ineffective test does not provide any information to predict PRD performance upon demand and therefore the PRD does not receive any credit for the test/inspection date. The inspection still will get some credit if an overhaul was performed in that the valve is assumed to be returned to service in like-new condition, and the in-service duration is calculated from the ineffective inspection date.

3) Inspection Updating

4) Example – Bayesian Updating Calculation

5) Updating Failure Rates after Modification to the Design of the PRD

7.2.5 Protected Equipment Failure Frequency as a Function of Overpressure 7.2.6 Calculation Procedure

7.2.7 Overview

7.2.8 Calculation of Probability of Leakage 7.2.9 Calculation Procedure

7.3 Consequence of PRD Failure to Open 7.4 Consequence of Leakage

7.5 Risk Analysis

7.6 Inspection Planning Based on Risk Analysis 7.7 Nomenclature

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7.8 Tables

Table 7.7 – Inspection and Testing Effectiveness Inspection

Effectiveness Component Type Description of Inspection

Highly Effective A

Pressure Relief Device

A bench test has been performed on the PRV in the as-received condition from the unit and the initial leak pressure, opening pressure and the reseat pressure has been documented on the test form. The inlet and outlet piping has been examined for signs of excessive plugging or fouling.

Rupture Disk None Available.

Usually Effective B

• A bench test has been performed, however, the PRD was cleaned or steamed out prior to the bench test. Additionally, a visual inspection has been performed where detailed documentation of the condition of the PRD internal components was made.

• An in-situ test has been performed using the actual

process fluid to pressurize the system.

Rupture Disk The rupture disk is removed and visually inspected for

damage or deformations.

Fairly Effective C

• A visual inspection has been performed without a pop test, where detailed documentation of the condition of the PRD internal components was made.

• A trevitest or in-situ test has been performed where the

actual process fluid was not used to pressurize the system.

Rupture Disk

The space between the disk and the PRV is monitored for leakage in accordance with the ASME Code and API RP 520 Part 2.

Ineffective D

Pressure Relief Device No pop test was conducted.

Rupture Disk No details of the internal component were documented.

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8 HEAT EXCHANGER TUBE BUNDLES 8.1 General 8.2 Methodology Overview 8.3 Probability of Failure 8.4 Consequence of Failure 8.5 Risk Analysis

8.6 Inspection Planning Based on Risk Analysis 8.6.1 Use of Risk Target in Inspection Planning 8.6.2 Example

8.6.3 Inspection Planning Without Inspection History (First Inspection Date) 8.6.4 Inspection Planning with Inspection History

a) Effect of Inspection on Probability of Failure

The information gained from an inspection of the tube bundle can be used to assess the actual condition of the bundle and to make adjustments to the probability of failure rate curves as necessary.

An inspection provides two things:

1) Reduction in uncertainty due to the effectiveness of the inspection resulting in the use of a more accurate failure rate curve, e.g. moving from a 50% AU curve (no inspection history) to a curve 20% AU curve (Usually Effective Inspection), see paragraph 8.6.4.b for a discussion of inspection effectiveness.

2) Knowledge of the true condition of the bundle. This can result in a shift of the failure rate curve to the right or to the left. The current condition of the bundle could either be quantified by remaining wall thickness data or by an estimate of the remaining life that comes directly from an actual inspection, see paragraph 8.6.4.c.

b) Reduction in Uncertainty Due to Inspection Effectiveness

If the tube bundle has been inspected, the uncertainty is reduced (probability of failure curve moves to the right) and the probability of failure at any time decreases. In this way, the API RBI methodology allows inspection knowledge to reduce probability of failure and the calculated risk.

At this point the concept of inspection effectiveness is introduced, similar to the methodology used in other modules of API RBI. Table 8.5 provides the recommended default values for the uncertainty applied to the failure rate curve as a function of inspection effectiveness.

As improved inspection techniques are used, the amount of uncertainty decreases and the Weibull plot shifts to the right. Using this concept will result in more rigorous inspection techniques being implemented as the bundle reaches end of life.

In the example bundle problem, the impact of more rigorous inspection techniques can be seen by evaluating the predicted duration as a function of inspection effectiveness in Table 8.5.

The discussion of inspection effectiveness is continued in Annex 2.C.

c) Shift of POF Curve Due to Knowledge of True Bundle Condition d) Predicted Future Failure Date Based on Estimated Remaining Life e) Adjustment to Failure Rate Curve Based on Actual Condition of Bundle

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8.6.5 Effects of Bundle Life Extension Efforts 8.6.6 Future Inspection Recommendation

8.7 Bundle Inspect/Replacement Decisions using Cost Benefit Analysis 8.8 Nomenclature

8.9 Tables

Table 8.1 – Basic Data for Exchanger Bundle Risk Analysis

Inspection

Effectiveness A, B, C, D or E per Table 8.5 No

Table 8.5 – Inspection Effectiveness and Uncertainty Inspection Effectiveness Inspection Cost

($)

Uncertainty (%)

E – Ineffective 0 50

D – Usually Not Effective 1,000 30

C –Moderately Effective 2,000 20

B – Usually Effective 3,000 10

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PART 2 DETERMINATION OF PROBABILITY OF FAILURE IN AN API RBI

ASSESSMENT

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PART CONTENTS

1 SCOPE ... 8

2 REFERENCES ... 8

3 DEFINTIONS ... 8

4 PROBABILITY OF FAILURE CALCULATIONS ... 8

4.1 Overview ... 8

4.2 Calculation of Probability of Failure ... 8

4.3 Generic Failure Frequency ... 8

4.4 Damage Factor ... 8

4.4.1 Overview ... 8

4.4.2 Damage Factor Combination for Multiple Damage Mechanisms ... 8

4.4.3 Inspection Effectiveness Category ... 8

4.5 Management Systems Factor ... 8

4.5.1 General ... 8

4.5.2 Overview ... 8

4.5.3 Auditing Technique ... 8

4.5.4 Calculation of the Management Systems Factor ... 8

4.6 Nomenclature ... 8

4.7 Tables... 9

5 THINNING DAMAGE FACTOR ... 10

5.1 Scope ... 10

5.2 Screening Criteria ... 10

5.3 Required Data ... 10

5.4 Basic Assumptions ... 10

5.5 Determination of the Damage Factor ... 10

5.5.1 Overview ... 10

5.5.2 Inspection Effectiveness ... 10

5.5.3 Calculation of the Damage Factor ... 10

5.6 Nomenclature ... 10

5.7 Tables... 10

6 COMPONENT LINING DAMAGE FACTOR ... 15

7 SCC DAMAGE FACTOR – CAUSTIC CRACKING ... 16

7.1 Scope ... 16

7.2 Description of Damage... 16

7.4 Required Data ... 16

7.6.1 Overview ... 16

7.7 Nomenclature ... 16

7.8 References ... 16

7.9 Tables... 16

8 SCC DAMAGE FACTOR – AMINE CRACKING ... 18

8.1 Scope ... 18

8.4 Required Data ... 18

8.6.1 Overview ... 18

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8.7 Nomenclature ... 18

8.8 References ... 18

8.9 Tables... 18

9 SCC DAMAGE FACTOR – SULFIDE STRESS CRACKING ... 20

9.1 Scope ... 20

9.4 Required Data ... 20

9.6.1 Overview ... 20

9.7 Nomenclature ... 20

9.8 References ... 20

9.9 Tables... 20

10 SCC DAMAGE FACTOR – HIC/SOHIC-H2S ... 22

10.1 Scope ... 22

10.4 Required Data ... 22

10.6.1 Overview ... 22

10.7 Nomenclature ... 22

10.8 References ... 22

10.9 Tables... 22

11 SCC DAMAGE FACTOR – CARBONATE CRACKING ... 24

11.1 Scope ... 24

11.4 Required Data ... 24

11.6.1 Overview ... 24

11.7 Nomenclature ... 24

11.8 References ... 24

11.9 Tables... 24

12 SCC DAMAGE FACTOR – PTA CRACKING ... 26

12.1 Scope ... 26

12.4 Required Data ... 26

12.6.1 Overview ... 26

12.7 Nomenclature ... 26

12.8 References ... 26

12.9 Tables... 26

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13.1 Scope ... 28

13.4 Required Data ... 28

13.6.1 Overview ... 28

13.7 Nomenclature ... 28 13.8 References ... 28 13.9 Tables... 28 14 SCC DAMAGE FACTOR – HSC-HF ... 30 14.1 Scope ... 30 14.2 Description of Damage... 30 14.3 Screening Criteria ... 30 14.4 Required Data ... 30 14.5 Basic Assumptions ... 30

14.6.1 Overview ... 30

14.7 Nomenclature ... 30

14.8 References ... 30

14.9 Tables... 30

15 SCC DAMAGE FACTOR – HIC/SOHIC-HF ... 32

15.1 Scope ... 32

15.4 Required Data ... 32

15.6.1 Overview ... 32

15.7 Nomenclature ... 32

15.8 References ... 32

15.9 Tables... 32

16 EXTERNAL CORROSION DAMAGE FACTOR – FERRITIC COMPONENT ... 34

16.1 Scope ... 34

16.4 Required Data ... 34

16.5 Basic Assumption ... 34

16.6.1 Overview ... 34

16.7 Nomenclature ... 34

16.8 Tables... 34

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17.1 Scope ... 36

17.4 Required Data ... 36

17.6.1 Overview ... 36

17.7 Nomenclature ... 36

17.8 Tables... 36

18 EXTERNAL CLSCC DAMAGE FACTOR – AUSTENITIC COMPONENT ... 39

18.1 Scope ... 39

18.3 Required Data ... 39

18.5.1 Overview ... 39

18.6 Nomenclature ... 39

18.7 Tables... 39

19 EXTERNAL CUI CLSCC DAMAGE FACTOR – AUSTENITIC COMPONENT ... 41

19.1 Scope ... 41

19.4 Required Data ... 41

19.6.1 Overview ... 41

19.7 Nomenclature ... 41

19.8 Tables... 41

20 HTHA DAMAGE FACTOR ... 43

20.1 Scope ... 43

20.4 Required Data ... 43

20.6.1 Overview ... 43

20.7 Nomenclature ... 43

20.8 Tables... 43

21 BRITTLE FACTURE DAMAGE FACTOR ... 45

21.1 Scope ... 45

21.4 Required Data ... 45

21.6.1 Overview ... 45

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21.7 Nomenclature ... 45

21.8 Tables... 45

22 TEMPER EMBRITTLEMENT DAMAGE FACTOR... 46

22.1 Scope ... 46

22.4 Required Data ... 46

22.6.1 Overview ... 46

22.7 Nomenclature ... 46

22.8 References ... 46

22.9 Tables... 46

23 885 EMBRITTLEMENT DAMAGE FACTOR ... 47

23.1 Scope ... 47

23.4 Required Data ... 47

23.6.1 Overview ... 47

23.7 Nomenclature ... 47

23.8 References ... 47

23.9 Tables... 47

24 SIGMA PHASE EMBRITTLEMENT DAMAGE FACTOR ... 48

24.1 Scope ... 48

24.4 Required Data ... 48

24.6.1 Overview ... 48

24.7 Nomenclature ... 48

24.8 References ... 48

24.9 Tables... 48

25 PIPING MECHANICAL FATIGUE DAMAGE FACTOR ... 49

25.1 Scope ... 49

25.4 Required Data ... 49

25.6.1 Overview ... 49

25.7 Nomenclature ... 50

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1 SCOPE

2 REFERENCES 3 DEFINTIONS

4 PROBABILITY OF FAILURE CALCULATIONS 4.1 Overview

4.2 Calculation of Probability of Failure 4.3 Generic Failure Frequency 4.4 Damage Factor

4.4.1 Overview

4.4.2 Damage Factor Combination for Multiple Damage Mechanisms 4.4.3 Inspection Effectiveness Category

Damage factors are determined as a function of inspection effectiveness. Inspection effectiveness discussion and example tables are provided in Annex 2.C of this document. The five inspection effectiveness categories used in API RBI are shown in Table 4.3

Inspections are ranked according to their expected effectiveness at detecting damage and correctly predicting the rate of damage. The actual effectiveness of a given inspection technique depends on the characteristics of the damage mechanism.

. The inspection effectiveness categories presented are meant to be examples and in order to provide a guideline for the user infor assigning actual inspection effectiveness. The actual effectiveness of any inspection technique depends on many factors such as the skill and training of inspectors, and the level of expertise used in selecting inspection locations.

The effectiveness of each inspection performed within the designated time period is characterized for each damage mechanism. The number of highest effectiveness inspections will be used to determine the damage factor. If multiple inspections of a lower effectiveness have been conducted during the designated time period, they can be approximated to an equivalent higher effectiveness inspection in accordance with the following relationships:

a) 2 Usually Effective (B) Inspections = 1 Highly Effective (A) Inspection, or 2B = 1A b) 2 Fairly Effective (C) Inspections = 1 Usually Effective (B) inspection, or 2C = 1B c) 2 Poorly Effective (D) Inspections = 1 Fairly Effective (C) inspection, or 2D = 1C Note that these equivalent higher inspection rules shall not be applied to No Inspections (E). 4.5 Management Systems Factor

4.5.1 General 4.5.2 Overview

4.5.3 Auditing Technique

4.5.4 Calculation of the Management Systems Factor 4.6 Nomenclature

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4.7 Tables

Table 4.3 – Inspection Effectiveness Categories Qualitative Inspection

Effectiveness Category

Description

Highly Effective The inspection methods will correctly identify the true damage state in nearly

every case (or 80–100% confidence).

Usually Effective The inspection methods will correctly identify the true damage state most of

the time (or 60–80% confidence).

Fairly Effective The inspection methods will correctly identify the true damage state about half

of the time (or 40–60% confidence).

Poorly Effective The inspection methods will provide little information to correctly identify the

true damage state (or 20–40% confidence).

Ineffective

The inspection method will provide no or almost no information that will correctly identify the true damage state and are considered ineffective for detecting the specific damage mechanism (less than 20% confidence).

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5 THINNING DAMAGE FACTOR 5.1 Scope

5.2 Screening Criteria 5.3 Required Data 5.4 Basic Assumptions

5.5 Determination of the Damage Factor 5.5.1 Overview

5.5.2 Inspection Effectiveness

Inspections are ranked according to their expected effectiveness at detecting thinning and correctly predicting the rate of thinning. The actual effectiveness of a given inspection technique depends on the characteristics of the thinning mechanism, (i.e., whether it is general or localized).

Examples of inspection activities for general and localized thinning, respectively, that are both intrusive (requires entry into the equipment), non-intrusive (can be performed externally), and buried components are provided in

Annex 2.C, Tables 5.57.1, 7.2, and 7.3through 5.7, respectively. Examples of inspection activities for general

and localized thinning, regarding tank shell courses and bottoms are provided in Annex 2.C, Tables 7.4 to 7.6. Note that the effectiveness category assigned to the inspection activity differs depending on whether the thinning is general or localized.

For localized thinning, selection of locations for examination must be based on a thorough understanding of the damage mechanism in the specific process.

The effectiveness of each inspection performed within the designated time period must be characterized in

accordance a manner similar to withthe examples provided in Annex 2.C, Tables 5.57.1 through 5.107.6, as

applicable. The number and category of the highest effective inspection will be used to determine the damage factor. If multiple inspections of a lower effectiveness have been conducted during the designated time period, they can be equated to an equivalent higher effectiveness inspection in accordance with paragraph 4.4.3

5.5.3 Calculation of the Damage Factor

. Note that for tank bottoms, credit is given for only one inspection.

5.6 Nomenclature 5.7 Tables

Table 5.5 – Guidelines for Assigning Inspection Effectiveness – General Thinning Inspection

Category

Inspection Effectiveness

Category

Intrusive Inspection Example Non-intrusive Inspection Example

A Highly

Effective

50 to 100% examination of the surface (partial internals removed), and accompanied by thickness measurements

50 to 100% ultrasonic scanning coverage (automated or manual) or profile radiography

B Usually

Effective

Nominally 20% examination (no internals removed), and spot external ultrasonic thickness measurements

Nominally 20% ultrasonic scanning coverage (automated or manual), or profile radiography, or external spot thickness (statistically validated)

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C Fairly Effective Visual examination with thickness measurements

2 to 3% examination, spot external ultrasonic thickness measurements, and little or no internal visual examination

D Poorly

Effective Visual examination

Several thickness measurements, and a documented inspection planning system

E Ineffective No inspection

Several thickness measurements taken only externally, and a poorly

documented inspection planning system

Table 5.6 – Guidelines for Assigning Inspection Effectiveness – Local Thinning Inspection

Category

A Highly

Effective

100% visual examination (with removal of internal packing, trays, etc.) and thickness

measurements

50 to 100% coverage using automated ultrasonic scanning, or profile radiography in areas specified by a corrosion engineer or other knowledgeable specialist.

B Usually

Effective

100% visual examination (with partial removal of the internals) including manways, nozzles, etc. and thickness measurements.

20% coverage using automated ultrasonic scanning, or 50% manual ultrasonic scanning, or 50% profile radiography in areas specified by a corrosion engineer or other knowledgeable specialist.

C Fairly Effective

Nominally 50% visual examination and spot ultrasonic thickness measurements

Nominally 20% coverage using automated or manual ultrasonic scanning, or profile radiography, and spot thickness measurements at areas specified by a corrosion engineer or other knowledgeable specialist.

D Poorly

Effective

Nominally 20% visual examination and spot ultrasonic thickness measurements

Spot ultrasonic thickness

measurements or profile radiography without areas being specified by a corrosion engineer or other knowledgeable specialist.

E Ineffective

No inspection Spot ultrasonic thickness

measurements without areas being specified by a corrosion engineer or other knowledgeable specialist.

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Table 5.7 – Guidelines for Assigning Inspection Effectiveness – Buried Components Inspection Category Inspection Effectivenes s Category Intrusive Inspection Example Non-intrusive Inspection Example Non-intrusive Inspection Example A Highly Effective 100% internal inspection via state-of-the-art pigging and in-line inspection technologies (UT, MFL, internal rotary UT, etc.)

100% external inspection of equipment that is only partially buried using an NDE crawler with circumferential inspection technology (MFL, lamb-wave UT) Complete excavation, 100% external visual inspection, and 100% inspection with NDE technologies (UT thickness measurement such as handheld devices at close-interval grid locations, UT B-scan, automated ultrasonic scanning, guided-wave UT global search, crawler with circumferential inspection technology such as MFL or lamb-wave UT, digital radiography in more than one direction)

a. Cathodic Protection (CP) System maintained and managed by NACE certified personnel and complying with NACE SP0169 [14

b. Close Interval Survey (at excavation sites) to assess the

performance of the CP system locally

]– includes Stray current surveys on a regular basis

c.a. Sample soil and water resistivity and chemistry measurements along entire structure

B _EffectiveUsually

Internal inspection via pigging and in-line inspection technologies (UT, MFL, internal rotary UT, etc.) of selected areas / sections, combined with statistical analysis or extreme value analysis (EVA).

External inspection of equipment that is only partially buried using an NDE crawler with circumferential inspection technology (MFL, lamb-wave UT) on selected areas / sections, combined with statistical analysis or extreme value analysis (EVA).

Excavation at “Selected” locations, 100% external visual, and 100% inspection with NDE technologies (UT thickness measurement such as handheld devices at close-interval grid locations, UT B-scan, automated ultrasonic scanning, guided-wave UT global search, crawler with circumferential inspection technology such as MFL or lamb-wave UT, digital radiography in more than one direction)

a. CP System maintained and managed by NACE certified personnel and complying with NACE SP0169 [14

b. Close Interval Survey (at excavation sites) to assess the

performance of the CP system locally

] – includes Stray current surveys on a regular basis

c. Sample soil and water resistivity and chemistry measurements along entire structure d.a. DC Voltage Gradient (DCVG) to determine coating damage C Fairly Effective Partly inspection by internal smart pig or specialized crawler device, including a representative portion of the buried pipe. (<25%)

Partial excavation guided-wave UT global search inspection in each direction of pipe. Corrosion Inspection and Maintenance managed by NACE certified and CP specialist, or equivalent

---D Poorly Effective

Hydrostatic testing Spot check with conventional NDE equipment of local areas exposed by excavation

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---Table 5.8 – Guidelines for Assigning Inspection Effectiveness – Tank Shell Course Internal Corrosion Inspection Category Inspection Effectiveness Category Inspection A Highly Effective

a. Intrusive inspection – good visual inspection with pit depth gage measurements at suspect locations.

b.a. UT scanning follow up on suspect location and as general confirmation of wall thickness

B Usually Effective

a. External spot UT scanning based on visual information from previous internal inspection of this tank or similar service tanks.

b.a. Internal video survey with external UT follow-up.

C Fairly Effective Eternal spot UT scanning based at suspect locations without benefit of any internal inspection information on tank type or service.

D Poorly Effective External spot UT based at suspect locations without benefit of any internal inspection _{information on tank type or service.}

E Ineffective No inspection

Table 5.9 – Guidelines for Assigning Inspection Effectiveness – Tank Shell Course External Corrosion Inspection Category Inspection Effectiveness Category Inspection A Highly Effective

a. Insulated – >95% external visual inspection prior to removal of insulation b. Remove >90% of insulation at suspect locations, OR >90% pulse eddy current

inspection.

c. Visual inspection of the exposed surface area with follow-up by UT or pit gauge as required.

a. Non-Insulated - >95% visual inspection of the exposed surface area with

follow-up by UT or pit gauge as required.

B Usually Effective

inspection.

C Fairly Effective

inspection.

D Poorly Effective

inspection.

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E Ineffective

a. Insulated – No visual inspection of insulation surface area or removal of insulation.

a. Non-Insulated - <5% visual of the exposed surface area Table 5.10 – Guidelines for Assigning Inspection Effectiveness – Tank Bottoms Inspection

Category

Soil Side Product Side

A Highly Effective

a. Floor scan 90+% & UT follow-up

b. Include welds if warranted from the results on the plate scanning

c.a. Hand scan of the critical zone

a. Commercial blast

b. Effective supplementary light c. Visual 100% (API 653) d. Pit depth gauge

e. 100% vacuum box testing of suspect welded joints

Coating or Liner a. Sponge test 100%

:

b. Adhesion test

c.a. Scrape test

B Usually Effective

a. Floor scan 50+% & UT follow-up

OR

b.a. EVA or other statistical method with Floor scan follow-up if warranted by the result

a. Brush blast

b. Effective supplementary light c. Visual 100% (API 653) d. Pit depth gauge

Coating or Liner a. Sponge test >75%

:

b. Adhesion test

c.a. Scrape test

C Fairly Effective

a. Floor scan 5-10+% plates; supplement with scanning near Shell & UT follow-up; Scan circle and X pattern b. Progressively increase if

damage found during scanning c. Helium/Argon test

d. Hammer test

e.a. Cut coupons

a. Broom swept

b. Effective supplementary light c. Visual 100%

d. Pit depth gauge

Coating or Liner

a. Sponge test 50 – 75% :

b. Adhesion test

c.a. Scrape test

D Poorly Effective a. Spot UT

b.a. Flood test

a. Broom swept

b. No effective supplementary lighting c. Visual 25-50%

Coating or Liner

a. Sponge test <50 :

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6 COMPONENT LINING DAMAGE FACTOR 6.1 Scope

6.2 Screening Criteria 6.3 Required Data 6.4 Basic Assumptions

Inspections are ranked according to their expected effectiveness at detecting the specific damage mechanism. Examples of inspection activities that are both intrusive (requires entry into the equipment) and non-intrusive (can be performed externally), are provided in Annex 2.C, Table 7.7.

6.5.26.5.3 Calculation of the Damage Factor 6.6 Nomenclature

6.7 Tables 6.8 Figures

(30)

7 SCC DAMAGE FACTOR – CAUSTIC CRACKING 7.1 Scope 7.2 Description of Damage 7.3 Screening Criteria 7.4 Required Data 7.5 Basic Assumptions

Inspections are ranked according to their expected effectiveness at detecting caustic crackingthe specific

damage mechanism and correctly predicting the rate of damage.

Examples of inspection activities for caustic cracking that are both intrusive (requires entry into the equipment) and non-intrusive (can be performed externally), are provided in Table 7.2Annex

The effectiveness of each inspection performed within the designated time period must be characterized in accordance with

2.C, Table 7.8.

Table 7.2. The number and category of the highest effective inspection will be used to determine the damage factor. If multiple inspections of a lower effectiveness have been conducted during the designated time period, they can be equated to an equivalent higher effectiveness inspection in accordance with paragraph 4.4.3

7.6.3 Calculation of the Damage Factor .

7.7 Nomenclature 7.8 References 7.9 Tables

Table 7.2 – Guidelines for Assigning Inspection Effectiveness – Caustic Cracking Inspection

Category

A Highly

Effective

Wet fluorescent Magnetic particle or dye penetrant testing of 25-100% of welds/cold bends; or Dye penetrant testing of 25-100% of welds/cold bends.

Shear wave ultrasonic testing of 25-100% of welds/cold bends; or Radiographic testing of 50-100% of welds/cold bends.

B Usually

Effective

Wet fluorescent Magnetic particle or dye penetrant testing of 10-24% of welds/cold bends; or Dye penetrant testing of 10-24% of welds/cold bends.

Shear wave ultrasonic testing of 10-24% of welds/cold bends; or Radiographic testing of 25-49% of welds/cold bends.

(31)

C Fairly Effective

Magnetic particle or dye penetrant testing of less than 10% of welds/cold bends; or Dye penetrant testing of less than 10% of welds/cold bends.

Shear wave ultrasonic testing of less than 10% of welds/cold bends; or Radiographic testing of less than 25% of welds/cold bends.

D Poorly

Effective

Visual inspection Visual inspection for leaks

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8 SCC DAMAGE FACTOR – AMINE CRACKING 8.1 Scope 8.2 Description of Damage 8.3 Screening Criteria 8.4 Required Data 8.5 Basic Assumptions

Inspections are ranked according to their expected effectiveness at detecting amine cracking and correctly predicting the rate of damage.

Examples of inspection activities for Amine cracking that are both intrusive (requires entry into the equipment) and non-intrusive (can be performed externally), are provided in Table 8.2

.

Table 8.2. The number and category of the highest effective inspection will be used to determine the damage factor. If multiple inspections of a lower effectiveness have been conducted during the designated time period, they can be equated to an equivalent higher effectiveness inspection in accordance with paragraph 4.4.3.

8.6.3 Calculation of the Damage Factor 8.7 Nomenclature

8.8 References 8.9 Tables

Table 8.2 – Guidelines for Assigning Inspection Effectiveness – Amine Cracking Inspection

Category

A Highly

Effective

Wet fluorescent magnetic particle testing of 100% of repair welds and 50-100% of other welds/cold bends.

None

B Usually

Effective

Wet fluorescent magnetic particle testing of 20-49% of welds/cold

Shear wave ultrasonic testing of 50-100% of welds/cold bends; or Acoustic

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bends. Emission testing with follow-up shear wave UT.

C Fairly Effective

Wet fluorescent magnetic particle testing of less than 20% of welds/cold bends; or Dry magnetic particle testing of 50-100% of welds/cold bends; or Dye penetrant testing of 50-100% of welds/cold bends.

Shear wave ultrasonic testing of 20-49% of welds/cold bends.

D Poorly

Effective

Dry magnetic particle testing of less than 50% of welds/cold bends; or Dye penetrant testing of less than 50% of welds/cold bends.

Shear wave ultrasonic testing of less than 20% of welds/cold bends; or Radiographic testing; or Visual inspection for leaks.

(34)

9 SCC DAMAGE FACTOR – SULFIDE STRESS CRACKING 9.1 Scope 9.2 Description of Damage 9.3 Screening Criteria 9.4 Required Data 9.5 Basic Assumptions

Inspections are ranked according to their expected effectiveness at detecting sulfide stress cracking and correctly predicting the rate of damage.

Examples of inspection activities for sulfide stress cracking that are both intrusive (requires entry into the equipment) and non-intrusive (can be performed externally), are provided in Table 9.2

.

Table 9.2 The number and category of the highest effective inspection will be used to determine the damage factor. If multiple inspections of a lower effectiveness have been conducted during the designated time period, they can be equated to an equivalent higher effectiveness inspection in accordance with paragraph 4.4.3

9.6.3 Calculation of the Damage Factor .

9.7 Nomenclature 9.8 References 9.9 Tables

Table 9.2 – Guidelines for Assigning Inspection Effectiveness – Sulfide Stress Cracking Inspection

Category

A Highly

Effective

Wet fluorescent magnetic particle testing of 25-100% of weldments.

Shear wave ultrasonic testing of 25-100% of weldments, transverse and parallel to the weld with the weld cap removed; or Acoustic Emission testing with follow-up shear wave UT.

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B Usually Effective

Wet fluorescent magnetic particle testing of 10-24% of weldments; or Dry magnetic particle testing of 25-100% of weldments; or Dye penetrant testing of 25-100% of weldments.

Shear wave ultrasonic testing of 10-24% of weldments; Radiographic testing of 50-100% of weldments.

C Fairly Effective

Wet fluorescent magnetic particle testing of less than 10% of weldments; or Dry magnetic particle testing of less than 25% of weldments; or Dye penetrant testing of less than 25% of weldments.

Shear wave ultrasonic testing of less than 10% of weldments; Radiographic testing of 20-49% of weldments.

D Poorly

Effective

Visual inspection Radiographic testing of less than 20%

of weldments.

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10 SCC DAMAGE FACTOR – HIC/SOHIC-H2 10.1 Scope S 10.2 Description of Damage 10.3 Screening Criteria 10.4 Required Data 10.5 Basic Assumptions

10.6 Determination of the Damage Factor 10.6.1 Overview

10.6.2 Inspection Effectiveness

Inspections are ranked according to their expected effectiveness at detecting HIC/SOHIC-H2

Examples of inspection activities for HIC/SOHIC-H

S cracking and correctly predicting the rate of damage.

2S cracking that are both intrusive (requires entry into the

equipment) and non-intrusive (can be performed externally), are provided in Table 10.2

.

10.6.3 Calculation of the Damage Factor .

10.7 Nomenclature 10.8 References 10.9 Tables

Table 10.2 – Guidelines for Assigning Inspection Effectiveness – HIC/SOHIC-H2 Inspection Category S Cracking Inspection Effectiveness Category

A Highly

Effective

Wet fluorescent magnetic particle testing of 50-100% of weldments, plus additional shear wave UT for subsurface cracking.

None

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Effective particle testing of 20-49% of weldments.

testing of 20-100% of weldments; or Acoustic Emission testing with follow-up shear wave UT.

C Fairly Effective

Wet fluorescent magnetic particle testing of less than 20% of weldments; or Dry magnetic particle testing of 50-100% of weldments; or Dye penetrant testing of 50-100% of weldments.

Automated shear wave ultrasonic testing of less than 20% of weldments; or Manual shear wave ultrasonic testing of 20-100% of weldments.

D Poorly

Effective

Dye penetrant testing of less than 50% of weldments; Visual inspection for hydrogen blisters.

Manual shear wave ultrasonic testing of less than 20% of weldments.

(38)

11 SCC DAMAGE FACTOR – CARBONATE CRACKING 11.1 Scope 11.2 Description of Damage 11.3 Screening Criteria 11.4 Required Data 11.5 Basic Assumptions

11.6 Determination of the Damage Factor 11.6.1 Overview

Inspections are ranked according to their expected effectiveness at detecting carbonate cracking and correctly predicting the rate of damage.

Examples of inspection activities for carbonate cracking that are both intrusive (requires entry into the equipment) and non-intrusive (can be performed externally), are provided in Table 11.2

.

11.6.3 Calculation of the Damage Factor .

11.7 Nomenclature 11.8 References 11.9 Tables

Table 11.2 – Guidelines for Assigning Inspection Effectiveness – Carbonate Cracking Inspection

Category

A Highly

Effective

Wet fluorescent magnetic particle testing of 100% of repair welds and 50-100% of other welds/cold bends.

None

B Usually

Effective

Wet fluorescent magnetic particle testing of 20-49% of welds/cold

Shear wave ultrasonic testing of 50-100% of welds/cold bends; or Acoustic

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bends. Emission testing with follow-up shear wave UT.

C Fairly Effective

Wet fluorescent magnetic particle testing of less than 20% of welds/cold bends; or Dry magnetic particle testing of 50-100% of welds/cold bends; or Dye penetrant testing of 50-100% of welds/cold bends.

Shear wave ultrasonic testing of 20-49% of welds/cold bends.

D Poorly

Effective

Dry magnetic particle testing of less than 50% of welds/cold bends; or Dye penetrant testing of less than 50% of welds/cold bends.

Shear wave ultrasonic testing of less than 20% of welds/cold bends; or Radiographic testing; or Visual inspection for leaks.