An Overview of the API Section 10

An Overview of the API Section 10: Assessment Of Components Operating In The Creep Regime

Rohit Rastogi Reactor Safety Division

Bhabha Atomic Research Centre Mumbai

Indian Nuclear Society COURSE ON DESIGN OF COMPONENTS OPERATING AT HIGH

TEMPERATURE

July 25-29, 2005

[email protected]

Introduction to API 579, Section 10 Page 1 of 18

mailto:[email protected]

INDEX

1. Introduction___________________________________________________ 3

2. Applicability and Limitation of the procedure ______________________ 4

3. Data Requirement______________________________________________ 6

4. Assessment Levels ______________________________________________ 7

5. Level 1 Assessment _____________________________________________ 7

6. Level 2 Assessment _____________________________________________ 8

7. Level 3 Assessment ____________________________________________ 11

8. Remaining Life Assessment _____________________________________ 12 8.1 Creep Rupture Life __________________________________________ 13 8.2 Creep-Fatigue Interaction _____________________________________ 14 8.3 Creep Crack Growth _________________________________________ 14

9. Remediation__________________________________________________ 18


1. Introduction API 579 Section 10 gives Fitness-For-Service (FFS) assessment procedures for pressurized components operating in the creep regime. The temperature limits for the creep regime are defined in Table 1 for different materials. The procedures in the section can be used to qualify a component for continued operation or for re-rating. Table 1: Temperature limit to define the creep range

Material Temperature Limit

Brinell Hardness

Carbon Content

Carbon Steel UTS ksi ≤ (60) 343°C (650°F) 95 --- Carbon Steel UTS ksi > (60) 371°C (700°F) 100 --- Carbon Steel – Graphitized 371°C (700°F) 100 --- C-1/2Mo 399°C (750°F) 110 --- 1-1/4Cr-1/2Mo – Normalized & Tempered 427°C (800°F) 130 --- 1-1/4Cr-1/2Mo – Annealed 427°C (800°F) 120 --- 2-1/4Cr-1Mo – Normalized & Tempered 427°C (800°F) 140 --- 2-1/4Cr-1Mo – Annealed 427°C (800°F) 130 --- 2-1/4Cr-1Mo – Quenched & Tempered 427°C (800°F) 150 --- 2-1/4Cr-1Mo – V 441°C (825°F) 180 --- 3Cr-1Mo-V 441°C (825°F) 180 --- 5Cr-1/2Mo 427°C (800°F) 130 --- 7Cr-1/2Mo 427°C (800°F) 130 --- 9Cr-1Mo 427°C (800°F) 140 --- 9Cr-1Mo – V 454°C (950°F) 180 --- 12 Cr 482°C (900°F) 180 --- AISI Type 304 & 304H 510°C (950°F) --- 0.04 AISI Type 316 & 316H 538°C (1000°F) --- 0.04 AISI Type 321 538°C (1000°F) --- 0.04 AISI Type 321H 538°C (1000°F) --- 0.04 AISI Type 347 538°C (1000°F) --- 0.04 AISI Type 347H 538°C (1000°F) --- 0.04 Alloy 800 565°C (1050°F) --- 0.03 Alloy 800H 565°C (1050°F) --- 0.04 Alloy 800HT 565°C (1050°F) --- 0.05 HK-40 649°C (1200°F) --- 0.3


The FFS assessment procedure for components operating in the creep regime requires an estimate of remaining life. Assessment procedures for determining a remaining life are provided for components with and without a crack-like flaw subject to steady state and cyclic operating conditions. If the component contains a crack-like flaw, and is not operating in the creep regime, then Section 9 of the API 579 can be used for the fitness-for-service assessment. The assessment procedures in this section can be used to determine the remaining life of a component operating in the creep regime. The use of these procedures is not normally required for equipment design to a recognized code or standard that is operating within the original design parameters. Conditions that may warrant a FFS evaluation include:

o Operational upsets that result in a operating temperature and pressure, or other loading conditions that may result in creep damage and were not included in the original design.

o Metal loss in the component beyond that provided for in the original design;

metal loss in this category will result in component stress above those originally accounted for in the design.

o Fire damage that can result in a short time heating event.

o The discovery of a crack-like flaw; both initial fabrication and service

induced crack-like flaws should be evaluated.

o The discovery of an LTA, pitting damage, weld misalignment, out-of-roundness, bugle, dent, or dent gouge combination that can result in localized creep stain accumulation and subsequent cracking; both initial fabrication and service-induced flaws should be evaluated.

API 579 is organized in modular fashion based on type of material damage or flaw to facilitate its use and updating. It incorporates a three-level assessment approach. The level of conservatism decreases with increasing level of assessment, but detail of analysis and data increase with increasing level of assessment.

2. Applicability and Limitation of the procedure The Level 1 assessment procedures in this section apply only if all of the following conditions are satisfied: a) The original design criteria were in accordance with the following codes

o ASME B&PV Code, Section VIII, Division 1 o ASME B&PV Code, Section VIII, Division 2 o ASME B&PV Code, Section I o ASME B31.3 Piping Code o ASME B31.1 Piping Code o API 650


o API 620 b) The component has not been subject to operational upsets that were not considered in the original design. c) The metal loss on the component is less than that provided for in the original design. d) The component has not been subject to fire damage, or the component has been subject to fire damage and the assessment procedures of Section 11 have been satisfied. e) The component does not contain:

o An LTA or groove-like flaw o Pitting damage o Weld misalignment, out-of-roundness, or bulge that exceed the

original design code tolerances o A dent or dent-gouge combination o A crack-like flaw

The Level 2 assessment procedures in this section apply only if all of the following conditions are satisfied. a) The original design criteria were in accordance with codes listed above b) A history of the component can be provided covering both past and future operating conditions. c) The component has been subject to less than 100 cycles of operation including startup and shutdown conditions. d) The component does not contain any of the flaws listed above. e) Material properties for the creep regime are available to determine a remaining life. A Level 3 Assessment should be performed when the Level 1 and 2 methods cannot be applied or when these assessments produce overly conservative results. Conditions that typically require a Level 3 Assessment include the following.

o Advanced stress analysis techniques are required to define the state of stress because of complicated geometry and/or loading conditions.

o The component is subject to cyclic operation.

o The component contains a flaw listed earlier. A detailed assessment

procedure is provided for a crack-like flaw; however, this procedure cannot be used to evaluate crack-like flaws that are caused by stress corrosion, oxide wedging, or similar environmental phenomena.


3. Data Requirement The Level 1 Assessment is a screening criteria based on the original design of the component, the past and future operating conditions, and flaw characterization. This assessment can be performed based on the following information.

o Original Equipment Design Data o Maintenance and Operating History

Significant input data are required to perform a Level 2 or Level 3 Assessment. Details regarding the required data are discussed in paragraphs later. The accuracy of these data and stress conditions will determine the accuracy of the assessment by the procedures in this section. A stress analysis is required for a Level 2 or Level 3 Assessment. a) Level 2 Assessment – An elastic stress analysis is required. Handbook solutions may be used if these solutions accurately represent the component geometry and loading condition. Otherwise, numerical analysis techniques such as the finite element method may have to be utilized to determine the stress field at the crack location. b) Level 3 Assessment – a stress analysis using a numerical analysis technique such as the finite element method is required to determine the stress state at major structural discontinuities where creep damage or creep crack growth is normally manifested. In these cases, it is highly recommended that this analysis include the effects of plasticity and creep to account for the redistribution of stresses that occurs in the creep regime. This is particularly important because the stresses at major structural discontinues relax to magnitudes that are significantly less that those computed using an elastic stress calculation. Since the stress results are used directly in the assessment procedure and the remaining life from this procedure is sensitive to the magnitude of stress, the results from an elastic analysis will typically over estimate the creep damage and result in a conservative estimate of remaining life. The material properties required for analysis are presented in Appendix F of the API 579. The material data presented in Appendix F is from the MPC Project Omega data that is based on a strain-rate approach, and the creep rupture life data from API RP 530. Both types of data can be used in the Level 2 or Level 3 Assessment procedures to determine a remaining life. However, if the component has a crack-like flaw, then the Level 3 Assessment procedures require the use of the MPC Project Omega data. The Project Omega data is also required in a Level 3 creep buckling analysis. The creep rupture data is given in the form of minimum and average properties in terms of the Larson-Miller parameter, If the component contains a crack-like flaw, parameters for the creep-crack growth equation are required. Recommendations are provided in Appendix F. In addition, the fracture toughness is also required because an evaluation of the flaw using the FAD based assessment procedures of Section 9 is required. It should be noted that


although brittle fracture is unlikely at elevated temperature, it might be a possibility during the start-up or shutdown phase of the cycle. In addition, the FAD assessment is required to place a limit on the plastic collapse of a component containing a crack-like flaw.

4. Assessment Levels The three assessment levels used to evaluate creep damage are based on the data and details required for the analysis, whether the component contains a crack-like flaw, the degree of complexity required for a given situation, and the perceived risk. Level 1 Assessments are based on a comparison of operating conditions to a lower bound creep regime cut-off temperature. In addition, a check on material properties in terms of hardness or carbon content and a visual examination of the component is made in order to evaluate the potential for creep damage based on component distortion and material characteristics such as discoloration or scaling. Level 2 Assessments can be used for general shell structures where the stress components can be readily computed using elasticity theory, either from closed from solutions (i.e. cylindrical shell or fired heater tuber) or from a finite element analysis. Level 3 Assessments can be used to evaluate those cases that do not meet the requirements of Level 1 or Level 2 assessments. A detailed stress analysis is required to evaluate creep damage or creep crack growth at a major structural discontinuity.

5. Level 1 Assessment The Level 1 acceptance criterion is based on the original design conditions of the component. a) If the component operating temperature is below the value in Table 1, then the Level 1 Assessment criterion is satisfied. b) If the component was originally designed for temperatures that are greater than the values in Table 1, the Level 1 Assessment criterion is satisfied if:

o For components made from carbon steel and low alloy materials, the

hardness is greater than the values listed in Table 1.

o For components made from austenitic stainless steels and high alloy steels, the carbon content is greater than the values listed in Table 1.

If the component does not meet the Level 1 Assessment requirements, then the following, or combinations thereof, can be considered:

o Re-rate, repair, replace, or retire the component. o Conduct a Level 2 or a Level 3 Assessment.


6. Level 2 Assessment The creep damage based upon the results of a stress analysis is computed as follows: STEP 1 – Determine a load history based on past operation and future planned operation. The load histogram should include all significant operating loads and events that are applied to the component. If there is cyclic operation, the load histogram should be divided into operating cycles as shown in Figure 1. Define K as the total number of operating cycles.

Figure 1: Definition of multiple cycles in a load histogram

STEP 2 – For the current operating cycle k, determine the total cycle time, t

k, and divide the cycle into a number of time increments, tn as shown in Figure 2-3. Define N as the total number of time increments in operating cycle k.


Figure 2: Actual parameter variation

Figure 3: Idealized Parameter Variation Using Average Values Of Parameters

1) The time increments used to model the operating cycle should be small enough to capture all significant variations in the operating cycle. Smaller is the time increment, the more accurate the remaining life predication. 2) If the component is subject to corrosion or erosion, the time increments should be set small enough to capture changes in the wall thickness.


STEP 3 – Determine the temperature, Tn, and compute the primary stresses ( 1 2, , 3σ σ σ ) for the time increment tn. These can be calculated using finite element calculations. Solution of principal stresses in terms of temperature for spheres and cylinders are given in the code. STEP 4 – Compute the effective stress using the following equation:

STEP 5 – Check that the value of the effective stress, n

eσ , is less then the value of the yield strength, ysσ , evaluated at temperature Tn at time increment tn . If

en ysσ σ≥ then go to STEP11; otherwise proceed to STEP 6.

STEP 6 - Determine a remaining life at the stress level n

eσ and temperature Tn for time increment tn by utilizing creep rupture data for the material, and designate this value as Ln . Section 10 gives two methods to make this estimation. One is based on MPC Project Omega data and the other is based on Larson-Miller parameter. The procedure of estimation using Larson-Miller parameter is presented here. The value of the LMP (σ ) function for different materials is given in Appendix F of the code.

Where

STEP 7 - Repeat Steps 3 through 6 for each time increment tn in the kth operating cycle to determine the rupture time, Ln. STEP 8 - Compute the accumulated creep damage for all points in the kth cycle using the equation shown below. In the following equation, tn is defined as the time increment where the component is subject to a stress level n

eσ at a corresponding operating temperature Tn, and Ln is the permissible remaining life at this temperature based on material data.


STEP 9 - Repeat Steps 2 through 8 for each of the operating cycles defined in STEP 1. STEP 10 – Compute the total creep damage for all cycles of operation.

STEP 11 – The creep damage prediction is complete for this location in the component. The allowable creep damage, , is usually taken as 1.0 unless an alternative value can be justified.

allowcD

o If e

n ysσ σ≥ for any point in the operating history, then the component is not acceptable for continued operation and the component should be repaired or retired.

o If the total creep damage, , is less than the allowable creep damage,

, then the component is acceptable for continued operation. The remaining life for operation can be determined by analyzing additional load cycles and determining the time at which .

totalcD

allowcD

total allowc cD D=

o If the total creep damage, , is greater than the allowable creep damage,

, then the life of the component is limited to the time corresponding to . If this time is less than the current operating time, the

component should be repaired or retired.

totalcD

allowcDtotalcD allow

cD=

If the component does not meet the Level 2 Assessment requirements, then the following, or combinations thereof, can be considered:

o Re-rate, repair, replace, or retire the component.

o Adjust the future corrosion allowance; note that this does not apply if based on the current operating time. total allow

c cD D≥o Conduct a Level 3 Assessment.

7. Level 3 Assessment The Level 3 assessment procedures provide a means to evaluate the remaining life of a component using advanced stress analysis techniques. These procedures can be used to evaluate a component containing one or more of the flaws listed in paragraph 2.e. If the flaw is volumetric (i.e. LTA, pitting damage, weld misalignment, out-of-roundness, bugle, dent, or dent-gouge combination), then the


stress analysis model used to evaluate the remaining life must include the flaw so that that localized stresses and strains are accounted for. These stress results are then directly used in the assessment. If the component contains a crack-like flaw, then the stress analysis used for remaining life can be based on an un-cracked body analysis. The effects of the crack are accounted for in the assessment procedure. As in the case for the Level 2 assessment, the predominant failure mode for components operating in the creep regime is creep rupture. If the component is subject to cyclic operation, then the effect of creep-fatigue interaction needs to be evaluated. Both of these damage mechanisms involve a time-based failure mode; therefore, a remaining life needs to be evaluated as part of the assessment.

8. Remaining Life Assessment A remaining life calculation is required for all components operating in the creep regime. The assessment procedures in Level 1 and Level 2 for components subject to loading conditions where the stress states can be computed using linear elastic analysis and significant stress redistribution does not occur. In addition, these assessment procedures are limited to components that are not subject to cyclic operation and/or components that do not contain a crack-like flaw. The assessment procedures described here provides the best estimate of the structural integrity of a component operating at elevated temperature. Five assessment procedures are provided in the API 579. Creep Rupture Life: This assessment procedure is used for components that are subject to steady state operation in the creep regime which do not have crack-like flaws. A nonlinear stress analysis where creep material behavior is modeled is recommended for this assessment. If a linear stress analysis is used, the methodology provided in following codes is recommended.

o ASME Code, Section III, Subsection NH o Nuclear Electric R-5 o BS 7910 o EPRI Remaining-Life of Boiler Pressure Parts–Crack Growth Studies o WRC 440 A Synthesis of the Fracture Assessment methods Proposed in the

French RCC-MR Code for High Temperature. Creep-Fatigue Interaction: This assessment procedure is used for components that are subject to cyclic operation in the creep regime which do not have crack-like flaws. A nonlinear stress analysis where creep material behavior is modeled is recommended for this assessment. Creep Crack Growth: This assessment procedure is used for components that are subject to either steady state or cyclic operation in the creep regime which contain crack-like flaws. A nonlinear stress analysis where creep material behavior is modeled is recommended for this assessment.


Creep Buckling: This assessment procedure can be used to determine the time at which a component in the creep regime may be subject to structural instability due to a compressive stress field. The procedure can be used for a component both with and without a crack-like flaw. Creep-Fatigue Assessment Of Dissimilar-Weld Joints: This assessment procedure can be used to determine the suitability of a dissimilar-weld joint in a component operating in the creep regime.

8.1 Creep Rupture Life The following analysis procedure can be utilized to evaluate a component operating in the creep regime using the results from a stress analysis. The evaluation can be made based on the stresses and strains at a point in the component, and the associated operating time and temperature. If a nonlinear stress analysis is used in the assessment, a material model is required to estimate the creep strains in the component as a function of stress, temperature, and accumulated creep strain (strain hardening model) or time (time hardening model). A strength check is included in the procedure if the computed stresses are determined using an elastic analysis. This strength check is not required if a nonlinear stress analysis incorporating the effects of plasticity and creep is used to determine the stresses for the assessment. The assessment procedure in this paragraph provides a systematic approach for evaluating the creep damage for each operating cycle that is applied to the component. The total creep damage is computed as the sum of the creep damages calculated for each cycle. The creep damage based upon the results of a stress analysis can be computed using the assessment procedure shown below. This procedure is similar to the procedure in Level 2 except for Steps 5 and 11. STEP 5 – If an assessment is based on the results of an elastic stress analysis, then check that the value of the effective stress, n

eσ , is less then the value of the yield strength, ysσ , evaluated at temperature Tn at time increment tn . If e

n ysσ σ≥ , then go to STEP 11; otherwise proceed to STEP 6. STEP 11 – The creep damage prediction is complete for this location in the component. Determine the acceptability for continued operation using the criteria

o If en ysσ σ≥ for any point in the operating history, then the component is not

acceptable for continued operation and the component should be repaired or retired.

o If the total creep damage, , is less than the allowable creep damage,

, then the component is acceptable for continued operation. The

totalcD

allowcD


remaining life for operation can be determined by analyzing additional load cycles and determining the time at which . total allow

c cD D=

o If the total creep damage, , is greater than the allowable creep damage, , then the life of the component is limited to the time corresponding to

. If this time is less than the current operating time, the component should be repaired or retired.

totalcD

allowcDtotalcD allow

cD=

Note that in this criterion, the strength check based on the effective stress does not need to be made if the stresses in the assessment are computed using a nonlinear stress analysis that includes the effects of plasticity and creep.

8.2 Creep-Fatigue Interaction If there are significant cyclic operations during the operating period, then the effects of combined creep and fatigue damage must be evaluated. The assessment procedure given by Level 3, creep rupture life can be used to evaluate the creep part of the damage, and the assessment procedure in Appendix B of the API code, can be used to evaluate the fatigue part of the damage. The combination of creep and fatigue damage is then evaluated using the equation shown below. The permissible creep-fatigue damage fraction, , is usually taken as 1.0 unless an alternative value can be justified.

allowcfD

In addition to satisfying the damage criterion of equation above, a limit on the total accumulated inelastic strains should be set to a value that will not limit the operability of the component.

8.3 Creep Crack Growth The following analysis procedure can be utilized to evaluate a component operating in the creep regime using nonlinear stress analysis methods. The evaluation can be made based on the stresses and strains at a point in the component, and the associated operating time and temperature. In the nonlinear stress analysis, a material model is required to estimate the creep strains in the component as a function of stress, temperature, and accumulated creep strain (strain hardening


model) or time (time hardening model). If the computed stresses exceed the yield stress of the material at temperature, plasticity should also be included in the material model. STEP 1 – Determine a load history based on past operation and future planned operation. The load histogram should include all significant operating loads and events that are applied to the component. If there is cyclic operation, the load histogram should be divided into operating cycles. STEP 2 – Determine the material properties; yield stress, tensile strength, fracture toughness and creep properties. STEP 3 – Determine the damage in the material ahead of the crack prior to cracking, Dbc. If the component is not in cyclic operation, then the damage prior to cracking is the creep damage computed using the procedure in paragraph 8.1. The creep damage is computed using the equation shown below where Kbc is the total number of operating cycles prior to cracking.

If the component is subject to cyclic operation, then the damage prior to cracking is the creep fatigue damage computed using the procedure in paragraph 8.2. The creep-fatigue damage is computed using the equation shown below where Kbc is the total number of operating cycles prior to cracking.

STEP 4 – Determine the initial crack-like flaw dimensions from inspection data, ao and co. The flaw should be categorized using the procedure in API Section 9. Initialize the initial flaw dimension sizes and the staring time for the cycle:

STEP 5 – For the current operating cycle k, determine the total cyclic time, tk, and compute the stresses, ijσ , through the section containing the crack-like flaw for each point n in the cycle. STEP 6 – Determine the reference stress, refσ , at time ti using Appendix D based on the crack-like flaw dimensions ai and ci and the corresponding stress distribution.


STEP 7 – Perform a FAD assessment at time ti using the procedures in Section 9 of API based on the crack like flaw dimensions ai and ci, and the corresponding stress and temperature distribution. When using this procedure, the load ratio (x-axis of the FAD) shall be computed using the equation shown below. If the resulting FAD point is outside of the FAD failure envelope, go to STEP 18; otherwise, go to STEP 6.

In this equation, ysσ is the yield strength at the temperature being evaluated and

is the stress to cause 2% creep strain in 100,000 hours at the temperature being evaluated.

FADcσ

STEP 8 – Determine the damage in the material ahead of the crack growth, Dac, at time ti based on the crack-like flaw dimensions ai and ci, and the corresponding stress and temperature distribution.

The calculation of is based on a set of equations which is given in the code. i

acL STEP 9 – Determine the reference strain rate, refε , at time ti based on the crack-like flaw dimensions, ai and ci , and the corresponding stress and temperature distribution. The detailed set of equations is given in the code. STEP 10 – Determine the stress intensity factor at the deepest point, , at

time t( )90 ,I i iK a c

i and surface point, , of the flaw based on the crack-like flaw dimensions a

(0 ,I i iK a c )

)

i and ci, and the corresponding stress and temperature distribution using Appendix C. STEP 11 – Determine the crack driving force at the deepest point, C a , and

surface point, (90 ,t i ic

( )0 ,t i icC a , of the flaw at time ti based on the crack-like flaw dimensions ai and ci , and the corresponding stress and temperature distribution. This is calculated as a function of C* integral, KI, refσ and refε . STEP 12 – Compute the crack growth rates at time ti using the equations shown below.


Equations to determine Cc and µ are given in the code. STEP 13 – Compute the time step for integration at time ti using the equation shown below. An explicit time integration algorithm is used in this procedure. A value for the explicit time integration parameter that has been used is Cintg = 0.005. A sensitivity analysis should be used to qualify this value because it is a function of the creep strain rate and crack driving force. STEP 14 – Update the flaw dimensions ai and ci, and the accumulated at time in the cycle, ti.

STEP 15 – If the current time in the cycle is less than the total time of the cycle, ti < tk, then go to STEP 6 to continue to grow the crack. Otherwise, proceed to STEP 16. STEP 16 – If the component is subject to cyclic loading, then the increment the crack size to account for crack growth from fatigue using the equations shown below. Otherwise, proceed to STEP 18.

STEP 17 – If this is the last cycle in the histogram, go to STEP 18. Otherwise, set ti = 0.0 and go to STEP 5 to continue to grow the crack based on the next cycle of operation. STEP 18 – The crack growth prediction is complete for a location in the component. If another location is to be evaluated, go to STEP 3. If this is the last location in the component, evaluate the crack growth results. If the points on the FAD predicted during crack growth are all within the FAD failure envelope, then the component with the crack-like flaw is acceptable for future operation. The remaining life for operation can be determined by analyzing additional load cycles and determining the time at which the FAD assessment point lies on the FAD envelope.


If a point on the FAD predicted predicated during crack growth lies on the FAD failure envelope, then the life of the component is limited to the time corresponding to this point. If this time is less than the current operating time, the component should be repaired or retired.

9. Remediation For components that do not contain a crack-like flaw, if the component does not satisfy the creep damage creation within the required service life, or if the sensitivity analysis indicates unacceptable results, then remedial action is required. One of the following may be considered. Change In Service Parameters – a change in service parameters (load, temperature, desired service life) may be made and the assessment repeated either to demonstrate acceptance or to estimate at what time replacement will be necessary. Use Of Thermal Linings – conversion of existing hot-wall pressure vessel and piping systems to cold wall design that utilize a Thermal lining (i.e. refractory) have been performed. In these cases, the thermal lining is designed to reduce the metal temperature to a value below the creep regime thereby preventing future creep damage. For components containing a crack-like flaw, if failure by excessive crack growth is indicated within the required service life, or if the sensitivity analysis indicates unacceptable results, then remedial action is required, such as repair of the component or removal of the flaw. Alternatively, a change in service parameters (load, temperature, desired service life) may be made and the assessment repeated either to demonstrate acceptance or to estimate at what time repair will be necessary. Finally, it may be possible to obtain data on the material actually used in the component to remove pessimisms in the assessment resulting from the use of bounding data.


Documents

An Overview of the API Section 10