PL Risk Based Assessment

Date

The date in the header shows the last Internal/External Corrosion Assessment date. In the example on the image: Jan 1, 2007, for Internal and the last assessment date for External Dec 31, 2009.

Traffic Light

The traffic light's purpose is to draw attention to sections that are not going to reach their intended life.

RED → Less than 1 year remaining.

ORANGE → Less than 3 years remaining

YELLOW → Remaining life of more than three years but DesignLife/Required life is not going to be reached.

GREEN → DesignLife/RequiredLife is going to be reached or exceeded.

Remaining Life

The formula used to calculate the RL date Is: RL date = Assessment date + Remaining Corrosion Tolerance / FutureCR

In the first row of the Internal corrosion grid:

Assessment date = Jan 1, 2007

CT Remain = 0.76 mm

Future Cr = 0.07 mm/y

Remaining Life = Jan 1, 2007 + 0.76/0.07 = Jan 1, 2007 + 10.8 y = Nov 16, 2017

Note: If the CTremain is negative then the Remaining Life is calculated backwards using the past corrosion rate.

Start At

The rows are a cross-section of anything that can affect RBA outcome, including Corrosion Rate Assessment, Consequence, and Pipe Data sections.

Length

Past CR

The Past Corrosion Rate that was specified in the Internal/External corrosion module. It is used to calculate the wall loss from the Assessment date back to the last IP run or the Installation date or Date in service if the IP run is not performed.

See also column WallLoss.

Future CR

The Future Corrosion Rate was specified in the Internal / External corrosion module. It is used to calculate the remaining life.

Nom WT

The Nominal Wall Thickness of the section.

CT Defect

The minimum Corrosion Tolerance for that section based on Fitness For Service calculations on ILI run data. If the CT Defect cell is empty in the grid, then there are no Defects in that section.

Note that the ILI run should be before the Assessment date otherwise CT Defects are taken from the previous ILI run.

In case of a Dig-up or sample inspection after the ILI run, as specified in the FFS module, the coverage of the dig-up will override the defects in that section from a complete ILI run. So, if the pipeline is 3000 meters long and the ILI run was in 2015 and if a dig-up was after 2015 from 100 to 200 meters, then the Corrosion Tolerance from the Defects in the Dig-up will override the Corrosion Tolerances in the ILI run.

CT Int Morph CT Ext Morph

For a section (row) without Defects / Inspections, the Corrosion Tolerance is calculated based on the user-specified Morphology in the Internal and External Corrosion Assessment (this is also displayed in column Type).

See the picture below: the CT Morph is a line from (0,0) to the curve setting with:

• General corrosion: Length = 1000 * wall thickness

• Grooving corrosion: Length = 80 * wall thickness

• Pitting corrosion: Length = 20 * wall thickness

If there is no IP run, the user has to specify one of the following Methods in this grid:

• Original ASME B31.G

• Modified ASME B31.G

• DNV RP-F101 2010

• DNV RP-F101 2015

• DNV OSF (only available for Pipelines having Design Code “DNV OSF” specified in the Design Data.)

• API 1111 (only available for Pipelines having Design Code “API 1111” specified in the Design Data.)

CT Override

This column can only have a value if the MAT Override has been specified. For more details see appendix 1.

Wall Loss

The Wall loss from the Assessment Date to the last IP run or the installation or in-service date if the last IP run is missing.

Formula:

WallLoss = (assessment date-last IP run date) * PastCR or

WallLoss = (assessment date – Installation date) * PastCR (external corrosion)

WallLoss = (assessment date – In service date) * PastCR (internal corrosion)

In the example above the last IP run was Jan 1, 2016. So, for Internal Corrosion the Assessment Date – Last IP run date = 7 years. On the first row the Past CR = 0.27 mm/y then the WallLoss = 5 * 0.27 = 1.35 mm.

CT Remain

This is the Corrosion Tolerance Remaining (CTRemain) at the Assessment Date used to calculate the Remaining Life.

If cell CT Override has a value then:

CT Remain = CT Override – WallLoss

If cell CT Override has no value and CT Defect has a value then:

CT Remain = CT Defect – WallLoss

Otherwise:

CT Remain = CT Int Morph – WallLoss CT Remain = CT Ext Morph – WallLoss

LW

A warning, an L in this column means that CT Defect is less than CT Int Morph or less than CT Ext Morph.

Assessment Code

Method is from FFS if defects are found for the section, is user selectable if no defects were found.

Note: In case no FFS was carried out the you to select a method here!

Corrosion Morphology

Can be Grooving, General, Pitting or Defect Based. Grooving, General, or Pitting selection is read-only and has to be specified in the tab Corrosion Morphology in the Internal and External Corrosion Assessment phase.

Start At

The rows are a cross-section of anything that can affect RBA outcome, meaning Corrosion Rate Assessment, Consequence, and Pipe Data sections.

Length

Thickness

Nominal Wall Thickness of the section.

MAT Override

If the site has specified a MAT Override value then this value will be shown here. For more details see Appendix 1.

Defect ID

Empty for a section without Defects / Inspection. Otherwise the defect ID of the Defect with the lowest CT.

Defect Depth

Empty for a section without Defects / Inspection. Otherwise depth of deepest defect, including depth sizing accuracy.

MAT Defect

See Appendix 1.

CT Defect

See the description above in the RL and Integrity Status tab.

MAT Int Morph or MAT Ext Morp

See Appendix 1.

CT Int Morph

See the description above in the RL and Integrity Status tab.

CT Override

This column can only have a value if the MAT Override has been specified. For more information see the appendix

WallLoss

See the description above in the RL and Integrity Status tab.

CT Remain

See the description above in the RL and Integrity Status tab.

CT Defect msrd

The Corrosion Tolerance of the defect without in-accuracy added in the FFS calculation, the measured (msrd) defect depth.

CT Override msrd

The CT override without in-accuracy added.

CT Remain msrd

The CT remaining used the CT Defect msrd in the calculation.

Design Factor

The Design Factor for the section.

MAOP

The Maximum Allowable Operating Pressure.

Material Grade

The material grade of the pipe section.

SMYS / SMUTS

Specified Minimum Yield Strength and Specified Minimum Utile Strength for the material grade.

Remaining Life

RL date = Assessment date + RCT/FutureCR

Remaining life in this column is the reported RL (same value as in the Integrity Assessment Table tab in the right lower pane). It is the CT Remain from tab Corrosion Tolerance (thus including accuracy).

On the first row in the Internal corrosion grid:

Assessment date = 1-Jan-2015

CT Remain = 1.74 mm (see tab Corrosion Tolerance)

Future CR = 0.05 mm/y (see tab Corrosion Tolerance)

Remaining Life (in tab Intermediate Results) = 1-Jan-2015 + 1.74/0.05 = 1-Jan-2015 + 34.8 y = 28-Sep-2049

Remaining Life msrd

RL date = Assessment date + RCT/FutureCR In this column the CT Remain msrd is used for the calculation. Thus, the CT without adding the inaccuracy to the defects.

Remaining Life (NID)

The RL used for the NID calculation = max(RL, RL measured).

Assessed CR

The assessed Corrosion Rate is the average corrosion rate over the pipeline’s design life/required life based on the Past CRs from the degradation assessment and the Future CR from the degradation assessment.

Let’s assume the following example:

Install date = 1-Jan-1976

End of required life = 1-Jan-2020

Past CR 1-Jan-2006 = 0.01 mm/y

Past CR 1-jan-2007 = 0.08 mm/y

Future CR 2007 = 0.08 mm/y

Then

((2006-1976) * 0.01 + (2007-2006) * 0.08 + (2020-2007)*0.08 / (2020-1976) = 0.03 mm/y

CT General Morph

The Corrosion Tolerance for morphology-type general corrosion is used to calculate the Design Corrosion Rate.

Design CR

Design CR = CT General Morph / Design Life period.

For the first row Design CR = 1.99 / 30 = 0.066 mm/y

StF

Susceptibility to Failure factor = Assessed CR / Design CR This value is used to determine the Criticality.

Design intent

Using this option, the calculation of Susceptibility to Failure is based on the Design Life of the Pipeline. If the Design Life has passed, this option is not shown.

Interval Factor (IF) is determined from the following matrix:

Fit for purpose

Using this option, we don’t consider the Susceptibility to Failure. The Consequence of failure is used rather than Criticality of the failure. IF is determined from the following Matrix:

.

Extended Life

Using this option, the same approach as Design Intent is used with one major difference: the calculation of StF is based on the Required Life instead of the Design Life.

IF will be determined from the following matrix: