PL Internal Corrosion Assessment

To open the Internal Corrosion Assessment module:

• Navigate to the Equipment Main Screen.
• Find your Equipment.
• Click on the Equipment ID.
• In the header of the applicable Equipment Details Page, click on the Internal Corrosionbutton.

The Internal Corrosion Assessment module consists of several sections. The first one is:

Internal Corrosion Assessment

The Internal Corrosion Assessment section is divided into five sub-sections:

 ECH

In this grid, an overview of previous Assessments will be shown.

 In the example below one Assessment was performed in Jan-2015.

The Indicator is colored based on the comparison of the Worst Future CR compared to the Design CR which has been calculated in the RBA module. The indicator is colored:

• Red: if the Worst Future Corrosion Rate is more than four times the Design Corrosion Rate or if the Past and/or Future Corrosion Rate is missing.
• Orange: if the Future Corrosion Rate is between one and four times the Design Corrosion Rate.
• Green: if the Worst Future Corrosion Rate is less or equal to the Design Corrosion Rate.

A black circle around the Indicator means the ECH has been Final Approved.

Note: The Condition date is the Assessment date that will be used in the RBA module to calculate the Remaining Life. 

Creating a New Internal Corrosion Assessment

To create a new Internal Corrosion Assessment ECH from this section:

• Click the Plus button.
• Enter the required data in the pop-up window.
• Click Save when done.

On the ECH Detaiils Page of the ECH you created, the "GENERAL" checklist will already be selected and under Actions performed "INTERNAL CORROSION ASSESSMENT" option will be set to "Yes". The Checklist section displays the Internal Corrosion Assessment Graph with the Sectioning section and Confidence Rating questionaire. 

Note: In case you do not see the sectiones mentioned above, on the ECH Details Page, in the Checklist section, under Actions performed click on the Grid button.

Adding Pipeline Sections to the ECH

Next you have to create Pipeline sections and add their Past and Future Corrosion rates and Corrosion Morphology type.  If there are previous Assessments, the Pipeline Sectioning will be copied from the last Assessment but the Past CR and Future CR have to be specified.

• On the ECH Details Page of the newly created ECH, scroll to the Checklists section.
• Click on the Plus button.

Click on the Plus button to create a new Section and add Past and Future CR.

• In the Start At field, enter the distance from the very start of the pipeline to where this section begins.
• In the Past CR field, enter the past corrosion rate for that section of the Pipeline.
• In the Future CR field, enter the future corrosion rate for that section of the Pipeline.
• From the Corrosion Morphology drop-down menu, select the applicable option. 
• Click Save.
• Repeat the process to add additional Sections.

Next, you will have to fill in the Confidence Rating questionnaire: 

• Click Edit.
• Tick the checkbox(es) next to the applicable questions.
• Enter a Comment if needed.
• Click Save.

Lastly, Final Approve the ECH.

Internal Corrosion Assessment Graph

The second sub-section contains a graph where Internal Defects are shown in blue.

Note: A maximum of 500 Defects will be shown based on the CT Ranking. 

Different Corrosion Rates are shown as described in the legend, for example, the Hydrocor BWC rate is represented by a blue line, and the Corrosion rate calculated from the ILI data (Long CR) is represented by a red one. The Specified Sections are shown as orange lines.

If you zoom to the red dots, then you will see a triangle with a length on the x-ax. This length corresponds to the nodes in Hydrocor. If there is no Hydrocor case available then the length is equal to the length of the pipeline divided by 2001 (the maximum number of nodes in Hydrocor). The height of the triangle is the maximum corrosion rate in this section. So, not necessary that the red dot at the height will correspond with a defect.

 

Corrosion Rate and Morphology Grid

The third sub-section contains a grid with the following parameters:

Confidence Rating - Internal

For the Confidence assessment, a questionnaire is provided. The user has to read carefully the statements made. The tick mark provided (or not provided) should be backed with arguments through the Comment option.

The Confidence Rating is calculated based on selected questions. The default Confidence Rating is Medium. There are five questions in total and upon checking the box for each question Confidence Rating changes.
The default/starting level is Medium, and the 1st and 5th questions are negative. The other questions are positive. Checking a negative question will lower the level of confidence by one class and checking a positive question will raise the level of confidence by one class. The levels are: Very Low, Low, Medium, High, and Very High.

The Confidence assessment is performed for the entire Pipeline, not per Section. In the Design data, the user specifies whether the Pipeline/Flowline is "Onshore", "Offshore" or both. For Internal Corrosion, the questionnaire is the same. For External Corrosion, different questionnaires are available if the Pipeline is Onshore or Offshore.

The Confidence Rating questionnaire for Internal Corrosion is thus the same for both Onshore and Offshore. See the explanations for the questions in the table below:

The Corrosion Morphology Plot

This chart shows three categories: Pitting, Grooving, and General.

If the Length of the Defect divided by the Depth of the defect is:

• less than 20, then the Defect is in the category Pitting.
• greater than 80, then the defect is in the category General.
• otherwise the category is Grooving.

The blue lines, L/d = 20 and L/d = 80 divide the graph into a Pitting, Grooving, and General area.

By clicking on a row in the Corrosion Rate and Morphology grid above, the Defects of that Section will be shown in the graph.

The Remnant Life Plot

The Remnant Life plot illustrates the Wall Thickness trends over time, featuring the Nominal Wall Thickness, estimated values at Assessment dates, Limit State, and the depth of the most severe defect found during inspection. 

In this graph, you can see:

• The blue dots represent the Nominal Wall Thickness, and the Estimated Wall Thickness at the Assessment dates.
• The red line shows the LimState if there are no Defects in the section, otherwise it shows the Minimum Required Thickness. 
• The red dots represent the Corrosion Tolerance based on the Defect.

The accompanying table presents the Assessment dates with their corresponding estimated Wall Thickness values and indicates the projected date when the Wall Thickness will reach zero.

Hydrocor

In this section, a new Hydrocor assessment can be started or edited and Hydrocor results will be shown. To learn more see Using Hydrocor Light

Hydrocor assessment

With the Hydrocor application, an estimation of the internal corrosion rate can be calculated.

After the assessment, the input parameters, which have been used in the Hydrocor module, will be shown in the grid. In the example below for 1-Jan-2015.

A new Hydrocor case can be created by
clicking on the + by clicking on the Hydrocor icon the application will be started.

Clicking the red cross x will delete the hydrocor case.

After clicking the + the following dialog will be shown:

The date should be the date of the hydrocor assessment. The Name is the case name. The default Application Level is by default Standard and can be changed into Expert or Expert plus if the user the rights in his/her profile.

After clicking the  icon, the web-Hydrocor application will be started and the following screen will be shown:

The graphs and the results in the output tabs are also visible in PLSS.

By clicking the button Back to internal corrosion (right upper corner) the application will go back to IMS-PLSS:

Notes: 

1. it is required to follow the Hydrocor training to use the full functionality of the application
2. in previous releases the Hydrocor date was the assessment date used in the RBA module to calculate the remaining life. From release 3.13B the condition date of the ECH will be used as the assessment date.

Hydrocor results

• The pane on the right side contains six tabs: Output Graph, Corrosion, Flow, Factors, Miscellaneous, and Inhibition.
  
  
  
  These tabs show the results from the Hydrocor calculations. They contain the same information as the output sections in w-Hydrocor. A description of these tabs can be found in the Hydrocor user manual.