CP on Pipes and Tanks

For Cathodic Protection (CP) systems to function properly, they should be inspected, monitored and maintained frequently. For this purpose, a Potentials / Anode Inspections / RF Inspections section, for capturing CP data during an inspection, can be enabled on the PEI Equipment Details Page (the available sections will depend on the type of Equipment). 

For Equipment of Type "Pipe", "Piping System", "Vessel", and "Tank" you can enable the Potentials section. Here you can enter the measurements on the CP Survey data tab and then view and analyze the data on the CP Potentials graph and the CP Potentials map tabs. The CP data can also be approved here. 

The Potentials section on a Pipe Equipment.

Note: Anode Inspections and R/F Inspections are recorded on Rectifier Equipment.

Enabling the Potentials section

Normally the Potentials section is hidden. To enable the Potentials section:

• Go to the Equipment's Details section.
• Click Edit.
• Check the Has Cathodic Protection box. Note: You can also check the Has Cathodic Protection box already when creating the Equipment.
• Add the Rectifier(s) if applicable (for impressed current CP) . Note: You will be presented with Equipment from the Equipment Group: "CP Rectifier" to select from.

Rectifiers can be defined in IMS with Equipment Group: CP Rectifier.

• Click Save. 

An Equipment with Cathodic Protection enabled.  When you have added a Rectifier or Potential data, then this checkbox will become disabled, i.e., you will not be able to remove the Potentials section any more. If you want to remove it, you will first need to delete all data in the Potentials section and remove all Rectifiers.

Recommendations

The objective of Potential measurements is to determine the actual Potential at the Structure-to-Electrolyte (soil, water, etc.) interface with respect to a reference electrode, such that the effectiveness of CP can be assessed. We advise that the Structure-to-Electrolyte Potential measurements should be performed according an applicable standard, e.g., ISO 15589, NACE SP0169, or NACE TM0497. The voltmeter positive terminal should be connected to the structure, and the negative terminal to the reference electrode.

Instruments should be checked for accuracy before use, by comparing readings to a standard voltage cell, to another acceptable voltage source, or to another appropriate instrument known to be accurate. If an instrument is insufficiently accurate, the instrument should be recalibrated.

Reference electrodes should be positioned as close to the structure as practical.

When recording Potentials inside tank dike areas, etc. you should ensure the area is safe before operating a voltmeter and making connections to measure Potentials.

For routine CP Surveys, where tanks have either permanent reference cells or access tubes, we recommend at least one under-tank Potential should be recorded. For Aboveground Storage Tanks (ATS), it’s recommended to take Potential readings in all 4 quadrants (rim). It’s not recommended to take Potential readings on ASTs that are empty.

CP Survey data Tab

A CP Survey is a detailed assessment of the CP protected Equipment to determine the performance of the installed CP system. Included in this Survey is the Potential measurements. These are Structure-to-Electrolyte Potential voltage measurements along protected pipes and structures (On / Off Potentials). At some sites, the measurements of the Off Potentials may not be practical due to the amount of Rectifiers or other factors. In these cases the sites can develop a study to determine the IR drop affecting their structures. The interruption of the Rectifiers should be systematically evaluated to assure the Off Potentials are polarized Potential readings. 

Representative Potential measurements should be obtained for each CP system.

Manually Capturing Potential Data

To manually input a new measurement:

• Scroll to the Potentials section on your Equipment Details Page.
• Click the plus button.

Click + to capture a Potential. 

• Select a Data point. Note: From here you can also create new points or edit or delete a point.
• Enter the Inspection date (mandatory).
• Enter the On and Off Potentials (in Volt). Note: For Tanks you will have four points for each - North, South, East, West.
• Enter the Native Potential. The Native Potential will be used to calculate the Polarization. Note: For Tanks you will have four points - North, South, East, West.
• You can also add Comments and a Forward plan.
• If the selected Data point has an Isolation Kit (see Creating Potential Data Points), then also fill in:
  • Isolation - check either Acceptable or Shorted.
  • On Potential (in Volt). 
  • Off Potential (in Volt).
• Click Save.

Note: If later you decide not to include this measurement in the analysis, you can edit the record and check Omit. 

Defining New Potential Data Points

To add a new Data Point:

• When adding a Potential, next to Data point click on the plus button. 
  Click + to create a new Data Point.
• Add a Description.
• Check Isolation Kit if applicable. Note: In this case you will also be able to capture Potentials On and Off for the Isolation.
• Enter (or select) a Longitude and Latitude.

Click the location button to select the Longitude and Latitude on the map. 

• Enter an Altitude in meters.
• Click Save.

Bulk Importing Potential Data

You can also import the measurements in bulk. To do so:

• Go to Settings\Data Transfer\Import Data.
• Download the desired CP Potential or CP Potential for Tanks template.

Download the applicable template. 

• Fill in the template.
• Select the desired import and click Browse to upload your template.
• The Import Wizard will guide you further.

CP Potentials graph Tab

This tab provides a graph of the captured data. You can use this for further analysis of the Potential data.

You can either view the Potentials for all Data points plotted over time, or check the Graph for potentials box, to view all Data points Potentials on one selected date.

Check the Graph for potentials box, to view only for a specific date. 

The -0.85V line will always be shown as a reference.

CP Potentials map Tab

On this tab you can see the Data points mapped according to their Longitude and Latitude.

Approving the Potential Data

When done, you need to approve the Potential data:

• Open the CP Survey data tab.
• Click the Approve button.

Click Approve.

Note: Whenever you add new data, you will again need to Approve the measurements.

For more information see IMS Approvals.  

CP Barriers

You can also define the CP Barrier (per Component-Degradation Mechanism) in the Corrosion Loop. Here you can set the Barrier Status as well. See Defining Barriers (and linking to IOWs).

An Impressed Current Barrier defined on a CL.