Procedure for Installation of Cathodic Protection System

This article is about Procedure for Installation of Cathodic Protection System and focusing to the engineers, technicians and supervisors. You will find lot of documents related to this article.

Cathodic Protection System Installation Procedure

Following points to be followed on site before installing cathode protection system.

• All material received at site shall be inspected, handled and stored upon receipt in accordance with Project Procedure for “Field Material Control”.
• Installation inspections shall be conducted by the Electrical Supervisors and witnessed by QC Electrical Inspector.
• The cathodic protection system shall be installed in accordance with the project specification, manufacturer’s instruction and reference standard installation detail.
•  Preparation of required tools and materials necessary for the installation work.

Installation of Cathodic Protection Equipment

• Equipment shall be installed accurately with respect to their position, arrangement and directions.
• Lifting shall be carried out using properly tested and approved slings.
• After completion of installation the following points shall be checked and corrected if necessary.
• Check the level and alignment with the adjacent equipment are correct.
• Check if the doors can be open and close normally.
• Check if there is any damage to the paint coating.
• Check the anchor bolts and set bolts have been tightened.

Test Box Installation

1. Test box shall be installed in accordance to the approved detail drawings.
2. Test box foundation shall be check in conformance to the drawings prior to equipment installation. Concrete foundation shall be cured for a sufficient period of time. The concrete shall extend 150mm minimum above ground.
3. Steel support shall be hot dipped galvanized. It is set in concrete which shall completely cover the buried steel.
4. After installation of equipment; adjust their alignment and level.

Cathodic Cable Installation

1. Check the actual cable length. Cables shall be cut from the drums to which they allocated in accordance with the cable schedule and drum allocation sheet.
2.  In cable drum haulage, cables shall be rotated in the direction of the arrow.
3.  Cable laying shall be performed by individual cable being placed in orderly arrangement and/or bundle.
4.  Both ends of each cable shall be firmly sealed with insulating tape and/or other   sealing materials to prevent dust & moisture.
5. Sufficient length shall be provided for both ends of each cable in the measurement of cable lengths.
6. Sand filling, protection cover and backfilling work shall be conducted as early and promptly as possible.
7. Cathodic protection cables shall be properly identified before backfilling for later connection to the test points. Connection method must be referred to vendor drawings.

MMO Ribbon Anode & Reference Electrode Installation

A Mixed Metal Oxide (MMO) ribbon anode is a specialized type of anode used in cathodic protection systems to prevent the corrosion of metallic structures, such as pipelines, tanks, and reinforced concrete structures. MMO ribbon anodes are composed of a thin strip of titanium or other substrate material coated with a mixed metal oxide catalyst. This coating enhances the electrochemical reactions that occur during cathodic protection, making the anode highly efficient and effective in preventing corrosion.

The MMO coating on the ribbon anode consists of a combination of metal oxides, typically including oxides of metals like ruthenium, iridium, and titanium. These oxides possess excellent catalytic properties that accelerate the cathodic reactions and significantly improve the performance of the anode.

1. Check above ground tank foundation level. Refer to Typical Installation Detail for Tank.
2. Perform welding machine adjustment and test. Anode to Anode conductor bar to conductor bar anode to conductor bar. Ribbon to conductor, about 1 to 3 sec but to be changed depending on fixed condition. Power feeder continuity check. Electrical resistance between both ends of power feeder before installation.
3. Cut ribbon anode from reel to specified length that is shown on the relevant drawings.
4. Cut specified length of conductor bar. Required length is shown on the relevant drawings.
5. Laying of conductor bar. Verify material, spacing interval, overlap and installation. Spacing intervals vary depending on each tank to be protected.
6. Laying anode ribbon on conductor bar.
7. Spot welding at all cross points of anode and conductor bar. Verify spot welding, one spot weld at cross point between anode and conductor.
8. Install power feeder on Titanium conductor bar. Verify materials, installation and connection as per Vendor Drawings.
9. Connect power feeder cables outside of tank through 2”dia. PVC conduit. Secure wiring without tension and cable end with tag.
10. Power feeder continuity check before and after backfilling. Resistance between two power feeder shall have a value of 5 ohms or less.
11. The reference electrode are to be installed at the location specified on the approved construction drawing.
12. Soak pre-packed reference electrode into potable fresh water for 12 hours just before installation. Verify material.
13. Install reference electrode lead cable and power feeder. Verify material, size, location and level.
14. Installed pre-packed reference electrode. Verify installation and soil covering around reference electrode.
15. Connect reference electrode lead cable outside of tank through 2”dia. PVC conduit. Check wiring without tension and cable end with tag.
16. Potential difference after installation shall be checked. Verify material specification and potential difference using portable reference electrode.
17. Cable end treatment during civil work until wiring to junction box or test box.

Inspection of Cathodic Protection Installation

1.  During working period, inspection shall be carried out on insulation testing by suitable instrument on insulating joints before and after welding or fitting.
2. Soil and sand resistivity measurements of anodes and ground bed location.
3. Visual inspection of cathodic protection anodes and cables.
4. Visual inspection of transformer-rectifiers, test boxes and stations prior to installation.
5. Potential readings of permanent reference electrodes with respect to a calibrated one in the same electrolyte conditions prior to laying.
6. All cathodic protection removable links inside the accessible equipment shall be left open and no impressed current stations shall be energized without COMPANY’s approval.
7. Checking of all accessible cathodic protection equipment; their wiring, correct polarity (+/-), terminations and cable tagging.

Testing and Records

1.  All monitoring and measuring devices used shall be calibrated and have valid calibration certificate during the time of inspection as per Control of Monitoring and Measuring Equipment Procedure.
2. Quality records shall be prepare as per Inspection and Test Plan (ITP), inspect and signed by authorized Electrical Inspector for the completion of Mechanical Completion prior for Commissioning Phase.
3. All testing & inspection forms shall be developed as pre-requisite to ITP.

Some Definitions

• Aboveground storage tank: A stationary container, of greater than 500 barrel capacity usually cylindrical in shape , consisting of metallic roof, shell, bottom, and support structure where more than 90 percent of the tank volume is above surface grade.
• Anode: Refer to MMO ribbon anode. The electrode of an electrochemical cell at which oxidation or corrosion occurs.
• Backfill: Material placed in a hole to fill the space around the anode, vent pipe and buried components of a cathodic protection system.
• Cathode: Refer to structure / pipe. The electrode of an electrochemical cell at which a reduction reaction occurs.
• Cathodic protection: A technique to reduce corrosion of a metal surface by making the entire surface the cathode ofb an electrochemical cell.
• Electrochemical cell: An electrochemical system consisting of an anode and a cathode immersed in an electrolyte so as to create an electrical circuit. The anode and cathode may be separate metals or dissimilar areas on the same metal. The cell includes the external circuit which permits the flow of electrons from the anode toward the cathode.
• Electrode potential: The potential of an electrode as measured against a reference electrode.
• Electrolyte: A chemical substance containing ions that migrate in an electric field. Electrolyte refers to the soil or liquid adjacent to and in contact with the bottom of an aboveground storage tank, including the moisture and other chemicals contained therein.
• Impressed current: An electric current supplied by a device employing a power source that is external to the electrode system.
• Membrane: A thin, continuous sheet of non conductive synthetic material used to contain and/or separate two different environments.
• Rectifier: A device for converting  alternating current to direct current. Usually includes a step-down AC transformer, a silicon or selenium stack (rectifying elements), meters, and other accessories when used for cathodic protection purposes.
• Reference electrode: An electrode whose open circuit potential is constant under similar conditions of measurement.
• Structure-to-electrolyte voltage: (also structure-to-soil potential or pipe-to-soil potential): The voltage difference between a metallic structure and the electrolyte which is measured with a reference electrode in contact with the electrolyte.

Test station:

A small enclosed box –like housing and the usual termination point of one or more test leads.

Read Also:

1. What is Cathodic Protection System? Technical Guide for Engineers
2. Cathodic Protection Design Package Preparation SABP-X-001 Download
3. CATHODIC PROTECTION INSTALLATION DETAILS
4. CATHODIC PROTECTION INSTALLATION METHOD STATEMENT
5. Cathodic Protection Commissioning Reports