Procedure: Monitoring and Reporting on Cathodic Protection Systems

Purpose. This procedure describes how technicians take, record and act on cathodic protection readings at test points, rectifiers and sacrificial anode beds on steel mains and facilities.

1.Scope

Cathodic protection prevents corrosion on buried steel mains, city gates and regulator station pipework. This procedure applies to routine monitoring, annual surveys and defect follow-up on every cathodic protection unit in the asset register.

2.Step 1: Prepare

The technician must download the schedule from the work order, check the calibration of the reference electrode and multimeter, and review the last readings for each test point so that changes can be recognised on site.

3.Step 2: Take readings

At each test point the technician must record the pipe to soil potential with the reference electrode placed on moist soil directly above the pipe. At rectifier units the technician must record the output voltage and current and check the enclosure, fuses and earthing.

• Pipe to soil potential at every test point
• Rectifier output voltage and current
• Anode bed current where fitted
• Physical condition of posts, cables and enclosures

4.Step 3: Assess

Readings outside the protection criteria in the network standard must be flagged as defects. A reading that has moved by more than 100 millivolts since the last survey must be investigated even if it remains within criteria, because it can indicate a coating defect, a foreign structure or an interference source.

5.Step 4: Record and report

Readings must be entered against the asset in the Network Asset Register on the day they are taken. Defects must be raised as work orders with a priority set by the Maintenance and Integrity Manager. An annual cathodic protection report must be compiled for the safety case review.

6.Step 5: Rectify

Rectifier faults must be repaired within 30 days. Coating defects must be excavated and repaired under a work order and the reading retaken after backfill.