CORR-RAD 

 ENGINEERING AND MARKETING

Pioneers in Pipeline Protection

Interference Mitigation  

Investigation shall be made for stray current electrolysis of the pipeline due to foreign pipelines / structures, high voltage DC lines and sometimes rectified grounded AC.

Measurement including pipe to soil potential, pipeline current etc. on the pipeline being cathodically protected shall be made to investigate the current discharge and collection locations.  

In case of fluctuating stray currents, investigation shall be made continuously over a period of time and if required simultaneously at different locations to find out the stray current source. Recorders shall preferably be used for measurements over a long period of time.  

Where a foreign pipeline, unprotected or protected by independent CP system runs in parallel to the pipeline in same trench or very near to the pipeline and is not bonded to the pipeline, then investigation shall be made of current discharge points on the pipeline.  

Mitigation measures depending on the type of interference shall be provided. These shall include installation of bond with variable resistor and diodes, installation of galvanic anodes for auxiliary drainage of current, adjustment / relocation (if possible) of offending interference source, provision of electrical shield etc.  

Bonding with foreign pipeline / structure as a mitigation measure shall be provided where the owner of the foreign pipeline structure ahs on objection. Otherwise, alternative mitigation measure shall be provided. Where bonding is provided for mitigation, the bonding resistor shall be adjusted for optimum value for minimum / no interference. Galvanic anodes installed as a mitigation measure shall be sized for the life specified for permanent CP.  

Voltage measurement shall also be made on the pipeline at an HT power line crossing to find out continuous induction of voltage beyond safe limits. In such a case, the installation of pipeline grounding through magnesium ribbon anode via surge divertor has to be checked and made all right.  

Close Interval Potential Survey  

This survey is carried over the entire length of the pipeline by computerized potential logging method to identify suspected holiday spots on the pipeline coating after the back-filling has been consolidated sufficiently and CP system has been stabilized.  

MONITORING :

The ICCP System shall have to be monitored by taking readings initially every week  for 3 months and subsequently on a monthly basis.