CATHODIC PROTECTION – SURVEY
Preliminary Surveys required before design of Cathodic Protection System :
To firm up a Cathodic Protection System Design certain data is absolutely necessary to estimate the bill of materials for an effective C.P. System. For this purpose we need to carry out preliminary surveys like :
SOIL RESISTIVITY SURVEY
The Soil Resistivity Survey gives us an idea of the corrosivity of the soil.
PIPE TO SOIL POTENTIAL SURVEY
The Pipe to Soil Potential Survey reveals the extent to which the pipelines are prone to corrosion.
CURRENT DRAINAGE SURVEY
The Current Drainage Survey projects the estimated current required to protect the pipeline effectively. Once the protective current required is known then the number of Transformer Rectifier units, weight of the Anodes, Cable lengths etc. can be worked out.
It is essential that the above mentioned surveys have to be carried out before designing the Cathodic .Protection System
The Soil Resistivity Survey is generally carried out by 4 Pin earth resistivity meter as per Wenners Four Pin method.
Natural Pipe to Soil Potential Survey is done with Standard Cu/CuSO4 reference electrode at test points and other locations where metallic contact with pipeline is possible for making above ground connection with voltmeter.
Current Drainage is generally done by impressing a direct current to the pipeline and measuring the results. This forms a basis for estimating C.P. current density and the numbers, locations and size of Transformer Rectifier Units.
After carrying out the above mentioned surveys, Survey report and recommendations and a detailed proposal is made for Design, Supply, Installation, Testing and Commissioning of Cathodic Protection System for your piping is made.
Underground pipeline can be saved from future leakages only by providing Cathodic Protection System with a design life of 20 years or more.
Cathodic Protection System shall be effective only for underground pipelines and not for any above ground pipeline or structures.
Thus if Cathodic Protection System is provided at an early stage it will ensure that the piping does not get corroded during itsdesign life.