Today there are only 30% of all metal reserves produced during the time of humanity existence. Other billions of tons had disappeared mainly by reason of corrosion. Economists in different countries always try to assess corrosion damage for national economy.
The main components of corrosion protection costs are anticorrosive protection cost, cost of replacement of corrosion-damaged units, loss from equipment corrosion fatigue and other possible crashes.
Technologies, providing equipment operating reliability, are in great demand in modern economics. These methods allow decrease of operating expense and increase of qualitative measures of equipment exploitation.
It is very important to provide underground anticorrosion protection in oil and gas industry.
As a rule, underground pipelines and other underground structures are protected from corrosion by insulation. Unfortunately, corrosion destructs insulation coating materials and electrochemical corrosion processes appear in defective zones.
Underground metal constructions have potential from -0,5 to 0,7V according to the soil properties. If the potential pipe-soil value can be decreased from -0,85 to -0,95V by means of cathode current, then corrosion speed would be significantly low.
In practice, power supply sources are located at large distance from each other and create small excess of potentials near a power supply source with decrease of potential difference with a distance. One cathode protection station allows protection of a pipeline of 1-10 km length, depending on the soil properties and pipe insulation condition.
You can see the video-clip where one cathode protection station allows protection of a pipeline of 1-10 km length, depending on the soil properties and pipe insulation condition.
Due to application of the cathode protection station, the service life of the pipeline can be extended to 30 years. Constructing and operation costs of the cathode protection station are small comparing to total costs. The ratio between the cathode protection costs (including periodic measurement of system operating parameters) and repair costs varies from 1:40 to 1:50. Due to its economical feasibility, the cathode protection stations became an integral part of the active oil and gas pipelines.
There are three types of ECP for underground structures:
There are three types of ECP for underground structures: Protector (A), Cathode(B), Electric drainage (C)
- pipeline;
- protector;
- anodic earthing;
- control-measuring unit;
- rail;
- cathode protection station;
- drainage protection installation.
Conclusion
ECP together with insulation materials protection are used practically in all cases. Thus, the ECP currents «cure wounds of insulation» appearing during the pipeline’s exploitation. Moreover, due to ECP, salt sediment forms in pores and fractures, filling all defects. Thanks to this compatibility, insulation materials in combination with ECP are used everywhere.
