Articles Corrosion protection from pipeline corrosion: equipment, operating principles

Corrosion protection from pipeline corrosion: equipment, operating principles

Cathodic Protection Stations and other devices to fight against the corrosion extend the metal construction service life and preserve its technical and physical properties. Efficiency of protective methods depends on both the protective technology quality and application conditions. Cathode-based devices appear to be the best in preserving the metal constructions.

Operating principle

Cathodic protection against corrosion works as follows: negative terminal of outer power source is connected with an object, for example, a steel or copper pipeline, as a result cathode is polarized, its potential becomes anodic. This helps to reduce the corrosion of the protected object to the lowest level.

Equipment

A corrosion-protected method for the underground constructions employs special equipment - stations within the overall facilities to maintain the pipelines. Cathodic Protection Stations (SKZ) is a constant source of current for a metal object. This equipment is used in water-, gas-, and oil pipelines, heating systems. SKZ consists of the following units:
  • current converter;
  • anodic ground electrode;
  • cable for the connection with a protected construction.
The stations are divided into transformer-type and inverter-type ones. Transformer-type stations are believed to be obsolete with a cathodic protection thyristor converter or low-frequency transformer being the basis for them. Pulse-displacement capacity controller or more functional controllers are used to manage the thyristors. Transformer-type devices adjust the voltage readings, to level off the protective potentials. Their disadvantage is a high pulsation rate for output current at a low power coefficient. Inverter-type stations are believed to be more cutting-edge with pulse high frequency converters. They are known for their high efficiency coefficient of 95 % vs 80 % for transformer-type units. Inverter-type stations are characterized with a number of advantages, such as being compact which makes them convenient for usage in challenging areas. These units pay back quite fast and require minimum investment into their maintenance. Cathodic Protection Device is supplied in different bodies, dimensions and forms. Adequate evaluation of the characteristics in accordance with the parameters of the protected unit optimizes the costs on equipment installation, storage and transportation.
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