Scheme of Electrochemical Protection of Pipelines and Gas Pipelines with Extended or Distributed Anodes
When using traditional scheme of cathodic protection, protective potential is unequally distributed along the pipeline. As a result, excessive protection too close to the drainage point occurs or, in other words, a significant electricity loss happens, and protection zone installation declines. Such a drawback could be eliminated by using scheme with extended and distributed anodes.
Scheme of extended anode application (pic. 2.10) is using special cable type anodes which consist of metallic conductor (wire). It is covered with special electroconductive elastomer coating. The process of using such anodes that are laid over the entire length of the pipeline, is considered to be the most rational.
Pic.2.10. Technological scheme of the ECP system, using extended anodic earthing
1 - the 10 kV overhead line,
2 - mast station cathodic protection with low power transducer,
3- control and measuring column,
4 - extended anode earthing (grounding),
5 - pipeline,
6 - controlling output from the pipe.
Technological scheme of the ECP system, using extended anodes increases the length of the protective zone and facilitates an even distribution of protective potential, unlike the scheme of the cathodic protection with lumped anodes.
Along with using such scheme of electrochemical protection of distributed anodes, other schemes of anode earthing layout can be used as well.
The simplest one is the scheme of anodic earthings that are evenly installed along the pipeline (pic.2.11).
Pic.2.11 Technological scheme of ECP system with anodic earthings that are evenly distributed along the pipeline.
1 - transducer of cathodic protection installation (CPI),
2 - - air line of direct current (DC),
3 - adjusting resistors,
4 - anodic earthings,
5 - pipeline that is being protected,
In most cases, it is recommended using the following combining scheme – anodic grounding and additional grounding in places of protective potential “fails” (pic.2.12).
Pic.2.12. Technological scheme of ECP system with combining allocation of the anodic earthing.
1- basic concentrated sacrificial anode,
2- additional allocation of the anode grounding in place of protective potential "fails",
3 - adjusting resistors,
4 - installation of cathodic protection,
5 - air line of DC,
6 - pipeline that is being protected.
Setting and regulation of protective potential is achieved through change of the anodic grounding of the current using adjusting resistance or any other device that provides a current change in the desired range.
ТMoreover, during the process of implementation of schemes of many grounding earthings, protective current can be regulated through adjusting the number of switched-on earthings.
Most often, earthings that are closer to transducer have greater transfer resistance.