Cathodic protection of in plant piping

[midris]

Hello all,

A requirement has been raised in the operating company I work at for impressed current cathodic protection of buried carbon steel piping which has begun to corrode rapidly in recent years.

The FEED study has been awarded to an EPC contractor for proposing the most suitable impressed current system design, and the proposed design was a distributed close CP system utilizing MMO canister anodes. The piping will also surely be recoated.

My concern is, that since the buried piping runs in concrete trenches and is backfilled in soil. With the anodes installed outside the trenches, will the concrete not act as a form of isolation thereby rendering the CP system useless? Furthermore, will this not lead to large amounts of stray current to surrounding plant structures?

In the past, I have dealt with such piping being protected by sacrificial magnesium ribbon anode buried inside the trench and in very close proximity with the piping.

It is quite a lengthily post, and I would greatly appreciate your valuable input as always.

Thanks,

 

[midris]

I would also like to add that I have considered the option of replacing the impressed current distributed close system of MMO canister anodes with MMO ribbon anode but the deterring factor is the very large scope of UG piping which is around 2 kilometers in length in total and I was thrown off by the cost. However, this is considering my concern with canister anodes and whether it is valid to begin with.