Protection of underground RGS conduits protection due to stray current corrossion

[kkmaj1948]

In rail transit industries, stray current related corrosion is predominant. NEC is silent (or suttle about it) in a way that Authority in Jurisdiction can decide the need for protection against corrosion of RGS (Rigid Steel Conduits) or other underground metallic infrastructure near 3rd rail (the one carrying DC 650 volts power for train traction).
I know underground storage tanks are usually coated with corrosion resistant tapes/paint, or encased in concrete.
Many Transit systems 9NYCT, etc.) require all underground conduits in concrete encasement as a sound engineering practice.
Do you know of any standards/code, etc that may insist on such requirements? If not, why not? Why NFPA 130 addresses such requirements.

I would appreciate input from forum

Thanks.

Kaushal

 

[petersonra]

I think this is more of a design issue than a code issue, which may be why it is not directly addressed. Other NFPA standards are more design oriented and might address it.

About the only thing that you could look at in the NEC is some general requirement to provide corrosion protection where it is required. But, whether it is required, and what you actually do to provide that protection is really a design issue.

I don't see requiring UG conduits to be in concrete in general to be a sound engineering practice. It probably makes sense in certain cases where you may desire additional protection for the conduit beyond what being buried provides. As additional protection in the event of a derailment or similar incident it might well make a lot of sense.

I don't know if being encased in concrete provides much in the way of additional protection against this type of corrosion or not.

 

[mgookin]

Codes are first and foremost for protection of life, and a very far second, for protection of property.

If it's not a safety issue, it's not likely to appear in code.

 

[kkmaj1948]

I know for fact that the concrete encasement provide additional resistance to stray current. Other acceptable practices are bitumenous paint coating, or similar tapes. Most of the traansit industries have incorporated in their standard specifications. Underground pipes or storage tanks in some areas where they find stray current, isuch applications is comon practice. The issue is, I don't know why it is not considered in any of the codes (NEC, NFPA 130, ANSI, etc.) - is there one!!

 

[petersonra]

I know for fact that the concrete encasement provide additional resistance to stray current. Other acceptable practices are bitumenous paint coating, or similar tapes. Most of the traansit industries have incorporated in their standard specifications. Underground pipes or storage tanks in some areas where they find stray current, isuch applications is comon practice. The issue is, I don't know why it is not considered in any of the codes (NEC, NFPA 130, ANSI, etc.) - is there one!!

As I mentioned in a previous post, I don't know if concrete encasement provides additional resistance to this type of corrosion or not. I just do not know. I do know that it is common in at least some places to coat steel conduit that is encased in concrete in the belief that the concrete is itself somewhat corrosive to steel conduit. I also do not know whether concrete is itself corrosive toward steel conduit.

As I also mentioned, the whole issue of corrosion seems like a design issue to me and thus not one for the NEC to deal with. It is somewhat analogous to selecting the type of enclosure to be used. For instance, all kinds of enclosures are suitable for general purpose use indoors. How you come to select a specific one is a design choice.