Coating Systems vs Cathodic Protection For Buried Carbon Steel Pipes (< 60 degrees Celsius) 1

[Timeyin]

Hi All,

I'm faced with a little issue and i'm really hoping you guys will enlighten me.

I've designed and routed an underground water pipe system (fire ring main) for a gas handling facility. A 10" header at 600mm from top of pipe to the finished ground level, distributes water to all the branch out.
My main issue here is with regards protective coating for the section of the pipe that will be buried.
I'm conversant with coating code LC4-N which involves the use of Epoxy Primer 2 coats of epoxy and a total minimum NDFT of 500μm. But my client is insisting that my specified coating system (LC4-N)be used in combination with cathodic protection. Quite frankly i'm not too familiar with cathodic protection systems and would try to avoid it as much as possible.

My question is - Is my specified coating system adequate to protect the pipe from corrosion?
Is my client right?
If yes, Which code/standard validates my client's point?
When is it absolutely compulsory to cathodically protect a buried pipe?
Which code/standard can point me to the right path.


I look forward to hearing from you guys.

 

[brimmer]

I'll give youi my experiences / code in Canada. I don't know what coating code LC4-N is, so can't comment. So for Canada, what is typically done is the fire water system, and all other piping is protected with a CP system (obviously all pipe is coated as well). The underground piping (gas) requires CP as per CSA Z662, typically plant piping is protected on a "flood" system, and the fire water piping is made electrically continuous with this system. It is not the coating standards which will tell you if you need CP, but the design/construction codes. In Canada it is compulsory to cathodically protect all underground pipe.

As far as whether that particular coating will protect in those particular conditions, I don't have details so can't comment but in general when you coat underground piping you will want to apply CP. The issue is what happens when the coating is damaged, has a holiday, degrades, etc? That particular area will corrode. As far as documents which explain, NACE RP0169 is good, lots of literature on coatings used in conjunction with CP.

I am a little surprised that gas facility does not already have a CP system you can just tie the fire water system into.

 

[Timeyin]

brimmer -

Thanks for your reply.

There is actually a CP system in place and the fire water system will tie into it.
I just wanted to know if CP wasn't compulsory for all buried pipes, depending on soil composition, type of coating or any other consideration.
Apparently, there isn't (based on my little research). I found NACE SP0169 really helpful.

Thanks alot.