Cathodic Protection

[paipisan]

Dear All
During my recent CP Survey on Onshore facility, I found out the buried section of pipeline had almost reading to the above ground pipeline, differentiate only about 100-150mV. The facility is using ICCP System and monoblock is install between buried section of pipeline and above ground pipeline. Any idea how this may happened, as I suspected it was due to voltage leakage.

 

[LittleInch]

From the very limited amount of data you provide, either your monoblock has failed or more likely there is some connection on the buried side of the monoblock which is earthing your buried section (often a support or an earthed instrument) and lowering the potentials accordingly. Either that or your ICCP is not working properly.

Lots of possibilities but without some photos, plans, sketches, data etc it is difficult to say much more.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[paipisan]

Hai LittleInch
This area is having four season. The TR connected to this onshore facility located at 52KM away. The pipeline is buried under sand soil with high soil resistivity. Nearer to the TR (0 KM), the reading registered as -13++mV and nearing to the export facility (52KM), the reading increased around -70 to -120mV. The facility just recently been installed (year 2010). I can not upload attachment in PDF format to this thread, for clear understanding.

 

[LittleInch]

That sounds a long way away.

You can upload attachments via the ...or upload your file to ENGINERERING.com at the bottom of the posting box. Just click it and follow the instructions.

It does sound like you need more help than an forum can give you, but try and upload the information first.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[LittleInch]

I'm not a CP engineer so the results wouldn't make a lot of sense to me, but a lot more read this forum. I do know that the voltage reading needs to be relative to a Cu/CUso4 electrode and not the above ground pipe as your readings above look very odd.

The upload to engineering.com looks fine to me, so give it another go.

http://files.engineering.com/upload.aspx?referrer=http://www.eng-tips.com

Open the link, browse to where your file is on the computer and click upload

Don't forget to click the link on the last page and it appears on the bottom of your post.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[paipisan]

dear all
I conducted the survey as per normal practice, and had taken on on every Test Post (1 Km apart). On the 52km, I took the reading on the buried section and above ground section (with monoblock in between both section). The difference between buried section and above ground section was only around -100 to -150mV.