Cathodic protection system for underground pipeline 1

[hoangvantan]

We are installing a 2km 4" ASTM â Gr.B Denso tape Coated pipeline under a high resistivity soil 500ohm.m(measured in dry season). we submit the calulation to Client and recoomended that the CP is not needed because the pipeline wall thickness is 6.02mm (calculation shown that only 2mm is enough) and the pipeline is coated already (pipeline is design for 10 years), Client is not satisfied due to the following reasons:
- CP is required for buried pipeline as required by ASME B31.8 and NACE standards.
- Soil resistivity in rainy season is not available and the CP may needed.

Could anyone suggest the suitable CP system to be installed (the pipeline is installed in a Industrial zone and land acquisistion is problem)

 

[EGT01]

To add to your client's reasons...
If you are dealing with transport or distribution of a hazardous material, some extra insurance makes sense. Besides, coatings and the application of the coating will likely not be perfect. Even if the coating is shop applied perfectly, there is always the chance of the coating getting damaged either as the pipe is delivered to your site or as you are installing the pipe and that is beside any coating that has to be applied on site such as at your pipe joints. You may want to consider spark testing the pipe coating before burial.

It has been some time since I've worked with cathodic protection on pipelines but I think there are only 2 basic types of systems, either impressed current or sacrificial anode. Forgive me if I sound critical, but I find it odd that you are able to advise your client that cathodic protection is not needed and not be aware of these two basic systems. Do yourself and your client a favor and get someone experienced in underground pipeline corrosion control and cathodic protection systems involved with your project.

In the meantime, here's a link to one cathodic protection system provider that has some good info, I'm sure you could find others.

http://www.cpdesigncenter.com/

Offhand, if your electrical current requirements are not large, then you should be able to accomplish what is needed with a sacrificial anode system. This type of system can be installed in the immediate vicinty of your buried pipeline and does not require the additional space that an impressed current system would.

 

[EGT01]

To add to my last post, be sure to check with your client, they may already have some company specific standards for cathodic protection of buried pipelines.

Also, as a matter of trying to re-educate myself on the subject, I found some really good references on the internet.

http://www.piping-toolbox.com/51.html

They provide a link to an US Army Corp of Engineers manual, EM 1110-1-4008. That manual references some other US government type engineering guides that really seem to cover the subject well.

http://www.usace.army.mil/publications/armytm/TM5-811-7

http://www.keesler.af.mil/A76pubs/A...s, Manuals and Pamphlets/Mil HDBK 1004_10.pdf

 

[ScottyUK]

Another site with some useful information if you dig around a bit into the materials & products

http://www.corrpro.com/Default.htm

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