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Cement Lining for Seawater application 1

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Weko

Materials
Feb 28, 2011
48
Dear All,

I would like to know the mechanism how Cement Linning protect Carbon Steel from seawater corrosion. As I know, cement should have porosity. And through year the chloride content in the porosity will rise up, accelarating the corrosion? So what would be the estimated deign life time of the CS Cement Line piping?

Is Cathodic protection used in the CS Cement Line piping? Recently I've visited an old Exxon Mobile LNG train plant, probably built in the 1970' to 1980'. On the surface of the pipe, they installed a "Rod" and a "Bracelet" (please see picture in the attachment). A vendor told me that the "rod" is used for cathodic protection and the "bracelet" is used to anticipate Thunder striking to the pipe. But I'm still not sure about it. Since nowdays, I don't see those "rod" and "bracelet" installed in the Cement Lined pipe.

And regarding the the cost of Cement Line vs FRP. Which one is cheaper considering the bulk material cost and installation cost. Some said that bulk material, cement line is cheaper. But installation cost is higher, which come fromhandling of the cement line pipe would be difficult, since the cement line tends to crack if the handling sub-contractor / vendor is not good.

Thank you


Regards,
Weko Abhinimpuno
 
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for some reason I couldn't view your image. In any case, advanced search of the archives of all these forums by keywords as well as F.W. Lea's Chemistry of Cement and Concrete book may be helpful references. I believe depending on operational characteristics cement mortar linings have a generally quite successful service history for carrying most waters, including many theoretically quite aggressive like sea/saltwaters. While you are correct various degrees of quality and application of cement mortar linings have various degrees of porosity or permeability (as frankly do to at least some degree also most polymeric etc. materials used for pipe or coatings/linings), the cement lining is generally some thicker than traditional polymeric paints or coatings and in general it is quite probable the leaching or corroding activity becomes sort of self-stifling, as the pores in the lining in essence becomes plugged with rather minor corrosion and/or dissolution products (see . With regard to some of your other questions, I believe that the well-known city of Hong Kong has decades of experience with an extensive salt water flushing and fire protection systems, and I believe many of its most critical supply lines are cement mortar lined (e.g. see mid-latter part of specs at
See also that in the discussion thread at
relating also to sea water service, respondents to that thread mention that "cement lined pipe is very reliable" and also "our main cooling water line which is cement lined pipe in service for about 50 years". It appears one potential problem area of cement lined carbon steel systems, if same have areas left bare for field-welding, is that such areas have for whatever reason not gotten lined or lined with as good a quality patch application as factory spun lining elsewhere.
I am personally aware of other sorts of aggressive water lines wherein cement mortar linings in other sorts of pipe materials have in fact serviced for more than 90 years. While I suspect cement lined pipes are not entirely problem free, I'm not sure any paints, and for that matter even very few piping materials can claim such a proven durability record! Have a good weekend.
 
There appears to be no electrical connection to the rod and bracelet arrangement which would imply that it is not for provision of cathodic protection. It is also doubtful that it is serving as a surge diverter for lightning strikes. Perhaps it is simply a mechanical stabilisation device?

When considering the cost comparison of GRP with the cement lined pipe, it may be more useful to think in terms of total lifecycle cost. The GRP is likely to be more expensive but, when correctly installed, will have much lower maintenance requirements. If the line is buried, the GRP will not require external coating or cathodic protection. Each material will have its own installation difficulties and it is quite easy for inexperienced contractors to have trouble with either.

Steve Jones
Materials & Corrosion Engineer


All answers are personal opinions only and are in no way connected with any employer.
 
I was able to view image today. What I saw was some exposed what appeared to be painted/coated steel piping, most of which was weld fabricated and also had welded joints. While I do not know exactly what has been called "bracelets" and "rod" for the purposes hypothesized, I did see two what appear to be bolted, stuffing-box type flexible sleeve couplings on the lengths of upper piping (ala' Dresser, Smith-Blair, Romac et al?). Such are typically not "restrained joint" couplings, that can withstand unbalanced pressure thrust from e.g. adjoining bends, so it appears the designer and/or installer welded lugs on adjoining pipes and restrained "across" these two couplings with threaded/bolted restraint rods, likely one each side?
While like Mr. Jones I did not see anything in the image that smacked of thunder or corrosion arresters (other than the coating for the latter), I hope this information helps in understanding.
 
what?? corrosion and thurderstrike ?? That is just tie rod for expansion joint ! It has a pair. The other one at the far side.
 
Thanks for the answer.

For the "rod", I agree that it seems to be installed for mechanical purposes. Altough I am courious why using the "rod". Since the temperatur of the pipe is ambient. So expansion seems will not be an issue (?)

As for the "bracelet". I think is not used as mechanical purposes. I attahed, a more clear picture that they installed many of those "bracelet".
 
 http://files.engineering.com/getfile.aspx?folder=71d42229-7569-4bd2-92bd-fc0c65acf87b&file=Bracelet.JPG
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