Refer to "Piping Systems for Chlorine injection" - Chlorine institute ...

https://bookstore.chlorineinstitute.org/mm5/mercha...;

It has been my experience that these systems are typically small diameter, (less than 2"NPS) and sometimes involve multiple injection points. Shedule 40S should be acceptable ...

That old Process chemical horse,.... C276 ......provides both internal and external corrosion protection.

MJCronin
Sr. Process Engineer

KSoon, if you are talking about the seawater piping after Cl injection then I would look at C276 also for that.
It usually does not cost much more than 625 and it has much better corrosion resistance in this environment.
There are many guides to handling seawater.
What part of the world is this?
https://www.nickelinstitute.org/media/3795/nickelp...
https://www.nickelinstitute.org/media/1724/materia...
https://www.nickelinstitute.org/media/1687/guideli...

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P.E. Metallurgy, Plymouth Tube

Agree with Ed ....

More information required ...

How much salinity or What type of seawater ? (low strength Baltic Ocean or high test Arabian Gulf ?)

Design temperature ?

What is the injection and Seawater Main Pipe diameter ?

Design flowrates ?

Will the seawater system have any periods of shutdown ? (you may want to consider some kind of purge)

MJCronin
Sr. Process Engineer

Is metallic piping a requirement? I see fiberglass piping used in this application on ships.

ISO 21457. EEMUA 194. Energy Institute Guidance on corrosion management in oil and gas production. Assume the question is related to breaking the 30 deg C threshold for super duplex stainless steel.

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

Thanks for you all kind inputs.

The piping system I mentioned above is located at the downstream of sodium hypochlorite injection.
GRP is not preferred due to the maximum velocity and pressure limitation.

The operating temperature is expected to be 35-45 degC, I just wondering the suitability of Alloy 625 in this application.

If referred the ISO 21457, it seems like C276 might be the best suit MOC.

Once again, thanks for all your kind recommendations.

Best regards,
KSoon.

Any time I see seawater I think Titanium. Apparently it resists corrosion from chloride solutions as well.

https://www.azom.com/amp/article.aspx?ArticleID=12...

TugBoat,
Yes Ti has great corrosion resistance, but ...
It is fairly low strength
It has a very low modulus (very flexible)
Field welding can be very difficult
And when you talking about large thickness parts it gets very expensive.

For very thin heat exchanger tubes and such it is fine.

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P.E. Metallurgy, Plymouth Tube

Normally, hypochlorite is injected into the low pressure end of the system ahead of the high pressure pumps. This piping would be a candidate for GRP. It is assumed that the question relates to the part of the system upstream of the deaerator, since deaeration will bring all of the usual players back into the equation, including carbon steel. For the aerated system, N10276 and N06022 are safe, but expensive, options: NACE Corrosion 2008, Paper 08251; NACE Corrosion 2016, Paper 7196.

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

Thanks for all the inputs.
May I know the temperature limit specified at Table 10 of ISO 21457 still applicable for the piping system downstream of vacuum deaeretor tower (with dissolved oxygen of 10 ppb)?
Cheers.

I think it depends on the category you will apply for.
If it is classed as "injection of deaerated sea water", table 7 is applicable. Although the controlled oxygen content(10 ppb) seems quite low but the oxygen content is to be monitored carefully, referring to clause 6.3.
On the other hand, if it is classed as "utility of sea water carrying system", table 10 is applicable. Based on my view, it does not mention any difference of material selection whether deaerated or not once it is chlorinated to kill bacteria.


Lee SiHyoung,

If it's deoxygenated to that level why not carbon steel?

Steve Jones
Corrosion Management Consultant

www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

Hi, to maintain the cleanliness of seawater the client is not preferred to use the carbon steel at the upstream of injection pump; downstream of the pump is allowed.