[MW:7132] MW: 7127] Material for Sea water piping for Offshore environment.

 

Hi Prakash,

 

In a seawater environment depending the design requirements there’re a few choices. Cupro-Nickel is traditionally popular due to resistance to general corrosion, marine fouling, pitting and crevice corrosion. It’s a suspect in sulphide containing  environment. The other choices in terms of increased resistance to  general corrosion and  stress corrosion cracking would be :-

·        Conventional austenitic S.S-., 316L, 317L,or 317 LN up to  30⁰ C max, 904L would be slightly better compared to these alloys

·        Duplex series, workhorse duplex 2205, super duplex FERRALIUM® alloy 255 (UNS S32550),super duplex 2507 all are quite proven for offshore environments.

·        The next series would be super austenitic 6Mo alloys such as Avesta /Sandvik 254 or 654 SMO, or ALX-6N (Allegheny Ludlum).

 

The corrosion resistance of all of the above alloys in chloride media is expressed by this factor stated below. Higher is the PRE more is the resistance to chloride induced pitting and SCC.

 

1.     PREN = Cr + 3.3Mo + 16N

OR

2.     PREN = Cr + 3.3(Mo +0.5W) + 16N

 

Some of the above alloys may be more expensive than Cupro-Nickel but availability may be easier.

 

My feeling is that Carbon steel, whether bare or galvanized would have very limited life. FRP’s may be good for low temperature storage purposes  and have design limitations( as per API  15LR and 15HR) but for pipe work getting the desired level of quality as that of the above mentioned alloys  could be a suspect.

 

I’ve attached a generic good engineering document Norsok,M-001 for materials selection in offshore environment. Note this document is for guidance purposes only. Designer may have to make his/her own judgment call after discussion with the client.

 

I hope this would help you to arrive at a decision.

 

Thanks

 

Pradip Goswami, P.Eng

Welding & Metallurgical Engineer/Specialist

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

 

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of prakash kamathuru
Sent: Tuesday, September 21, 2010 5:57 AM
To: materials-welding@googlegroups.com
Subject: [MW:7127] Material for Sea water piping for Offshore enveronment.

 

Hi All,

 

Can any one tell me which is the best suitable material for Sea water application in offshore environment.Client specification shows Cu-Ni material,we are facing problem with procurement(Long lead time).So i am planning to replace it by Galvanized Carbon steel,Is it computable for Long term use.If any one have experience please share me.

 

I know we can use some FRP material,but still i want to go for metallic material.Please share me some of your experiences.....

 

Regards,

Prakash

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