Materials & Welding: [MW:5713] Chloride stress Corrosion for SS316(For Sea Environment)]

Wednesday, June 23, 2010

[MW:5713] Chloride stress Corrosion for SS316(For Sea Environment)]

Hi Prakash,

I support the opinions of Kristian Lund Jepsen. If there is a choice , restrict the use of 300 series of Austenitic S.S in sea water environment due the facts:-

· It's prone to chloride SCC

· It’s prone to pitting.

Sometimes for 300 series of austenitic alloys both of the above damages go together and may cause premature failure. The typical CPT (critical pitting temperature) for 316 S.S is 20-25⁰C max under ASTM G-48 testing environment. Hence this alloy would always be a suspect at the temperature range 80⁰C.

For the temperature range of 80⁰C, the best choice should be:-

1. Super Duplex-2507

2. Superaustenitc alloy, 254 SMO

3. Superduplex 255 or Zeron 100—Both of these alloys may have availability issues ?

4. Duplex 2205.

Note : Selection of best alloy cannot ensure premature failures. To deal with such alloys as mentioned above one need to have good welding and inspection specifications.

If you use 316 S.S gasket on duplex piping or flanges, chances of galvanic corrosion and resultant crevices would always prevail, since 316 S.S is weaker of the two. The materials for gaskets should same as piping or flange material (duplex or 254SMO, whatever is chosen).

I have attached an excellent illustration on SCC of stainless steels in chloride media. Hope you would find this interesting.

Last of all if you want to follow the generic good engineering practices for offshore services, refer the Norsok standards. Below I have attached the link for Norsok M-630,piping materials standards and data sheet.

You may refer this document with your judgement to select the best materials for design in offshore environment.

Thanks.

Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Ontario Power Generation Inc.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

http://www.standard.no/PageFiles/15177/M-630d4r5%20090708%20.pdf

---------------------------- Original Message ----------------------------

Subject: RE: [MW:5709] Chloride stress Corosion for SS316(For See Enveronemt)

From: "Kristian Lund Jepsen (KUJ)" <KUJ@ramboll.com>

Date: Tue, June 22, 2010 9:53 am

To: materials-welding@googlegroups.com

--------------------------------------------------------------------------

SS316 shall not be used for seawater service at all. Also not if the temperature is only 20 deg. C.

You actually did not wrote what the fluid inside the piping is???

That is very important to give you an alternative, but duplex or super duplex is probably good alternatives.

The 60 deg C temperature limit stated in for example NACE MR0175/ISO 15156 is concerning risk of chloride induced stress corrosion just from the air in an marine environment - i.e. from the outside of the piping.

If your piping instead is in duplex or super duplex SS, the 316 gasket will be the weak part - i.e. it will be subject to galvanic corrosion and to some extend also crevice. Your spiral wound gasket or ring (for RTJ flange) need to be in duplex also.

regards

Kristian

________________________________

From: materials-welding@googlegroups.com

[mailto:materials-welding@googlegroups.com] On Behalf Of prakash kamathuru

Sent: 22. juni 2010 13:44

To: materials-welding@googlegroups.com

Subject: Re: [MW:5704] Chloride stress Corrosion for SS316(For Sea Environment)

Hi Babu\Bathula,

Thanks for your advices,

If i am using the SS316 Gaskets for Duplex steel and the temperature is 80 deg C,is it acceptable.

I am thinking that when gaskets are compressed the stress corrosion may not occur

Please give your feedbacks

Regards,

Prakash K B

On Tue, Jun 22, 2010 at 12:02 PM, Kathalingam Babu <kathalingam.qaqc@ppl.com.sg> wrote:

For the sea environment (Where sea water exposure or low flow

rates) SS316 will not be suggested.

Rgds,

K.Babu

----- Original Message -----

From: prakash kamathuru <mailto:prakashkbp@gmail.com>

To: materials-welding@googlegroups.com

Sent: Tuesday, June 22, 2010 5:49 PM

Subject: [MW:5700] Chloride stress Corrosion for SS316(For Sea Enveronemt)

Hi all,

Can any one advise me usage temperature for SS316L in offshore environment.

As for as i know it can be used up to 60 degc. But now i have temperature of 80 Deg C. If any one knows and have information abt this pls reply me.

And the same Case is Applicable for SS316 L RTG Gaskets also.

Regards,

Prakash K B

On Mon, Jun 21, 2010 at 7:06 PM, Sandeep Kp <sandeepkp99@yahoo.com> wrote:

Dear All,

I am going to conduct CSWIP 3.1 Examination on coming 05-july-10.

Any body have latest(2010) model questions of the same? or can advice any web sites.

Thanks,

Sandeep.k.p

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