Re: [MW:14475] Sulphide Stress (SSC) and Chloride Stress Cracking (CSC) corrosion requirement

Dear Govindan,

The SSC/SCC test environment is not going to change for both 12" x 8.38mm and 4" x 3.05mm materials,

You can try to justify your stand point by the following exercise,

1. Compare your pitting and crevice corrosion test results and see which has given the best result.
2. Check the heat input and interpass temp.recorded on the respective PQRs for 12" x 8.38mm and 4" x 3.05mm materials, which one has recorded the lowest.
3. Check your base material chemistry from the test certificates and calculate the PREN values for both 12" x 8.38 and 4" x 3.05mm materials, particularly check the N% of 4" x 3.05mm material, if its higher than 12" x 8.38mm material then it is better.

If all the above comes out positive for the 4" x 3.05mm material then there is a good chance that 4" material will perform better in your SSC/SCC testing.

Finally if TM0177 doesn't permit for 3.05mm thick, ask you client for the code / standard reference for conducting SSC/SCC testing on 4" material and acceptance criteria for the same.



Regards,

Praveen


--- On Tue, 6/5/12, perumal govindan <perumalgovindan@gmail.com> wrote:

> From: perumal govindan <perumalgovindan@gmail.com>
> Subject: [MW:14464] Sulphide Stress (SSC) and Chloride Stress Cracking (CSC) corrosion requirement
> To: materials-welding@googlegroups.com
> Date: Tuesday, June 5, 2012, 10:13 AM
> Dear Experts,
>
> Please clarify the below mentioned particulars,
>
> we have carried out a SDSS PQR with 12" Dia. x 8.38mm thick,
> matl.
> grade: ASTM A 928 Cl.1 (UNS S32760), thickness qualified
> range: 8.38mm
> to 16.76mm - carried out corrosion tests (like, pitting,
> crevice,
> chloride stress and sulphide stress), all physical and
> chemical tests
> are passed.
>
> Hence for covering the thickness range, we have also carried
> out a PQR
> with 4" Dia. x 3.05mm, matl. grade: ASTM A790 (UNS S32750),
> qualified
> thickness range: 1.525mm to 6.1 mm. Here we got stuck up due
> to
> Sulphide stress (test as per NACE TM-0177)and chloride
> stress (test as
> per ASTM G-36) due to lower specimen thickness. As per NACE
> TM-0177
> the minimum reqd. thickness for sulphide stress corrosion
> test is
> 3.81mm.
>
> Now my PMC/Client is insisting to carry out the SSC
> corrosion test
> also in 4" Dia. x 3.05mm PQR test coupon. (Filler wire used:
> ER 2594,
> same batch & Lot Number used also in 12" Dia. x 8.38
> mm)
>
> Hence, kindly advise me that whether SSC test is required
> for the 4"
> Dia. specimen or not.
>
> Thanking You.
>
> Govin
>
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