8 replies to this topic

[Zauberberg]

Please refer to the NACE MR0175 standard as I remember it gives the definition off SCC/HIC conditions (pH vs. H2S partial pressure), including guidelines for material selection.

[chemsac2]

HIC is independent of stress and hence can not be alleviated by doing PWHT alone. To avoid HIC, you have only two options:
- Select parent material as per requirements (limitations on S, P etc in parent material)
- Or test selected material to see if requirements are met (crack length ratio, crack thickness ratio etc as per NACE TM 0284)

As against this, probability of SSC can be reduced by PWHT/stress relief/limiting hardness to 22 HRC etc.

Note that although HIC is independent of stress, another phenomenon of SOHIC (Stress oriented HIC) depends on stress concentration and steel needs to be stress relieved to avoid SOHIC.

Appendix A of API 945 gives good information on SSC, HIC and SOHIC mechanisms and ways to counter them.

Regards,

Sachin

[vittorio6]

If you are in Oil&Gas upstream sector then you've to refer to the ISO 15156/NACE 0175 while if you are in a refinery you've to use the NACE MR 0103. Based on the partial pressure of H2S and pH of the fluid there are 4 different "regions" with different level of severity in terms of material requirements. Also HIC can occur at partial pressure of H2S below the threshold for SSC.

material selection oil & gas

http://www.documenta...rrosion2004.pdf

http://www.techstree...duct_id=1148365

Vitt

corrosion prevention

[Zauberberg]

Nomi,

See attached file, I believe it will be useful to you.

Attached Files

•  Stress Corrosion Cracking.pdf   675.5KB   102 downloads

[breizh]

Hi ,
May this booklet offer you some help :

http://www.ssina.com...ons/design.html

Hope this helps
Breizh