SOUR Service chemical composition restriction and NACE ISO 15156-2 Option 1 selection 1

[svi]

Many Company Spec includes a restriction on the chemical composition of the steel. A typical one is like this C 0.2 wt %, Mn 1.3, P 0.01, S 0.002, Si 0.4, Cu 0.4, Ni 0.4, Cr 0.3, Mo 0.12, V 0.015, Ni 0.015, Ti 0.02, B 0.0005
A Carbon equivalence CE = C + Mn/6 + (Ni+Cu)/15 + (Cr+Mo+V)/5, limited to 0.43.

NACE ISO 15156-2 allows selection of pre-qualified material through option 1 for SSC zones 1,2, and 3.
Does not the above restriction of the determination of the CE for material selections apply only to those selected through option 2?
In other words, if a recommended material specification and grade is selected through option 1, a verification of the CE limit is not necessary?

 

[SJones]

1. The limit applies to whatever is stated in the "Company spec." Specifying a composition doesn't automatically make the selection Option 2
2. If CEV is a criterion of the purchasing specification for the material, it will require conformity assessment

The composition restrictions can be partly aimed at HIC resistance that is separate from SSC options.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[svi]

The spec does not say the reasoning but a consultant states it for enhanced HIC resistance. NACE does not require this, neither for option 2. This cannot be applied for off the shelf components which uses standard specification grade and is NACE compliant to the ISO 15156-2.

If this provides the value addition, why is it not recognized by NACE?

 

[svi]

Does through thickness property value steel have an advantage on HIC resistance? Another requirement not identified in NACE.

 

[SJones]

Does the 'Company spec'also require HIC testing because that won't come off the shelf either? Indeed, the chemistry requirements are geared more toward HIC, but they are beneficial for SSC resistance too. The value of the requirement is that it forces a specific type of quality steel production which is not likely to be held by many stockists. As to why it is not included in ISO 15156, most probably because the document covers so many product forms that it is not practical. Compare the Company spec composition requirements with those of API Spec 5L sour service (assuming that the question is related to pipe or linepipe). Similarly, imposing a Z quality requirement also forces a quality steel production that is likely to have satisfactory HIC performance. It's possible that these issues were discussed in the drafting of the ISO standard, but they probably didn't achieve consensus for incorporation.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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

 

[svi]

Company needs an industry aligned specification. Supplementary requirements makes non standard material specifications and has to be a mill order. On smaller projects especially for modifications or revamps this becomes difficult. HIC testing to the requirements per NACE are industry standard, but when supplementary requirements such as new definitions for the crack length may not conform to the norm. Chemical requirements when specified over the ASTM grade makes it difficult to source. The end user of this specification for SOUR service material has to evaluate the composition ranges of the ASTM specification. Instead of giving maximum limits of the constituent contents, the specification should say whether say, ASTM A234 Gr WPB is acceptable or not. The specification calls for 0.2% C against a max allowed of 0.3 C for WPB. Generally used product forms, including A234 are covered in NACE and it says that most CS product forms are acceptable.
API 5L (ISO 3183) Annex K does not state a composition limit or Z quality requirement but covers volumetric examination. Pipeline quantities are invariably large and can be mill order.

 

[SJones]

Simply use Material Data Sheet MDS IC003/IC003S/IC003SH from IOGP S-563

https://www.iogp-jip33.org/library/

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

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