F22 Modified Vs X60 (SSC issues)

[GabrieleB]

Can anyone explain me why in high H2S content conditions the use of F22 Modified materials is preferred to the X60. I want to clarify that the F22 Modified has SMYS=60 Ksi (identical to X60).
The justification I fuond is:

"Initial problems discovered very early on were related to the X60 piping which was found to contain hard welds, which made it susceptible to sulphide stress corrosion cracking (SSCC). The material also possessed poor resistance to brittle fracture (BF)"

As far as i know the X60 material is fine grain material and therefore is easily weldable, in fact it is commonly accepted material with Sour Service application applying the Appendix H of API 5L.
As far as I know the F22 has more issues during welding execution than common carbon steels due to the Cr-Mo carbide that can precipitate at grain boundary. In fact the PWHT is usually mandatory despite the X60.

According to the above I cannot understand the better behaviour of F22 modified in place of X60 and the huge replacement on going on Kazachstan Fields due to H2S issues.

Thanks anyone can give me good and clear explanations.

 

[SJones]

"Initial problems discovered very early on were related to the X60 piping which was found to contain hard welds, which made it susceptible to sulphide stress corrosion cracking (SSCC). The material also possessed poor resistance to brittle fracture (BF)"

Where does this quote originate from, and what, specifically, does it relate to?

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.

 

[GabrieleB]

The justification is included in the specification from the Client that had experencied in the past such problems on Field. That's why they have substituded the items. I have no more information than this, that's why I need somebody that knows something about this and can give me more details.

 

[weldstan]

Many years ago, a friend on the AGA Welding Supervisory Committee, stated that his company purchased X42 pipe to be used in a Sour Gas application but high hardness welds were obtained because the X42 pipe also met X60 requirements (the beginning of the one size fits all steel manufacturing philosophy). I responded that we always specified the chemistry for our X42 pipe to be used in similar applications to assure meeting the weld hardness requirements. X60 can be manufactured to any number of carbon equivalents that would affect as welded hardness.

 

You raise a good point weldstan.
Dual certification is done for stocking reasons, and is legitimate in some cases such as 304/304L.
In general I take a dim view of the practice, and dual certification of X42 with X60 is beyond the pale.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[SJones]

Just as much can go wrong with the F22, so the chances of having material quality issues are about equal. Specifications that have had some thought put into them tend to place a limit on the maximum yield strength of X or L grades to prevent suppliers overcooking the material. Have you got hold of the internal version of an end user's specification that provides reasoning and explanation for the requirements that have been generated? The full failure analysis of the Kashagan X60 pipelines doesn't appear to have been published yet, but bear in mind that those pipes would have been subject to intensive Purchaser scrutiny throughout manufacture, shipping and installation.

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.

 

[GabrieleB]

Thanks for your answer but as far as I can see nobody can understand the reason of that choice like me. Anyone had similar experience with this issue will be well accepted.

 

[SJones]

It seems to be a knee jerk reaction to poor supplier selection.

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.