Alloy 625 in H2S wet natural gas 1

[arcc]

The system operates at 1435 psi and a temperature 40 to 105 degrees f. The patrial pressure of the H2S is 215 psi.
With these conditions how will the 625 hold up to SSC and HIC?
Or, is their another material that will hold up under these conditions?

 

[SJones]

First point: HIC is a failure mode peculiar to carbon steel and will not affect 625.

Point 2: H2S resistance will also depend to some extent on the CO2 content that, as another acid gas, will drive the pH.

Bruce Craig's published work with NiDI remains seminal in this field.

http://www.nickelinstitute.org/inde...words=Craig&ci_id=6511&Submit.x=12&Submit.y=8

Take a look at Figure 7 in the above paper; you may find that 625 is perhaps over specified and that you may be able to apply 825.



Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[EdStainless]

This tipping point between Fe based alloy and the Ni-Cr-Mo alloy will be pH and Cl content.
One reason other than chemistry that you see 625 used is for its higher strength.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[SJones]

Good point on strength but I suspect that clad carbon steel will be the order of the day reducing the focus on mechanical properties.

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/