Super Duplex Stainless Steel for Sour Service (ISO 15156-3 Annex A) 2

[KlausTruelsen]

Hello people.

I have a small question regarding the chloride limits for Super Duplex stainless steel for sour service in accordance with ISO 15159-3 Annex A.

Table 24 stipulates that Super Duplex can be used at any chloride concentration that:

“Occurs in production environment”

I would like to hear if anybody knows a more precise limit on the chlorite levels acceptable.

The processing parameters I’m looking at are

170-180 Celcius
~10 kPa H2S pp
65 000 mg/L of Chlorid.

Based on the entry in ISO 15156-3 Annex A table 24 it seems that Duplex can be pre-qualified for the service but the quote above has me slightly worried and I would like to get something more concrete.

Hope someone can point me in the right direction.

Regards

K Truelsen

 

[rneill]

In looking at Table 24 of Part 3 of ISO 15156-2009, it doesn't seem to me to be quite as open ended as that and there are specific limits on temperature and partial pressure listed.

For Fpren between 30 and 40, Duplex SS can be used with any chloride concentration provided the max temperature is less than 232 C and the partial pressure H2S is no greater than 10 kPa.

For Fpren between 40 and 45, Duplex SS can be used with any chloride concentration provided that the max temperature is less than 232 C and the partial pressure H2S is no greater than 20 kPa.

Note that at these relatively low partial pressures, it may be significant whether you are calculating based on absolute or gauge pressure and the limits posted in ISO would be based on absolute pressure.

 

[SJones]

65,000 ppm is not a massive amount of chloride and is a normal value for a gas field water. Oil fields can get up to saturation and that would still be considered a normal production environment. If your concern still remains, you have two options:

1. Find literature data to give you comfort (start with NACE Corrosion 98, Paper 95)
2. Test the material under simulated service conditions (which is how the ISO 15156-3 limits have been derived anyway)

Your biggest concern should be ensuring that the heat treatment and microstructure are correct.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[KlausTruelsen]

Thank you SJones.

I think that was what i really needed to hear.

 

[strider6]

have a look also at this paper

“A Guideline To The Successful Use Of Duplex Stainless Steels For Flowlines”, Plenary Lecture, Duplex 2000, Houston TX, USA, 29 Feb - 1 March 2000. SMITH L.M, CELANT M. and POURBAIX A.

http://www.intetech.com/images/stor...f?phpMyAdmin=da2b7f4483f7d9630453667795e437cf

there are different chlorides limits based on H2S content, is not a standard but maybe it can help u

S

Corrosion & Rust Prevention Control

 

[fadysabbagh]

Dear all,
Please note that NACE MR0175/ISO15156-Part 3 has mentioned in para. A.1.3: NOTE 4 in preparing the materials selection tables, it is assumed that no Oxygen is present in the service environment.
So do you have oxygen in the service or not?

Second point:
Even the issue of the oxgen is still controversial and many others mention that other species (such as CO2 and H2S) may act as oxidizing elements in the corrosion environment.

Third point:
65000 ppm of Cl- is not massive amount, but it is twice as seawater, and we all know that seawater is the most corrosive environment.

I believe that the only solution is test the material under simulated service conditions (which is how the ISO 15156-3 limits have been derived anyway)

Fady