[MW:6688] FW: 6686] Sour Service

 

 

Hello Manav,

 

Your query is specifc to upstream (oil and gas production) or downstream (oil refinning) industries. A far as down stream is concerned the definitions of " sour service" is as follows:-

The outcome of the consensus approach has resulted in the following guidelines on what constitutes a sour service in downstream units(as per MR-0103):-

The fluid must contain a free water phase and:

• >50 ppmw dissolved H2S in the free water (in recognition that significant levels of dissolved H2S can result in SSC even in low-pressure systems), or
•  A free water pH <4 and some dissolved H2S present (in recognition that in low-pH environments, significant charging of materials with atomic hydrogen can take place irrespective of H2S level), or
•  A free-water pH >7.6 and >20 ppmw hydrogen cyanide ion (HCN) and some H2S dissolved in the free water (in recognition that at high pH, the HCN ion is stable and results in significant charging of ferritic materials by poisoning the formation of a protectiveiron sulfide scale), or
•  >0.0003 MPa abs (0.05 psia) partial pressure H2S in a process with a gas phase (based on the historical MR0175 definition of sour service, without the 0.4 MPa abs [65 psia] minimum pressure requirement).

For upstream environment(oil and gas production) the difinition of sour environment is primarily based on the mole fraction of hydrogen sulfide  vs pressure as explained by this curve  and elaborated further as such:-

 

Sour service environments are defined by NACE International specification MR0175 as "fluids containing water and hydrogen sulphide (H₂S) that is at a total pressure of 0.4MPa (65psia) or greater, and if the partial pressure of hydrogen sulphide in the gas is greater than 0.0003MPa (0.05psia)". The acidity of the environment is below pH 3.5, and carbon dioxide, and chlorides are also normally present.

 

 

The attached article is quite informative on both the above specifications.

 

Thanks.

 

 

Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Ontario Power Generation Inc.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Manav Malhotra
Sent: Tuesday, August 24, 2010 11:35 AM
To: materials-welding@googlegroups.com
Subject: [MW:6686] Sour Service

 

Dear Members,

 

Can anyone clarify whats the requirment of sour service. Some say presence of H2S or if H2S is more than 50 ppm.

 

Regards,

Manav Malhotra

 

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