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Refinery sour gas treatment units , what are the NACE MR0175 limits?

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Question:

We are now in the detailed engineering design phase of a sour gas refinery, and we have implemented NACE MR0175/ISO 15156 for design purposes. NaCl (sodium chloride) will come to the refinery through three-phase flow pipeline from offshore, after liquid separation in slug catcher; then the sour gas will go to gas treatment units for further processing. Table A.2 refers to chloride content in aqueous solution as mg/L; my question is in sour gas treatment units in which we use austenitic stainless steel, what are the criteria for the limitation of application of austenitic stainless steel? My idea is we have to comply with the first row of Table A.2. There is no means to identify the chloride content in the gas stream.

Answer:

It is assumed in Table A.2 that this is a mixed-phase environment with both a gas phase and a liquid phase. This is always true throughout the document.
The operator is responsible for determining the service conditions, including chloride content (see ISO 15156-1, 6.1) and the ISO Maintenance Panel cannot provide advice. As mentioned in ISO 15156-3, A.1.3, Paragraph 2: “The tables show the application limits with respect to temperature, pH2S, Cl, pH, S. These limits apply collectively.”
However, if, as an equipment user, you feel that ISO 15156-3, Table A.2 does not address your expected field conditions you have the freedom to test materials under alternative environmental limits and to use the outcome of successful tests to justify the use of a material outside the limits set in the standard. (See ISO 15156-3, 6.1, Para. 5.)

This question is in relation to NACE MR0175/ISO 15156-3 Table A.2

Reference: ISO 15156 Maintenance Panel Inquiry #2004-21

The information of this inquiry needs to be reviewed in light of the requirements of NACE MR0103. Talk to us to discuss sour service requirements for upstream and downstream applications.

 

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