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According to NACE MR0175, who is responsible to ensure sour service conditions are qualified?

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Question: As stated in Part 1 Clause 5: “Qualification, with respect to a particular mode of failure, for use in defined service conditions also qualifies a material for use under other service conditions that are equal to or less severe in all respects than the conditions for which qualification was carried out. ” The diagram Fig 1 Part 2 defines the severity in terms of the main environmental parameters, i.e., H2S partial pressure and pH but other parameters (temperature, stress level …) must also be considered. It is the equipment user’s responsibility to ensure the service conditions are equal or less severe “in ALL respects.”

Answer

1. This interpretation is correct for SSC qualification only since this diagram applies to SSC. If a material is qualified at a point in the diagram, it will be qualified for any conditions less severe than these conditions, i.e., higher pH and/or lower H2S partial pressure.
2. The diagram Fig 1 Part 2 defines the severity in terms of the main environmental parameters, i.e., H2S partial pressure and pH but other parameters (particularly stress level, temperature …) must also be considered.
3. It is the equipment user’s responsibility to ensure the service conditions are equal or less severe “in ALL respects.”
4. Guidance is also given in Part 1 Clause 5: “Qualification, with respect to a particular mode of failure, for use in defined service conditions also qualifies a material for use under other service conditions that are equal to or less severe in all respects than the conditions for which qualification was carried out”.

This question is in relation to NACE MR0175/ISO 15156-2 Clause 7.2.1.2

Reference: ISO 15156 Maintenance Panel Inquiry #2009-23, Part 1

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