Interpretation of Part 1 Clause 5 in Relation to Figure 1 of Part 2

This webpage provides an answer to a question about the interpretation of Part 1 Clause 5 in relation to the diagram in Figure 1 of Part 2. The question asks whether it is the equipment user’s responsibility to ensure that the service conditions are equal or less severe in all respects, given that the severity is defined in terms of H₂S partial pressure and pH.

Equipment User’s Responsibility for Service Conditions

The response confirms that the equipment user is responsible for ensuring that the service conditions are equal or less severe “”in ALL respects””, not just in terms of H₂S partial pressure and pH. The diagram in Figure 1 of Part 2 defines the severity of SSC in terms of the critical environmental parameters, but other parameters such as stress level and temperature must also be considered.

It is important to note that this interpretation is specific to SSC qualification only. Qualification of a material at a point in the diagram qualifies it for any conditions less severe than those conditions, i.e. higher pH and/or lower H₂S partial pressure.

Guidance in Part 1 Clause 5

Guidance is also provided 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 pertains to NACE MR0175/ISO 15156-2 Clause 7.2.1.2.

Reference

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

Implementation of NACE MR0175

At OGC Energy, we can assist in the interpretation and implementation of NACE MR0175.