API 6A 15 th -19 th editions included a maximum composition limit on Nickel:
API 6A 20 th edition deleted limit on Nickel. Reasons for change: – Nickel limit is not required for non-NACE equipment (Matls Class AA, BB, CC). – Deleting limit on Ni allows use of additional material grades such as 4340 for AA-CC. – Deleting limit on Ni allows use of full ASTM chemistry range of currently-used materials such as F6NM.
API 6A 20 th edition deleted limit on Nickel. Concerns about this change: – Users of undocumented equipment cannot base acceptance for sour service on hardness alone. – Practice of using hardness testing as basis of conformance to NACE MR0175 is prevalent. – Limits interchangeability of equipment. – Limits flexibility of repaired and remanufactured equipment. (Not addressed in Annex J)
API 6A 20 th edition deleted limit on Nickel. Questions about this change: – Is the benefit of using 4340 or unrestricted F6NM significant relative to the increased risk? – Are there other alloys/material grades that would also be used as a result of this change? – Should the change be addressed in Annex J? – Does this affect other product specifications that reference 6A/10423?
Proposed new work item: Convene a new task group or ask Materials Task Group to consider the effects of this change from 6A 15 th – 19 th editions, and make a recommendation to keep or reverse it.