What are the NACE MR0175 limits for ferritic ductile iron ASTM A395?
Question 1: Section A.2.4.1, part 2 (ANSI/NACE MR0175/ISO 15156-2:2015) states “Ferritic ductile iron in accordance with ASTM A395 is acceptable for equipment unless otherwise specified by the equipment standard” – does this imply that its use is acceptable for pressure-containing parts?
Question 2: Are there any partial pressure limits that would apply to using ferritic ductile iron in accordance with ASTM A395?
There is no restriction in ANSI/NACE MR0175/ISO 15156-2 regarding using ferritic ductile iron in accordance with ASTM A395 for pressure containing components. Note that there may be restrictions on using this material from other standards such as API standards that are outside the scope of ANSI/NACE MR0175/ISO 15156-2.
There are no partial pressure limits with respect to H2S for cast irons but note the warning that precedes the Scope of ANSI/NACE MR0175/ISO 15156-2. This warning states: Carbon and low-alloy steels and cast irons selected using this part of ISO 15156 are resistant to cracking in defined — H2S-containing environments in oil and gas production but not necessarily immune to cracking under all service conditions. It is the equipment user’s responsibility to select the carbon and low alloy steels and cast irons suitable for the intended service.
Reference: MP Inquiry 2017-02 (NACE MR0175 Part 2 A.2.4.1)