I currently have two B31.8 projects involving above ground, API 5L, low temperature piping systems. I have studied both B31.8 and API 5L concerning low temperature and I am seeking interpretation assistance.

B31.8, paragraph 812 essentially states the low temperature suitability of materials should be "given attention" for materials "... exposed to low ambient temperatures". My first question is if the MDMT project design criteria for pressure vessels and piping under other code jurisdictions satisfy the "low ambient" temperature value of paragraph 812? If not, what is considered accepted practice?

B31.8 paragraph 841.11(c) states that the fracture control and arrest requirements do not apply to pipe NPS 16 and larger with design hoop stress less than 40% SMYS or to pipe smaller than NPS 16 with design hoop stress less than 72% of SMYS. My interpretation is that this paragraph applies to any otherwise acceptable material (API 5L for instance)regardless of temperature or wall thickness and satisfies the "given attention" requirement of paragraph 812. Is this a valid interpretation?

According to API 5L, if PSL 2 is specified then impact testing is mandantory at 32F. On one of my current projects, I have API 5L piping NPS 16 through 24 with design hoop stress greater than 40% with a project MDMT of -20F. Based on my interpretation of B31.8, I should specify supplemental testing SR5 at -20F. Is this a valid interpretation and, if so, is equation (b) of B31.8 paragraph 841.11(c)(2) appropriate for determination of the CVN energy value?

Opinions and guidance will be greatly appreciated.