This is how I would (honestly, I would...) go about this:
1. Find out if there are any local or governmental statutory / regulatory requirements, failing which -
2. Re-read the owner’s specification as to what code to use, failing which -
3. Ask a colleague what practice was employed before at the company, failing which –
4. EIGA guideline for oxygen pipelines is an excellent reference
5. Self-cogitate and revisit your original reasoning behind the mountain of work you desire to create for a) yourself by using an unfamiliar code or b) sadistically specifying a code, for which your contractor’s price is going to be... a tad unexpected , failing which –
6. Examine the suitably of B31.9 or B31.8 if you must, failing which –
7.
