For those that cannot read B51.
Category E are strainers, filters, seperators, and steam traps. So do all 2 and 3 phase seperators fall under category E fittings or as pressure vessels. What if my steam trap in 4" and < 1.5 cuft? What about my seperator that is 6" and > 1.5 cuft. According to the flow charts, there are only pressure vessels and Category H fittings. What about minature pressure vessels? They are inspected by the manufacturer and < than 1.5 cuft but > 5 cuft. It is not even addressed in the flow charts, but they exist.