My job title is stated on my pay check as Engr XX-NLA. What is the meaning of NLA? Does it means I should expect more raise or my job is on the line? Please let me know what NLA means, if you know. By the way, I am in the US.
WPBN W8297 GT may be the heat number. If you have the mill test certificate on the reducer you can verify the chemistry and the design pressure with this information.
Since the threaded part of the reducer is a weak point as you said, I would evaluate the ability for that part to be able to retain the pressure. Is the reducer a standard reducer rated for your application? It is rated for your application per the appropirated industry standard (ANIS, ASTM...