Reducer Bush Fitting for Inert gas agent piping

[Miyazaki]

Hi All,

Could anyone please advise whether a reducer bush is allowed in inert gas piping because for halocarbons in most of the manufacturer manuals reducer bush is not recommended, this data I couldn't find in the inert gas manuals.

Can anyone please share with me some references stating why reducer bushes are not allowed in inert gas piping/clean agent piping.