RFWN Flanges exact application

It sounds like you have taken a little information from one place and mixed it up with information from another place and therefore are confused.

This part of your post is a valid concern:
"avoid weld material chips & other foreign particles to enter the turbines and damage it"
Flanges , Raised Fact or Flat Face may be involved but are not the primary issue here.

The issue is how to you make sure you do not get foreign particles and material chips into the bearings of Turbines and Generators.
1. Place a start-up Strainer ahead of the Filter
2. Make sure that the filter mesh is sized properly to allow the proper rate of oil flow even when partially clogged.
3 Make sure that all piping down-stream of the filter is/was fabricated, internally cleaned, sealed, wrapped, packaged, handled, shipped, unwrapped and installed in such a manner that NO foreign particles, mill scale, weld spatter, get inside the pipe.