I am in the process of tearing down a 500 ton CVHE and found an unusual wear pattern on the back side of the 2nd stage diffuser plate seemingly from the some of the vanes on the 3rd stage shroud and vane assembly. The wear pattern is not uniform and appears in ~75 degree sections at 3 o'clock and 9 o'clock. Is this normal?
Also, are the diffuser plates aluminum or stainless steel? They look Aluminum to me but I'm not sure. My latest oil sample analysis revealed a high Aluminum count and I am thinking this is where it came from since there is no abnormal wear on the impellers or labys.
Lastly, the drive end journal bearing was wiped. Any ideas what would cause this aside from insufficient lubrication?