Wetted Holes

[UchidaDS]

What is the meaning of wetted holes?
I saw this on the drawing and it does comes with the surface finish, for example 16Ra, 32Ra, etc.

 

[drawoh]

UchidaDS,

Do the holes have some sort of fluid passing through them? This might explain the surface finish.

--
JHG

 

[UchidaDS]

Yeah, it is for gas line.
It shows "ALL WETTED HOLES TO BE 16Ra OR BETTER SURFACE FINISH"
But why "wetted"? I just don't get it when using "wetted".

 

[tbuelna]

The term "wetted holes" does not seem like a good way to define the surface roughness requirement of internal flow surfaces. For example, is a chamfer or radius at the hole edge considered part of the hole? I think a better approach to defining the surface roughness of these features would be a general note stating something like "Surfaces exposed to fluid flows shall be treated using company process XXX to produce a finished surface roughness of 16Ra or better." It can be difficult to inspect the surface roughness of many long small diameter holes, even with a compact profilometer stylus. It would be better to rely on using a qualified/controlled process to ensure the roughness of internal flow surfaces meet requirements. The way the note is written, it would seem to require every "wetted hole" needs to be inspected for surface roughness.

I'm sure this note is a standard practice this company has used for many years. But it could definitely be improved.

 

[drawoh]

UchidaDS,

In a design rule, use of the term "wetted" is meaningful. On a fabrication drawing, there is no reason to assume your fabricator understands which holes are in contact with fluid. Your drawing should point explicitly to the faces.

--
JHG