valve ball surface finish

[falcon4]

I am trying to update our ball-valve ball specifications.
I need to provides specifications for a 1.0" dia ball made of 316 SS.

We currently called out 100v (valve grade balls) but there does not seem to be a specification for valve grade balls.
We require a 3 Rma surface finish, with a mirror finish.

Procuring 100v grade balls from some suppliers, we find they only have a 5 Rma finish, and it was dull not mirror.

Does anyone have a specification that addresses valve grade balls (which apparently have better surface finishes, but standard geometry tolerances)

As a side note, why would the 5 finish ball, not have a mirror finish? do I need to specify that? I would have thought a finish like that would have been mirror like.

 

[RXH]

falcon4:

What service are the valves meant for and why do you need mirror finish?

 

[unclesyd]

You cannot equate a mirror finish to a call out on surface finish. You can polish most finishes to a mirror finish. In others words you give a surface finish and have it polished.
We made parts for internal use with a very low surface finish with always a desire for a finer finish. Our problem was that the finer we got the duller(matt) the part got. Even though we were under a light band in flatness and finish they wouldn't sell until we polished the part.

 

[falcon4]

The valves are used to contain a 3000 PSIG nitrogen and CO2 mixture.

they require low actuation forces and extremely low leakage rates. Because of this we have been using balls with a 3 finish and they have always come in with a mirror like appearance. We were told they were grade 100V (valve grade)which supposedly meant they met grade 100 dimensionally but better than 48 for surface finish.