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valve ball surface finish

valve ball surface finish

valve ball surface finish

(OP)
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.


RE: valve ball surface finish

falcon4:

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

RE: valve ball surface finish

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.  

RE: valve ball surface finish

(OP)
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.

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