Flange face coating

[mariolucas75]

Dear Forum,

Your advise is needed.... in what cases the flange faces are coated ?
I have a spec where 20 mills coating thickness is specified on sealing face of a flange (RF flange ).... 20 mills makes 0.5mm and this is the order of depth of the flange face rings.
Isn't the sealing capability compromised in this case ?

Lots of thanks

 

[mfgenggear]

OP
The issue with plating, it does not plate uniformly. There has to be a note the flatness
Requirement applies after plating.

The plating house can not or will not guaranty flatness. So it's upto the machine shop to
Dust off the sealing surface after plating if it does not meet the flatness requirement.
If there is a conversion coating it will be removed and has to be reapplied.

 

[SnTMan]

Heat exchanger girth and nozzle flanges are pretty routinely coated with epoxies of various kinds. Given careful application and proper gasket selection it can work just fine.

Regards

Mike

 

[Trestala]

I've seen them used on 150# flanges with expanded graphite gasket. But, if you have higher rating, I doubt that you can prove they can seal the flange with 500 microns of coating and that much compression experienced by the coating and gasket. What kind of coating are you using by the way?

 

[r6155]

Be care with the roughness of spiral or concentric serrated. See 6.4.5.3 in ASME B16.5