Re: ANSI B16.5 Flange - Gasket Face Machining Allowance

• In PipingDesign@yahoogroups.com, "Steve McKenzie" <gyro-@...> wrote:
  >
  > Gents
  >
  > Just had a gasket blow on a piping joint, bugger. The gasket is
  between
  > a branch stub flange and a blind flange. The vent stream has cut a
  > groove in the raised face portion of the blind flange. Its 40NB
  Class
  > 900 with 32mm "hub" thickness plus 7mm raised face; 39mm overall.
  >
  > As far as I recall, it is permissible, by code, to machine damage
  off
  > the raised face portion provided the finished overall thickness is
  not
  > less than the minimum hub thickness (32mm).
  >
  > Anyone recall what the rule actually is, and where I can locate it?
  >
  > Thanks
  >
  > Steve
  >
  Steve,

I thought I would mention that referring to the American Petroleum Institute's API-570 is a good idea in these situations as well. That document is a repair / inspection code specific to B31.3 new pipe fabrication. Similarly there is API-510 for pressure vessels and API- 653 for above ground storage tanks. When other codes or jurisdictional requirements are not applicable, these documents provide excellent approaches to repairs versus the new construction codes.

Also, I have had experiences with the exact situation. It takes precious little time to cut a flange face through when it comes to HP steam. I usually write repair procedures that call for weld metal build-up and machining depending on the extent of damage.

Good luck,
Bob Goodwin Received on Thu Aug 09 22:09:00 2007