Flange Face Parallelism Standard 1

[marklobo]

Does anyone know of industry standards addressing parallelism of flange faces prior to installation? We have experienced a cracked fillet weld at the socket connection of a short lap-joint flange hub into a rigid pressure vessel. During installation, as the raised faces (piping flange and hub) were drawn together, the weld had to resist the strain-induced stress required to make the out-of-parallel RF faces parallel. The fillet weld complied with ASME BPV Code standards, but apparently that was inadequate to handle the structural bending load.

 

[pennpiper]

Try:
Pipe Fabrication Institute
ES3- "Pipe fabrication tolerances"

http://www.PFI.org

 

[pennpiper]

OOPS, wrong address, Sorry
Try
pfi@pfi-institute.org

 

[rconner]

I was just curious what you meant by "out-of-parallel" (are you talking about the central axis of one piping item/segment not aligned with the central axis of the other, while both alignments are being somehow rigidly held as attempts are made to bolt both together??, are instead one or both flanges "cupped" (as by welding etc.)?, or instead have the flange faces been somehow originally machined out of perpendicular plane with one or both the individual axes?, or what? While I don't doubt someone somewhere has attempted to account for some of this, with no more information the first situation at least sort of gives me the "heebie-jeebies" (if this is the case, could you essentially make the flanges "parallel" so as to be assembled out of the bind with the use of a thin custom, beveled flange filler with in that case a couple gaskets etc., or maybe even field or factory custom mill one or both of the faces for parallel joining out of a bind in the application?

 

[cvg]

In order to crack that weld, the installer probably also exceeded the torque requirements while tightening the bolts. I have run across this before where the flanges were slightly cupped and it required thicker gaskets and checking to make sure the maximum torque was not exceeded. The Contractor tried to use a cheater bar and exerting force with a backhoe. Luckily the bolts or flange didn't pop during the process!

 

[SJones]

NORSOK L-004

http://www.standard.no/imaker.exe?id=1358

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[abeltio]

See TEMA Stds

Figure F-1 for External Dimensions, Nozzle and Support Locations
and, just for general culture...
Figure F-2 for Tubesheets, Partitions, Covers, and Flanges.

Cheers


saludos.
a.

 

[marklobo]

Thanks to all those providing input. Of particular value were the recommendations of sjones and pennpiper (PFI ES-3 was only $25 through Global, and the NORSOK spec is public domain). Since we don't have a copy of the $250 TEMA standard, abeltio's reference didn't help, though it's nice to know that it exists for the heat exchanger industry.

Thanks to rconner and cvg for their anecdotal input.

Our objective is simply to establish the amount of strain that the weld connection of a flange hub would have to withstand when our flange is drawn to an axially aligned but out-of-parallel rigid flange face. We would hope that we can avoid a limitation on horsepower of a backhoe used to draw the flange faces together and simply reference an industry standard, such as PFI ES-3

 

[arto]

Way back when, we usta ship the vessel with a mating flange& blanking plate [= gasket thk] bolted on. That way, when it got to the field, they had the correct flange & could fit up the piping to where it was supposed to be.