Pressure Vessel - Want to machine Flange faces!

[BPVN]

Hi,
We have a pressure vessel (ASME VIII-Div1)on site that we have taken apart for inspections. We found that some flange faces have some corrosion and we would like to machine the SORF & WNRF flange faces. Can we do machining on site?
Can we allow to machine SORF/WNRF flnage? Which code we'll have to refer? This vessel installed in Canada.
Thanks in advance
BPVN

 

[vesselfab]

On site machining is done every day.

If you want to maintain dimensions and corrosion is deep, you may need to weld up area before machining with an approved procedure.

minor repair for NBIC

not sure about canada

 

[BPVN]

Hi,
Thanks for quick reply.
If corrosion is not deep, so can i do only machining flange without weld buildup?
Thanks in advance
BPVN

 

[vesselfab]

depends on how deep you have to go

will it still be within tolerances of standard b16.5 flange for thickness?

 

[chicopee]

If I am still correct because I have not kept up with the current codes, if corrosion is less than 50% of metal thickness yes you can do the above mentioned repairs of weld build up and machining.

 

[Zziggiz]

You can machine the face to the extent that the flange minimum thickness is maintaned. Please note that the raised face dimension is not critical.
To avoid welding and if the defecs are deep, you may machine the face just to make those defects whithin the acceptable range rather than completely remove them.

 

[jte]

ASME PCC-2 Article 3.5, Flange Repair and Conversion deals with this issue. Note that the RF underthickness in 3.1 is somewhat arbitraty. If this limit is exceeded, the approach is to simply treat the flange as a flat face flange, and recognize that there is reduced clearance for the OD of the flange to rotate and thus the bolt load may not be transmitted entirely to the gasket.

Note that this Article received some modifications in the 2008 edition, and more are in store for the 2010 edition.

jt