900# Weld neck flange design

[Mike2410]

I have an application for 6.00" - 900# flanges (3000 psi test pressure) in 2205 Duplex material. I believe I want to specify a full penetration weld for inspection purposes as well as to meet section VIII boiler and pressure flange standards.

I plan to machine the flange faces, bolt holes and ring joint after welding to a body. The flange blanks will be made from plate.

The standard weld neck height is 4.50" and I assume this is necessary to avoid weld distortion of a finished flange.

I would like to know if there is a standard that allows for a reduction in height and still meet section VIII.

thanks

 

[rneill]

There were not a lot of details around the flange design in your post but I would refer you to ASME Section VIII Appendix 2-2 as there are some specific rules for flanges manufactured from plate. Also applicable is Interpretation VIII-1-92-37.

 

[Mike2410]

For simplicity,the design can be considered a pipe section with a flange welded on each end. The key issue is the need to machine the faces after welding due to other equipment design considerations.

I see the limitations of hubbed flanges in section VIII and it appears to eliminate the weld neck option I was considering.

If I am interpreting correctly, it appears the limiations are only for hubbed flanges, are you aware of any limitations regarding hubless flanges made from plate?

thanks

 

[rneill]

I am not an expert but I think the limitation is just for hubbed flanges - my interpretation is the same as your's.

Int. 92-37:

Question: Is it permissible to fabricate a flange per Appendix 2, Fig. 2-4 sketch (7), by welding a 1" plate conforming to SA-36 to a 3/8" thick nozzle neck conforming to SA-106? The requirements of UCS-6(b)(1) through UCS-6(b)(3) have been met.

Reply: Yes.

 

[unclesyd]

You might want to look at this type of flange. We use quite a few of this type on some in line polymer filter. The mechanics love them, due to the small bolting.

 

[gr2vessels]

Mike,
I got a feeling that there is a misunderstanding between your post and the replies posted here (I might be wrong).
The standard you mention is ASME B16.5, which gives you the shape of the 900# flange you need to follow. Again, you cannot make the whole weld neck flange out of plate, you need to use a forging blank or alternatively you weld and forge a plate into a ring for the flange blank.
Please note the interpretation mentioned above uses a plate welded to a pipe neck, in order to emulate the fiber orientation of the forged flange. Also, the weld neck flange profile has been developed to withstand the operational stresses, not to prevent some welding distortion.
Cheers,
gr2vessels

 

[TWP]

only small WN/ hubbed flgs may be machined from bar;
to my memory limited to 4" OD (bar OD);
dicated by ASME piping code B31.3, ASME press vessel code (ASME VIII-1, App 2) and ASTM product spec's for flanges such as A182 + therein referenced ASTM's; see also ASME B16.5.

So, hubbed flgs not to be fabricated from bar unless size is relatively small. Plate can only be used for so called Slip-on flanges or for blind flanges. Slip-on goes with 2 fillet welds in total, not with butt welds (full pen.)

Slip-on commonly applied up to incl rating class 600; class 900 & Slip-on subject to client / design code acceptance

 

[MJCronin]

Since this is a duplex stainless application, specifically which material do you intend to use for machining ?

Is this duplex material permitted by ASME VIII pressure vessel code ?

What is your design temperature for your application ?

Which table within ASME B16.5 are you using for your permissable temperature/pressure combinations ?

Regards

 

[TWP]

Since 20 years we apply mainly ASTM A182-F51 (UNS S31803); similar to type 2205 (Sandvik).
This is the most common Duplex St Steel type in the Oil & Gas industry for moderate applications.
UNS S31803 material is ASME listed but not yet in all product shapes.
We fabricate piping systems with this material (oil & Gas business) on basis of ASME B31.3 piping code.
We use DSS for all piping components ; flanges, pipe, elbows, fittings, plugs, gaskets and studs/ nuts.
Pipe is an example of an ASME B31.3 listed product (ASME B31.3 Table A-1).
For unlisted components we derive the allowable stresses as per design code.
In that case we use yield and tensile values from Tmin to Tmax as per ASME Section IID.
If the values are not availabl than we use the values per suppliers' documentation.
As a rule Tmin = -50 Celsius (impact testing at this temp. is required) and Tmax is +325 Celsius.
Flange ratings as per ASME B16.5 for ASTM A182-F51 material grade.
Room temp. rating approx. 430 bar if I remember well (i'm at home/ holydays/ not in the company).
PS ; There are some ASME code cases for DSS

Regards,
TWP, PrVessel & Piping eng (NL)