slip-on flange vs weld-neck

[bte]

Hi,
Does anyone have any technical information why weld-neck flanges are better than slip-on fanges or vise-versa?
I know they are both rated the same.

Regards,
bte

 

Its related to the flange-to-pipe weld quality not the flange face quality (rating of the flange). I have forgotten most of the details but the if you look at the size/shape of the weldment you will see that for a butt weld (achieved with the WN flg) it is possible to get a far more robust weld than a lap weld (with the SO flg). If you look up welding in Google, or get a good welding handbook, it will give you all the details

 

[PAN]

How to decide between a slip on / weld neck flange?
thread378-16558

 

[reichertc]

If this is B31.3 piping, also note that the stress intensification factor for a weldneck flange is 1.0 whereas for a slip-on flange it is 1.2. This may affect a stress analysis on the system.

 

[welding1]

Slip on Flanges, because they are fillet welded are not suitable under fatigue conditions and for use at high temperature.

I think The British Pressure vessel code, PD5500, limits the maximum temperature for fillet welded flanges to about 370°C.

You can't do meaningful NDT on slip one flanges.


Regards

John

http://www.gowelding.com