min distance of adjacent welds

[Spoonful]

Hi all,

Got a question here,

On the body of the vessel, a nozzle and a tube-sheet need to be welded on opposite side of the body, (regardless of the reinforcement of the nozzle opening), is there a requirement of how close of these weld can be located?

The idea is, for a vertical vessel, the tube-sheet divide the vessel into upper and lower chamber. To drain the upper chamber, theoretically the bottom of the ID of a nozzle should be welded flush with the top face of the tube-sheet, but this will result weld on each side of the vessel wall too close or even overlap.


Is there an requirement in ASME stating about this issue? In AS1210 there is a requirement of adjacent weld min distance of 40mm or 3 times of thicknees of vessel wall, but for weld on the same side of the vessel wall, not sure if this apply to this case.

Any suggestion?

Thanks in advance

 

[lganga]

s it like to drain or vent a Reboiler.?
When you need to drain the shell side of a vertical HX, is an standard to drill a radial hole in the tube sheet , drill a distance till you save the gasket face, then you drill a vertical one so you connect both holes and then you have a path to outside.
On the tubesheet you can weld on the external face of the tubesheet, a nozzle and a socket valve.(about 1").
This job is done before you weld the tubesheet or the tube bundle.

 

[Spoonful]

lganga, from what i am understanding of you post, is have two holes 90 degree to each other and a let the fluid drain thro the tube-sheet,(provided that tube sheet is thick enough to be drilled along face direction.)But still have to weld the tube sheet on inside of the vessel and nozzle on outside of the vessel, still both weld are too close.

 

[gr2vessels]

The idea was to delete the additioal nozzle;- the method explained by lganga is the correct one (just remember to threaded the hole on the edge of the tubesheet to plug the drain during normal operation).
However, if you HAVE to weld the dreaded nozzle flush with the tubesheet, the code doesn't stop you to weld them next to each other, provided you follow up the approved welding procedure for this particular weld and perform all the required NDE's.
The mentioned 1 1/2" or 3 times the shell thickness is only recommended by the code to avoid special welding conditions.
Cheers,
gr2vessels

 

[Spoonful]

gr2vessels,


from what I understand is instead of using a nozzle, just tab a hole on the tubesheet and use a plug? Well, in that case why can't it be just a tab on the vessel wall?( provided that the vessel wall is thick enough) What about say vessel 600NB, use a 1 inch plug or 2 inch plug will still take forever to complete drain it.

Thanks for all the comments.

 

[AndyVictor]

I think the drain hole mentioned on the tubesheet is not in lieu of the drain nozzle. Drain nozzle can be provided a bit above the tube sheet. The drain hole is for draining the remaining liquid.

 

[Karloss12]

If the tube sheet is to thin a more expesive option would be to drill through the tube sheet and then pipe from underside of the tube sheet through the shell say 100mm below the tube sheet.

In PD 5500 a doubler pad cannot be within minimum of 40mm or twice the shell thickness.

And a nozzles weld must be atleast 12mm from a main seam or the nozzle must pass through the centre of the main seam.

 

[strauss2010]

In ASME it is usually 5 times the thicker plate,,but some people are using 50MM min distance between adjacent weld,,