Nozzle Reinforcement Requirements 1

[Ken_C]

Hello...first time posting in long time. We're reviewing vendor calculations for a Sect. VIII, Div 1 pressure vessel. We have a situation where the edge of the 24" manway is 1/2" from a circumferential shell seam (upper head attachment). For this manway, the vendor used Div. 2 4.5.5 to evaluate reinforcement requirements. The calculations (vendor used Compress) show that no reinforcement is required.

The inputs all appear to be correct, as it technically is not intersecting a Cat. A joint.

Is there any any other calculation aspects to check to confirm that nothing else is being missed here?

Thanks!

 

[0707]

If the calculations inputs are correct you can acept it, but, if you have doubts instead of a reinforcement for your manway you can use a forged reinforced peace manway.

 

[r6155]

I suggest you do the calculations to verify it.

Regards

 

[Ken_C]

thanks for your comments!

 

[david339933]

Sec. VIII Div. 1 allows any properly reinforced opening to be located in a welded joint.

 

[Geoff13]

The Code doesn't address weld spacing, so this isn't a Code violation. However I would say that only a 1/2" between the shell and nozzle butt welds isn't "good practice". Very likely that there will be no gap on the actual vessel.

I wonder if the 1/2" gap is just looking at elevations of the girth weld and neck top edge, or is after a detailed layout of the respective weld gaps and bevels. If it's the first, then the second is going to show some very nasty problems.

As a vessel designer/manufacturer we would have asked for the manhole be moved as soon as this conflict was noticed. Without knowing anything about the vessel I would still say we would have refused to leave the manhole that close to the girth weld. Either lower it to miss by 6" or more, or raise it to intersect the girth weld at a less tangential angle. A larger diameter insert plate would be another solution (looking similar to 0707's forging after installation) but being cylindrical below the girth and head shaped (spherical or elliptical) above make this almost impossible.

If the manhole can't be moved then you're going to wants lots of extra NDE before, during and after welding. Not my area of expertise so I won't make any suggestions.

I'm also wondering why the vendor switched to Div 2 reinforcing calcs on a Div 1 vessel. Did they do Div 2 for every nozzle as it's their standard practice, or just for this manhole? Did the Div 1 calcs show something they didn't want to pass along?

Good luck

 

[Ken_C]

They are employing Div. 1 Appendix 46 (e.g., Div. 2) for the (4) manways. All the other (20) or so nozzles are Div. 1 (including a 30" nozzle).

this vessel is a replacement for another (replace 316L with 2205 duplex). The former vessel had 20" manways (which gave a little bit of clearance from the upper head circ seam) with repads...no repads with the new vessel per Div. 2 calcs (which is one reason the vendor may have elected to use Div 2 for these).

Thanks for you help Geoff13...much appreciated.

 

[Christine74]

I'm not familiar with Div. 2 requirements and I could be wrong here but if your weld seam is only 1/2 inch away from the OD, I'm pretty sure that seam lies within the limits of reinforcement. I would think you need to account for that in your calculations if the joint efficiency of the seam is less than 1.0 (I know Div. 1 calculates the required cylinder thickness t_r assuming a seamless component with E=1.0).

Fortunately this is a circumferential weld seam not a longitudinal weld seam, so the area replacement calculations for the longitudinal direction are unlikely to be governing.


-Christine

 

[r6155]

Do not mix Div 1 and Div 2, the allowable stresses are different.

Regards

 

[r6155]

Should the hydrostatic test be in accordance with ASME VIII Div.1 or Div.2?

Regards

 

[Ken_C]

Div. 1 Appendix 46 requirements allow Div. 1 stress, with some caveats.

 

[XL83NL]

If the calculations inputs are correct you can acept it, but, if you have doubts instead of a reinforcement for your manway you can use a forged reinforced peace manway.

If your wallet is too big and needs (weight) reduction, that’s a fair option

Huub
- You never get what you expect, you only get what you inspect.

 

[0707]

good way to say expensive XL83NL!

 

[Krausen]

So long as vendor used VIII-1 allowable stresses in their calcs on this (per VIII-1, MA46 requirements), I would accept. It is a bit strange they got that to pass though. Most 24” nozzles designs on vessels will require reinforcement that I’ve seen. Depends on materials & design conditions though