Nozzles In Elliptical Head Knuckle Region

[RPRad]

Hi Folks

Any words of wisdom with regard to the design of nozzles (pressure vessel) which are located in the zone outside of 80% of the elliptical head diameter (other than don't put them there). The reinforcement issues seem reasonably manageable but it seems to be a bit dicey as the nozzle approaches the knuckle region. Does the Code deal with this anywhere specifically?

R

 

[chaulklate]

I don't think the Code deals specifically with this item. General rule of thumb is to not claim any excess area from the head. It's acceptable provided your client has no issue with it. As always, make sure there are no jurisdictional restrictions. I have personally designed many nozzles in knuckles.

 

[doct9960]

RPRad,

If the nozzle has no piping loads, e.g. instrument nozzles, tr in the reinforcement calcs of UG-37 should be determined by UG-32(d) or Appendix 1-4(c). This is in accordance with ASME Interpretation VIII-1-98-117:

Question: A nozzle is located in an ellipsoidal head, such that part of the opening or its reinforcing extends beyond the 80% limit as specified in the definition of tr in UG-37(a) of Section VIII, Division 1. Shall the required thickness of the ellipsoidal head, as determined by UG-32(d) or Appendix 1, 1-4(c), be used in determining the required area of reinforcement on each side of the opening for all planes?
Reply: Yes.

If the nozzle has piping loads, I suggest that FEA be performed.

 

[RPRad]

Yes the nozzles are self reinforced, that is to say the reinforcement area has been reduced to essentially the OD of the nozzle...would there be any benefit in doing a WRC on it,or would it even give you any useful info...just a bit concerned about any stress concentration effects resulting from locally stiffening up the knuckle in the area...or is that just over thinking it

R

 

[RPRad]

Doct9960

Yes reinforcement calculations were done utilizing that methodology.

Good point on the loading, although I am told the loadings are not significant...although perhaps that doesn't apply in this situation

Also I owe you a beer, they successfully used the flexible plugs (pigs) to clear the residual air out of the heater coils and were thereby able to perform a hydro test and avoid the whole issue of a pneumatic test

Thanks
R

 

[MJCronin]

http://www.eng-tips.com/viewthread.cfm?qid=127987

http://www.eng-tips.com/viewthread.cfm?qid=67661

I think that the ASME code could be made clearer on this obvious issue

 

[RPRad]

It doesn't seem the Code has changed much on this issue since you originally posted about it in 2003. That thread 67661 makes for entertaining reading...especially once it diverges from the main issue. I wonder where the youngster is today 9 years later?

R