Axial Nozzle offset in elliptical heads

[KellyP]

My question is related to axial nozzle offsets in elliptical heads for heat exchangers. A senior engineer at work told me you cannot offset a nozzle by more that 80% of the shell diameter. Anyone heard of a similar rule. I would like to read/learn more about it.

Thanks in advance.

 

[prex]

Per UG-37 when and opening and its reinforcement in an ellipsoidal head are located within a circle that is 80% of shell diameter, the thickness to compensate is not the minimum thickness of the head, but the thickness of a sphere with a radius specified by code: this results in less reinforcement required.
There is however no prohibition of putting the opening outside that circle.

prex

http://www.xcalcs.com

Online tools for structural design

 

[waskillywabbit]

No prohibition for putting nozzles outside the 80% limit as noted above. Maybe a company's particular specification however. I'd find out which from the so-called "senior" engineer.

Brian

 

[roca]

This is a requirement in the British Pressure Vessel Code - PD5500 and is normal practise in Europe and amongst most major clients.

 

[MJCronin]

I am sorry... I do not understand

What, exactly, is meant by an "axial nozzle offset" ?

How do you measure or dimension this ?

 

[SnTMan]

prex, my interpretation has been that there are no specific requirements in the Code when the nozzle and its reinforcement fall outside the 80% limit, i.e. is is a U-2 (g) design, therefore I tend to avoid placing nozzles out there.

It is your practice to use the minimum head thickness per UG-32(d) in your reinforcement calculations, rather than the thickness of a sphere as per UG-37? Nobody kicks about it?

Anybody else use this technique? It would be very useful.

Thanks in advance.

MJCronin, it is a nozzle with its axis aligned with the vessel long axis and parallel to it, off centerline.

Regards,

Mike