Hi All,

I hope u all will be aware about the limitations of WRC 107/297 with regard to the geometric parameters(radius/thk ratio etc..) and the curve values.

I understand from the foresaid bulletins that the theory on which they are based are not valid if certain limitations are exceeded and so obviously the stresses calculated would not be reliable. How Coade deal with this?.

I've also seen some client specifications calling for FEA when such limitations are exceeded. I even know certain companies who write these spec's do not follow this requirement due to commercial implications.

Can somebody put some light on this issue?

As far as WRCB-107 is concerned, I believe based on my experience and judgement that it is always be perfect design when you limit Beta <=0.5 for analysis on cylindrical shell and U <=2.2 for analysis on spherical shell. In certain cases due to the same you might require to increase the thicknesses but that may be more economical than FEA at many places/cases.

If you have FEA facility available than you can do the same.

PV Elite only gives warning when curves values exceed and when geometry is out of the scope of WRCB-107/297.

Hope above is clear.

Mukesh

Dear JJP,

As an Engineering Software provider, we program the software according to the method described, in this case WRC 107/297. When the geometry is out of range one or more curve values are usually exceeded. In this case the only possible choice is to use the last curve value. This may or may not be conservative depending on the slope of the curve and which side was exceeded. So, in many cases you may notice a note, notifying you that a curve value was exceeded. As a Vessel Designer/Engineer, you then have to make a decision based on the available data and your experience as to whether or not you have a level of stress at the junction you can live with.

I hope this helps.

Thaanks for your response Mukesh & scott

Dear mukesh,

may be, this is silly question for you but could you please tell me in WRC 107/297 where we have to mention the Beta and U values? and what the Beta value is for? please reply.

B and U values will be calculated based on nozzle OD (when analysis is performed at nozzle to shell junction) and pad OD (when analysis is performed at pad od i.e pad edge). You can't modify nozzle OD. But for analysis at pad edge which is governing in most of all the cases, you can vary B and U values by varying pad OD.

B and U are dimensionless paramenters as specified in WRCB-107.