WRC-107 Nozzle Orientation 5

[jdog1]

First off, I'm new to the forum and pressure vessel design.

I'm helping out on a vessel that has several nozzles on a cylindrical shell that are at compound angles to the vessel, i.e., they are not perpendicular to the vessel as is typically shown in WRC-107 sketches.

The customer supplied nozzle loads in global coordinates(Fx, Fy, Fz, Mx, My and Mz) and asked that we translate these loads to local nozzle loads( WRC-107 convention). After an embarassingly difficult review of statics, I was able to perform the nozzle load translation, but I'm not sure that this is the correct approach.

I haven't seen anything in WRC-107 that addresses how you treat a nozzle with such an orientation. Specifically, how do I apply P, Vc, Vl, Mt, Mc and Ml?

I'm leaning towards treating the nozzle as if it were perpendicular to the vessel, use the supplied global nozzle loads and use the developed opening on the vessel as the nozzle diameter.

Any guidance, advice, other places to look, things to try?

Thanks!

 

[unclesyd]

This is not the complete answer but it may help.

This ia a paper by Randall W. Whiteside P.E.

http://www.pdhonline.org/courses/m205/m205content.pdf

 

[JStephen]

WRC 107 doesn't cover hill-sided nozzles. If the nozzles aren't TOO hillsided, it would probably be a good approximation.

Otherwise, it seems that resolving the loads as you mention would be a reasonable approach IF the nozzle neck is fairly heavy (IE, closer to a rigid plug).

 

[jdog1]

The nozzles are at pretty steep angles. At first glance, it appears that the developed opening could be double the nozzle diameter.

The latest plan is to treat the nozzles as if they are perpendicular to the vessel and use the developed opening as the nozzle diameter.

Is this a common problem people encounter with WRC-107? Is there a more appropriate approach to what I'm trying to do?

 

[TGS4]

You're really pushing the limits of what WRC-107 was intended for. I would recommend that you consider a finite element analysis-based approach. If no one in your company is intimately familiar with FEA, then I would consider a consultant before buying a piece of commercial software.

 

[vesselguy]

jdog1,

I agree with TGS4 in that based on your description of your hill-side nozzle, it can only be solved via FEA. I suggest your company purchase the FE-Pipe package. It has an excellent model for your geometry. They made this package so good that you don't even have to know anything about FEA to use it (a real black box).

The paper recommended by Unclesyd is a good paper. The method outlined in there is exactly what I used to do for these hill side nozzles before FEA was affordable. Yes, you have resolve the forces and moments to the axis needed by WRC-107. Keep in mind WRC107 is already a ball park approximation, and it was good for the longest time. But it was never meant for an elliptical opening, and when you stretch the theory for this application know that you are getting a ball park approximation of a ball park approximation. The calculation may not be accepted by a Boilers Branch for registration.

 

[vesselguy]

Sorry, brain on neutral this morning. Boilers branch don't really care about your external nozzle load cals; they are concern about the code calculations. Hence, what ever theory you use for addressing the external cals are your business/risk.