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Nozzle on Head

Nozzle on Head

Nozzle on Head

I have a nozzle at 56 degrees from the vessel CL. It's not radial, perpendicular or hill side. How do I model this nozzle?

RE: Nozzle on Head

I know how to calculate nozzle reinforcement if I had to
do a hand calculation. The problem is, how do you input the data in the software?

RE: Nozzle on Head

This sounds like a "tilted" nozzle whose axis is at 56° from the vessel axis.

COMPRESS provides for tilted nozzles attached to cylindrical shells: Select the tilted nozzle option and specify the tilt angle of 56°.

However, such an option is not available for nozzles attached to heads. A radial nozzle on the head might have its centerline tilted at 56° to the vessel axis. But this is based on the nozzle axis lying along the geometric 'normal' vector to the head at that location. This implicitly fixes the location of the nozzle's distance from the vessel axis. A more general condition exists in that given the distance of the nozzle from the vessel axis then the nozzle axis might be at any generalized angle from the 'normal' vector (compare to 'tangent' vector) to the head at the intersection of the head surface and the nozzle axis.

The latter condition was rarely encountered in the "olden" days of pressure vessel design. Now, odd orientations seem to be relatively common as they are dreamed up by the process or piping engineers.

It is possible to model such a nozzle in COMPRESS by designing a nozzle whose inside diameter matches the largest chord opening of the tilted nozzle. The reinforcing area calculations should be reasonably accurate. Because openings in the head do not consider the "F" factor of Figure UG-37 this is not an issue. To check the requirements of UG-45 for minimum nozzle thickness a radial nozzle of the actual nozzle size should be modeled.

Of course, if the actual nozzle is something like the 2" tangential nozzles I saw once on a vessel then the results may not be accurate. These 2" nozzles resulted in something like a 2" wide by 20" long "slit" opening in the shell. This is a condition not addressed by the elementary rules of the ASME Code.

  Tom Barsh
  Codeware Technical Support

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