Nozzles – How can I prevent an error message when nozzles are too

close together?

Intergraph CAS

Ray Delaforce

Have you ever had this annoying message?

The nozzle spacing is computed by the following:

= Sqrt( ll² + lc² ) where ll - Arc length along the inside vessel surface in the long. direction. lc - Arc length along the inside vessel surface in the circ. direction

If any interferences/violations are found, they will be noted below.

Diameter Limit clash between : N2 and N1 . The Centerline Dist. is 10.00 while the sum of the limit Radii is 12.62

Is there any way out of this situation when I cannot move the nozzles further apart? The answer

is: Yes. However, you may introduce other problems which you have to fix.

Displaying the interference on the 3D screen

This only works if you are working in one of the ASME codes.

If you are not aware, it is possible to show the limits of reinforcement on your 3D screen. To see

this, place your mouse cursor and press the right mouse button. You will get this drop down

menu:

Let your mouse cursor hover over the item: Visibility and another menu is displayed:

If you look now at your 3D screen, you can clearly see the interference like this:

Interference means that the two nozzle are sharing the same piece of shell metal to reinforce the

nozzles that the code does not allow.

Changing the Diameter Limits

If we could reduce the diameters of those circles representing the reinforcement diameter limits,

we eliminate the error message such as displayed at the beginning of this article. There is a field

in the nozzle dialogue screen that allows us to do just that. Here it is:

If you change the diameter limits for both nozzle, your model now shows that the nozzles no

longer interfere:

Consider that the reinforcement is adequate

When you reduce the diameter limit, you also reduce the amount of shell metal that is available

to adequately reinforce the nozzles. So you should look carefully at the status line of the nozzle

dialogue screen, here:

If the information turns red, it means you so not have enough metal to reinforce the nozzle.

There are several ways you may be able to overcome this problem. You could increase the

Schedule wall thickness of the nozzle, or perhaps add a reinforcing pad. None of these methods

may work, and you will be forced to select a thicker cylinder of head. You just have to try to

solve the problem by trial and error.