UG-42 : Reinforcement of Multiple Openings 1

[mg75]

I have a question regarding ASMEVIII Div1 UG-42

When two similar nozzles are installed on a longitudinal line of a vessel, and both nozzles are radial, I have no problem using UG-42 since whatever the plane I consider, the finished diameter d of the opening (as defined in UG-37) is the same. Let's say this is case A.

Where I get confused is with two nozzles that are non radial, but still in a plane perpendicular to vessel axis. To put it easier, imagine two identical horizontal manholes at the bottom of a cylindrical horizontal vessel, and let's call it case B.
It this case B, the finished dimension d of the non-radial opening depends on the plane under consideration (UG-37). Now, which value of d shall I use to check if nozzles limits of reinforcement overlap ? The smallest one (thus same value of d as in case A) that is measured in the plane that actually contains both nozzle axis, or the biggest one measured in the plane perpendicular to shell axis, although this plan does NOT contain both nozzles ?

My concern behind this is that I would rather neither increase the distance between the nozzles, nor change the angle between nozzles and shell. Consequence would be to have a reinforcing pad larger in the circumferential plane of the vessel than in the longitudinal plane.
Might a third party accept it and would my boiler worker hate me for the fancy pad ?

Thanks for your thoughts

 

[gr2vessels]

mg75,
'd' is always measured in the plane containing the nozzle centreline, regardless weather it also contains or not the vessel longitudinal centreline. Now, from your description I understand that the manways centrelines are contained in two separate planes perpendicular to the vessel centreline, with an offset "x", which will generate a certain ligament distance between the two openings.
The UG-42 is fairly clear as the available reinforcement in ligament is contained in the shortest length, ie in the plane containing the point of intersection of both manways centreline and the vessel ID. The real distance would be measured on some spiral on the vessel ID, but close enough (and conservative) is the projection of it measured in the plane containing the two points of intersection of manways centreline and vessel ID, and the point of intersection of the vessel long centreline and the plane perpendicular on it at the mid distance between manways centrelines. From there, the rest of UG-42 is trivial, I don't believe it is an issue.
I imagine the common reo pad will look some fancy and will not make you many friends in the workshop, but if you are convinced that the arrangement you mentioned is the only one possible, it can be calculated per UG requirements and the error due to the ligament orientation would be minimal, most likely compensated with a bit of extra pad thickness.
Does it make sense to you all the above? Perhaps a bit over-descriptive...
Cheers,
gr2vessels

 

[mg75]

gr2vessels,

Thank you much for your advice. It is clear and being descriptive actually helped me.
I think I got it, but your first comment let me think I could miss something.
I agree 'd' is measured in a plane containing the nozzle centerline. But there is still in infinite number of planes that contain the centerline, and for a non-radial nozzle, 'd' will depend on the plane selected.
So, if I understood your point of view : the plane in which I shall measure d1, for the first nozzle (to deal with the nozzles proximity issue) is the one that contains the centerline of the nozzle and the point of intersection of the second nozzle centreline and vessel ID. Then I do the same for the second nozzle to get d2, and I check the ligament measured as you mentionned is long enough to prevent overlap.
If this is all, then it is indeed no big issue.
Now, just have to sell it to the manufacturer.
Many thanks again,
mg75

 

[gr2vessels]

Correct. Good luck.
Cheers,
gr2vessels

 

[unclesyd]

Here is some very good information given by R.W.Whitesides on "Openings in Pressure Vessels".

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