Definition of "CLUSTER" mentioned in ASME VIII Div.1 para. UG-36(c)(3(-d)

[CrisDom]

Hi folk,
can anybody help my to understand the correct meaning of "cluster" mentioned at para. UG-36(c)(3)(-d)?
I'm trying to understand wheter my 3 openings (N4, N3 and N10) are 3 unreinforced openings in a cluster.

Actually they're unreinforced, I mean that, as per Code rules, they do not require to be checked for the available reinforcement against the required one.
But do they form a cluster or not?
Does "cluster" mean that openings have to be aligned?
Does "cluster" mean that openings have to be placed to forma regular pattern o something like that?
I have always thought that "cluster" meant simply a group, but I have now some doubts.

Can anybody help me?

Thank you so much.

Best Regards

Cristiana

 

[Rputvin]

Cristiana,
UG-36 (c)(3)(-d) doesn't define a cluster, the same as UG-36 (c)(3)(-c) doesn't define "isolated" when referring to two openings.

I would check N10, N3, N4, and N2 and ensure their locations don't fall within the defined limits of either (-c) (no two closer than the sum of the diameters) or (-d) no two in a cluster of 3+ closer than (1+1.5cosΘ)(d1 + d2).

It seems the intent is to maintain a little more distance between openings along the vessel's longitudinal axis when there is more than one other non-reinforced opening nearby.