Unreinforced openings according to AS1210-2010 1

[Ray2020]

Hi,

I'm having some confusion regarding the limitations of multiple openings according to AS1210. There are 3 clauses that talk about the distance between each opening and I believe each one can give a different answer. Can someone please provide some insight on the interpretation of each of the below.
The first and third clause are related to Class 1H/2H vessels but I'm not sure whether the second clause is still valid for Class 1H/2H vessels. Regardless the first and third clause are still not the same.
As an example let's say we have two openings which are 200 mm and 100 mm in diameter. I will provide the minimum distance between centerlines under each clause.

Clause 3.18.5.1 (b): "The distance between the centrelines of adjacent nozzles shall not be less than the sum of their internal largest opening radii.
The calculated distance is: Sqrt{(l[sub]c[/sub]/2)[sup]2[/sup] + (l[sub]l[/sub]/3)[sup]2[/sup]}
where,
l[sub]c[/sub] the component of the centreline distance in the circumferential direction,
l[sub]l[/sub] the component of the centreline distance in the longitudinal direction
For openings in a head, or for openings along the longitudinal axis of a cylindrical shell, l[sub]c[/sub] = 0.
For openings around the circumference of a cylindrical shell, l[sub]l[/sub] = 0."
Answer: Assuming the nozzles are apart in the longitudinal direction only, Min distance should be approx. 520 mm.

Clause 3.18.6.2: "Two unreinforced openings may be located in the cylindrical, conical or spherical portion of a vessel, provided that the projected width of the ligament between any two adjacent openings shall be at least equal to the diameter of the larger opening, unless the ligament efficiency has been taken into account in the requirements of Clause 3.7."
Answer: Min distance should be 350 mm.

Clause 3.18.6.2 (b): "No two unreinforced openings shall have their centres closer to each other than 1.5 times the sum of their diameters where the distance is measured on the inside of the vessel wall."
Answer: Min distance should be 450 mm.

 

[BJI]

Clause 3.18.5.1, starts with "Other than unreinforced openings in accordance with 3.18.6". So if you are interested in unreinforced openings the first clause does not apply (but check your calculation). The third clause 3.18.6.2(b) is specifically applicable to class 1H, 2H, 1S and 2S, so you have to follow these more stringent requirements if applicable, rather than the general requirements of 3.18.6.2. The ligament efficiency check would always be applicable for more than two unreinforced openings.

 

[Ray2020]

Thank you for your answer. Is it possible to provide an example scenario where Clause 3.18.5.1 (b) needs to be applied?

Thanks in advance.