Opening range of the head
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When calculating the reinforcement for openings in heads, there is a limit of 0.8Di. Does this limit refer to the distance from the center line of the opening to the center of the head, or rather to the distance from the farthest point of the opening to the center of the head?
Distance from the center line of the opening to the center of the head
The farthest point of the opening should be within the range of 0.8Di, meaning that the entire opening is within this 0.8Di range.
I quite agree with your view; since the stress is high in the transition zone, the openings should be avoided in that area. If it’s along the center line, a large opening might end up in the transition zone.
It can be understood in this way: the center of the opening in the elliptical head should lie within a circle with a diameter of 0.8D, centered on the centerline of the elliptical head. Beyond this area lies the structural discontinuity (the junction where the spherical shell at the top of the elliptical head meets its lower end).
Reply to 3# xtq: I agree with your view; holes must definitely be made within the transition zone. There is stress concentration in that area, and the thickness reduction in that region is also significant during processing
Holes can also be made in the transition zone; the specific location is determined by the size of the pipe.
I wonder if the standards for this regulation specify it
There is no such restriction anymore. This is the requirement for version 89