The issues of uniform distribution and centered distribution of flange stud holes at the mid-span
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I’m a complete novice when it comes to pressure vessels, and I have a question for the experts here. The bolt holes on the flanges of equipment and piping are usually arranged evenly across the center. Under what circumstances is such even distribution achieved? I would appreciate it if the experts could give me some guidance.
It is commonly used at the mid-span; it refers to a centered distribution, meaning that the center line of the bolt holes coincides with the center line of the mid-span, right? Assuming that flange installation is rather complicated, such as when working with pipe flanges in seawater, it is first necessary to insert a long bolt there as a guide before securing the flange; alignment is required for this purpose. Once the top bolt has been inserted, the flange remains in place due to gravity, making it easier to insert the other bolts ； When using the mid-span method, 2 bolts need to be inserted at once so that no external force is required to align the flange in place. I am not aware of the alignment on land.
The purpose of spanning is to prevent leakage from reaching the bolts, so in principle, there is no need to consider alignment.
There are two reasons for not splitting it at the mid-span: the angle of the valve, and the fact that liquid leakage will not drip onto the bolts
For pressure vessels, it is required that they be arranged with the holes in the mid-span area; therefore, when designing the vessel, simply place all the flange bolt holes in the mid-span area. In particular, there are interfaces against the wall, which are not horizontal during operation.