When the structural characteristic coefficient (or actual reduction coefficient) k of the boiler header cylinder is ≤ 0.4, does 16507 need to remain synchronized with 16508 without any reinforcement?

Refer to 16508.3-2013, page 103, sections 13.3.4~13.3.7

A closed tag means the sentence isn’t finished yet; it’s still talking about the same thing: it refers to a single hole. If both holes exceed the maximum allowable diameter of an unreinforced hole and form a hole bridge, this situation is unsafe. No calculation method is provided in 16507; such a structure is considered unacceptable at present and should be avoided – this is mentioned in Li Zhiguang’s book.

In other words, as stated in 16507.4-2013, clause 11.2.6, \"for a hole bridge in which the equivalent aperture of both holes is greater than the maximum allowable diameter of the unreinforced hole, it cannot be calculated in accordance with the provisions of this chapter (section 11), regardless of whether the characteristic coefficient of the cylinder’s opening structure is ≤ 0.4!\" Measures should be taken to avoid this situation, such as increasing the wall thickness to raise the maximum opening diameter value and meet the calculation requirements of Section 8.5, etc. In short, measures should be taken to enable calculation using conventional methods. Am I understanding correctly?

In other words, the preconditions stated in 13.3.5 on page 103 for shell-and-tube boilers should be consistent with those for water-tube boilers; when the diameter of one or two of the holes in the hole bridge is greater than the maximum allowable diameter of the unreinforced holes, certain additional preconditions or finite element analysis must be satisfied. As shown in the figure.

Previously, in the strength calculations for the inlet and outlet headers in organic heat carrier boilers, it happened that the actual weakening coefficient of the header cylinder was around 0.18, which is less than 0.4; four holes were arranged longitudinally at equal intervals, with the pitch being slightly less than the critical pitch. The thickness was then calculated using the weakening coefficient associated with those holes. (Subsequent manual calculations showed that the maximum diameter of the holes without reinforcement, when the actual weakening coefficient was taken into account, was still less than the original hole diameter.) The inspection passed without any requests for modifications. At the end of Section 12-5 in Li Zhiguang’s \"Modern Design and Development of Industrial Boilers,\" it is stated that \"there have never been any accidents in history caused by insufficient strength of the hole drains.\" It was left unresolved.

Yes. I understand it the same way, and that’s how it’s done in the design as well.