REINFORCEMENT OF OPENING ON FLAT HEAD 1

[ME231]

UG-39(b) seems to suggest that for openings in a flat head, only half the area required by UG-37 is needed to satisfy the reinforcement requirements for the opening. Is it safe to assume that a head needs only half the reinforcement area of a similar opening on a shell?

 

[jte]

sp-

A shell and spherical or ellipsoidal or similar head carries the load imparted by the internal pressure through membrane stress. This stress is directly proportional to the thickness. On the other hand, a flat head resists the pressure through bending. The stress in this case is proportional to thickness squared. So very roughly speaking, the required reinforcement provides the same increase in strength if you double the thickness of a shell or take 150% of the thickness of a flat head. Thus, reinforcement of an opening on a flat head requires half of the reinforcement of an opening on a shell. Before we get off debating the details, keep in mind that the concept of area replacement can be debated ad infenatum.

jt

 

[prex]

Well, sp231, your wording is a bit confusing. The required area is based on the required thickness t_r, and this one will be of course different for any given vessel part, be it a shell or a flat head. What you can say is that, for the same t_r, the area required by a flat head is half the one required by a shell, but that's exactly what the code tells you.

prex

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[unclesyd]

A little more complied information of nozzles in flat heads will be found in this paper by RW Whitesides.

http://www.pdhonline.org/courses/m205/m205content.pdf

 

[ME231]

prex,
I am trying to compare the area required by UG34(c) and UG39(b)1

 

[gr2vessels]

Perhaps 'ad infinitum'...(ie endlessly)? Other than that, spot on reply to sp231.
Cheers,
gr2vessels