UG-36(b)(2) Lareg openings in Formed heads 1

[Ganfoss2]

Dear alls,

with the present to ask you some clarification on the interpretations in the design of large opening in heads (consider only 1 single opening, centered respect to the head).

FOREWARD: UG-36(b)(2) states: "Properly reinforced openings in formed heads and spherical shells are not limited in size. For an opening in an end closure, which is larger than one-half the inside diameter of the shell, one of the following alternatives to reinforcement may also be used: ..." that point to solutions like SHELL-REDUCER SECTIONS (see UG-36 pictures).

Questions:

1) What does mean "Properly reinforced openings" compared with the following phrase "(opening) not limited in size"?

Mean that it is possible to use a large opening on a head(with d > 0.5 head diameter) if the opening fullfill the requirements of the classical code calculation of openings (UG-37, UG-40 and UG-41)?

If the reply is YES, how I have to interpretate UG-37(b)? Seem that do not allow to use the classical code calculation of openings for large openings. Is this my interpretation og UG-37(b) correct?

2) What does mean "alternatives to reinforcement MAY also be used"? This mean that in case of large opening I'm not obliged to use reducers (otherwise MAY should be replaced with SHALL).

Many thanks for the reply.

 

[prex]

The answer to 1) is NO: UG-37(b) clearly states that large openings per UG-36(b)(2) may not be treated by UG-37 rules on reinforcement. You could however use a different reinforcement approach and justify it per U-2(g) (or more likely use the rules of UG-37 with some additional considerations justified per UG-2(g)).
That's why the use of one of the alternatives UG-36(b)(2)(a) to (d) is not an obligation. Therefore the answer to 2) is: YES.
BTW can't see how an opening larger than one half the diameter would be called otherwise than a 'reducer'.

prex

http://www.xcalcs.com

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[Ganfoss2]

Many Thans.

Additional clarification: you have stated that: "You could however use a different reinforcement approach and justify it per U-2(g) (or more likely use the rules of UG-37 with some additional considerations justified per UG-2(g))."

Could you give me an example of "additional considerations justified per UG-2(g)"? I want to use FEA as last resource.

NOTE: APV Software (for example) do not give any WARNING on this issue (for torishperical/Elliptical Head, only a flag is avaiable to allow APV to change the ecalclation procedure of tr if the Opening with its reinforcement along the head go beyhond the 80% ID Head).

Many thanks in advance.

ANN

 

[prex]

Well I don't know really, was only giving an interpretation of the rules as you requested. It is possible that the AI will accept a simple reinforcement calculation per UG-37 if there is a comfortable margin.
And of course FEA is an alternative: it's not a reinforcement like approach, and will require the approval of the AI per U-2(g).
My point is instead: why are you not using one of the alternatives of Fig.UG-36? I guess that any head with a large opening will be very much like one of them.

prex

http://www.xcalcs.com

: Online tools for structural design

http://www.megamag.it

: Magnetic brakes for fun rides

http://www.levitans.com

: Air bearing pads