Reinforcement of flat heads
Reinforcement of flat heads
(OP)
I am looking for a method for analyzing a flat head design with welded, radial stiffeners. UG-47 does not seem to apply. Thanks for any help.
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Reinforcement of flat heads
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RE: Reinforcement of flat heads
RE: Reinforcement of flat heads
Also radial stiffeners are not necessarily the best choice, as the center portion, with highest stresses, will require the ribs to be heavily welded together.
The italian code for pressure vessels has a method for that.
First check is that the thickness of the flat wall satisfies the rules for unreinforced flat heads with a diameter equal to the largest circle that may be inscribed between the ribs, and, using the method of UG-34, with C=0.2.
Then one has to calculate the ribs, but the detailed method is too complex to be repeated here.
However you can simply calculate the ribs with the participation of the flat wall as an equivalent T beam, by taking the following limits (t is wall thickness):
-width of participating flat wall not higher than 20t (and of course you can't account the same material for separate ribs, this holds for the central portion of your radial ribs)
-height of ribs between 5 and 15 times their thickness
-rib thickness between 0.75t and 1.5t
prex
http://www.xcalcs.com
Online tools for structural design
RE: Reinforcement of flat heads
Not sure I agree with you about rib stiffening not being permitted by Div.1. See U-1(a)(3). Do you have a reference?
I do agree it is hard to prove and there may be better choices.
RE: Reinforcement of flat heads
Brian
RE: Reinforcement of flat heads
I think deanc is right. ASME VIII does not prohibit rib stiffened flat heads... it just doesn't give the rules for it.
Steve Braune
Tank Industry Consultants
www.tankindustry.com
RE: Reinforcement of flat heads
You need to go back to the erly 1940 I have seen calculation set in the State of Ohio
Leonard@thill.biz
www.thill.biz
RE: Reinforcement of flat heads
look in sec VIII-1 vessels of rectangular configurations, calcs for stiffeners on the flat surface.
ER
RE: Reinforcement of flat heads
Sometimes that thickness increase you are suggesting might be for an expensive material, while ribbing can be plain old (formerly) cheap carbon steel.
we used to do flat side side and flat head designs for evaporator equipment made of CU/NI material, and it was obviously much more cost effective to make the CU/NI thickness minimal, and pour on the ribbing.
Secondly, now-a-days, some head and covers are limited in maximum weight by specifications so that they can be lifted by a single person without the aid of lifting devices, in which case, ribbing would produce a lighter piece than thickening.
rmw
rmw
RE: Reinforcement of flat heads
RE: Reinforcement of flat heads
RE: Reinforcement of flat heads
RE: Reinforcement of flat heads
the area of staying will be part of the stiffeners calcs.,
the needis the same.
I am looking into the calculations myself and it is not easy. I will keep looking.
ER
RE: Reinforcement of flat heads
Stiffeners for crossectional areas as previously stated by prex are in Italian Codes RACCOLTA VSR and VSG for vessels and boilers respectively.
Plate between stiffeners are also in these codes but in others too because in its crossectional versión is a tipicaly boiler used construcction. Out of my head is UNE 9300, new EN (12935?)for pirotubular Boilers, TRD perhaps.
It's based in calculate thicknes with the major circle diameter with three supporting points, a factor for other auxiliar circles of 0,75D with two supporting points which center are off the main circle (thats forms a oval area)and another factor for the stiffening method. Rectangular areas must be also considered with a factor for the rectangular form.
RE: Reinforcement of flat heads
V.Dwaraka Krishna.
RE: Reinforcement of flat heads