Dished End Minimum Straight Flange
Dished End Minimum Straight Flange
(OP)
Is there a code requirement (ASME, BS, EN, AS) for the minimum length required for a dished end straight flange or can you in effect have no straight flange and weld the shell directly to the head tan line?
This would mean that you are applying weld in the overstressed knuckle area.
This would mean that you are applying weld in the overstressed knuckle area.





RE: Dished End Minimum Straight Flange
Cannot help with the other Codes.
Regards,
Mike
RE: Dished End Minimum Straight Flange
regards,
athomas236
RE: Dished End Minimum Straight Flange
It is my understanding that there must be a minimum "straight flange" for a rolling machine to grasp the piece when as it is formed.
Fabricated heads, of course, can be made without an SF.
The SF length is typically between 1.5 and 3.5 inches.
Why is the SF a problem and why are you asking this question ?
Is this a real world application or just an idle question ?
-MJC
RE: Dished End Minimum Straight Flange
UG-32 (l): "All formed heads thicker than the shell and concave to pressure, intended for butt welded attachment, shall have a skirt length sufficient to meet the requirement of Fig. UW-13.1 when a taper transition is required."
One additional point for rethought or interpretation: UW-3 (1) defines Category A for a circumferential welded joint as: "connecting hemispherical heads to main shell".
UW-3 (2) defines Category B for a circumferential welded joint as: "… connecting formed heads other than hemispherical to main shell".
How about a spherical / torispherical head with no skirt?
Is it going to stand under category A or B ?
RE: Dished End Minimum Straight Flange
On f&d & elliptical heads, the straight flange is there during manufacturing and trimmed by head manufacturer to maintain the proper depth. It also allows the head manufacturer to have an area to adjust to maintain strapping as the "dished" portion of the head is not perfectly concentric or located correctly due to pressing operations.
RE: Dished End Minimum Straight Flange
I have always seen / used dished 2:1 and torispherical heads with a SF of approx 50 - 75 mm dependent on wall thickness.
I have just recently seen a head on a vendor drawing with a thickness of circa 100mm and a SF of 50mm.
The SF just seemed a little small to me on first inspection
Thanks to all for all the replies
RE: Dished End Minimum Straight Flange
SF= 2 x shell thickness but not less than 50mm.
I dont know where (if ever) I read it but I always find the results visually appealing.
For hemispherical heads, there should not be any straight flange.
RE: Dished End Minimum Straight Flange
The industry standard SF is 1.5 inches, but the fabricators can be flexable.
For common types and finshes, see this website:
http://www.brightontruedge.com/types.htm
Contact the fine folks at Brighton in Cincinatti, OH(formerly ENERFAB)with specific questions.
-MJC
RE: Dished End Minimum Straight Flange
haven't seen a 1 1/2" called in years except on standard manufactured tanks that are not custom.
RE: Dished End Minimum Straight Flange
RE: Dished End Minimum Straight Flange
Regards,
Mike