Dear members

Is there any straight flange length calculated in hemispherical heads?

Which type of weld is used for hemishperical head to shell joint reference to asme section VIII div 2.



with reference to the joint (j) in UW-13,

our shell id is 2506

shell thickness is 80mm, head thickness is 40mm.

we cant get the joint dimensions as per the relations specified.

do you have any solutions???

Dear Wijeesh,

Regarding Sketch j of Figure. UW-13.1, tangent line is shifted a distance of at least 3y. In your case, it would be 120 mm maximum. There shall be no straight flange in hemispherical head. You will cut your hemispherical head 120 mm short from the ends. You will increase shell length 120 mm more on each end (total 240 mm more length). This extra length shall be the part of the hemispherical head. What is the advantage of shifting the tangent line by this way? you will not to do weld build up.In this case 120 mm is the part of thinner member although it looks that this is is part of thicker member.
If you do not do so, what other option is you have to do a taper transition on thickness from a higher thickness 80 mm towards a lower thickness 40 mm. So you have reduced the thickness below the required thickness in certain portion, you can not do this unless you deposit a heavy build up.Because you are reducing the thickness than that required. Now in this case, you are reducing the thickness from the thicker member.

For the joint design between hemispherical head and the shell, please see paragraph 4.2.5.2 and Table 4.2.5 in Section VIII-2.Here in this table detail 4 and 5 are like the same as in sketch j of Figure.UW-13.1.

Please let us know if you are not still clear.

_________________
Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402

Dear Mr Nasir

Thank you very much for your valuable reply.
We are considering an offset of 15mm towards ID between shell /head thickness center lines, hence we are getting around 110(>3b of 105). But the problem is that we have to increase the head ID to 2516mm (2506+10mm). Is there any problem with that?
Moreover is there any requirement for Hemispherical head to skirt joint. Is the skirt is welded to shell in this case?

Thanks & Regards
Vijeesh

_________________
Vijeesh

Vijeesh,

You are going to cut 110 mm head short right? your head ID is 2516 and shell ID is 2506 mm right?
15 mm offset between centerlines of head and shell thickness is okay, no problem, Code permits the offset up to 20 mm in your case.
You are going to do a taper both side on the shell. I mean you are going to make a transition at outside and inside the shell, so applicable sketch shall be k of Figure UW-13.1.
I have drawn your case in Auto-Cad and found you meeting the Code requirements.

_________________
Thanks & Regards,
Nasir
Welding Engineer
DESCON Engineering Limited.
Lahore, Pakistan.
Mobile # 0092-336-4145402

Dear Mr Nazir

Thank you so much for your effort and help. It was very much helpful to me.

Regards
Vijeesh

_________________
Vijeesh