Joint Efficiency for Seamless Hemispherical Dished End 2

[ashaykadam]

We are having a case where,
Hemispherical Dished End = Seamless
Hemispherical Dished End to Shell Joint = No radiography

We have three queries:

1. As this Hemispherical Dished End to Shell welded joint is of Category-A, neither clause UW-11(a)(5)(-b) nor UW-12(d) will be applicable. Is our understanding correct?

2. What Joint Efficiency shall be considered for calculation of thickness for Hemispherical Dished End in this case?

3. PVElite software consideres following for Hemispherical Dished End : (File Attached)
a. Longitudinal Seam Efficiency = 0.85
b. Circumferential Seam Efficiency = 0.7
However, considers values of E = 0.85 in Design Calculations. Is that correct?

Please advice.

Thanks.

Ashay Kadam
Mechanical Engineer
India.

 

[TomBarsh]

Use of E=0.85 for the design thickness of the hemispherical head is correct. Refer to UW-12(d) for joint efficiency of seamless vessel sections or heads. "For...thickness of seamless heads, E = 1.0 when the spot radiography requirements of UW-11(a)(5)(b) are met. E=0.85 when the spot radiography requirements of UW-11(a)(5)(b) are not met,..."

 

[MechD]

As the hemispherical end is seamless, the Longitudinal Joint Efficiency should be considered as a joint without imperfection i.e. Joint Efficiency E = 1. If you do 100% radiography of a welded joint it can be treated as a "perfect" joint, assuming no imperfection, and therefore no requirement for an additional factor of safety. A seamless dished end has no joint, so it does not require this factor of safety. In any case, where would you do the radiography for long seam on a seamless dished end?!

The Circumferential Joint Efficiency is based on the weld between the dished end & the shell. As you have not carried out any radiography, this should have a Joint Efficiency of E = 0.7. Carrying out spot radiography on the welded joint would allow you to use E = 0.85, and if you carried out 100% radiography you could use a joint efficiency of E = 1.0.

 

[ashaykadam]

Thanks MechD.

I just referred the solved example no. L-1.5.3 (d) of Appendix-L from ASME Sec. VIII Div. 1 (2011 Add.) & found your reply in line with it.

Refer attachment:

Ashay Kadam
Mechanical Engineer
India.

 

[21121956]

Hello everybody:

In addition to the above noted, you can see the following link:

http://www.pveng.com/ASME/ASMEComment/WeldEffic/Weld_Efficiencies_Notes.pdf

El que no puede andar, se sienta.

 

[Duwe6]

Great link, 21121956