Shell-Dish Joint weld applicability

[K.P.M.]

Hello,

I come to across a vessel which has 800 mm ID with 40 mm thk with Full RT.
Now due space constrain, Shell to dish joint is not possible with both side V groove weld (table-U-12-Type-1) & also due to project requirement, a backing strip is not permitted so table-U-12-Type-2 can not apply. So need to proceed with weld type table-U-12-Type-3 only. I have to ignore the limitations of this weld type which is acceptable?

With this configuration, can I consider the joint efficiency of shell 1 for long. seam & 0.6 for circumference seam?


Regards,
KPM

 

[DekDee]

If it is Full RT you use a Type 1 joint - Single Vee or Single Bevel welded one-side with no backing strip

 

[fleischfresser]

Type 1 joint definition per table UW-12:
-Butt joints welded from both sides or
-Butt joints welded from one side only without a permanent backing strip, that are verified as having achieved full penetration and fusion as required by UW-35.

In your case, the second bullet point applies if UW-35 is met. I have heard from many inspectors and ASME team leaders that UW-35 should only be met if the root surface can be visually inspected. But that's just these guys' opinions. There is an interpretation from the committee (Only the Committee has the authority to provide official interpretations of the Code)
Code Interpretations - VIII-1
Interpretation: VIII-1-10-33
Subject: Part UW, Table UW-12, Joint Efficiency (2007 Edition, 2009 Addenda)
Date Issued: December 2, 2010
File: 09-1015
Question: Is it permitted by the rules of ASME Section VIII, Division 1, Table UW-12 for a Type 1
weld joint to be assigned a joint efficiency from Table UW-12 when visual examination of the interior surface of the weld is not performed?
Reply: Yes, provided the requirements in UW-35 and UW-37(d) are met.

As DekDee mentioned, if full RT is performed you have the evidence that the requirements of UW-35 and UW-37(d) are met.

If you consider the join as type 3 you do not met UW-11(a)(5)(-a) and the category A seam of the shell can only have a joint efficiency of 0.85, even if this seam has got full RT.





Regards - Juergen

 

[david339933]

If you consider the join as type 3

This joint cannot be considered a Type 3 and be Code compliant.

 

[fleischfresser]

david339933 in this case you are right as the thickness is greater than 16 mm

Regards - Juergen

 

[david339933]

And over 600mm OD.

 

[r6155]

How do you plan to achieve 100% RT if access is not possible?

Regards