Jacketed Vessel Closure Bar Welds

[Speckworm]

Regarding ASME Section VIII Appendix 9, Fig.9-5 sketch (f-1): Are both welds required to be continuous? If the design is for a furnace, how is concern about air gap between welds to be handled with regard to pressure build up high temperatures?

 

[CodeRef]

Yes, read general paragraph 9-2 which states the following .....

This Appendix shall apply to jacketed vessels having
jackets which cover the shell or heads as illustrated in Fig.
9-2 and partial jackets as illustrated in Fig. 9-7. Jackets,
as shown in Fig. 9-2, shall be continuous circumferentially
for Types 1, 2, 4, or 5 shown and shall be circular in cross
section for Type 3.

If the design is for a furnace, how is concern about air gap between welds to be handled with regard to pressure build up high temperatures?

In reference to your term "furnace", Section VIII is for unfired pressure vessels...verify the vessel is within the scope of Section VIII-1 by reading the introductory paragraphs within U-1..there is no concern for the gap between welds...as long as it passes the Code required initial hydrotest and periodic jurisdictional inspections while inservice...

FAQ731-376

 

[Speckworm]

Thank you for the response. This is a vacuum furnace - definitely a Section VIII vessel. I read the term "continuous circumferentially" in 9-2 as applying to the jacket specifically, rather than the welds. I would like to have the external weld be continuous all around for seal and other (inside wall of the jacket) to have stitch or least some break to prevent sealed off air gap. Are you saying that air gap is negligible and both welds should be welded continuous? Just trying to clarify. Thanks.

 

[CodeRef]

Yes, sketch (f-1)requires continuous fillet because of two reasons outlined below:

1)In ASME Section VIII Division 1 it is stated that typical nonpermissible corner joints are identified in sketches (o), (p), and (q) of FIG. UW-13.2 ATTACHMENT OF PRESSURE PARTS TO FLAT PLATES TO FORM A CORNER JOINT (CONT’D)

2) General Paragraph 9-1(b) of Appendix 9 states the following:
(b) All other Parts of this Division shall apply unless
otherwise stated in this Appendix.
.....if it is not otherwise stated for sketch (f-1)...it is required because the Appendix 9 rules "supplement" the general rules of Section VIII Division 1, thus it is required.



FAQ731-376

 

[jamesl]

I agree with 11622ABIN. If you are concerned with air traped between two fillet welds, you should use full penetration weld plus fillet.

If you are concerned with air pressure when you have fillet welds on both sides of the bar, then you definitely need to be concerned pressurized air acts on only one side of fillet weld.