ASME VIII Div. 1 - Minimum distance between welds of pads

[fedefer85]

Hello everyone.
I did a research in the design code trying to find a specific minimum distance between welds of re-inforcements. It seems that there is no restriction in how closer a nozzle can be put from another, just beware of the HAZ zone.
Does anyone know if there is a specific distance in the code or in an european code?
Thanks.
Regards.

 

[Don56]

To which Code are you inquiring?
Nozzle size?
Shell/head thickness?

 

[marty007]

It seems that there is no restriction in how closer a nozzle can be put from another, just beware of the HAZ zone.

If you are working to ASME VIII-1, you must ensure you do not have overlapping limits of reinforcement for nozzles. (See UG-42).

 

Try searching the eng-tips archives for this classic question. I think it just came up again recently.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[0707]

There is no specification on this matter IMO. If we have too close welds seams there is the possibility of HAZ sobreposition which affects the metalography of the two adjacent welds and its mechanical properties if a minimum distance can´t be respected.

The link below shows the comum practice used by the industry on this subject.

luis

https://pt.scribd.com/document/125978352/Minimum-Distance-Bw-Welds

 

[david339933]

UW-14 limits nozzle proximity to other welds (1/2"), for nozzles exempt from reinforcement per UG-36(c)(3).

 

[r6155]

Try to avoid reinforcing pads.

Regards

 

[Some Curious Guy]

The minimum distance between welds is dictated by various End User or Client specification. I did not come across an explicit requirement in standard design codes.
You have to however take care of overlapping reinforcement limit in design. Appendix A of WRC-297 also has some guideline of min width of RF pad if you are considering pad thickness to reinforce shell thickness. These are however design guidelines.

I have come across weld toe to toe distance requirement ranging from 1 inch to 2 inch or some multiple of component thickness like 2T, 3T etc. The purpose of this as many have pointed out is to avoid overlapping of Weld HAZ. Weld HAZ are relatively more hardened than base material and can become points of initiation of cracks. Hence they are best kept away from localized high stress discontinuity zones.

if nothing is specified I would advice you to maintain a min distance of 1 to 2 inch between weld toe to toe rather than debating later with the your client. Contracts are written such a way that equipment owners have more power of dictating terms if nothing is specified. Better take precaution early if you want to avoid time consuming debates with client on who or what is right.

 

[r6155]

See PD 5500 3.5.4.9.2 and 3.10.1.2

Regards

 

[Dhurjati Sen]

https://www.eng-tips.com/viewthread.cfm?qid=342321

https://www.eng-tips.com/viewthread.cfm?qid=194119

https://www.eng-tips.com/viewthread.cfm?qid=466230

https://www.eng-tips.com

and many many more

DHURJATI SEN
Kolkata, India

 

[staticmh]

The minimum toe to toe weld gap is normally specified by the client specification. Whereas it is a good engineering practice some time case to case it very but the most often i have seen to advice the draftsper to verify the all the nozzle pad to other attachment toe to toe weld gap with 50mm.

I'll refer to you some Shell DEP unfired pressure vessel specification, which some of the client always directed to comply with it. If you are lucky to found that document at internet i am sure that document will be quite helpful for you.

The document no is : 31.21.00.31-Gen which you can search on internet by writing the same and refer to relevant appendix. Thanks!

 

[r6155]

See PIP VESV1002
Vessel Fabrication Specification
ASME Code Section VIII, Divisions 1 and 2

Plate layouts shall be arranged so that longitudinal and circumferential weld
seams clear all nozzles, manways, and their reinforcing pads by 2 inches
(50 mm) minimum, measured from weld edge to weld edge

Regards