×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Posthydro welding

Posthydro welding

Posthydro welding

(OP)
We have an ASME Code Vessel that has been completed through hydrotesting.  The question has now been asked if we can move the nameplate bracket to a new location.  My understanding has always been that if we weld on it again we will have to rehydro it.  I have seen an answer in another thread that if the welding is for an external attachment (IE; Nameplate bracket) we don't have to rehydro it.  Is this correct?  Where in the Code does it specify this?

RE: Posthydro welding

The answer is no for Section VIII, Div 1. If you read UG-99 (a) 1, it seems clear to me that the hydrotest is final. Attaching a nameplate by welding is part of final fabrication (in my opinion).

Put yourself in the position of the AI. Let's suppose we decide to fillet weld brackets to a pressure vessel and let's suppose something went wrong and introduced a crack. Now you have a potential problem with a new vessel. I agree, the above scenario is remote if proper weld practices are followed. Codes are conservative.

If this were a boiler, Section I does permit some flexibility for post hydro weld repairs to P-No 1 base materials. However, it is up to the AI for these types of weld repairs as final acceptance.
 

RE: Posthydro welding

you can do a "standard repair" with R-1 form.

Not in code under NBIC repairs.

RE: Posthydro welding

Attaching a Pressure Vessel/Boiler nameplate is usualy no more than a couple of tack  welds on the exterior shell of a thick-walled vessel, affecting no more than few 1/4 inch areas.  Adds less than what can be felt by hand to even the nameplate, much less the tank itself.

Yes, it is "welding", but why would you consider that enough heat to material affect metal properties?   

RE: Posthydro welding

racookpe1978;

Quote:

Yes, it is "welding", but why would you consider that enough heat to material affect metal properties?
It makes no difference what you or I think regarding the above. It is a Code requirement regarding no fabrication welding after hydrotesting.

If you need to re-attach the nameplate do it after the vessel is commissioned under the NBIC.
 

RE: Posthydro welding

racookpe1978
Unfortunately, very small welds can easily create cracks in the pressure part HAZ depending on chemistry and cooling rate and weld filler metal selection. Will they grow under the loading conditions - maybe not, maybe so.

RE: Posthydro welding

(OP)
Thank you all for your responses, I thought the answer was that we would have to rehydro.  The vessel isn't in service yet so if they really want to move the NP bracket we will just rehydro and time it for the A.I.'s next visit.

RE: Posthydro welding

Wouldn't be the first time a vessel had an R stamp before being put into service. Attaching a nameplate bracket can be a very minor exercise. Under NBIC would I be *required* to hydrotest a repair such as adding a nozzle with no calc's? Or is the hydrotest left to the AI's discretion?

Often a nameplate would be placed near a manway. Often manways have structural connections near them such as manway davits or platform clips. Welding to these should not be an issue if such a location would be acceptable.

jt
 

RE: Posthydro welding

jte;

Quote:

Under NBIC would I be *required* to hydrotest a repair such as adding a nozzle with no calc's?

No.


Quote:

Or is the hydrotest left to the AI's discretion?

The rules for alternative exmination and laternative testing methods are very clear - NDT or pressure test.
 

RE: Posthydro welding

With a view towards getting around issues such as these, I once was called to the field where they used rivets instead of welds to affix the nameplate to a plate heat exchanger.

They simply rivetted it to the plate pack.

They avoided the welding, and avoided redoing the hydrostatic test, but for some reason, it still leaked.

How I wish this wasn't a true story.

Regards,

SNORGY.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources