×
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

PWHT of API Tank Shell Nozzles

PWHT of API Tank Shell Nozzles

PWHT of API Tank Shell Nozzles

(OP)
Per API 650 section 5.7.4.2 and 5.7.4.3, certain shell nozzle penetrations require PWHT depending on material group, shell thickness, and nozzle size.  When that is the case, "openings...shall be prefabricated into the shell plate or thickened insert plate and the prefabricated assembly shall be thermally stress relieved...prior to installation."  

This requirement is pretty cut and dry on a new tank but when API 653 is consulted regarding nozzle replacement on an existing tank, you are referred to the current standard of 650.  Does that mean that if I have an existing tank that requires a shell nozzle replacement, I need to remove a larger portion of the shell(say 3'x3'), weld the nozzle into that 3'x3' insert plate, PWHT, butt weld the insert assembly into the shell, and then weld a repad onto it?  It might be easier to do that for a thickened insert plate assembly but those are not preferred in my refinery.  The section of referenced above does not seem to make an allowance for repads in the even of replacement.

Any help or opinions on the matter would be appreciated.

Thanks!

RE: PWHT of API Tank Shell Nozzles

The repad is part of the assembly that is stress-relieved.

On a new tank, this would normally be a full-height section of the shell ring, not just a square cut-out.

RE: PWHT of API Tank Shell Nozzles

(OP)
JStephen, I understand about the application of API in the event of new construction.  That seems very clear.  If you read the section though, it states that

"...all opening connections NPS 12 or larger in nominal diameter in a shell plate or thickened insert plate more than 25 mm (1 in.) thick shall be prefabricated into the shell plate or thickened insert plate, and the prefabricated assembly shall be thermally stress-relieved..."

It does not mention a repad, only a shell plate or thickened insert. Do you see my confusion?

RE: PWHT of API Tank Shell Nozzles

I'd weld the entire nozzle with repad into a shell insert plate, PWHT the whole assembly then install it in the tank.

RE: PWHT of API Tank Shell Nozzles

Also, look at using a thick shell insert plate to eliminate the repad welding & testing.  Just taper the insert-plate edges to meet the shell thickness.  Will be cheaper to do it this way if you can get milling [or large lathe] work done in-house and/or cheaply.

RE: PWHT of API Tank Shell Nozzles

(OP)
Thanks everybody.  It does seem like the whole assembly needs to be PWHT, shell, repad, and nozzles.  They try not to use thickened inserts out here but in this case I don't think there is a way aound it since it will be a low-type repad and we have to deal with the corner weld.

RE: PWHT of API Tank Shell Nozzles

I read this with interest.  I don't think everyone has replied completly to tankerator's question.

Assuming his nozzle is not a flush type.   So, if he chooses to use a repad and his shell insert plate of Group I,II,III/IIIA is less than 1" thick, and the nozzle is not larger than 12", then he does not have to PWHT the assembly.  That's my interpreation of 5.7.4.2.  
 

RE: PWHT of API Tank Shell Nozzles

Unless the shell material is group IV or above, then it needs to be PWHT no matter what the size if the shell is greater than half inch.

RE: PWHT of API Tank Shell Nozzles

Since he referenced "certain nozzles", I assumed the nozzle in question fell into that category.  I think the last post is off, but would have to look it up later.

RE: PWHT of API Tank Shell Nozzles

If it is my last post that is "off", please see 5.7.4.3

RE: PWHT of API Tank Shell Nozzles

Does API 653 allow you to reference the As-built code of construction for a replacement nozzle?  If the tank is an older tank, you might be able to get away from the PWHT by refering to the edition of API 650 that the tank was built to.

RE: PWHT of API Tank Shell Nozzles

IFRS- the opening "Unless" should be "When" in your statement per 5.7.4.3.

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