Nozzle Flange Replacement

[dforce]

Hello,

I had a simple question about the replacement of a nozzle flange face on a vertical storage tank that falls under API 650/653. According to 650, the nozzle assembly has to be thermally stress relieved because of its material grade, shell thickness, NPS...

My question: Is it allowable to just replace flange face only with a new weld neck flange without any thermal stress relief (i.e. not having to shop fab and insert the entire assembly)? I could not find anything in the code that governs this but I was wondering if anyone out there had any experience.

Thanks
D

 

[JoeTank]

I can't cite the API-650 paragraph at this time, but the nozzle flange can be welded on after PWHT if it's outside the area of reinforcement. That's 4 times the neck thickness from the shell surface.

Joe Tank

 

[IFRs]

API 650 Section 5.7.4.2 which reads IN PART:

"The stress-relieving requirements need not include the flange-to-neck welds or other nozzle-neck and manhole-neck attachments, provided the following conditions are fulfilled:

a. The welds are outside the reinforcement (see 5.7.2.4).

b. The throat dimension of a fillet weld in a slip-on flange does not exceed 16 mm (5/8 in.), or the butt joint of a welding neck flange does not exceed 19 mm (3/4 in.)."

However, there are also other considerations. This is just a partial quote. Please review the entire section to be sure you qualify.