Minimum nozzle projection to first weld from vessel?

[nickelkid]

Working on an ASME vessel alteratation, adding a 10" sch 160 nozzle in the top of a 2:1 ellipitical head.

What would be considered a reasonable minimum distance between the weld on the shell to the next weld on the nozzle?

We are in a very tight space. Some on the project feel that having a nominal 2 to 3" long nozzle projection from the head is acceptable.


The head material is SA516-60 normalized and welding will be 100% radiographed, nozzle SA-106-B

 

[gr2vessels]

Hi Fatso,
For the minimum distance between weld toes you should be looking for a minimum of 2 x nozzle neck thickness, ie 2 x 28.6 mm = 57.2 mm, say 57 mm. If you add the head to nozzle weld thickness and the nozzle to flange weld thickness, plus the flange thickness and the 57 mm, you are looking for some 135 mm for a slip-on flange class 150#, more for any other arrangement or class.
Cheers,
gr2vessels

 

[Bobfromoh]

I've had to attach weld neck flanges directly to the vessel wall (no nozzle neck at all). I just didn't use any of the flange for reinforcement.

 

[gr2vessels]

Correct Bob,
Daddy, just be aware that you have to remove sometimes the flange bolting!
Cheers,
gr2vessels

 

[arto]

how about the sqrt[Rt] for a length? that'll be ~2.5"

 

[JoeTank]

ASME VIII uses 2.5 times the nozzle wall thickness as the limit of reinfocement provided by the nozzle neck. If you stay outside this range, you will not have to deal with the area replacement issues of the Code. If you get closer than that, you need to check the nozzle reinforcement area.

Joe Tank

 

[sbush]

Have you considered using a studding outlet (a.k.a. pad flange, boss flange)? We buy them from Forged Vessel Connections in Houston, TX. This method puts the flange connection very close to the vessel while eliminating the problem with clearance for bolts/nuts.

S. Bush

http://www.water-eg.com