Increase asme b16.11 coupling length

[leon_har_dt]

Hi!
hope you are doing well.
I was doing some research looking in the VIII asme code and b16.11 I couldn't find any clue to my answer.
I need to increase the length of a coupling because of thermal insulation in my vessel.
The first solution in my mind it is to weld a pipe 1" or 3/4" into the vessel and then weld the threaded coupling(1/2" #6000) into the pipe.
But, how is need to be this weld? I can't put a 1/2" pipe because the thread it's equal to the OD of the pipe. That's why i'm thinking in 1" pipe and do some fillet weld into the coupling, but this is allowed?

I would be grateful with any answer

Regards
L.

 

[GDHTX]

B16.11 couplings can be manufactured as reducing fittings and as combination fittings.
So you could specify a 1" socket weld x 1/2" threaded 6000 coupling.

 

[leon_har_dt]

WOW! really?
I would check with my supplier. Thanks a lot for your answer.
Still, I'm curious to know if it can be done what I propose.(I'm not always going to find the specific coupling because of the location where we are manufacturing)
Regards.
L.

 

[JStephen]

Thread-One-End couplings are routinely available in 6" or so length. For example, scroll all the way to the bottom of this pdf:

https://www.chemoilproducts.com/pdf/piping products/Forged Steel Fittings.pdf

 

[r6155]

Never use socket weld under insulation.
Try:
1) as say JStephen - best practice
2) NPS 1 1/4 XXS or NPS 1 sch 160 full penetration weld to the coupling 1/2 6000

Regards

 

[IdanPV]

Fittings not exceeding NPS 3, may be attached to vessels by a fillet weld from outside only.
This is permissible under the stipulations outlined in UW-16(f)(3).
These fittings must conform to standard specifications (ASME/ANSI) or to a manufacturer's standard. These fittings must adhere to the minimum thickness requirements specified in Table UW-16.1.

In essence, you have the flexibility to create your own fitting design, as long as the thickness parameters defined in Table UW-16.1 are adhered to and you have your own manufacturer's standard.
Code Case 3035 is also an applicable reference in this context

 

[leon_har_dt]

Thanks you for all the answer! This definitely expands all our options and makes me learn a lot

I will analyze all options and decide which is best for the case.

Regards

L.

 

[r6155]

Corrosion and leaks can begin in socket weld and then it is difficult to detect in insulated pressure vessels. Full penetration weld is the best practice.

Regards