EXTENDING EXISTING NOZZLE REINFORCEMENT PAD

[roca]

Hi
We have a brand new finished vessel which has incorrectly been designed by 1barg lower than it should have been due to a fundamental error in specifying pressures in bar absolute and bar gauge.
The vessel is actually designed to the UK code PD5500 and the nozzle failing it's reinforcement is a manway.
Options are remove existing nozzle / pad and replace with new.
However we are suggesting to add a ring extension to the existing reinforcing pad and in effect making it larger in overall diameter pad.
This will require an in-fill weld where the new ring meets the existing reinforcing pad fillet weld.
Additonal ring will be in the region of 30 - 50mm wide. It might also be easier to apply the the additonal ring in segments rather than one complete ring - although this will add welding work.
We also intend to discuss with the Notified Body to gauge their thoughts.
Anyone done this before?
Thoughts?
Cheers

 

[GenB]

Couldn't open the link. Pls send again. ASME will not allow it on as is basis since the pad have to be one PC. Or segmented if 100% xray. Two things you may do to get approval. Segmenting will need to RT1 before welding to vessel. Once welded to vessel RT1 the joint, if welded correctly you may pass the test. Good luck. Genblr

 

[GenB]

Thinking, you may get away with it with just doing number one since the ring weldbead will joint the two PCs attached to the vessel.

 

[roca]

Thanks
Not sure how to add attachments?
Is there some help on this subject?

 

[chicopee]

By adding a reinforcement, you may exceed the limits of reinforcement.

 

[Duwe6]

". .you may exceed the limits of reinforcement." Excellent point.

Perform all calculations first, including AI's approval. If you exceed the limits, you will have to use a replacement repad, that is thicker. Or use a thickened insert plate. Might be easier & cheaper to use a thick insert plate rather than remove a repad and replace it with a thicker one.

 

[marty007]

roca,

I'm not familiar with your code, but in concept I don't see any issues as long as everything is joined with full-pen welds and all other code rules (reinforcement area, etc...) are followed.

GenB, per ASME you don't necessarily require 100% x-ray on a segmental repad weld if it is oriented carefully. Per UG-37(h)(2), as long as the weld seam is located at least 45deg from the longitudinal axis of the cylinder, you do not need to x-ray or take a penalty on the reinforcement area.

Cheers,

 

[JStephen]

Is it feasible to add a second smaller repad on the inside?

 

[roca]

Thanks Guys
We have checked the calcs and the increased ring is still within the reinfocement limits.
Adding a ring to the outer of the existing pad is the preferred option as this will be the least work and most cost effective. As the vessel / nozzle is manufactured removing the existing pad and replacing with a new one or even cutting out the nozzle and adding a thicker insert plate will of course be more costly and time consuming.
The additonal ring would be full pen welded to the existing pad.
As this is not my vessel and I am not dealing with it direct I can't tell you yet which way we will go - will try to remember and post it later on.

I have managed to add the attachment - I wasn't reading the instructions correctly..!

 

[Bmechz]

Roca..

Try to add internal RF pad, ie. inside of the vessel you can add pad to get more reinforcement area..


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