Welding Platform Knee Brace Backer Plates Over Vessel Weldments 2

[TBell47]

(Re: Pressure Vessels or Non-Pressure Vessels)

Can anyone tell me if an ASME Code or another applicable code exists for the retro-fit design/installation of a circular platform with knee braces that DOES NOT ALLOW weldment of the new platform's connector brackets OVER an existing horizontal or vertical weld on the vessel.

I have, over the years, always heard that this is not an acceptable practice and tend to agree, for obvious reasons. But, is there a code that restricts the placement and weldment of these connection brackets over the vessel's welds?
Or has it only become an accepted industry practice over the years?

Thank you, in advance, for any assistance in this area.

TBell47

 

[JoeTank]

For oil storage tanks... API-650 does not permit such a practice. I haven't memorized it, but I recall that there is a spacing requirement forr shell attachments of 3 or 6 inches. The only exception is for stiffening rings or wind girders, which by necessity must cross over vertical veld seams. API-650 does permit the placement of shell openings thru weld seams, but there is an additional NDE (radiography) requirement and controls on the angle at which the welds intersect.

ASME VIII is so lax on weld spacing I do not believe that you will find a specific prohibition. However, there is a nozzle repad requirement. If the shell weld will be covered by the repad, one must RT the area before it is covered.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com

 

[deanc]

See UG-82,requires that the weld be ground flush or the pad coped. You must also consider loadings per UG-22. Look at Appendix G for some suggestions.

Remember depending on the jurisdiction this may need an "R" stamp. Suggest you contact them.

 

[unclesyd]

I think that the caveat here is that the weld has to assessable, meaning visual, for inspection mainly during a hydrotest. I have seen it questioned only once or twice over many years. We were caught with the same problem when we combined 4 columns to make 2 which required new ladders and platforms. One thing we were nailed on was we use some existing ladders which were too long, the distance between lands exceeded the maximum permitted.

Our solution when crossing welds was to weld brackets/hangers to the column and bolt the bracing to the hangers. This way we could essentially clear all the welds.

 

[ab1234]

Please note that as mentioned in previous responses, the ASME code does not put any restriction of placing Knee bracing on vertical seam. By taking proper NDT, in this case Radiography it is permitted. However as a good enginnering practice care shall be taken to measure increased hardness of weld seam and HAZ.
BS2654 Code [A Code for Vertical Stoage Tanks] in clause 11.15.2 prohibits placing vertical attachemnts 150mm away from any vertical seam and horizontal attachments 150mm away from horizontal seams.
ab