Can I weld supports to repad after hydrotest? 8

[ljas]

Do to time restraints and scheduling of the outside inspectors I would like to weld the supports onto the re-pads of a pressure vessel after we hydrotest the shell. Is this ok since the welds from the pads to the shell are already done?

Thanks

 

[sanshu1111]

Lets take an example of a small PV where a simple support (a simple plate)is directly welded (without any pad) to the shell (pressure part). This support may be bolted or welded to another structural member for vessel mounting, is this weld or bolted connection within code scope? In my opinion, its not. Providing a properly designed support is still a responsibility of manufacturer


I think all of us would prefer to have a completed vessel including the supports before the hydrotest. We are however trying to understand the scope limit of the code.

I think it is also better not to call such structural pads as "Reinforcement pads" which are not a code requirement but provided as a good engineering practice or to meet the criteria of local loadings

 

[stesw90]

We have a R-stamp exchanger for which we are only making bonnet side along with tube and tube sheet ,
We have manufactured it and have conducted hydro test but the name plate bracket was not welded to the vessel ,we can't weld it to the saddle since it is in the site and we r only manufacturing tube side which is in shop,
My concern is that is there any clause under which i can make the welding after hydrotest with a relevant argument,
although i have gone through the entire discussion above and have come to a conclusion that there is no escape from this as per code,
but slight expectation i m putting my concern in to the discussion

Stephen

 

[metengr]

Is this for a new vessel or for weld repairs to an existing vessel? Your post is rather confusing.

 

[stesw90]

this exchanger was manufactured four years back,
now it had repair in tube sheet and tubes so we manufactured new tube side only , we are using old shell for shell side and it is a kettle type exchanger

Stephen

 

[metengr]

This is an in-service repair and a pressure test (not hydrostatic test) or NDT can be performed in accordance with the NBIC or API 510.

 

[stesw90]

Pressure test is performed in accordance to what in such cases---

Stephen

 

[jte]

doct-

Regarding your "would you sign off on it?" question: Yes, I would.

Regarding accountability: CYA is all well and good. I had more typed up here, but I'll just point out that there are more "opportunities" for difficult decisions when evaluating in service equipment than in designing new stuff. I'll leave it at that.

 

[MrPDes]

This is confusing. I have only ever considered Reinforcing Pads as the the pads placed around nozzles. For this thread the pads in question seem to actually be support pads or doubler pads or stress spreading out pads.

For America:

The ASME AI is interested in the design and fabrication of pressure envelope and any components welded directly to it such as a support pad. With respect to fabrication, this is where the ASME AI's accountability ends.

The AI is interested in the local stresses in the pressure shell that are the result of loading on the supports or brackets attached to the support pad, however the AI is not interested in assessing the design of the support itself or inspecting anything to do with the attachment of the support to the support pad. You could attach supports or brackets to the support pad using bubble gum and the AI wouldn't care.

End Note 3 specifies the termination point of the vessel is the surface of the support pad and “Nonmandatory” Appendix G "suggests" good practice regarding design of supports and attachments. There are no compulsory requirements.

The support would ideally be designed by a structural engineer but the immediate support bracket is often designed by a vessels engineer. The design and fabrication of the support bracket including the pad attachment weld should be inspected by a 3rd party structural inspector.

For Europe:

In order for the vessel to be CE marked, the design of the whole assembly of vessel and supports is assessed in accordance with PED by a 3rd party organisation that has both vessel and structural design appraisers. Similarly another organisation will have fabrication inspectors that are certified to inspect both vessel and structural fabrication.

I suspect when your AI is saying "NO", maybe he actually means "I don't care, it is nothing to do with me, but just in case I'll cover my back side by saying NO".