Nozzles to API650/653

[KiwiTanks]

When installing a new nozzle in a tank to API653 (and hence API650) is it permissible (to API) to add strengthening gussets that run along the nozzle and span between the tank and the nozzle flange?
(ie if the nozzle and tank produce an H,
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then the gusset fills in the top of the H (area marked XXX below)
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|XXX|
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In this instance I have a client standard detail of a 20-25NB pipe (NP3/4 - NPS1), which complies in every other way with an API650 nozzle, except I can't find if a strengthening gusset is acceptable.

One can guess that it's been placed there to stop the nozzle from being over stressed if someone chooses to stand / force the valve etc.

 

[jte]

Unfortunately, "gorillas" exist everywhere, and them 3/4" nozzles are put there for them to stand on to reach something else... I'd take the approach that "what isn't prohibited is permitted." Adding gussets is ok. Though I'd prefer to see the outlet upgraded to a 2" flanged (1.5" Long Weld Neck ok too). A 2" connection has the structural robustness you're looking for, you can put a 3/4" connection on a reducing flange if needed, and they won't plug up as easily.

jt

 

[JStephen]

I would agree that the gussets would be permitted if not prohibited, and some form of additional reinforcement might be required due to applied external loads.

 

[gr2vessels]

kiwi,
As the boys above said, the gussetted nozzles are OK;- however, it also depends on the elevation of nozzle from the bottom and how you weld the gussets. The low elevation nozzles are subject of some degree of rotation and the supporting gussets (being rigid brackets) could overstress the joint of the nozzle and the shell, causing the crack or even rupture of the weld (when and how is subject of Murphy's law). Remember, the shell bulging in the lower strake applies to the nozzle also, but if you prevent the rotation of the nozzle with the shell, something has to give, ie the joint weld will give.
Perhaps it would be safer to consider jte's second suggestion...
cheers,
gr2vessels

 

[KiwiTanks]

Thanks guys,
The Client would really like to use their standard design, as changing from it takes a lot of hoop jumping. BTW the nozzle and gusset is stainless.
Also this nozzle (or series of nozzles) is for sample points so is about about 1m (3') above the floor joint. (a little harder to stand on)

We have a standard design ourselves which utilises a 6" nozzle with a series of smaller (stainless) nozzles stabbed through the flange blank. This allows easier inspection (incl NDT), internal lining, etc of the larger nozzle.