nozzle neck thickness

[mecanic123]

Looking for some clarification on part 3.7.6. of API 650, about shell nozzles and flanges.
Is there any way to reduce the nozzle neck thickness (tn) included in column 3 of table 3.6?. Why is this thickness so strong?.

thanks.

 

[TankDude]

To my knowledge there is no way to reduce the nozzle neck thickness per the Standard. I think that the neck thicknesses are heavy to resist corrosion, external nozzle loads, etc. You can, however, reduce the thickness of the reinforcing plates for reinforcement.

 

[MJCronin]

mecanic..

Why would you want to reduce the nozzle thickness ?

Do you feel that there is any significant materials savings here ?

A "thick" (stiffer) nozzle ensures that the moment resisting capabilities of the tank shell is fully engaged under piping loadings.

Thinner nozzles, while acceptable from a pressure-resistance viewpoint, are not desirable based on piping imposed loads.

My opinion only..

-MJC

 

[gr2vessels]

mechanic123,

While agreed with the previous comments, there are other considerations for your nozzle thickness. You could use thinner nozzle neck if you can anchor the connected pipe and prevent the nozzle rotation with the fluid levels up and down in the tank, by means of additional reinforcement, but all this must be documented with supportive calculations. If it is a vent nozzle, probably you might be able use thinner pipe without additional calculations. Also, you might be able to weld support brackets on the shell for a level bridle fitted with support trunnions, to unload the level nozzles, so you might use thinner nozzles.
But again, if anything goes wrong with the tank, it's your neck for not following the API 650.
Cheers,
gr2vessels