For a 30" I.D x 80" T-T. vertical vessel, Client wants one handhole (4" Class 150) in shell near bottom head. I told Client that at least two handholes are required, but they said that vent nozzle (3" Class 150 LWN) located in top head can serve as inspection opening per UG-46(f)(7). Vent nozzle is located off center near the head knuckle and is vertical in position. Is this acceptable?

I know the vent nozzle meets UG-46(f)(7)(a). What I don't know is if it meets UG-46(f)(7)(b) which says, "the connections are sized and located to afford at least an equal view of the interior as the required inspection openings." Does the term "equal view" mean that the nozzle needs to be located in the center of the head? If the said nozzle is located in the shell, how can one have an "equal view" of interior?

Also, how do Authorized Inspectors perform internal inspection of vessels with small inspection openings like 2" threaded openings? Do they use optical devices like borescopes? Or do they just use mirrors (similar to dentists) to view the inside of the vessel?

Hope to hear some feedbacks.

Thanks,

Mike

Dear mcmd28,
it is acceptable.use boroscope

In the facbrication stage you can perform visual inspection of vessel internal prior to close seam fit up and for close seam inspection use boroscope.


Thanks

Ajimon

Not acceptable .

Nozzle can not be located in Knuckle portion . Not even RF Pad .
See UG 37

Rathnam,

Obviously, you are ignorant of ASME Code rules. Can you be more specific and tell us where in UG-37 does it say that nozzles or repads are not allowed in the knuckle region?

UG 37 talks about reinforcement area required for openings in shell / head sections. This is an old formula based on Hetenyi's Analysis . This formula is applicable in "spherical portion of the formed head' .
See the definition of 'required thickness tr' .

So what about Knuckle portion ? What is clear is that this formula can not be used as it does not apply to knuckle. So you get three options as below -

a Stick to the code & don't mess with that knuckle .

b. Use Design by Analysis i.e. use FEM or similar method. This of course has to be reviewed by AI.

c. Use another formula acceptable for this purpose. I am told East German code (yes , there was such an animal) used to give such a formula. Since I have not used this code I can not vouch.

ASME Sec VIII does not prohibit nozzles in Knuckle portion. It is merely silent . Some codes are not silent .For instance, Indian code IS 2825-1969 is very specific and does not permit nozzles in knuckle portion.

To conclude UG-37 does not say any thing about nozzles location in knuckle and some thing else has to be used .

Rathnam

In my opinion UG-37(a) at the definition tr (c) gives advantage to have the opening in the spherical portion. Otherwise there is no advantage and the required thk "tr" is the thickness calculated for the head. That's it. Therefore Code considers openings in formed head, any position.
Regards.
mauro

I am agreed with Gonzaga.