nominal thickness and finished thickness

dear all,

what is the difference between nominal thickness and finished thickness. all the calculation is based on finished thickness in pvelite then what is the significant of this nominal thickness featured.

Nominal Thickness is used for weight calculations. It can also affect stresses due to seismic loading.

thanks for reply kunal,

what is the difference? can you please explain me more in detail.
is every time we have to specify this nominal thickness.

As per Kunal said, nominal thickness is used for weight calculation.

Finish thickness that mean min.thickness, this thickness will used to all calculation like MAWP (maximum allowable working pressure & local stress analysis (WRC 107 & 297.

normally we specify nom & finish thickness due to element through process forming like head. To accuracy of design, nominal & finish thickness is better to specify. That all my sharing..

ZUL

Hello Folks
If, this is a case then i am not agree with above explanation. I have tried the run one case. Pl. find an attachment.

Brief :
vessel with Ellipsoidal d'end is modeled. One side of d'end is given Nominal thk & other side of d'end without specifying Nominal Thk.

PVELITE Calculated MAWP of both d'end different.

Therefore, I conclude that MAWP of element is calculated based on the Nominal thk.

Regards
Vishal Tailor

Dear Vishal Tailor,

MAWP should be calculate as per UG-32... which finish thickness is use to calculate MAWP. Kindly pls see attachment for your reference.




Regard,

ZUL

HELLO ZUL
I HAD MENTIONED THE CONSIDERATION OF PVELITE.

Vishal Sir

PV Elite is calculating MAWP on basis of minimum thck. & not on nominal Thck.

Pl. check it again.

Mayank
You may be right. But, it see details output of PVELite with and without nominal thk for ellipsoidal d'end. Hope you will surely observe difference in MAWP values in both case.

Dear Vishal,

MAWP is based on min thickness (i.e. finished thickness after forming). If you see the report of your PVElite model following are the results;
1. MAWP of Bottom dish end = 8.285 bars
2. MAWP of Bottom Dish end straight face (SF) = 8.195 bars
3. MAWP of shell = 8.195 bars
4. MAWP of Top dish end = 8.25 bars
5. MAWP of Top dish end SF = 13.626 bars

PVElite considers (Finished thickness-CA) in the calculation. But in case of dish end when Designer mentions nominal thickenss PVElite considers the same thickness for the SF MAWP calculations, becuase for dish ends nominal thickness is min thickness (finished thickness) for SF.

Since you have mentioned nominal thickness of Top dish end, PVElite considers nominal thickness for the calculation of SF for MAWP. So MAWP of SF is different for both the dish ends.

So there is no glitch in PVElite atleast at this point.

@ princeR;

Nominal thickness is the thickness of the plate available in the market.
Finished thickenss is the thickness of the vessel after fabrication process.
In case of dish ends finished thickness is less than the nominal thickness because of thinning of the dish ends at knuckle area in forming process of dish ends. However for the cylinder in broader way finished thickness is same as nominal thickness.

If Designer doesn't mention nominal thickness in PVElite model, software considers finished thickness in calculation as stated above.

Nominal thickness plays role in calculating weight of equipment (mainly cylindrical parts).

Thanks & Regards

Prashant

Grt learning from prashant sir

Thanks Prashant in sharing knowledge regarding caln of MAWP in case of D/Ends