Effect of external corrosion allowance on UG-40 normal to shell limit calculation

[RiyadhBPV]

Dear all
If the shell has an external corrosion allowance and i need to calculate UG-40 normal to shell limit (nozzle reinforcement thickness limit). How can i include the external corrosion allowance in this calculation.
Many thanks

 

[jt1234]

Treat all nomenclatures as the final corroded thickness. That's all, so simple, no magic.

 

[RiyadhBPV]

Treat all nomenclatures as the final corroded thickness. That's all, so simple, no magic.

Thank you for your reply but i want to elaborate my issue regarding the calculation of normal to shell limit:
For example:
Shell nominal thickness: 1.8125 in
internal corrosion allowance: 0.125
Nozzle nominal thickness: 1.5 in
No reinforcement pad
Solution:
Shell corroded thickness, t=1.8125-0.125=1.6875 in
Nozzle corroded thickness, tn=1.5 - 0.125 = 1.375 in
Normal to shell limit = Min(2.5t , 2.5 tn)=Min(2.5*1.6875 , 2.5*1.375)=Min(4.219 , 3.4375) = 3.4375 in
PV Elite gives 3.4375 in ------ Match.
When we add external corrosion allowance of 0.125 in (only for shell):
Shell corroded thickness, t=1.8125 - 0.125 - 0.125 =1.5625 in
Normal to shell limit = Min(2.5t , 2.5 tn)=Min(2.5*1.5625 , 2.5*1.375)=Min(3.906 , 3.4375) = 3.4375 in
PV Elite gives 3.125 in -------- No match.
This is my problem.

 

[SnTMan]

It seems PVE is applying external CA to the nozzle. 2.5 x 1.25 = 3.125.

Regards

Mike

 

[RiyadhBPV]

It seems PVE is applying external CA to the nozzle. 2.5 x 1.25 = 3.125.

Regards

Mike

Is this due to the change in the shell outer reference

 

[SnTMan]

RiyadhBPV, I'd say no, it is due reduced nozzle thickness with application of external CA, as the arithmetic shows.