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

RiyadhBPV

Mechanical
Joined
Mar 22, 2024
Messages
5
Location
LY
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
 
Treat all nomenclatures as the final corroded thickness. That's all, so simple, no magic.
 
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.
 
It seems PVE is applying external CA to the nozzle. 2.5 x 1.25 = 3.125.

Regards

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

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