Dear All,

I'm a newbie who have just using CAESAR.
And I have a stupid question:
Currently i modeled a riser with all it's properties, and i also performed a hydrotest case on it.
My question is does the corrosion allowance automatically reduced the nominal wall thickness when I inputted it on the input listing?
Or it is not necessary to input the corrosion allowance if we performed hydrotest case?

Thank You,

Hi Jheopardy

1) for sustain, exp, occ stress checking corrosion allowance is deducted from pipe wall thickness
2) for restraint load checking corrosion allowance is not deducted
We get result for worst possible scenario by doing the above.

For hydro test case since it is done beginning of plant start up logically there is no need to deduct corrosion allowance from pipe wall thickness.
However you do not have to take out corrosion allowance from Caesar spread sheet.
I understand Caesar should automatically consider that.

Regards

Habib

Thank you for your explanation Habib.

I have another stupid question:
But how we differ between the sustain and restaraint checking in CAESAR?

Regards,

Caesar will automatically consider
1) sustain stress--- corrosion allowance deducted
2) restraint load---corrosion allowance not deducted.

You need to input corrosion allowance in caesar spread sheet.


Regards
Habib

You need to be careful with corrosion. CAESAR II will deduct the corrosion allowance from the thickness when computing the section modulus for the stress computation - in those load cases in which the Code says to do so. That last phrase is important, not all Codes corrode all load cases. For example:

- B31.1 doesn't say to corrode anything, therefore by default CAESAR II doesn't corrode any B31.1 load cases - regardless of your specified corrosion allowance.

- B31.3 doesn't say to corrode the Expansion case, therefore by default CAESAR II won't corrode this load case.

You can override this behavior in the Configuration, but turning on the ALL_CASES_CORRODED option.

Dear sir Ricahard, May you help me by showing me in what Paragraph that B1.3 say not to consider corrosion allowance for Expansion Case?
Thank you

Hi Richard

Thanks for your response. I like some more clarification from you.
For expansion case without corrode thickness is more conservation (flexibility point of view) hence no issue if Caesar ignore corrosion thickness.
If I am not wrong for sustain & occasional cases Caesar deduct corrosion thickness from pipe wall thickness to calculate sustain & occasional stress,
Is it right?

Regards

Habib

302.3.5 says that the thickness used to compute Sl (i.e. a component of SUS and OCC) shall deduct corrosion. There is no such statement for EXP.

A subtle point here...

CAESAR II will not use corrosion in calculating the pipe volume and, therefore, load. CAESAR II will not use corrosion in calculating pipe stiffness.

Corriosion affects stress. So in the appropriate load cases, CAESAR II will use corrosion in the A of F/A and the Z in M/Z.

Corrosion is also considered in the wall thickness evaluation performed in the error check.

Thank you for your info Richard.

I have got another question which is still related to hydrotest.
If we input marine growth on wave input.
Does it also be considered in the hydrotest case?
Because what i have here the hydrotest case is WW+HP+WAV1

Regards,

Yes, the marine growth would be considered in the hydrotest.

Thank you for all the answers.
Really appreciate.

Regards,