verification of stress on hydrostatic test condition

[Fario]

Hy guys

How I can to check the stress in hydrostatic condition when the corrosion tolerance is zero?

Does is possible to define the MAWP equal to design pressure when corrosion tolerance is zero?

My problem is follows:

The MAWP must be calculated (equations) in corroded condition of vessel.
Hydrostatic test is 1,3xMAWPxLSR, then...
If we want to calculate the verification of stress on hydrostatic test condition, we will have stress 1,3 times bigger (or plus) than admisible stress, as the corrosion is zero so the thickness of MAWP is equal to thickness in hydrostatic test.

For example

LSR = 1
corr. = 0,0 mm
Pd = 10 barg
t req = 10,5 mm
t defined = 14 mm

a)MAWP calculated to 14 mm = 13 barg @ Td, then HT = 16,9 barg @ T HT
Stress on hydrostatic test condition > S adm @ T HT

b)If I take MAWP = 10 barg @ Td, then HT = 13 barg @ T HT
Stress on hydrostatic test condition < S adm @ T HT (OK !!)

Is it mandatory to calculate the MAWP using the equations described in the standard (corroded condition) or is it possible to define it as a value equal to the Pd, in this case?

 

[prex]

If you are required to calculate the MAWP, you need to do so by code rules.
For the hydrostatic test you normally use, as limits, 90% of yield stress for primary membrane stresses and 135% for primary membrane+bending stresses (normally found in flat heads only). But you are not normally required to check these stresses.

prex
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[TGS4]

What's your Code of Construction?

 

[Fario]

Trevor, ASME BPVC VIII D1

 

[TGS4]

There is no limit, in VIII-1, on the stress during the hydrostatic or pneumatic test. Your first situation is perfectly acceptable.

 

[Fario]

Thanks Trevor

 

[Fario]

prex
Thanks for your advice and help, but I apologize to you for my post and may be I am not writing clearly.