PVDean
Mechanical
- Mar 26, 2009
- 21
We have a spherical storage tank made from A-212 B firebox material (1965) and are in the process of re-rating the MAWP (currently 3500psi) based on the MDMT/MAT. The vessel is 2 inches thick, and is used for a number of commodities (this recertification commodity is GN) as an outdoor storage tank. We have no proof of normalization outside of the A-212 material spec that says anything >2" shall be produced to fine grain practice, again though we can't verify that tank manufacturer bought plate of this variety, and no proof of PWHT (also no temperature associated with the hydrotest).
This puts us on Curve A of Fig 3.4, and at an MAT of around 100 F. Now to calculate the CET...Are there provisions to raise the CET from 15 degrees higher then the isothermal lines of the lowest one-day mean temperature figure published in API650? Would accurate site temps for 5 years be enough?
Sanity check, the plan is to re-rate the vessel at a pressure that buys down the MAT based on the stress ratio graph of fig 3.7 to the point where it is lower then the CET.
TIA.
This puts us on Curve A of Fig 3.4, and at an MAT of around 100 F. Now to calculate the CET...Are there provisions to raise the CET from 15 degrees higher then the isothermal lines of the lowest one-day mean temperature figure published in API650? Would accurate site temps for 5 years be enough?
Sanity check, the plan is to re-rate the vessel at a pressure that buys down the MAT based on the stress ratio graph of fig 3.7 to the point where it is lower then the CET.
TIA.
