U-1 from 1954 1

[JSmothers]

I have a U-1 form from a vessel constructed in 1954 from A212-B. The form is generally consistent with current U-1 forms, but there is section 17 parts f and g of the form which list hydrostatic stress in longitudinal joints and an "Allowable operating stress" based on this hydrostatic stress (2/3 of hydrostatic stress in longitudinal joints). Here is an image:

This "Allowable operating stress" is less than the allowable stress listed in 1952/54a for A212-B. 17,500 in the code vs. 13,760 on the U-1.

My questions:
What is the basis of the 13,760 psi listed and how is this used for design of the vessel at time of construction? For my rerate am I permitted to use 17,500 and ignore the 13,760 listed?

 

[pdiculous963]

That actually appears to be a Form No. 1 from the API-ASME Code. The hydrostatic testing section of that Code and its first footnote is shown below:

The completed vessel (after stress-relieving, when stress-relief is mandatory) shall satisfactorily pass a hydrostatic test in accordance with the procedure outlined below, except those vessels covered by W-526 and W-527. The test pressure shall be based on the maximum allowable pressure· as computed from the formulas and rules for design in this code on· the thickness of the shell (or head if weaker) as fabricated, and the maximum allowable stress values at the test temperature; all other loadings that may exist during this test should· be taken into account. If the nozzles and other pressure attachments on the vessel have not been selected or designed to withstand the proposed maximum hydrostatic test pressure, the application of this test pressure might cause a permanent deformation of the flanges or other surfaces machined to fit. If such might be expected, a lower hydrostatic pressure shall be used; however, in no case shall the hydrostatic test pressure be less than 1-1/2 times the maximum design pressure to be marked on the vessel, increased in proportion to the ratio of the stress value in Table W-306.1 for the test temperature to that at the most severe condition [see W-304 W-529(a), and Definition A-2, Appendix A].

This test requires that only the weakest part of the vessel be subject to a maximum stress as defined in {a). If the vessel is designed so that this test will not produce this stress in the strongest longitudinal Joint, subsequent periodic tests will be found necessary as described in I-213 as the metal added for corrosion allowance disappears during the life of the vessel, except that in those cases where the longitudinal welds have been found satisfactory by radiographic examination, these subsequent hydrostatic tests are not necessary. Also the necessity for these subsequent tests is obviated if the vessel is of such design that the strongest longitudinal joint is given a maximum stress as defined in (a) during the first hydrostatic test.

And I-213 states:

Vessels subjected to internal pressure, not previously tested hydrostatically under a pressure that caused a metal stress in the strongest longitudinal Joint at least equal to 1-1/2 times the allowable working stress at the test temperature, shall be given a hydrostatic test in accordance with W.-525, R-525; or F-525 as they apply, except that the limitation placed upon the vessel's test temperature and the hammer test may be omitted.

It appears to be a requirement that the vessel is subject to a hydrostatic test that will stress the limiting component to at least 1.5 times the allowable stress. I imagine that as long as you perform calculations and ensure that the test pressure is at least equal to 1.5 times the limiting component's MAWP, it would be acceptable for the rerate. This would all need to be confirmed with the jurisdiction and/or the AI however.

 

[JSmothers]

pdiculous963,
Thank you for the quick reply and code sections. I tracked down API-ASME 1951 today to educate myself. You are correct and this does explain. I appreciate your time and suggestion.