I thank all the colleges who replied to my question concerned the lowest stress ratio for calculation of the test pressure value (fizza453, mk3223, prex). But to my mind, the HIGHEST ratio should be used. I think, the material which has the lowest stresses ratio is affected by the temperature rise at the least extent and is, consequently, the strongest among the others in the vessel structure. On the contrary, the material with the highest ratio is the weakest one. So, when using the lowest stresses ratio for the calculation of the test pressure value we obtain its lowest value. Moreover, the LOWEST ratio value does not take account of the presence of the weaker materials in the vessel structure at all. As I see, we all think that the stress ratio is introduced into the test pressure value calculation formula with the aim to expose during the test the vessel structure weakest material to the pressure adequate of its operating condition. But, in my opinion, the ratio must be HIGHEST. Please, tell me if my considerations are wrong.
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