Operating or design conditions for nozzle loads

[stressone]

To the best of my knowledge, API 610 does not specify whether the loads obtained from operating or design conditions should be used when comparing nozzle loads to the allowables.

Is it up to the discretion of the client or are there fixed rules?

 

[bvi]

If you look closely at ASME B31.3, you will find that "design conditions" are only used in that code with respect to pressure design. It is the combination of pressure and temperature (that can occur together) that results in the greatest wall thickness or highest pressure rating. It is not necessarily the highest temperature, or the condition that gives the greatest load on the pumps. For flexibility analysis, from which loads on pumps are deterined, the code specifies "metal temperature for the thermal cycle under analysis." See para. 319.3.1. Having said that, a designer or owner could choose to have the design conditions considered as one of the thermal cycles to be evaluated, which is commonly done, but this is not a code requirement.