Hi,
I am a relatively newbie in this field. I am doing an analysis for an air-cooler inlet line. The project site is located in a seismic active zone.
For stresses in occ cases, the code allows us UPTO 1.33 times normal allowable stresses. My question is what about nozzle loads ? I am aware that the codes do not have anything to say about nozzle loads. It is upto the industry standards and the project standards. Since this forum has highly experienced members from across the industry, they might be able to tell, what is the normal practice for considering nozzle loads in OCC (Seismic) case. If there is a practice of allowing higher nozzle loads, then is this practice only for pressure vessels or heat exchangers ? What about Pumps, Turbines, Compressors, Air cooled exchangers etc. ? Please help me.
Best Regards
John Wright

John,

The nozzle loads can be analyzed using Welding Research Council bulletins 107, 297 etc. When you use the WRC-107 bulletin in CAESAR II (and in our other software) then you can enter the loads in different categories, Sustained, Expansion and Occasional. The stresses from the occasional run are combined the sustained and allowables are increased by 20 %. Here are allowables for all the combinations:

where,
S = code tensile allowable
k = 1.2 increase factor for occasional stresses
Savg = average of the hot and cold stresses (this may be up to 2Sy in some cases)

Note: when running the WRC-107 analysis, remember to run these cases,

with or without occasional (regular and when earthquake hits)

with or without thermal expansion (hot and cold condition)

to catch all the scenarios. This is necessary because when combining stresses some of them can reduce the others depending upon their signs.

Regarding the other equipment, I do not know. But, I suspect there is similar procedure. Can some body else fill that in.