Aslam,
WNC case is not a hypothetical case and WNC case may have significant effect on nozzle loads. Consider 36" cooling water/ liquid line with spring support near nozzle to carry load in operating condition.
for 36" std sch. pipe weight of water/liquide will be 75% of weight of water + weight of pipe.
That means when line is drained out, 75% of spring load will pull the Piping system up ward and based on geomery of system it may cause enough moment and force to damage the nozzle.
Other typical case for consideration of WNC case is a sytem in which for a perticular period of time operating fluide is in gaseous form and normally it is in liquide form(example De coking system ). With WNc case you can simulate both the system in a single CAESAR file.

Regards ,
khalid