first of all, I think considering the stress range case is only usefull for tempratures with different signs or if you have an on-off condition for a part of your system and its by pass.
stress range case means a case that your system first gets to the lowest temprature and then gets heated unless it reaches to the highest one. as if your base temprature is your min. temprature and the highest temprature is the operating one while it has been prestressed by the condition of your real base temp. to min. operating temp. so consequently that would be the highest value of your expansion stresses because your system has experienced the largest movement.