Servus,
First: usually W only is usually run for the weight the hanger has to carry.
Second: the hanger selected should "work" for both operating cases that is it should remain in the Minimum Maximum load range and its variabilty should not exceed ~25% or so. So both operating cases are equally important.
Third: Size and spring rate are important but the hangers must be preloaded at time of order. To do so the vendor needs to have either a cold load set, or hot load set and travel. See the hanger vendors ordering requirements in their catalog.
Fourth: Horizontal movement means operating displacement in X OR Z. Assuming the spring selected is a rod hanger the hanger rod must be long enough to prevent a swing ange from exceeding ~ 4 degrees.
These are all very basic questions... as I see it you need to do some self education quickly, read John Breens reference closely. My Deutsch is kleine I hope your Amerikanishen is better than my Deutsch!
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Best Regards,
John C. Luf