Dave,

I agree with your equation Above.
But the point still remains that, How this gets conveyed to vendors? Generally Vendor Catalogues do not define 'Balance load' and also they do not consider "Design for Cold Load" thing.

The Variability equation in Catalogue is fixed since ages.
While preparing Spring Hanger Specification, this Balance load should be Tabulated against each spring, so as to have correct variability calculation.

Any comments or suggestions Please.