stripper over desing extra margin

[BZLAM21]

hi every one
coudl you please help me about Prefractionation Unit Stripper Margin

what is the purpose to add a design margin to the Stripper column system ?
it makes sense to specify valve plates for good fractionation and turndown 50%?

Best regards.

 

[georgeverghese]

From memory, variable valve plate trays can turndown to at least 30%, maybe 25%.