Dear All,
Svrcek in his famous article recommends a three phase separator with boot when the amount of heavy liquid phase is less than 15-20 wt %.
In fact boot permits a reduction in the drum size by eliminating the heavy phase layer on the bottom of drum.
But suppose that the process engineer size the separator for boot and weir type and find that there is not any significant difference in terms of dimensions for these two types. In this case which one do you select?
Have weir type any benefit against boot?
Your valuable comments are appreciated.

I guess Mr. Montemayor & Zauberberg may have covered most of the points. I just lay some points in my mind...
i) general understanding... lower quantity of heavy liquid, a boot is preferred as the
material cost is lower. How low is low ? Huh... i have seen many guidelines but with no one indicating same range as it is more to company, project and individual preference...
ii) Having boot with lower material cost, it does not mean it is cost effective.
Fabrication cost may be higher as it involve more complicated procedures...
iii)
Cost for space or overhead. Separator with boot save material and area occupied. However, it impose additional cost for overhead. For onshore facilities, normally head room is not a problem... however, offshore platform could be major cost factor.
iv) Separator with boot reduce weight (by material and inventory) and reduce
cost for support...
v) Low heavy liquid preferentially goes for separator with boot. As it increase the
controllability of interface...especially light and heavy liquid density are very close e.g. heavy crude and water...
vi) Separator with boot, there is
limitation of the boot diameter over separator diameter (check with Mechanical engineer...)...generally this will roughly define the limitation of heavy liquid quantity...
vii) As there is boot diameter limitation, increase boot length is the only direction to increase interface controllability.
Extended boot length is not really cost effective as all other cost factor increase.
ix) Boot will results vessel cutting and more welding compare to internal weir.
Higher risk...
x) Boot is fixed once it is constructed but weir can still be changed (especially removable weir)... weir installation increases
flexibility on made-good for uncertain fluid characteristic.
Read a bit more hereWith these factors, you will understand that there is no one rule for all and everybody has their own rule...