Large diameter shafts are a natural for split seals. Shaft damage is too expensive and pump disassembly is a big problem. Split seals changed all of this and shaft damage can be eliminated entirely. If you mount a split seal on a split sleeve you can often change side entering mixer seals with out emptying the mixer. Leaking product can be a pollution problem.
Seals consume less power than packing.
There is no adjustment needed to compensate for wear. In many cases the flushing water can be eliminated. Shaft damage and wear can be eliminated. This will allow you to use a solid shaft that will resist shaft deflection and bending. Leaking packing and the water hose that is needed to clean up the area are the major causes of premature bearing failure.