DRIVESHAFT SEALS
Packed gland
Sealed by several layers of asbestos or cotton yarn
Sometimes used two boxes with intervening space separated by steam Problems:
Too tight strain on shaft, heavy wear
Too slack contamination
Magnetic drives
Easy seal as seperate parts, shaft does not penetrate vessel
One driving magnet, one driven magnet
Liable to slip at high power consumption
Can get some cellular grinding (disruption)
Very common in non-viscous fermentation broths at lab scale