The more you agitate dilatant fluids the more viscous they become, and in many cases they can solidify.
Any time a fluid becomes viscous it can interfere with the ability of the mechanical seal to follow shaft “run out” or vibration. This hysteresis or delay will allow solids to penetrate between the lapped faces or allow fugitive emissions to escape to the atmosphere.
- Dilatants are commonly used in industries that manufacture cleaners. You need this increased viscosity to hold the cleaner on a vertical surface. Many sugar syrups and clay slurries fall into the same category. In the paper industry the product “Kaoline” or china clay is a common example.
To insure proper sealing you must insure that the product circulates through the stuffing box only one time.
This would be the case if you used a suction recirculation line connected close to the face of the seal, at the bottom of the stuffing box, to the suction side of the pump, or some other low pressure point in the system.
In this application it is important to use either seals that have no spring or springs in the fluid, or metal bellows seals.