Meaning
The boundary values of velocity gradients applied to a fluid during processing define the operational envelope for maintaining material stability and pump efficiency. Setting shear rate limits prevents the degradation of shear-sensitive polymers and avoids unexpected viscosity increases in non-Newtonian mixtures. These thresholds do not apply to simple Newtonian fluids whose viscosity remains constant under varying shear stress.
Fluid Dynamic
Polymer melts and complex emulsions undergo structural changes when exposed to high velocity gradients during extrusion or mixing. If the process exceeds the designated shear rate limits, the molecular chains can break, resulting in a permanent loss of product performance. This structural degradation reduces the quality of the final output, rendering the batch useless for high-precision applications.
Process Control
Instrumentation systems monitor nozzle velocities and impeller speeds to ensure the fluid is processed within safe boundaries. Automated controllers adjust the flow rate when the shear rate limits are approached. This preventative intervention maintains product consistency.
Equipment Protection
Excessive shear can also cause localized heating and accelerate tool wear in high-pressure pumps. Operating within established boundaries protects the internal components from premature failure and reduces maintenance downtime. This careful monitoring extends the service life of industrial machinery.
