Low Shear Equipment Principles

Fluids flowing in a process plant are often subjected to the shear forces induced by various process equipment. Some fluids are more sensitive to the effect of shearing than the others. Multiphase fluids as well as non-Newtonian fluids may change their physical properties while experiencing certain level of shearing. Quite often it is not desired in the process system.

 

The equipment that controls the process conditions, such as pressure, flow rate and fluid level, is often the source for fluid shearing. By applying low shear principle to the design of this equipment it is possible to reduce shearing of the fluids substantially. Following design modifications of different equipment are presented here.

Low shear valve principles

Conventional control valves shear and emulsify the multiphase flow. A low shear valve has its purpose to reduce the turbulence and shear forces acting on the fluid mixture. Less emulsified fluid stream is more easily separated into own phases. This article describes low shear valve design principles and its benefits for regulating multiphase flows.

Low shear pump principles

Pumps transfer liquids in  many industrial processes. While passing through the pumps, liquids may be subjected to high shear forces. Certain types of liquids, such as multiphase mixtures, are shear sensitive. It is important to pay attention to shearing characteristics while choosing a correct pump for transferring these types of liquids.

Low shear mixer principles

Mixing is a common technique for obtaining certain qualities of materials and substances. Shear sensitive materials such as polymers, adhesives and structured food products, tend to have a threshold of shear rate above which materials start to alter their properties. This behavior is referred to as shear degradation.  Low shear mixing is characterized by blending the substances without reducing the particle sizes during the process.