Abstract: Apparatus and processes are provided for handling fluids in numerous industrial applications. Materials addition devices, including venturi hoppers, and other eductor assemblies, are joined in compact, horizontal, and/or vertical configurations, with one or more shearing devices, including, high and low velocity shearing devices individually, as well as, a combination high and low velocity shearing device. Pipe and valve configuration allow several alternate paths through or around such assemblies and devices, in alternate directions, including the option to backflow through the high velocity shearing device for the removal of obstructions. In the high velocity shearing devices provided, a special jet insert is provided, along with jet insert installation related apparatus, by which the jet insert is easily retained in, and removed from, the piping in the high velocity shearing device.