Lobestar^® Shear-Mixer

The unique design of the Lobestar® Mixing Nozzle creates an open path for solid additives to enter the mixing chamber with no obstructive, protruding nozzle on which to accumulate and bridge.

Typically, 1-3 pounds of solids per each gallon of motive liquid is achievable. The bulk density, solubility, absorbency, and flow characteristics of the specific solid additive all factor into the actual, achievable concentration ratio. Motive liquid properties such as saturation or solubility also have an impact on the achievable concentration ratio.

A) Motive liquid viscosity of 300 centipoise (1475 SSU) or less. Higher viscosity levels have a negative impact on Lobestar® Shear-Mixer function.

B) Existing discharge piping diameter and geometry. The discharge piping diameter should be at least as large as the diameter of the Lobestar® Shear-Mixer from the mixer to the discharge point. The pressure loss throughout the discharge piping should be minimized by keeping the overall length as short as possible, maintaining a low vertical lift, keeping the number of elbows and fittings to a minimum, and/or increasing the pipe size if possible.

C) Motive head differential across the mixer. Optimum function of the Lobestar® Shear-Mixer requires a motive head differential between 115 – 185 feet of motive head.

Ideally, additives should be fed into the open Lobestar® Shear-Mixer suction port steadily and gradually. Flooding the hopper or funnel connected the suction port with additives is not optimal since this has potential to cause overflow if the hopper is not designed to avoid bridging or ratholing.

The Radial Premixer is integrated with the Lobestar® Shear-Mixer suction port and is designed to create a fluid vortex that not only washes down additives and forms a liquid barrier to the atmosphere, but also prevents fisheyes from forming in the mixed slurry.

The Radial Premixer is required whenever using the Lobestar® Shear-Mixer to mix sticky, hydrophilic additives that swell, cake or form fisheyes when they become wet; whenever mass flow rates are relatively high; when mixing slurries that are sensitive to air entrainment; or whenever discharge piping is long, has significant vertical lift, or both.

While entraining solid additives, the Lobestar® Shear-Mixer suction is open to atmosphere and will certainly draw free air into the slurry stream. This air forms bubbles in the slurry which gradually expand as the pressure gradient in the pipe approaches atmospheric pressure. The resulting larger bubbles within the discharge piping take up space and limit the suction flow rate. The washdown effect of the Radial Premixer provides a water seal that minimizes the volume of free air that can be drawn into the slurry.

High discharge line pressure has a negative effect on the Lobestar® Shear-Mixer as well as any venturi eductor. The discharge pressure must be less than half of the motive inlet pressure of the Lobestar® Shear-Mixer for it to function. Strong consideration should be given to the discharge piping geometry, and the overall vertical lift height, as well as the number of elbows and fittings should be kept to a minimum. Increasing the discharge pipe size to a diameter larger than the Lobestar® Shear-Mixer can also help minimize the overall pressure drop through the system.

Yes. Lobestar® Shear-Mixers are often used in batch mixing scenarios and the molded polyurethane construction material of the nozzle and diffuser tube inserts for most standard Shear-Mixer models is preferred because of its strong resistance to abrasion. Of course, polyurethane is not chemically compatible with all types of slurries, but different materials of construction can be substituted depending on the application and slurry content.

Having a valve at the Lobestar® Shear-Mixer suction port is used during startup and shutdown of the slurry mixing pump. It should be closed during both conditions because the discharge line pressure at these times is higher than when the pump is running, and the closed valve prevents the contents of the discharge line from backing up into the feed line or hopper. At pump startup, once the required, constant motive fluid velocity for operation is established, the valve can be opened for additive introduction. The valve should always be closed prior to pump shutdown, especially if the discharge line elevation is higher than the Lobestar® Shear-Mixer, because it prevents backflow of the discharge line from the suction port.

There is not an exact velocity for optimal function. The fluid velocity in the discharge line should be low enough to minimize overall pressure in the line, yet high enough to keep undissolved solids moving to prevent settling. In most applications, fluid velocity of 6-8 ft/sec is sufficient.