Armaturenwerk Hötensleben (AWH) has developed the new VPureMix magnetic coupled mixer with special sensor technology. Thanks to the magnetic coupling, there is no physical connection between the tank’s interior and exterior. This eliminates the risks of a conventional shaft feedthrough, such as leaks or contamination. Thanks to its low shear forces, the mixing head with ceramic bearings also ensures gentle mixing of the product and risk-free tank drainage, even while in operation. The encapsulated sensor permanently records all functions and displays them directly on a control unit. Even the rotation direction of the mixer can be monitored this way.
“In pharmaceutical production it is often a matter of homogeneously distributing different ingredients over the entire volume of a product. For example, for the fractionation of blood plasma, it must first be mixed to a uniform consistency,” says Martin Jaspers, product manager at AWH. “Of course this process must be completed entirely hygienically.” For this reason, the drive unit and mixing head of the VPureMix mixing system are connected to one another through a magnetic coupling, so that unlike a conventional shaft feedthrough there is no physical connection between the interior and exterior of the tank; for instance, via a shaft, gasket or O-ring. As a result, leaks and contamination are not possible, and the integrity of the tank and the product is never compromised.
The powerful magnets allow effortless torque transmission without generating shear forces. This guarantees a gentle, product-preserving mixing operation, even at high mixing speeds. This is of crucial importance, particularly in applications with bacteria or yeast cultures: “In fermentation processes, nutrients or gases should be evenly distributed to the microorganisms in the medium by the mixing process, and the resulting heat conducted away,” says Jaspers. “If the shear forces are too high, however, the cell walls of the bacteria can be destroyed, which must be avoided at all costs.”
Compared with other magnetically-driven mixers, the model from AWH also stands out due to its completely vibration-free ceramic bearings: The silicon carbide bearing bushing and the bearing pin made of zirconium dioxide are chemically inert, certified to USP class VI and almost completely frictionless. This also makes it impossible for the product to become contaminated. Furthermore, the special combination of ceramics ensures that even dry running is possible without any problems. “In an ongoing mixing process, the medium can be removed from the tank; that means that you can simply let the system run empty and residual quantities of the product do not have to be thrown away,” explains Jaspers.
Both completely maintenance-free ceramic components are manufactured from a single piece, without grooves, corners or edges on which the product could accumulate. In order to exclude contamination of the medium through the ceramic bearings alone, the VPureMix was subjected to friction testing by an independent institute, both in operation with particle-free water and while dry running.
The stainless steel mixing head, which consists of two rings and four rotor blades. The open construction, ensures barrier-free access for cleaning agents of all types. Residue-free cleaning is guaranteed, particularly in the case of treatments with steam, overheated water or autoclaving. The use of ultra-pure water and the generation of waste water are also reduced, which leads to a reduction in plant downtimes and saves a great deal of time. “Many of the previous mixing head models have a closed design,” explains Jaspers. “In these cases, the cleaning agent does not reach all of the corners and edges so easily; therefore, a thorough cleaning takes longer.”
Because it is open to the top, the mixing head of the VPureMix can even be easily removed and replaced with a new one. The motor, which can be continuously adjusted up to 490 revolutions by means of a frequency converter, is only attached with a simple clamp. It can be pivoted 360° as needed and thus effortlessly mounted under the tank, even in confined spaces. Furthermore, the mixer’s drive unit and tank frame can also be cleaned without much effort since the lack of protruding bolts and screws ensures a smooth surface. An anti-bacterial coating of the drive unit also reduces the risk of microbial contamination.
A distinctive feature of the VPureMix magnetic coupled mixer is the encapsulated sensor, which provides permanent monitoring, regulation and data collection of the mixing process. For example, it enables control of critical information, such as the position of the mixing head, the speed or data on any production-related downtimes, and thus it guarantees maximum product reliability. “The sensor system is comprised of a two Hall sensors, in which the pulse skips from one to the other, so that even the mixing head’s direction of rotation can be determined,” says Jaspers. “The sensor generates one pulse per revolution: when it draws electricity, the LED on the converter unit turns green; if an error is detected, it turns red.”
The data from the sensor can be easily transmitted via a standard connection to an existing software program and the exact error messages can be read out. In addition, the compactly designed converter unit can be positioned almost anywhere around the drive unit by means of a bracket that swivels 90°; this ensures that the LED is visible at all times. Furthermore, the converter unit is housed in a stainless steel tube instead of a plastic tube, in order to prevent damage when the motor is installed or removed.
The VPureMix is available in the versions LS50 to LS2000 for mixing volumes from 20 to 2,000 liters. Over the course of the year, additional models for mixing volumes of up to 20,000 liters should be added. An online configurator on the AWH home page also helps to determine the appropriate model for the respective application: “Only a few basic parameters have to be specified, such as tank base, tank diameter, tank volume or viscosity of the medium,” explains Jaspers.
The new mixing system will be presented in hall 4, booth 4-261 at POWTECH 2017 in Nuremberg. Martin Jaspers will be on hand to answer questions about the VPureMix and his design.