Due to the higher requirements of biopharmaceutical for the sterility and risk control of the shaft seals of stirrers, industrial magnetic stirrers came into being in Sweden in the 1980s. Now, the lower magnetic stirrer has become the mainstream of the market, and continues to develop in the direction of simplicity, large torque, large shear force or very low shear force, bearing material safety, easy online cleaning, online sterilization. For example, the lower magnetic stirrer for bioreactor, the lower magnetic stirrer for high shear homogenization, etc. Whether it can prove that the agitator can be cleaned online and sterilized online, and the material safety of bearings has become the gold standard before the selection of biopharmaceutical agitators.

Desktop magnetic agitator

A magnetic stirrer

The working principle of the desktop magnetic stirrer is to use the same and exclusive characteristics of magnetic materials to promote the rotation of the magnetic stirring rod by constantly changing the polarity of both ends of the base. The disadvantage is that the energy conversion efficiency is low and it is only suitable for small volume liquid stirring.

The working principle of the industrial magnetic stirrer is that it is separated by two internal and external magnetic steels, separated by an isolation sleeve, and driven by a motor, the internal and external magnetic steels produce magnetic coupling to achieve the purpose of transmission. The most widely used in pumps, magnetic pumps can achieve complete leak-free, and the most efficient energy conversion. The upper magnetic agitator corresponds to the lower magnetic agitator. Because the risk of shaft seal has not been completely removed, the application field is limited.

As agitation is an experimental science, the enlargement of agitator is a complex problem related to the process. So far, it can only be enlarged by step-by-step experience. According to the enlargement basis obtained, it can be extrapolated to the industrial scale. At present, the enlargement of the lower magnetic agitator mainly depends on the simulation test of the common buffer solution as the main mode in the manufacturing enterprise, and the finalization and enlargement based on it. All the customized models are improved on the basis of the standard models, such as material customization, power customization, blade shape customization and so on. Correct selection of mixer and proper selection of mixer have become a problem that must be solved before users.

Multi-point magnetic stirrer without heating is suitable for synchronous stirring applications.

The speed range of IKA multi-point magnetic agitator is 0-1200 rpm, 5, 10 and 15 points are available. The magnetic coil technology is used to provide multi-point uniform noise-free stirring. The rotational speed is constant, even if the load-bearing weight changes. The closed compact design is easy to clean and protects the instrument from liquid infiltration.

The stirring effect of the lower magnetic agitator is influenced by the following factors: the properties of the medium, the properties of the solution and the purpose of stirring, the hydrodynamics-tank shape, the ratio of liquid height to diameter, the installation position of the agitator, the different liquid height of the same tank, the shape and speed of the stirring head, the technology of the application point of the agitator, the budget and the type of the lower magnetic agitator.

Installation, Use and Maintenance of Lower Magnetic Mixer

The welding of the bottom plate was once a difficult point around the domestic manufacturing enterprises. Segmental welding was needed, and the key point of installation was to control the welding temperature of each welding section. Gradually subdivide into 16 equal parts.

The installation/disassembly sequence of the rotary head, bearing and motor is a special link in the installation and use of the lower magnetic agitator, which will directly affect the service life of the agitator.

Asepticity Verification of Lower Magnetic Stirrer

For example, CIP method of low-speed magnetic stirrer: open tank bottom valve open 360 sprinkler ball water cleaning open stirrer, rotating speed is about 100 rpm, each time about 10 minutes, 4-5 times. The specific method and repetition times need to be determined according to the different properties and viscosity of material and liquid. If the spraying ball can only clean the upper part of the tank, it does not need to be exhausted. The magnetic stirrer needs to be soaked and cleaned, and then exhausted, repeated, or circulating spraying for a period of time. After exhaustion, the distilled water can be repeatedly sprayed several times.

The application of magnetic stirrer desktop magnetic stirrer and magnetic rod has been widely used, but only limited to research and development, small-scale level, people often have the illusion of magnetic stirrer, that magnetic stirrer is weak, low power, can not be used for large volume, as well as dead angle, online cleaning (CIP) and online sterilization (SIP), etc. However, this view has already been in reality. Used overturned. At present, the lower magnetic stirrer can be used for 40 tons of water stirring, even larger, and there are many kinds of applications. Generally speaking, the magnetic stirrer consists of a rotor with negative bearing, a positive bearing, a welded plate at the bottom of the tank and a motor. There are several permanent magnets (not ring) in the motor drive head, and the corresponding position in the rotary head has the same number of permanent magnets. Polarity just attracts each other. When installed, the magnetic coupling between the motor drive head and the permanent magnet in the rotary head, the motor drive head runs, and the magnetic force drives the rotary head to run. The two are completely separated by the bottom plate of the tank, and there is no mechanical transmission shaft through the tank.

The design of the turning head, the connection between the turning head and the bearing, and the clearance between the turning head and the bearing are directly related to the effect of CIP/SIP. Generally, the more open the turning head, the better. The material of the turning head is 316L stainless steel, inner permanent magnet, bearing material is mostly silicon carbide ceramics, completely inert, suitable for pH 1-14, small thermal expansion, in the case of water lubrication, can withstand up to 5000-6000 RPM speed without wear. Because the magnetic stirrer under working condition is completely immersed in the solution, the existence of lubrication tank can make the solution pass through, thus making the whole solution pass. The friction interface is always covered by water film. When rotating, the friction force is very small and will not appear.