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Home → Products → FFS → FFS for industrial fermentors
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FerroLabs, Inc. makes FFS for industrial fermentors with a working capacity of 0,025…6 m3 (Fig.1, 2). 100 specimens of such FFS were put to extended tests in the conditions of industrial manufacture of vaccine.
The specific feature of these seals is a possibility of working at great shaft wobbling (up to 0.7 mm). FFS include a magnet assembly that consists of (see Fig.1) a permanent magnet 5 and pole tips 1 [2]. The magnet assembly is mounted on the rotary segment 4 of the composite casing. The intermediate sleeve is rigidly fixed in the stationary section 3 of the composite casing. Reverse placement of details is also possible, i.e. mounting the magnet assembly on the stationary segment of the composite casing, and the intermediate sleeve on the rotary segment. The sealed gap created by the pole tips 1 and the intermediate sleeve 11 is filled with ferrofluid 10. To improve the performance of the magnet assembly, circular grooves are made on the pole tips or the intermediate sleeve. The rotary and stationary sections of the composite casing are connected by the bearing support 2 that ensures stability of the sealed gap. The rotary section of the casing is connected to the shaft 8 by the shaft sleeve 6. The spots where these parts are jointed are sealed with elastic rings 7 and 9 that make radial/angular movements of details relative to each other possible. FFS is connected with the sealed fermentor 14 by a flange 13. The FFS casing 3 can also make radial/angular movements relevant to the elastic ring 12.
The FFS works as follows. Due to friction force of the rings 7 and 9, the rotation of the shaft 8 is transferred by the sleeve 6 to the rotary section 4 of the composite casing and to the magnet assembly consisting of pole tips 1 and a permanent magnet 5. The magnetic field created by the magnet assembly in the working gap of the FFS created by the rotating pole tips 1 and the stationary intermediate sleeve 11 holds ferrofluid 10 inside the gap, providing hermeticity.
Composite embodiment of the casing and mounting the bearing support 2 between its composite parts ensures uniformity of the working gap filled with ferrofluid on the
Fig. 2. FFS for industrial fermentors
perimeter of the intermediate sleeve 11. Mounting the bearing support 2 on the outer surface of the magnet assembly symmetrically to the pole tips 1 allows, first, eliminating the negative impact of the sealed medium, and second, keeping the effect that the bearing support wobbling has on the working gap uniformity as insignificant as possible. That allows obtaining sufficient accuracy of the sealed gap by using only one bearing support instead of two, as it’s usually done. Consider the seal functioning at the shaft wobbling. Wobbling compensation occurs due to non-rigid connection of the sleeve 6 of the shaft with the shaft 8 and the rotary section 4 of the FFS casing. Assume that originally, the cylindrical axes of the shaft 8, sleeve 6, intermediate sleeve 11, and pole tips 1 lie in one axis — the reference axis. As the shaft wobbles, its axis deviates from the reference axis by ? angle under radial mechanical load. Since the shaft sleeve 6 can move radially and angularly, its axis also deviates by ? reference angle. Meanwhile, the mechanical load is barely passed to the rotary section 4 of the composite FFS casing and, consequently, to the bearing support 2 which simplifies the work of the bearing support and extends the operational life. Thus, the shaft sleeve, passing the rotary motion from the shaft to the moving section of the composite casing, oscillates after the shaft wobbling and prevents its radial mechanical load’s effect on the FFS bearing support. It is important to note that as the shaft sleeve 6 rolls, its connection to the shaft 8 and the rotary part 4 of the composite casing remains hermetic due to the ring squeezing responsible for the connection hermeticity remains practically unchangeable. If the wobbling goes over the acceptable value, an additional flange 13 spacer — an elastic ring 12 — is needed. Meanwhile, the composite casing will be oscillating after the shaft wobbling, providing additional wobbling compensation. If the proposed wobble compensation scheme is used, the bearing support 2 remains practically unloaded. Applying the above configuration allowed a considerable increase of reliability of the FFS working at great shaft wobbling. Time to failure is 8 years.
The results of using FFS for lab and industrial fermentors for a long period of time have shown that they meet the requirements for biological industry. Using FFS gives a better guarantee of keeping the product sterile, increasing labor productivity, and decreasing the number of defective products. These FFS were introduced at the 53rd World Exhibition of Innovations in Brussels and were awarded gold medal and the special prize for commercializing the invention.
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