Rotates silently and unobtrusively

Sealing the agitator shaft of a mobile vessel is a very special task when dealing with a process in vaccine production. Liquid lubricated seals offer the best conditions for this application, but require a supply system. This conflicts with the flexible handling of the mobile vessels. With dry running seals this effort is eliminated.

At an international pharmaceutical company, EagleBurgmann demonstrated that the operation of dry running seals is as convenient as it is reliable and safe.

At the shaft passage, the seal must prevent the highly sensitive substances from becoming contaminated and from leaking into the atmosphere and endangering production personnel. The leakage of the supply medium for liquid lubricated seals must not exceed specified values; the supply medium itself must be matched to the product and installed in a vessel near the seal.

A further hurdle is synthetic carbon, the classic material for mechanical seals, which is not always approved for use in pharmaceutical production. The risk that particles will separate from the sliding faces due to abrasion and get into the product is too high. It would not only be very time-consuming to clean the vessel from wear particles; if the active ingredients were to become so heavily contaminated that they were no longer usable, production losses would be in the millions.

At the Asian pro­duc­tion site of the phar­ma­ceu­ti­cal group, the agitator shafts of a mobile vessel were there­fore equipped with seals of the SHJ series from EagleBurgmann in hard-hard pairing. During op­er­a­tion, however, the com­bi­na­tion of silicon carbide on silicon carbide re­peat­edly led to un­ac­cept­able squeak­ing noises during poor lu­bri­ca­tion con­di­tions.

At about the same time, the phar­ma­ceu­ti­cal company changed the re­quire­ments for ex­plo­sion pro­tec­tion at a European location. There, SHJ seals from EagleBurgmann had also been in­stalled on the top driven agitator shafts of mobile vessels. These now had to comply with ATEX category 1, zone 0 (tem­per­a­ture class T4) due to the pre­vail­ing ex­plo­sive at­mos­phere in the vessels. The seals were lu­bri­cated with glycerin and had been in use for more than a decade.

In the meantime, EagleBurgmann had de­vel­oped the SeccoMix R dry running seal, which was now the better solution as a single seal for mobile vessels. It requires no supply system and can be operated without lu­bri­ca­tion at the low speeds of the agitator shaft. Now only the issue of "noise de­vel­op­ment through hard-hard pairing" needed to be solved.

EagleBurgmann relied on the experience with DiamondFace for this. The surfaces of the seal faces were coated with microcrystalline, artificially produced diamonds in a special process. This makes them extremely wear-resistant and very effective at dissipating heat from the seal.

The SeccoMix R was then extensively tested in several stages. The basic technical principle of the seal was initially tested for wear and noise development. The subsequent test was meant to show whether the temperature development on the surface of the seal faces remains below the maximum permitted value despite dry running. A few weeks for optimization were necessary and then the field test started in the original machine. There was no noise, temperatures remained very low and the conditions of ATEX category 1, zone 0 were met. The sliding faces of the seal were as good as new thanks to DiamondFace. The pharmaceutical company gave the green light for use in production.

The advantage of the SeccoMix R is that it can be cleaned and sterilized without requiring disassembly. The smooth, dead space-free design allows easy cleaning according to the high sterile level in vaccine production. The materials for sealing elements such as sliding elements and secondary seals that come into contact with the produced active ingredients are approved by the FDA (U.S. Food and Drug Administration).

Since the end of 2018, twelve DF-SeccoMix R have been installed on the agitators of the vessels with a capacity of 200 to 500 liters at the European location. They prove their reliable and robust properties from batch to batch.

Operating conditions

• Shaft diameter: d = 35 mm (1.37")
• Pressure: p = 3 barg (43.5 PSIG)
• Temperature: t = 40 °C (104 °F)
• Sliding velocity: vg = 1.5 m/s (5 ft/s)
• Medium: pharmaceutical media

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