Product category:
Couplings, Seals, Gaskets
News Release from: Meco Shaft Seals | Subject: OFS-series
Edited by the Processingtalk Editorial
Team on 31 July 2006
Solving shaft leakage problems on
agitators
Top-entry agitator shafts on reactors, fermenters, crystallisers and similar machinery cause frequent sealing problems: seal replacement is the real problem, until the arrival of Meco OFS split seals
Top-entry agitator shafts on reactors, fermenters, crystallisers and similar machinery are a frequent cause of sealing problems Here is why: usually, the drive shaft is suspended from a coupling at the top, and ends at the bottom, inside the vessel
This article was originally published on Processingtalk on 26 Mar 2003 at 8.00am (UK)
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This lower end of the shaft is an inherent maintenance problem: if a lower bearing exists at all, it is practically inaccessible and is rarely, if ever, maintained.
Lower bearing wear, or lack of a bearing at all, allows the shaft to wobble as it turns.
This radial shaft misalignment causes seals at the top of the vessel to fail.
Further reading
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Most of these vessels have a packing gland at the top of the vessel, which also acts as a stabilising bearing, limiting shaft run-out.
However, you can imagine that as the packing becomes worn and compressed, shaft run-out increases, creating leak paths.
This can be an environmental or safety issue when the product contains harmful vapors and these escape.
Inaccessibility of the shaft seal only increases the problem.
One processor of shampoo had a vertical shaft vacuum mixer with lip seals at the top.
The seals themselves were inexpensive enough and the product was not hazardous by any means.
But about every four months a seal would fail and it would take two workers two days to lift the motor and gearbox up off the shaft coupling and slip a new lip seal over the shaft, then replace the whole assembly.
(Note: They even had to cut a hole in the cement ceiling to allow them to lift the motor up high enough to clear the coupling!).
Another problem inherent with vertical shafts is shaft floatation.
This often results from interaction between the agitator and process material, causing axial (vertical) motion of the shaft.
Thermal growth and shrinkage cycles can also produce axial motion, which compromises packing and most seals.
A remedy is at hand with the Meco recently patented OFS-series seal, which permits radial and axial shaft misalignments without compromising the integrity of the seal face.
Yes, it is a single-face seal.
A positive drive mechanism allows driveshafts to float axially through the seal without affecting the seal face, while maintaining spring force on the seal.
The seal design also permits radial eccentricity, while a companion steady bushing limits angular misalignment.
The OFS has proven effective in containing vacuums and a variety of gases, vapours and fumes, even at high speeds and temperatures.
Best of all, these seals are available fully-split.
No more holes in the ceiling. Request a free brochure from Meco Shaft Seals ...
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