Solving shaft leakage on top-entry agitators
A
Meco Shaft Seals product story
Edited by the Engineeringtalk editorial team
Aug 25, 2006
Top-entry agitator shafts on reactors, fermenters, crystallisers and similar machinery are a frequent cause of sealing problems.
Top-entry agitator shafts on reactors, fermenters, crystallisers and similar machinery are a frequent cause of sealing problems.
The OFS has proven effective in containing vacuums and a variety of gases, vapours and fumes, even at high speeds and temperatures
Usually, the drive shaft is suspended from a coupling at the top, and ends at the bottom, inside the vessel.
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.
Most of these vessels have a packing gland at the top of the vessel, which also acts as a stabilising bearing, limiting shaft runout.
However, you can imagine that as the packing becomes worn and compressed, shaft runout increases, creating leak paths.
This can be an environmental or safety issue when the product contains harmful vapours 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.
(The company even had to cut a hole in the cement ceiling to allow it 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 Meco's 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's 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 - so no more holes in the ceiling.
Not what you're looking for? Search the site.
Contact Meco Shaft Seals
Tel +1 207 371 2210
Other Meco Shaft Seals stories
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Meco launches HB standard-sized seals
Meco Shaft Seals has announced the launch of the HB range of standard-sized seals for screw conveyors and similar equipment. -
Meco seals solve contamination and vacuum issues
Meco Shaft Seals has revealed how its Meco-DR shaft seals can solve contamination and vacuum problems in drying applications. -
Meco shaft seals take stand at POWTEX
Meco custom-engineered shaft seals will be on exhibit at the 17th International Powder Technology Exhibition (POWTEX) in Tokyo on 28-31 October 2008. -
Air-purged seals clear caramelised sugar
Unlike traditional mechanical seals, MECO seal faces are soft, fault-tolerant and almost impossible to break. -
Seal upgrades meet ATEX requirements
Meco has adapted two of its seal designs to comply with ATEX, which considers packing glands unsuitable for service in potentially explosive atmospheres
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