Application of the Month
Mixing Up a High-Speed, Wash Down Solution
October, 2010 - View all Application Examples
Mixing and agitating applications can provide some of the most demanding requirements for gearboxes. Not only can speeds and loads vary dramatically, but environmental conditions can be difficult as well. High quality components, robust designs, and protection options are often necessary.
We had a customer provide us with an opportunity for a mixing application that turned food solids into semi-liquids. Typical products could include spreads, cheese dips, ice cream, and pie filling. The specifications, for two sizes, included 20 and 50 horse power capacities operating at full motor speed of 1750 rpm. The customer had tried a number of different bevel box suppliers, but none were lasting more than a few months under the rigors of the process.
The basic design was a large bowl with the mixing impeller shaft exiting out the bottom through a seal. The impeller shaft was to be inserted into the hollow output shaft of a spiral bevel 1:1 gearbox, which was then driven by the motor. Liquids and solids where introduced into the bowl, in a pre-determined fashion, and mixed accordingly.
The mixing process was extremely dynamic as initial shock loads occurred and then torque requirements varied as the mixture was converted. Some radial loads were also experienced as the impeller blades were positioned a distance from the gearbox bearing seats.
The environmental conditions were also a challenge. Machine washdown was required after each process and any product leaking from a worn bowl seal would drip down along the impeller shaft onto the gearbox seal. Many of the products included abrasive crystals.
The solution we provided was the Tandler spiral bevel gearbox. While typically a high precision gearbox, it was the inherent characteristics of the design that made it appropriate for applications requiring extremely rugged power transmission.
To no ones surprise, standard industrial spiral bevel gearboxes use standard industrial spiral bevel gears. While adequate for continuous high torque duty at slower speeds, the high torque shocks in this application revealed a problem with these designs.
Because of the lower quality gears used in the previous gearboxes, shock loads were focused on the high points of the gear flanks which then generated excessive forces onto very small areas quickly causing material fatigue. The higher quality, lapped as matched set, spiral bevel gears used in the Tandler gear boxes, distributed shock loads over a wider area of the tooth surface. This allowed the full strength of the gears to be utilized, eliminating shock failure and extending gear life dramatically.
To accommodate the wash down requirement, all gearboxes were provided with a two part white epoxy paint to resist corrosion and the harsh chemicals used in the cleaning process. On the upper vertical shaft a stainless seal shield was incorporated to deflect direct wash down spray and to protect against any abrasive product that might leak from the bowl seal above, to come in contact with the gearbox shaft seal.
Although it is true that the solution offered was more expensive than the previous gearboxes utilized, gearbox life was extended four to five times over what was being experienced. This significantly reduced service expenses and maintained viability of the machine design. The alternative was to kill the mixer line.
While the Tandler gearbox is more often used in applications requiring precise motion control, it is also used in a wide variety of applications requiring extremely heavy duty power transmission. The premium quality components used and the precise assembly tolerances make the design ideal for satisfying extremely demanding operational requirements.
The Tandler spiral bevel gearbox program offers the widest range of ratios, shaft configurations, and special options available. Dimension modifications and complete special designs are also possible for quantities as small as one piece. A variety of wash down and extreme environmental conditions protection options are also available to satisfy requirements for industries needing these types of design elements.
So, whether you have an application requiring precise motion control or one that requires extremely rugged, reliable power transmission, there is a Tandler spiral bevel gearbox that can handle the job. Please contact your DieQua representative for additional information.
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