Industrial gearboxes provide critical functionality in a wide range of services in industrial applications from cooling tower fans to driving a variety of turbo machinery equipment.
OPPORTUNITY FOR IMPROVED MTBR FOR INDUSTRIAL GEARBOXES
A frequent area for improved reliability with industrial gearboxes is containment of the lubrication that is vital to maintaining long-term functionality of this critical equipment.
There are various methodologies for providing lubrication to the gears and bearings in industrial gearbox applications:
1. Grease lubrication can be used in low speed applications up about 1,000 feet per minute (fpm), which converts to about 5 meters per second (mps).
2. Oil splash lubrication can be used for medium speed applications in the range of 2,000 fpm (10 mps) to 3,000 fpm (15 mps).
3. Forced oil circulation – either drop, spray or oil mist is used from about 2,000 fpm (10 mps) and higher.
Where oil is being used as the lubrication of choice in either the splash or force lubrication system it must be contained (sealed) within the gearbox in order to achieve its dual purpose of providing lubrication and removing heat.
The most common method of sealing oil lubrication in industrial gearboxes is an oil seal. A typical oil seal is shown below:
Figure 1: Oil seal on gearbox application
The dust lip and the primary lip are typically an elastomer material that provides a sealing function by being in contact with the rotating shaft. In many applications the elastomer materials wear sufficiently within a few months of operation to lose their functionality. The result is a steady loss of lubrication, loss of protection from external contamination resulting in not only housekeeping issues but also puts the reliability of the gearbox at risk.
MAGNETIC BEARING ISOLATOR PROVIDES BEST SOLUTION FOR PREVENTION OF OIL LEAKAGE IN GEARBOX APPLICATIONS
The optimal solution for sealing gearbox lubrication is a magnetic face bearing isolator. A typical contacting bearing isolator provided by IsoMag is shown below:
Figure 2: Isomag bearing isolator on gearbox application
The magnetic face bearing isolator provides a positive seal in vertical or horizontal positions and in all lubrication systems: grease, oil splash or oil force circulation.
The magnetic face bearing isolator maintains an engineered closing force on the seal faces (stationary face and rotating face) by the use of magnetic energy. The contacting faces form a positive seal against external contamination and provide a positive seal against oil lubrication leakage. The magnetic field is external, preventing internal ferrous materials from clogging the isolator. The collaboration between controlled range magnetic faces and a full labyrinth, provide superior containment of gearbox lubrication. Gearbox cycle life data collected in real time applications since 1994 indicate 100,000 hours of leak free normal operation can be expected.
The stationary adapter contains:
• A deep channel labyrinth
• Expulsion ports
These features enable the IsoMag bearing isolator to collect and retain oil lubrication within the gearbox.
There is no relative motion vs. the rotating shaft so there is no shaft damage as can occur with oil seals.
The IsoMag bearing isolators are easily installed with an o-ring interference fit and if necessary removed and reinstalled.
IsoMag contacting bearing isolators have been tested to an IEC ingress protection rating of IP 66 and IP 67 for ingress protection against solids and moisture contamination. These are the highest ingress protection ratings of any bearing isolator on the market.
IsoMag bearing isolators have replaced oil seals in hundreds of gearboxes providing multiple years of leak free performance in applications where oil seals only operated for six months or less before losing their functionality.
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