I thought "Taconite" seals were labryinth seals?

At least, thats what the ones in my SKF catalogue look like. ■

http://www.skf.com/portal/skf/home/p...&newlink=215 ■

Taconite seals come from the name of the USA iron ore on the Mesabi Range in Minnesota. It was developed to counter the many problems with lip seals and fine abrasive iron ore dust.

Rubbing shaft with fine abrasive taconite iron dust laps the shaft until a dangerous fine grove makes the shaft a failure hazard. Some Taconite seals do not have a contact outer seal and some do. Often, this depends on the local application. Certainly, SKF is aware of the hazards with highly abrasive fine powder.

A second issue is to keep the fine dust from entering the bearing cavity. Here on outer seal is often a horizontal labyrinth that is greased from the intermediate chamber between the outer labyrinth and an inner seal. The inner seal is applied to keep grease in the bearing cavity and keep out the intermediate grease laden with taconite dust. The fine dust will enter the labyrinth due to gas movement in the bearing cavity from heating and cooling.

There are a number of daughters from the mother Taconite bearing concept. Some use the grease from the inner bearing lube cycle to exit into the dust catch chamber.

The intermediate dust catch chamber is germane to all Taconite seals. When the chamber is lined with grease and one of its surfaces is spinning, dust will be encouraged, through motion of the gas, to plate on the grease and eventually be flushed out. The chamber does need to be greased, but not as often.

When special moisture sealing is required, the outer seal does have a lip, but also has a static wear ring so that the shaft is not damaged.

SKF, FAG, NTN, Falk, Flender, Hansen, David Brown and others have perfected various approaches to Taconite seals. It also depends if we are talking pillow block bearings, reducer bearings, motor bearings, holdback bearings, et al.

It can become a big subject. ■

Axel

In addition to the above valuable info, you also asked about the greasing intervals.

Essentially, if you can keep the bearing and grease clean, you only have to grease once in a blue moon. Hence you can get away with "greased for life" bearings. However, where your bearing is not greased for life because of the type of seals etc, one has to grease regulary. This is OK for low rpm bearings as they can handle being somewhat overfilled as they don't get hot.

I have found the best is to use individual automatic greasers, one per bearing.

They are the ones that look like small grease pump type guns that screw into the grease nipple hole. These apply a bit of grease constantly, thereby keeping the dust out until empty. Then you screw in a new one. They last quite a long time.

Regards

LSL Tekpro ■

The question over bearing cavity relube depends upon the brgs housing design > location of grease entry to the brgs etc

The TAC seal greasing interval etc is based on experience - but the rule of thumb was for a collar of grease to be visible at the seal ends and then purge till fresh grease comes.

We use labryrinth and taconite seals - we have had greasing issues, esp. with supplier designed custom housings.

Be careful with thos PC based relube programs, esp. for high value machines - seek expert advice from SKF, FAG etc

Cheers

James ■