I am e-mailing you a flie to help you with your bearing questions.

This mechanic prefers grease loaded bearings . ■

Hi Gary

U have not provided more specifics.

U should discuss your design with either SKF or FAG.

Some time bigger is not better.

eg SRB require some axial load to help rolling element skidding etc. Larger brgs means higher axial min. loads and these may not be present.

Grease is the most common lube but oil is used for particualr applications eg

high speed

high temperature

high axial loads leading to pumping of the grease out of the loaded zone in the raceway etc.

Need to consider shaft axial growth and seals for oil bath bearings plus any external cooling systems etc.

Cheers

James ■

And thee question is.............ARE BIGGER BEARINGS BETTER and reasons PRO AND CON.

Hello My friend Gary, How goes the battle in the salt mines?

I love this question: Bigger in vibrating screen bearings is not necessarily better....and here are some arguments for and agin.

These rules basically come from our bearing suppliers and usually pan out to be true in the field.

GREASE LUBE:

> nice, simple, easy system........usually a labrinyth seal system and typically hard if not impossible to overgrease, as the grease is pushed thru the seals and deposited on the sideplate, as expelled old, dirty grease.

> Typically limited top end speed with grease at which point the manufacturers will call up oil as the preferred lubricant.

* Here is where we see the benefit of oil vs grease at least on big diameter bearings. If I have say a 160 or 200mm bearing the top end speed will be limited to say.....810 on the 160 and say 750 on the 200mm. NO PROB RIGHT? Except, now we have to screen........something.....and the smaller it is........the faster I must run the screen and if the bearing is too big.......I am limited and can not screen worth a lick....

NOW, the concept of dual bearings or twin shaft units becomes a possible solution. Say, if I had a 8x20 screener and had a single shaft with say 160 mm set of bearings. A big heavy static weight unit that wants to screen BIG TPH. I could theoretically and in actual practice design with a twin 140mm shafts or 4 bearings total and this would allow me to speed the unit up to screen in the proper range allowed by VSMA and maintain an acceptable B10 OR L10 Bearing life calculation of minimum 10,000 operating hours. BASCIALLY ...it does not work as hard as a single shaft unit and does so with smaller bearings which allow more flexibility and top end RPM RANGE Needed to screen efficiently.

> Can you grease big, 160, 200mm spherical roller bearings on vibrating screens? All day long......but, running temps are higher than oil (EP2, EP1, EPO or SYNTHETHICs)

We deal with SKF, TORRINGTON and FAG bearing mfr companies who are all expert in the application of their products in vibrating screen shaft assemblies. We do follow their recommendations very closely. They all have specific books for vibrating screen bearing applications that are readily available to all.

In the good ole days.............all vibrating screen bearings stArted out with grease lube........and the technology has progressed to the point where most are EP RATED OIL applications.

Sorry for delay......I have been fishing for a week and then laying on a beach in S.C. for another week.......A nice rest........but, now back in the hunt.

Hope this helps..... George Baker, Moderator ■

Hey Gary: On a double deck unit, 140mm bearings should more than suffice. I assume they are wide 33 series bearings vs 22 series?

The tonnage at 1000 tph is not a prob, depending.

Are we scalping here, Are we overloading by chance (I know you would not do that*)

An 8x20 equates to 160 sq ft of screening area TIMES 2 deck for a total of 320 total sq ft.

To handle a 1000 tph ....on one deck.......unit would have to pass 6.25 tph per sq ft. and on two deck .......LESS depending on process trying to achieve. SCALPING lumps out of product or?

Very important:

HOW OLD is unit?

OBVIOUSLY has been problematic

Grease being used........spec? or OIl spec?

Lubrication schedule is critical

SHAFT marred at bearing race positions?

Bearings cut off when pulling or?

Lots of contributors to insufficient B10 or L10 bearing life. SPEED will drastically decrease (excess that is)

More to chew on.......

REGARDS, George. ■

SORRY: SHOULD HAVE read 140mm vs 160mm bearings.

George ■

Garry,

As usual I agree with Georges comment, but throw in the following thoughts.

While a larger bearing may give a longer theoretical life, remember that this is the calculated fatigue life (because that is the only cause of failure that is subject to statistical laws), but in the real world the majority of screen bearings will fail well before L10 life because of other reasons such as incorrect mounting, inadequate or unsuitable lubrication, unsatisfactory sealing, incorrect shaft fits etc. etc. which will render the bearing unserviceable after a working life that can not be calculated. ■

Hi John..............excellent information as usual.

Keep Smiling..........George ■