Manufacture of Bearing Race, DN 1200 and DN910

[SimonWC]

Hi All,
Currently refurbishing a clarifier centre drive. Turbine Bearing is nominal diameter 1200mm and Rake nominal 910mm. Operating speeds are less than 10rpm. Axial load is largest factor with assembly weight of approximatel 2500kg and 7000kg. Unit has been in operation for 25yrs.
The Turbine Bearing features two identical machined races, and I am wondering if anyone is familiar with appropriate grades of steel to use in manufacturing (I have seen references to grade 62100 through hardened bearing steel).
The Rake Bearing featured top, bottom, inside and outside insertion strips into the housing.
I am endeavouring to source races off the shelf from bearing suppliers (since they supply the balls loose) or alternatively manufacture if I have too.
I have previously used Steel 4140 (to AS-1444) quenched and tempered to 280 - 320 BHN and then induction surface hardened to 55 - 58 HRc for an effective depth of 5.5 to 6.5mm for Drier Drum Rollers and am considering using this.
Any advice would be appreciated.
Thanks
Simon

 

[diamondjim]

Simon,
I do not know about 62100 steel but
52100 steel is common. Bearing races
are often 4140, 4150, 1050, 4340, or
8660 where the races are induction
hardened rather than thru hardened.
I hope the bearing had a part number
and you possibly can buy an equivalent
bearing from other sources for comparison
shopping. I would suspect that the
hardness depth of 5.5 to 6.5 is a little
over kill. The fact that you say the
balls are shipped separately seems to imply
that this is some type of thrust bearing.
Are the balls separated by a metal cage?
I would be surprised to see a bearing
on the shelf in this size range.

 

[Hippo41]

You say that the bearingyou have has "featured top, bottom, inside and outside insertion strips"..

Do you mean that there are 4 hoops of hardened wire on which the balls run? If so, this sounds like a 'wire-race' slewing ring bearing which would be about right for a clarifier drive.

You can buy the replacement wores and balls loose (they usually come in standard dimensions), or you can buy them complete - but they are usually bespoke designs so you need x-sectional drawings.

If you can get me more information I may be able to offer more advice.

Lester Milton
NBC Group Ltd, Telford, Shropshire, UK

 

[SimonWC]

Gentlemen,
Thanks for your responses, I'll endeavour to answer each point.
DiamondJim
1. Materials for Races.
I have previously used the 41 and 43 series steels for various load bearing services, eg rollers, and saw a reference to 62100 from a FAG sheet. I will follow up on the 52100 and 8660.
2. Serial Number
Unfortunately the bearings do not have a serial number (or if they did it is not there anymore!). The bearings seem to be a custom fabricated, or special, design.
3. Hardening to 5.5/6.5mm won't be required for this job, just that I have done up to this depth previously, and anywhere in between is possible. The loads in this application are a lot less than previous, and shared over a greater contact area, so the depth could be a lot less (I will confirm this with the manufacturer we use).
4. The balls are shipped separately. Size is 1-1/2 and 1-7/16 inch, 48 off each size. The 1-7/16 serve as spacer balls between each of the 1-1/2's and hence there is no cage. Refer to Qu: at the end.
5. Firstly, the two bearings are installed horizontally with suspended loads of rake (DN910) and turbine (DN1200).
Note these are nominal sizes only as measured roughly on site.
One of the two bearings is could be primarily designed for axial load, this is the one with the spacer balls and the two races. The load is the axially suspended turbine. It has a small radial component from the pinion drive.
That being said the upper race exhibts sustantial wear on the inside while the lower race exhibits substantial wear on the outside (cold flow, cold working and spalling).
The two races, top and bottom are cut in a flat bottomed weir profile (hope that makes sense?).
6. Yes, Bearings in this size are definitely not "off the shelf" in my experience.

Hippo41 (Lester)
Lester, interesting that you refer to a slewing bearing, I am following up with crane contacts as we speak(type).
7. The lower bearing does feature the 4 inserts I referred to (this bearing carries the rake). Each insert is approximately 10mm wide, and depending on location (top or side) is curved in the appropriate diameter. I am not sure if the inserts were one piece and therefore a whole circle or if they were split into smaller arcs. The inserts have worn down so far it is impossible to tell. I suspect one piece but one of the old stores guy recollects arcs, which raises the question as to how the inserts were held in place, press fit perhaps (a bit difficult for the inner and outer "side" insert race)?
I take it that the technical name for these inserts is "wores" from your reply?
8. I have a cross sectional drawing (1979, paper only) but it is undimensioned so not worth too much. On site measurements are hampered by location (in situ), size (bigger than our current largest micrometer and calipers) and design (there is a large raised boss in the centre). The matching top half is too tight to fit a micrometer in.
9. Currently our bearing suppliers are saying supply of the balls is OK but not the races (turbine) and "wores" (rake).
10. The rake features 86 0ff 1-1/4 inch balls, with no spacer balls or cage.
11. I take it from your "bespoke" comment that the inserts actually come as arc segments of the total diameter? Is this the case for the inner and outer sides as well as the top and bottom? (Refer to comments in Item7)

Our aim is now to return the unit to service with, hopefully, enough information to fabricate roughly m/c'd components. In 12 months we will strip and remove the whole drive assembly and then harden and final machine the new races and balls. Aim is to minimise downtime to under a week.

With the Rake we are considering fabrication of angle races,
inner and outer "L" shaped with the balls to go in between (wish I could insert a drawing!) and machining up the lower rake drive to suit, then putting in the two matching halves instead of the top, bottom and side inserts ("wores&quot.

Qu : How do you calculate the diameters (inner, outer and centre) for the bearing when you know the number and size of the balls? Is there a simple formula for this please?

Thanks and regards
Simon

 

[Hippo41]

'Wores' should read 'wires'. Sorry!

If you can get me x-sectional drawings I may be able to offer more help. You may be able to use a standrad slewing ring to replace what you are using - that will save time and money probably.

Also, you mention that you are going to try and make some inner and outer 'L' shaped raceways. That's really re-inventing the wheel a bit as bearings like that (ungeared or with an ineer or outer gear) are readily available up to 1200mm OD, and even bigger on special order. If you want I can send typical catalogue pages (give me a fax or e-mail)


Lester Milton
NBC Group Ltd, Telford, Shropshire, UK

 

[diamondjim]

Simon,
If indeed it is a wire race design,
you might be able to order wires
and/or balls that are oversize to
fit in the same cross section.
Wires are often made in two 180 degree
arcs but I have seen complete 360 degree
wires. I worked for Rotek Inc. and they
made wire race bearings. They have plenty
of wire material in stock and could form
these to your requirements. The wire
conformity can be anywhere from 52 percent
to 60 percent of the ball diameter.
Standard wire sized are 6, 8, 10, 12, 16
millimeters in diameter and have the conformity
either ground or formed removing 30 percent
of the diameter to form the raceway curvature.
Eimco, Dorr Oliver, Baker Hughes, FMC and others
do make slewing ring bearings for clarifier
applications. The 1.5 diameter load balls
and 1.4375 diameter spacer balls have been
a standard in many slewing ring bearings.
I assume your drawing is faxable or in acad
format so you could send that to the different
bearing manufacturers to quote a replacement.
I have not seen a wire race design for this
type of application but it does make sense
to just replace the wires as they wear.
Rotek phone number is 330-562-4000 and you
could ask for Mark Gonczy or Harvey Sable
to take a look at this if you wish. They
both are familiar with clarifier designs.
I assume the wire design is 4 wires each
one about 45 degrees from the horizontal.
Rotek also has a refurb department if that
is your wish also. The guy there is Todd
Troyer. Normally the pocket for the wires
is a square disign with radii in the four
corners almost the same diameter as the
wires to reduce the stresses.

 

[SimonWC]

Thanks Gentlemen,
Lester, I have put something through to your work which has my contact details. Drop me a return and I will see if I can get a scan of the paper drawing I have, which doesn't have any dimensions unfortunately (DiamondJim).
Thanks for the leads too DiamondJim, I am following those up as well. I am in Western Australia which is pretty isolated for the US but I imagine that ony US or Europe will actually manufacture these in any quantity.
Regards,
Simon