Thank you for your input, Barry. I have to stay with Castrol. But, thats not to say we can't change it to another grease Castrol makes.

Are you familiar with Castrol brands?

Vibe King, your "rumbling" is the bearing knocking around in the housing. Your spectra show classic looseness indications. If you crank the resolution up on your spectra I bet you'll see 1/2 harmonics which to me always indicates "excessive" clearance, regardless of what the overall levels are. If I see 1/2 harmonics, I recommend changing the housings and bearings.

Another way to check for looseness is to check the roller clearance with a feeler gauge (sounds like you've done that already). Next do a lift check, but with the bearing bolted up tight ("tops on"). The critical step here is to afix your indicator base to the bearing housing (I usually put it on top) and indicate off the top of the shaft. This way you measure the "relative" movement between shaft and housing. If your roller clearance is 0.002" and the total clearance (lift check) is 0.006" (for example), then your race clearance is 0.004". This could be outer race to housing, or inner race to shaft (clearance there should be visible as fretting dust if you wipe the grease off).

Also, make sure the split lines are perfectly clean when the bearing is bolted up. That goes without saying, but I've seen crude on the split line cause clearance problems more than once.

When you do a lift check on a smaller fan like this, do not use a porta-power. Use a big pry bar instead (I like using a "pinch bar", about 6 ft. long). If the clearance is excessive you will be able to feel (and sometimes hear) a "bump" when you pry up on the shaft. If there is no discernable "bump" then the clearance is probably not causing a problem.

I think you have excessive outer race to housing clearance. The "corrosion" of the clearance spots near the split line indicates this has been going on for quite some time.

How long will it last? Who knows? (there is no way to know) But this problem needs to be addressed. Just recommend that, and if they don't want to do it, they don't have to... it's their machine. But you still need to make the recommendation.

Rusty,

I would be careful about suggesting only a vertical lift check, since the rotor is overhung and it is a belt drive. Gravity and belt tension may affect a vertical lift. I would slacken the belts and try both lifting and pulling down to see looseness in the sheave-side bearing. On some fans the shaft is trying to lift the bearing due to weight of rotor on the other end. It may also be wise to check side-to-side looseness because of the belt drive and the housing gap in the photo.

Walt

I'm not sure of the subtleties of checking an overhung rotor. Sounds tricky as Walt mentioned.

Just a comment about lift checks in general. There are a few other ways to do a lift check using a hydraulic jack on between bearings machines or vertical machines:

A - Two dial indicator method:
One dial indicator on the shaft and one on the bearing housing (mounted to a stationary reference). The bearing housing indicator should move a little as rotor weight is removed, then stay in place as rotor lifts, then start really moving as you start pushing the rotor up past its clearance.

OR even better:

B - Plot dial indicator movement vs pressure
The curve in theory has 3 pieces in order:
Horizontal section - pressure increases without much movement until you get to the pressure necessary to lift the rotor.
Vertical/hi-slope section - here the dial indicator increases rapidly with relatively small change in pressure... the rotor is lifting within it's clearance
Final horizontal section - here the pressure increases with little further movement - you are pushing beyond the clearance.
These curves are not pure horizontal and pure vertical, but you should be able to detect the two abrupt changes in slope between the three regsions. When you get to the third region you're done.

This message has been edited. Last edited by: electricpete,

Good point, Walt, about the overhung fan. And it points out that you have to always be thinking about what is physically going on with the machine, how it's set up, how it operates, etc. On an overhung fan, when checking the drive-end bearing, place the pinch bar (or jack) outboard of the fan-end bearing, between the bearing and the fan housing. When you pry here, the fan-end bearing becomes a pivot point, and the shaft will move down at the drive-end bearing.

I mount the indicator holder on the bearing housing because a pedestal (fans) or base (pumps, motors) can flex when using a pry bar and give you false readings.

You guys are great. Thank you so much for everyone's reply. I have recommended a change on one of the worst. I am looking forward to seeing the bearings when they come off. I will post a reply with pictures when I get the bearings.

Your right, its their fan. I'm just glad I keep good records of communication with the customer in case of a failure. Know what I mean?

I recommended refurbishing a 1000 hp motor with R.E.B. that had a "rumble". No discernable bearing defect, but looseness indications with a rumble. I told them specifically, "The bearing is not bad, but the fit in the housing is loose." Had them request the bearings be sent back with the motor. When it came back, the plant folks told me, "They said there was nothing wrong with the bearings." Right, so what is that staining and pitting all over the outer race?

Sometimes, no matter what you tell them, or how, "they just don't listen!"

Rusty,

How does the 6' pinch bar fit in your bucket?

Rusty,
I believe that is called fretting.
Things seem to get lost between initial report and their reply sometimes.

Hey, this is a technical forum with a touch of a support group. This is great.

Danny,

If you see Rusty walking with a stiff right leg, then you'll know where he keeps the 6' pinch bar!

Walt