Tilt Pad Bearings.

T-900 through 1600

Tilt Pad Bearings.

Postby j79guy on Tue Feb 10, 2009 7:02 pm

Some one care to explain a common sense method of "adjusting" these little devils to the correct clearance? I've been told that "bump" clearance check is not accurate, as the tilt pads, well, they tilt. But.....that is exactly what the spinning shaft inside the pads is doing, bumping up against the pads. So, in my mind, if I measure the "bump" of the shaft, up next to each tilt pad bearing, this should be an indication of the practical bearing clearance. I've rigged up a mini-stand where a stub shaft is fastened to a base plate, and the bearing assembly "bump" is measured by a .0001'" increment dial indicator. But, I still need someone to tell me what the "correct" bump clearance is. I stumbled upon an engineering report on Solar C16 compressors, where they describe the clearance as "A Ratio of 1.56 Mils per Inch" Whatever that means. I take it to mean .00156" for each inch of shaft diameter. If this is indeed the case, then a typical C16 compressor, with 1.750" diameter shafts should have about .00027" "Clearance" on the tilt pad bearings. But how does this relate to bump?
I've been fighting a particularily nasty C16 6-Stage gas compressor, that runs at 22,000 Rpm, that keeps shaking on one end, and I'm at my wit's end trying to get it to run. I now have the tilt pad bearing set up to give between .0024" and .0027" bump over each tilt pad, and am crossing my fingers. I don't relying on luck, and would prefer to "know" that the bearing setup is correct.

Robin.
j79guy
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