SAB128 Mk2 axial bearings set up

[garyb]

Hi Guys

In the middle of overhauling a SAB128 and having some issues getting the axial bearings set up. It has the 4 point ball bearings, l seem to have a looseness for lack of a better word, with the axial inner and outer races torqued up and the axial adjustment plate on and set as per the manual I still have a 0.5mm float that I can pull in and out by hand on the shafts. I have disassembled several times but can't see any problems, the races were all re pressed with a hydraulic ram after hot fitting. It seems like the discharge end inner races have not gone all the way home but I am running out of ideas as to what to do about it. The shims between the radial and axial brgs don't seem to make any difference to the float.
Any thoughts appreciated.

[RANGER1]

Garyb,
Have only done Sab202, but very similarI think, by cut away pictures.
Assume nothing changed or machined?
Discharge ports on male & female rotors installed & torqued up.

Spacer behind inner race was tight ( probably can’t tell now unless you pull rotors out).

Using same spacers from when pulled apart?
I cannot see where adjustment spacers are installed except behind roller inner race, what are you using to adjust?

The 202 you push rotor towards discharge end face with a spring installed to hold constant tension.
You only install back inner race of 4 point bearing, make sure home, then install 4 point bearing & assemble without “0” rings.
only after that is assembled but pushing on cover, dial indicator on rotor suction end taking reading.

On a 202 you can then change spacer for end clearance without pressing bearings on/off.

You

Before installing thrust bearing, using depth gauge you can check how much inner race protruded through past roller outer race as an indicator of end clearance.

[garyb]

Ranger1
Not done a 202 but 128 is quite similar just smaller. 163 and 128 don't have a spring but a bolt that you set and lock based on the DTI shaft movement. Discharge faces not changed. Bearing install is pretty much as you describe. I'll have to strip down again and start over but at least is a lot quicker being a smaller machine. I have some suspicions re the spacer where the female rotor passes through the discharge face but it otherwise appears correct. Shim sits between the outer races of the radial and axial bearings.

[josef]

Do you use genuine Sabroe tools?

Josef.

[RANGER1]

Ranger1
Not done a 202 but 128 is quite similar just smaller. 163 and 128 don't have a spring but a bolt that you set and lock based on the DTI shaft movement. Discharge faces not changed. Bearing install is pretty much as you describe. I'll have to strip down again and start over but at least is a lot quicker being a smaller machine. I have some suspicions re the spacer where the female rotor passes through the discharge face but it otherwise appears correct. Shim sits between the outer races of the radial and axial bearings.

Gary,
Sabroe tool have a spring, we cannot afford their tools, but a spring that loads thrust bearing when doing pre-load.
Do you have all the correct manuals & following it's instructions etc, as this has to be done to achieve accurate end clearance, as well as thrust bearing play on it's outer race.
If you need manuals & drawings let me know.

[garyb]

No we don't have the (outrageously expensive) Sabroe tool kit (does anyone south of the equator?). We have approximations made up over the years of doing various machines.
We have used the inner race of the 4P thrust bearing with the ID machined out as a dummy to allow easy removal of the outer race for setting up the thrust clearance. This has worked fine for years as the bearings are manufactured to a defined standard which is consistent across all brands. Have since discovered that for the 128s that the internal components are not consistent between brands with the SKF 4P having 11 balls and and the FAG 4P having 11 balls and therefore a different ball diameter thereby making the inner races between the two different. This created an additional clearance in the bearing corresponding to the end float i was seeing despite all the races being correctly positioned.
For the 163s this brand change over the years has not been an issue as the internals are the same but for the 128s the dummy races must match the brand to set up the thrusts correctly, at least for now.
For the 128 I had to buy an off the shelf SKF 4P bearing to get a suitable inner race to allow the bearing set up.
Moving forward I can see that getting some sleeves machined to match the inner race dimensions will be a must as a manufacturer could change the internal specs of the rolling elements at any time. The first time we might become aware of this is a situation like this. Luckily an additional 4P was available overnight however it was just that - lucky!
Before anyone tries to tell me how we that this is why we should have had the genuine tool kit, forget it. The cost of them is simply not an option so don't even go there.
Lots of learning but a good result in the end.

[RANGER1]

Gary,
Good that it is sorted, agree no one has genuine tool kit, s a lot of it is not required, like brackets for alignment.
A lot of people follow instructions & do not deviate, so you develop your own way, with what you have.
Mycom best, as require 2 locknut spanners for $500, not $15000 for Sabroe, or $25000 Frick, where you have to do course for another $25000 in USA to be able to buy.
Grasso $17000 for dowel alignment tool ( they will let you borrow though), rent is included in parts price of $100 an “0” ring, with 50% of them leftover when you finish.

Dummy bearing good for interference fit bearings when have to remove to alter end clearance.
The way that I see it, a dummy bearing is not really required the way manual suggests you do it, which I have done on Sab202.
If you assemble with back half of thrust, make sure seated, assemble other parts without “0” rings, end clearance check, can still change spacers Behind outer race.

Of course, do what works.

[josef]

Hi,
yes, you're right, tools are pointlessly expensive. My question was directed to the original because if you have not tested the thrust bearing pressure depth, you have such a problem. I don't think the bearings are properly pressed.

Josef.

[AKI]

Hi Garyb, I agree with RANGER and Josef about original tool , but I made a lot of overhaul on 128 and 163 with a tool made handmade. And never had a problem . Compressor running perfect . I think you made some big mistake . Like Josef sad maybe you not pushed bearings correctly or you mixed inner rings of axial bearings.