Interesting experience with some big roller bearings and synthetic oils.

[Shannow]

At work, there are some pretty big fans to shift air into the boiler furnaces, and flue gasses out of them.

The original design of the (cantilevered) shaft required shaft destruction to replace the bearings. & years ago, the design was changed to allow bearing replacement (tapered sleeve adaptors), but due to the shaft stiffness, the bearings were made bigger (10 inch roller centreline).

As a result, the spherical roller bearings are quite underloaded, and have been skidding. Operating temps were up to 110degrees C. We weren't seeing much damage, just temperature. (and ultimately sludge)

So we changed to a Castrol Synthetic oil. Temperature stayed up there, but the oil lived for just over 18 months with no dramas (changed annually, and there's only 5 litres per bearing).

The other day, the operators announced that the bearing was "hot" (about 130C). Inspection revealed that someone had opened the drain valve, and the thing had been operating oilless for 4 hours.

Refilled while running, and the temperature came to 55 degrees and stayed there - didn't move. Bearing vibration had increased from 1.4gs to well over 5.

Ran for another three weeks before we could pull it out, and it's shagged.

Still didn't get above 55 degrees 'though.

Nope we never found out whoe opened the valve (and removed the plug from the valve outlet).

 

[cheetahdriver]

from my industrial experience, i would give a suggestion. attach a high voltage line from the starter on the motor to the handle. the smell from the body of anyone who tried to open it will attract attention before much damage.

i have been through a couple of cases where synthetics made the difference. most extreme was a set of 96 wormgear boxes, used to drive spinning drums. (ok, if you haven't worked with fiberglass filters, this doesn't mean much) drums were 8ft wide and 6ft in diameter, run 24/7/365. when i got there, they would replace the oil (dino) every year, and would rinse the boxes out with gasoline as the oil had baked to sludge most of the time (constant 120F ambient temps). failures were also a bad problem. i had them switch to mobil 1 shc (i think 435?). one year went by, failures dropped significantly, and i had them drain one gearbox to prove that the oil was still in good shape. after 3 years, failures (except for seal failures, which i had them start changing) went to zero. at five years, when i left for greener pastures, the oil was still in good shape, and few could remember changing every year.

they still complained about using such an expensive oil, however. wonder if they ever went back to dino........... if they did, wonder if the figured out why things went south...........

 

[Shannow]

cheetahdriver, the hot wired drain valve handle is a great idea. Might even get a bonus for suggesting that (we're on a staff reduction drive at present

Understand the management's reluctence to use "expensive oils". The mills that pulverise the coal have a "filled for life" bearing, that oeprates in a 250F environment, and under ridiculous bearing loads.

Ten years ago, an engineer switched them toi synthetics, and the "life" became that of the mill roll, NOT the bearing or oil (which it was previously).

Now, we are being asked if us engineers can't figure out how to use cheaper oil.

 

[cheetahdriver]

yeah, i used to be in mining once upon a time, machinery lifetimes in that were measured in months. we got a batch of bad rollers once, and we lost the whole conveyor in about 3 months, when the fatigue life was supposed to be 10 years.

on the other hand, not too many people are able to say that they got to use primacord as "liquid wrench". works just fine on 3inch and up nuts. just don't use to much...........

 

[Shannow]

I'm gonna have to get some of that stuff for our next outage.

The fitters just get to use tha gas axe on stuck high temp fasteners on the turbine, Primacord (Detcord ??) would make a change for them.

 

[cheetahdriver]

yes, i forgot you "english" speakers call it detcord, as opposed to we "american" speakers.

worked with the blasting crew for a couple of weeks, their idea of fun was tossing a length with a fuse under the truck as i was about to start it.

really funny to see them arguing with a millwright "no, no, this needs THREE wraps, not just two." while everyone else is quietly leaving the area.