Anybody familiar with Raymond pulverizors? We put one manufactured in the '70 into service and after about a year of operation an oil foaming problem.

Gonzo,

I have worked on Raymond Coal Mills with excessive vibrations but not for gear lubrication issues. My suggestion for foaming oil:
1) Check for high oil level -- the level indicator may be incorrect
2) Check for lube oil pump for air entrainment/Cavitation -- measure high frequency vibrations or ultrasound on oil pump

Walt

Walt,

We were running at a constant oil level and seemed to have developed this problem almost overnight. I have to rule out the oil level as we both raised and lowered the level to see if that was our problem.

We run an external filtration kidney loop and shut the external pump off for several days but the foaming didn't subside.

Do you know how the oil is pumped to the upper bearing?

Gonzo

Gonzo,

I don't know the oil path. Perhaps the machine databook has a diagram. Did you check for water in oil? Is the gearbox properly vented? Has gear vibrations changed? Do you have the correct oil (that you think you have)? Has there been oil deterioration? Is there internal spray nozzle that may have shifted position? Have you contacted anyone at ABB Combustion Engineering in Windsor, CT?
Sorry, more questions than answers!

Walt

Walt,

Oil analysis shows no water. Vibration signantures have not changed (just a single reduction worm). Runnning a Castrol 1100/320 and no change in any of the additives, etc. The box is vented and the breather replaced when this problem started.

There are no internal sprays. The worm is horizontal, the gear shaft is vertical. It must be hollow and the oil somehow gets to the upper bearing housing, there is a return sight to verify this flow, however, there is no internal pump (we drained the oil and checked.)

I've never heard of ABB.

Gonzo

ABB = Asea Brown Boveri Ltd. By a rather long progression they are now part of Alstom. On your Raymond Industries Pulverizer, manufactured in the 70's. Raymond was taken over by Air Preheater who later became part of Combustion Engineering who later became part of ABB. Its a never endimng saga.

Make sure the oil you are using is for worm gears. Because of high sliding action these are are specially formulated.

Good luck.

John from PA

I guess the oil analysis showed no contamination either?

You may get more assistance if you contact the gearbox manufacturer directly.

I would look for the nameplate, get the model number and serial number and manufacturer's name and call them to verify that the lubricant is proper and to get a drawing of the drive showing the method for lubricating the top bearing. They should also be able to give you the bearing id's and the number of leads on the worn and teeth on the wheel. Some use an oil slinger attached to the input shaft. I wonder if damage to the slinger could create foaming?

Gonzo,

The large CE-Raymond coal mills that I worked on were pressurized by the PA Fan. If this is your case, I wonder if the shaft seal is leaking and causing aeration? How does the oil run up hill? I have never seen a slinger used for a vertical shaft! How can you run for an extended time with the external oil pump off? It seems like there are more things to check out to resolve this issue.

Walt

Although it probably isn't your basic underlying problem you should check with the OEM on the recommended lubricant. From my experience AGMA recommends an ISO grade 460 as a minimum for enclosed worm gears. Typically in all the applications I've run into the lubricant will also have "cylinder" as part of its name, like Mobil 600W Super Cylinder Oil which is a recommended lubricant for worm gears. The "cylinder" is due to the formulation being suited for applications that have a high degree of sliding, like a recip for instance.

The Castrol 1100/320 is probably too light since the suffix 320 indicates an ISO 320 oil. Also, when examining the Castrol Tribol 1100 spec sheet I noticed the list of "typical" applications fails to mention worm gearing although virtually every other type of gearing is listed.

John from PA

First I'd like to address Walt. A fan pulls the pulverized coal from the mill, so the mill should be negative. The air passing thru is 600F and the foaming may have begun when the mill was overheated, around 300F. I don't believe there are any oil slingers in the mill. The only bearing above static level is the upper bearing on the gear shaft, I'm assuming the shaft must be hollow and somehow oil is pumped up thru the shaft. The pump I referred to is an off-line circulation pump used only for filtration purposes.

Next, John. The manufacturer recommends ISO VG 460 but because of temp concerns here in northern MN and heat transfer characteristics of their 460 product, we are using VG 320. Castrol tech folks tell me the fatty oils in the product make it suitable for worms, at least at this speed. We use it on other worms with good results. Turns out, our operator / engineer responsible for this mill have spoken to the Alstom folks, and they're not familiar with this problem.


We will be shutting the mill down for the weekend. Will monitor for aeration next week.

Thanks, everybody for your help.

Running the mill now for a day and no foaming. We did nothing but let the air settle out.

We have 8 Raymond Bowl Mill pulverizer and have the same problem on only one of the mills. I have noticed that the foaming mill oil has to be changed more often than others due to increased oxidation (higher TAN). The oil moves up the vertical shaft via a groove on the vertical shaft. I believe this is called an akeli pump.

Gonzo,

On all Raymond (and similar) roller mills that I have experience with the fan at the top (referred to as the Whizzer) blows downward onto the rollers and forces the pulverized material to flow up the sides of the mill. There is also a fairly long drive shaft that separates the mill from the drive which makes me think that the airflow could not be a source of foaming in the oil.