Hi All,
We have recently seen increasing levels of water in our paper machine dryer lube circulating systems. We would normally run below 40% saturation until about 18months ago when it crept up to over 50%. We replaced an old tube cooler with an alfa lavel plate cooler and now our readings are contantly over 60% and would be over 100% but we are hiring a pall oil conditioner. online Oil moisture trends suggest the water levels steadily increase with sheet on, not so much during breaks, washups etc ( Some increase but we have changes our procedures now). When the sheet is on the atmospere around the gears cases and brg housings is very humid so it seems we are just breathing moist air into our housings, however this has always been the case so why the sudden increase. We sped the machines up about 10% in the last 2 yrs. Also our oil temperature has reduced from about 55degC to 40degC. Could this be contributing? Our other machine runs at 40degC with no water in oil issues.

Any help, suggestions etc much appreciated,
Cheers,
Mike Plant

Yes moisture saturation will vary with temperature. Check with your oil supplier and see if they can give some information about your oil.

Is it possible that the plate cooler has an internal leak to the oil as it passes. New does not mean it can not leak. How much oil does the reservoir hold?

The tank is pretty big at about 40,000 ltrs. We have checked before and after cooler samples and there is no increase (although we may not see a small leak)
We are currently taking samples from all over the dryer but nothing definate yet.
Cheers

You also asked about the temperature reduction 55C to 40C. At one time the water getting in your system may have been driven off at 55C. At 40C almost no water will be driven off. If possible it would be better to operate your oil at 55C to help keep the water as a vapor.

What was the reason for the temperature reduction?

Hi Don,
I think you are correct. Thinking about it some more, lower oil temperature would have 3 effects, Higher saturation levels recorded as cold oil cannot absorb as much water, less ability to flash off water, and more likely to condense water from the atmosphere. The temperature setpoint has always been 40 but the old cooler could never get it there especially in the last 2 yrs. After the new cooler was installed it easily controls to 40degC. We will raise the temperature back to 55 and see what happens.
Cheers

Definitely true.

Decreasing oil temperautre will increase % saturation even with ppm water constant.

For oil samples, most labs report the ppm water using Karl Fischer analysis (not the saturation fractio) since the temperature obviously will change by the time the sample is analysed. The only place I have heard of monitor saturation is in an on-line sensor. Out of curiosity, do you have an on-line moisture sensor, or do you have labs analyse oil samples for moisture?

Hi electricpete,
We have online Pall moisure sensors and also do lab samples every month for lube condition and contamination.
Even visually the oil appearance has changed so we know water PPM is going up.
Ill let you know what happens when we increase target oil temp back to 55degC.

Don't know for sure what type of steam joints you have on your dryers but i do know that in the past when our steam joints goes to leaking sometimes the the leaks are in the insulating tubes between bearings and therefor leak into the main lube, that may be one thing you look for.

Thanks Chad, I had a look at our drgs and any leaks in the insulating tube would have to get past the outside tube support gasket and would vent to atmosphere. Where they vent is very close to the brg labyrinth though so it is possible. We are repairing about 6 leaking steamfits on our shut tomorrow so will hopefully know then.
Cheers

Planty,
So how did your inspection and adjustments go? Has the oil dried up?

Hi All,
Temperature increased to 50degC about 3 weeks ago, Not much if any change in sat level, although we have just had a week long shut also so it may be a while before we get any usefull results. Will monitor for a couple of weeks then increase temp to 55degC.
Q, will the ability of oil to drive of water increase linearily with temp of exponentially?

Will let you know what happens.

The experience in our plant is somewhat linear. As oil saturation begins from condensation or leakage, oil temperature was too low for a period of time, as the temperature increased the water saturation would decrease. It did not happen over night but our reservoir was around 600 gallons. We did still have dissolved water so temperature had to remain at a level that controlled the problem. If we had a better oil conditioner at the time we would have been more successful with controlling the water content of the oil.

Update,
several days after our long shut the sat level went through the roof to 100% where it held for about a day. We turned every leaking steamfit off before it started dropping and are now running back at 50% (meter is in the return line to tank). We are fixing 22 steamfits today on our shut (being extra fussy about the smallest leaks) Also rechecking all breathers etc. Will keep you posted with results.
Cheers