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quote:
Originally posted by candy:
What equipment is it? What is it lubricating? Any cooling for the oil?


Critical stuff we need to know.


Turbine Oil 68 is normally for geared and non-geared steam turbines, gas turbines and combined cycle gas turbines. Are you using this in a GT, perhaps running on liquid fuel? Fuel dilution can cause rapid drop in the lubricant parameters you mention.
RM
Last edited by Registered Member
quote:
Originally posted by John from PA:
quote:
Originally posted by candy:
What equipment is it? What is it lubricating? Any cooling for the oil?


Critical stuff we need to know.


Turbine Oil 68 is normally for geared and non-geared steam turbines, gas turbines and combined cycle gas turbines. Are you using this in a GT, perhaps running on liquid fuel? Fuel dilution can cause rapid drop in the lubricant parameters you mention.


I already answered it in my previous reply, the equipment is a pump and the oil is lubricating the pump end bearings. The pump fluid is crude oil but there is no sign of any abnormalities in the mechanical seal monitoring parameters to suspect fuel ingression in the oil. Any experience accidental mixing of turbine 46 & 68??
RM
quote:
I already answered it in my previous reply, the equipment is a pump and the oil is lubricating the pump end bearings. The pump fluid is crude oil but there is no sign of any abnormalities in the mechanical seal monitoring parameters to suspect fuel ingression in the oil. Any experience accidental mixing of turbine 46 & 68??


True, we knew it was a pump, but a pump use where? It could have been a pump used in a GT installation.

You now also state "there is no sign of any abnormalities in the mechanical seal monitoring parameters to suspect fuel ingression in the oil." That makes me think that at least we have all the elements for fuel ingression, just that you think this is not a possibility at the mechanical seal. I would very carefully recheck for some source of lubricant dilution.

quote:
Any experience accidental mixing of turbine 46 & 68??


Depending on the proportions, this of course would explain a sudden decrease in viscosity but it does not explain a sudden decrease in the flash point. That generally would only be explained by ingression of something like fuel.
RM
Last edited by Registered Member
quote:
Any experience accidental mixing of turbine 46 & 68??

Traditional thought is the viscosity changes proportionately to the mixture.
If the fraction X is VG46 and the fraction (1-X) is VG68, then the viscotiy of the mixture at the reference temperature 40C should be:
X*46 + (1-X)*68 which of course varies between 46 and 68 for X between 1 and 0.

quote:
Within 1 month from the OIL CHANGE, what could be main factor for the viscosity and Flash point (26 & 90 respectively)to abruptly go down. The oil is Turbine Oil 68.

So you're saying that the viscosity of the VG68 oil is measured at 26cSt at 40C after one month??

If so, this would seem to me to suggest there is probably something other than contamination with VG46 oil going on.

On the other hand, contamination of some type is the most common cause of viscosity changes, and there are occasional unexpected effects when lubricants are mixed, so no guarantees.

Some links on causes of viscosity changes (sorry if you've already seen these):
http://www.machinerylubricatio...ity-trouble-shooting
http://www.machinerylubricatio.../oil-viscosity-drops

Other than contamination I guess ridiculously severe thermal aging might be a cause but certainly would expect some other indicators in that case.

I'd also look at sample contamination, lab error (perhaps just a followup sample to rule out both.

I'd ask my oil lab if they can help figure out the cause of the change. FTIR may be a good test... if new peaks show up that weren't in original oil that is usually good indicator of contamination and may point toward the nature of the contaminant.
RM
Last edited by Registered Member
quote:
Originally posted by spherical:
I visited the site and found the tank breather is apparently very dirty and the installed venturi tube to produce suction at the space between seal and bearing was having a pressure at 7.5psi. whereas the supply air pressure should be only around 1psi. Can these be enough to cause 1month contamination?


I would have to know a great deal more about your system to express an opinion. For instance, one question I would have would be how would this issue explain the change in flash point?
RM
I think electripete was asking, YES Pete the oil after 1 month from Oil change came down to 26cst at 40C while the low limit is 56cst and flash point low limit is 150C.

John, honestly conclusion is not yet arrive so we decided to change the oil as it is not healthy to run at very low viscosity and low flash point is also a safety risk. Oil sample will be taken after a day of running and after a month to verify this symptom. Tank breather and venturi air supply presure will also be adjusted.
RM

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