01-19-2017 09:50 PM
The Cat recommended oil and filter element change interval is 5,000 hours. But in gas compression, it is common for customers to run the engine oil for a year (8500 hours) using oil sampling with no issues and very little darkening of the oil. And I have seen several different brands of oil in my years of experience. The oil gets darker than when it is new, but not appreciably darker. Now the filter change period of 5,000 hours should NOT be extended or you run the risk of filter(s) collapsing and contaminating the complete lubrication system and a high probability of serious engine damage if the elements become too plugged and come apart. There is NO filter bypass valve on the G3600 like other Cat engines so you don't want to have the elements come apart.
Now the port, tube, etc. should always be flushed sufficiently to be sure that there is no residual uncirculated oil left that would be caught in the sample bottle. Also, if the sample line was not flushed enough, the residual material could be enough to cause the sample color to look darker if the lab technician did not carefully evaluate the visible conditions of the oil sample.
You are correct that the engine oil is sprayed up to the bottom of the piston crown for cooling. In addition oil is forced into the cavity in the piston crown and exits down on to the upper portion of the con rod and piston pin. But unless the oil gets really hot and run too long, this oxidation would cause some discoloration but I would not think I would describe it as black. The oil would have to be really bad to be called "black" from oxidation. And I don't believe the oxidation numbers on the oil sample report support this condition.
I am sorry your oil representative is not responsive. Apparently he is not fully aware of the potential cost of a major failure. I think many of our techs don't fully realize how much the G3600 engines they work cost. I would be glad to review another oil sample. The other sample report was not very readable. You could send it to my email address as an attachment; email@example.com. That might come through in a more readable condition.
I hope that my comments help. I was responsible for a dealer oil lab operation for about 10 years so I have some experience in this area even though I was not the lab technician.
01-19-2017 06:21 PM
The oil is changed when an analysis report shows a need to change it. I don't know if they are changing the filter at those hours. Looking through the manual I noticed that the oil is sprayed up against the bottom of the pistons to cool them. That would cause the oxidation and discoloration of the oil, though I don't know just how dark it may make the oil get.
I am going to have them install a dedicated oil sample line with a 1/4 turn ball valve at one of the other spots available on the oil thermostat housing. I think the previous person getting the oil samples may not have been flushing enough oil through the line. I watched the new person and they did not flush the line enough and also turned the valve off, then back on to fill the sample bottle. That could cause sediment to enter the sample.
I am wondring if the noted 'high visible sediment' comment is refering to the color of the oil. I cannot ever get any questions answered from our contact at Exxon Mobil. He hasn't ever replied to any of the many emails I have sent, nor has he ever returned a phone call, much less answer a call.
01-09-2017 06:49 PM
I'm pretty sure the hours listed on the oil are wrong because it was changed to get rid of the potassium problem. The mechanics found a leak and fixed it and the potassium level hasn't come back up. It's just the "high levels of visible sediment" that I am concerned with...and now the black color of the oil that you are indicating is wrong. Thanks for all your help!
01-09-2017 06:43 PM
This is the latest oil analysis, the one we took a few days after receiving this report hasn't arrived yet. I don't see any reason for the oil being black, do you? I am going to look at some Clarks tomorrow to see what color the oil is.
01-09-2017 05:55 PM
This is the correct place to take an oil sample with the engine running. The needle valve proably works okay if you flush out the valve/line with the first oil and then take the sample after that. A ball valve would be a little bit quicker.
Again, gas engine oil should not turn black like diesel engine oil does due to the lack of soot as a product of gas engine combustion; there just isn't anything to turn the oil black on a gas engine. So if the oil is really black, something else is going. Oxidation of the oil might lead to some darkening of the oil but if the oil is getting too hot, I would expect you to see a high oil temp alarm. How often do you change the engine oil? The recommended oil change interval on a G3600 is 5k hours but customers routinedly run the change interval to yearly (8500 hrs.) with no problems. You should NOT run the oil filter change out past the recommended filter change interval of 5K hrs. If you do, the filter element might collapse and then all of that debris goes into the engine. There is no oil filter bypass valve on the G3600 like all of the other Cat engines. So if the filter gets plugged, it will eventually just collapse instead of opening the bypass valve, which is not on the G3600.
01-09-2017 05:06 PM
Here is a picture of the oil sampling port. The first thing I see wrong is the use of a needle valve instead of a ball valve. Do you see anything else that should be corrected?
01-09-2017 12:55 PM
Thanks for your reply...I was just posting that picture at the exact same time. I'll head out to look at the engine again this afternnon and determine exactly where the valve is located. I'll try to take a picture to be sure.
The oil analysis reports come back fine, meaning everything like viscosity, TAN, TBN, etc are fine. But I always see black looking oil in natural gas engines.
01-09-2017 12:52 PM
Looking at this picture I found in a CAT Lubrication Systems manual, the oil is being sampled from #5, the oil thermostat housing. Still wondering if that is a good place to take the oil sample from for analysis.