Facing a challenge on a GE Frame 5 gas turbine. Lube oil header and differential pressure alarm and trip condition standing.
Filters have been replaced, oil lines have been flushed, oil completely drained and replaced with brand new oil. After all these the unit was started, it ran for 5 hrs and tripped again on lube oil header pressure low trip. At trip:
1.differential lube oil pressure was greater than 3.5bar and
2.differential hydraulic pressure was greater than 2.2 bar
3.control oil differential = 0 bar
Has anyone experienced this or any ideas on possible cause and solution on the problem?
I presume by differential lube oil pressure you are referring to the lube oil filter differential pressure? If you've replaced the filters and the differential pressure is already high again--and 3.5 bar is HIGH--then it certainly seems the lube oil might be dirty.
GE and its packagers usually filter cold oil (that is--lube oil that has already been run through the L.O. Cooler). Could it be that the L.O. Temperature Regulating valve is not working and the L.O. is extremely "cold," making its viscosity very high and causing a high L.O. Filter differential pressure, as well as a low bearing header pressure?
You didn't mention what the Aux. and Main L.O. Pump discharge pressures were. Are they normal, or higher or lower than normal?
The L.O. Bearing Header pressure regulating valve is sometimes located in the L.O. tank where it's not easily accessible. Are you sure it's working correctly?
The zero control oil filter differential pressure is concerning--usually when the other filter differential pressures are high and the control oil filter differential pressure is low it can mean that the control oil filter has ruptured and so there is no differential pressure.... Not always, but usually.
And, again, about the only two causes of high filter differential pressures and low pressures (downstream of the filters) is dirty oil and/or very cold oil. I have, though, seen when non-OEM filters were used that were not properly rated/sized for the application similar problems were caused.
Please write back to let us know what you find!
Thank you so much for you reply. The problem was traced to residual dirts in the system. After the trip the Main lube oil filters were removed and upon examination discovered to be dirty.
The filters were washed thoroughly, put in service, and the high differential pressure was eliminated. Unit is currently online and generating.
It's good to get an answer from people, but this is a kind of strange answer. Where did all this accumulated "dirt" come from? And why did you not see it as an increasing filter DP? Secondly, do you really clean your filters, you don't replace them?
The unit lube oil sump had never be cleaned in a VERY long time. The increasing DP was seen over time. Filters were swapped, but the dirts were still in the system. Yes, we do replace, but the filters used after the overhaul were new ones that just became clogged after running the unit for ~ 2 days. They were cleaned properly; the remaining dirts removed and the DP cleared.
How were the lines "flushed?"
By the way, I was as surprised as glenmorangie about "washing" the filters. I don't think I've ever seen that done.
And if the dirts in the L.O. tank had been allowed to build up until finally they were picked up in the turbulence and circulated by the L.O. pumps, one would think that if the oil was sampled, even occasionally, the presence of dirts would have been noted. Because dirts have to be circulated back to the tank where they will eventually settle out, until there is so much that turbulence will cause them to be dislodged and eventually picked up by the L.O. pumps.
The lines were flushed by using new lube oil to circulate the lines.
About the filter washing,its unorthodox but if its a new filter the results are good (the washing is done with Paint thinner).