Problems with the turbine control oil circuit
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I’d like to ask the experts: is there any oil return flow when the valve is closed during the normal operation of a turbine? Is there any oil return in the entire quick-shut assembly? The two return oil pipes here currently have a pressure level similar to that of the control oil temperature; there should be enough fluid in them. Recently, there have been many instances where power outages caused the speed-shutdown oil pressure to drop, leading to the shutdown of the machine. However, the oil pressure in the control circuit didn’t change much, while the pressure of the speed-shutdown oil did drop. I would appreciate some advice from those who know more about this issue. Thank you.
If the quick-shut oil loses its pressure, then the pressure of the control oil will certainly also disappear. The control oil is related to the amount of steam, right? And there’s no steam left at all
During normal operation, should there be any oil in the drain pipe on the quick-shut valve?
During normal operation! There is oil in both the quick-shut oil and start-up oil pipes! There is no oil in the return pipe!
There is a certain amount of flow, and the oil inlet pipe for rapid shutdown is slightly thicker; you can take a look at the diagram of the rapid shutdown cylinder. As for why the pressure from the rapid shutdown oil drops faster than that from the control oil, it requires further investigation – factors such as the distance between the pressure extraction point and the control oil accumulator, and whether there are primary valves at the extraction point that cause the two pressures to become out of sync in a short period of time, among other things, need to be examined carefully. It’s hard to say more about this
Generally, there should be no return oil, as it can cause instability in the shut-off oil pressure! In severe cases, it can cause the quick-close valve to shut down.