Engine, Wartsila 6L38, is physically running at proper RPM and set at fixed speed; shaft generator has proper Hz. And the engine monitoring system, the computer in the ctrl room, is reading proper 599-601 rpm.
But the local control panel reading, and analogue reading in control room/bridge, reads roughly 580rpm not 600.
Seems like something may be robbing some mA from the signal, and looks like the robbing of a few mA is causing the external stby pumps to kick on even though pressures are normal.
What's clever too is; it was a problem, and then during operations for the past 2 weeks the problem wasn't there, then it came back...
Only Differences I can currently think of:
Salt Water vs Fresh water.
No problem in salt water.
We're sitting deeper in fresh water...or difference in conductivity...
And we were in various states of loaded and unloaded during salt water operations and no issue. Currently loaded and into fresh water.
An interesting puzzle...
Any thoughts?