Almost 300 Ltr water is observed in lube oil tank (Lube oil was filled almost 4000 Ltr out of 6750 tank capacity) of Frame-V machine due to lube cooler tube punctured. Machine is gas fuel fired and having Mark-Vie control system.
Machine scheduled cranking/ratcheting is already done before observed the water contaminates inside the lube oil.
SRV/GCV/IGV Servo shall be affected due to contaminated oil ingress inside the servo port.
Kindly guide us to help out which field instruments shall be affected in case of contaminated oil circulated inside machine internals and what type of maintenance to be carried out from instrumentation side after clean/replacement of lube oil.
You have identified the most critical control devices which would be affected by water in the oil (lube oil and hydraulic oil).
You should flush the servo-valves with good oil to make sure they are okay; if it was just the period of cooldown operation and cranking they are probably okay.
But, a proper flush of BOTH the Lube Oil and Hydraulic Oil systems, using flushing blocks is best for both the bearings and gear boxes and hydraulic trip valves, as well as the servo-valves. ALWAYS refer to the P&IDs of the turbine systems (in this case, the L.O.-, Control Oil-, and Hydraulic Oil P&IDs), and find and use the Flushing Instructions in the Operations & Service Manuals provided with the unit, and the flushing blocks which should have been supplied with the spares left over after commissioning.
The flushing blocks will allow for high flows through the hydraulic system (which will cause the hydraulic system pressure to be low! but that's to be expected), to displace any water. It's important to remember that there is not much flow through the hydraulic system under normal circumstances.
Finally, if the unit has a hydraulic accumulator, it would be a good idea to flush the accumulator, also. And, the filters (Hydraulic, L.O, and Control Oil (if so equipped)) should also be replaced, after draining the filter vessels of any residual oil/water.
Hope this helps!