Control.com - Nerds in Control

We are running Frame 6B machine controlled by Mark V TMR, with HRSG in combined cycle mode at part load. Recently faced problem when load was increased, IGV was on manual mode and to control exhaust temp / Super heated steam temp IGV was tried to open from 57 Deg but it stuck up at 59 Deg. It can go back to 57 but can't open more than 60 Deg. 2 drums of lube oil topped up. Hyd oil pressure remains @ 90 bar steady. No Hyd oil filter DP increased. Lube oil temp. was maintained @ 60 -64 dg C. Servo current keeps increasing when actual and set point value differs. 1 month back during annual shutdown it was opened during water wash.
What could be the problem?

Hi,

We hope your IGV is controlled by servo valve and trip valve (20TV).

After maintenance, have you calibrated IGV, if Yes how was it performance?

Mostly varnish on servo valve may impact the operation. Next oppurtunity just replace moog valve and observe (or only it's filter).

Take care
G.Rajesh

@ G.Rajesh, Thanks for response
.
After shutdown it was calibrated and working ok. even after start up it was opened on an instance and worked ok. We are planning to replace Moog v/v filter in next available opportunity.

As Rajesh says, I think you have a sticky servo. How long has it been installed? How is your oil quality? Poor quality oil will accelerate varnishing effect.

Replace the servo and re-cal the system and I think your problem will disappear.

Thanks.

It's @ 17 years old machine and not replaced servo yet. even we have doubt on lube oil quality as we have not replaced total lube oil since 17 years, just topping up when required.

Absolutely incredible!! You haven't changed the oil or the servo in 17 years and the machine is still running. Have you ever done any oil analysis?

If your oil is so old and never been sampled I'm not surprised that you have had a sticky servo. If not yet, you are going to get a lot more "sticky" things.

You must get this oil checked immediately, and, depending on the results, dump the oil, flush the machine and replace with new oil. You really should change all the servos, dump valves and trip solenoids as well because all of these will cause problems with varnished oil sooner or later.

I can only speak of my Frame 7 experiences. I would be changing The IGV Servo and its local filter.