Can I know if we can /
Liquid to Gas fuel transfer is typically done at lower loads 20-30% load. Maximum load this is done is typically ~100 MW. that would prevent higher load LF to GF transfer.

For Gas to liquid transfer, this is pretty much unrestricted and can be done at any load. However it is a good practice to limit it to maximum load to 80% load to give some margin for IGV regulation and over-temperature protection.

 

Are you asking a question, NABIL007? (Questions end with question a question mark.) Because it reads like you are making statements and not asking any question(s).

For many machines transferring from gas to liquid is not easy and causes load swings, exhaust temperature swings, and (unfortunately) quite often trips (either because of high exhaust temperature spreads or low liquid fuel flow (loss of flame)). It's usually much easier to transfer from liquid fuel to gas fuel, at just about any load. Usually.

Frame 9FA machines are ... touchy. Especially the ones which were configured by GE Belfort. The auxiliaries can vary a LOT from one machine to the next, and are not as common as many would like to think. We don't know very much about the machine(s) at your site, if they have liquid fuel recirculation, or liquid fuel "reliability" systems. GE Belfort has come up with all kinds of fancy stuff, and while some of it works occasionally it's not always reliable. We also don't know if the unit have DLN 2.0, -2.6, -2.6+ or -2.6+e, and that can have a LOT of effect on fuel transfer reliability. Machines configured and packaged and installed by BHEL can have some of the very same issues.

The thing about reliable fuel transfers is: The unit has to regularly (as in about once every week--yes, once every week) the fuel transfers have to be performed to ensure check valves work properly, purge systems work properly, water injection works properly, air doesn't build up in the liquid fuel systems. There are A LOT of devices that ARE NOT directly controlled by the Mark* which all have to operate correctly for the fuel systems to work reliably--especially the liquid fuel, liquid fuel purge and water injection systems. Throw DLN combustion systems into the mix, and that adds another layer of complexity altogether.

For some reason the unit(s) at your site seem to be better at gas-to-liquid fuel transfers than most machines I had the pleasure of working on. Usually such transfers were only attempted at about 25-50% of rated load to try to limit load swings and trips; you say the unit(s) at your site perform these transfer between 80-100% of rated load. And on a 9FA--that's a LOT of load to lose if the unit trips. MOST sites would not even think of attempting transfers at such high load unless it occurred automatically because of loss of gas fuel supply pressure/flow, and even then if the gas fuel supply pressure/flow is dropping quickly the transfer to liquid fuel may not occur before low gas fuel supply pressure/flow causes flame to be extinguished and a resultant loss of flame trip. So, either your site has some fancy-dancy auxiliaries that actually work and are reliable or your site is EXTREMELY lucky and you should be buying lottery tickets.

If the unit(s) at your site have been reliably performing fuel transfers in the past but have begun to have problems and be unreliable, there is usually a mechanical issue or issues causing the problem and that's usually the result of lack of maintenance OR poor reassembly after normal maintenance outages. Or, sometimes operating conditions change or have changed and people overlook the effect such change(s) can have on reliable fuel transfers.

So, if you have a specific question--ask it. Don't assume we know from your statements what it is you want to know. Using question marks is not a sign of weakness or shame (as is thought in some parts of the world which shall remain nameless). Help us to help you, NABIL007.