Gas turbine frame 9E

I am a new CCR panel operator at Power Plant, after the startup of the turbine we notice that PT 96FL-2 upstream of VS1-1 stop valve is reading 3.2 bar but LCO filter skid outlet pressure is 5.2 bar, same LCO FWRD pump. What does that mean?
Can anyone advice.

Even as a CCR panel operator you MUST find and learn to understand the P&IDs (Piping & Instrumentation Diagrams) for all the systems on the turbine, auxiliaries and generator--the ones provided with the turbine, generator and auxiliaries as well as the ones provided by the architect/engineer (sometimes the A/E provides systems like Fuel Forwarding). In addition, it's very advantageous to actually take those drawings out and find the devices shown on them to get an idea of where they are located and how the physical system is constructed as opposed to the schematic drawing shown on the P&IDs. If you do this--and it's not a difficult task--you will be a very good operator.

USUALLY there is a fuel filter between the output of the fuel forwarding skid and the inlet of the liquid fuel stop valve. If that filter is dirty ("choked") that will cause a pressure drop such as you're seeing. That's the most likely cause.

I have seen the strainer which is usually upstream of the liquid fuel forwarding pumps also get clogged ("choked") and reduce flow to the point that pressure also begins to decrease. This isn't very common, but it has happened.

It's also possible there is some other valve in the liquid fuel supply line from the outlet of the fuel forwarding pump(s) to the inlet of the liquid fuel stop valve that may not be fully open. A walkdown of the liquid fuel supply line from the fuel forwarding pumps to the liquid fuel stop valve will usually reveal items which are suspect and which must be eliminated or proven to be the cause of any problem like this (when there might be several possible causes).

Many times troubleshooting is a process of elimination--checking and eliminating one item at a time until the root cause is identified. Sometimes, there is more than one cause, also. AND, proper testing is always important--just presuming this or that device isn't the problem, or doing a poor job of testing and recording results, can lead to lots of wasted time. And, time is money when generating power.

The next possible likely cause is a problem with the pressure transducer you mentioned, or it's valve positions, or the pressure transmitter is failed or failing.

Have a look at the P&IDs to identify the devices between the fuel forwarding skid output and the liquid fuel stop valve inlet and eliminate each one as a possible cause, and finally have someone check the calibration/operation/valve positions of the pressure transducer.

P&IDs, mate. That's the key to understanding operation--especially for an operator. Because most HMI/DCS graphics aren't complete and some don't even really match the P&IDs very well.... And, a really motivated operator will get out of the CCR and go and find the devices on the P&IDs and the actual physical layout/construction and can suggest how to troubleshoot and solve problems.

Best of luck! Please write back to let us know what you find and how you resolve the problem.
Many thanks CSA,
Sure I had looked to P&ID and we are trouble shooting the issue.
But my question is
Is it normal pressure to find that value is 3.1 bat while LCO filter outlet to the liquid fuel system is 5.1 bar.
Our unit is working in LDO and LCO
This happens when fuel is LCO.
Waiting your reply.

I’m going to guess that LDO is Liquid Distillate Oil, and LCO is Liquid Crude Oil. But those are guesses—because you didn’t tell us what those acronyms are. Every plant in the world DOES NOT use the same acronyms or even words and terms for the same fuels or equipment or processes. So, if you want a concise answer when you write to a World Wide Web forum for help with your problem(s) it’s best to do a little explaining.

For me to provide any further assistance I would need to be able to review the relevant P&IDs. II offered the best answer I could given the information provided. We don’t know A LOT about how your plant is operated or is supposed to be operated. It might be that the LCO is not at the proper temperature.

Best of luck.

You’re going to need it in your new career.

For others who follow these posts it would still be helpful if you wrote back to tell how the problem was resolved. Not ALL GE-design Frame 9E heavy duty gas turbine plants have the same systems and/or auxiliaries, and if GE Belfort was involved in any way with the design of the units you can be assured they have done their resolute best to needlessly increase complexity while reducing reliability. Why? Because they can.

Blessed day.
Thanks a lot for keeping in contact.
You are right. LDO is Liquid Distillate Oil, and LCO is Liquid Crude Oil.
And the problem was pressure decreasing continuously from 5.2 bar to 2.8 we checked the fuel compartment to check if there is leakage and when the maintenance team opened the doors of the compartment.
Turbine tripped by fuel compartment fans by loss of ventilation.
After the trip, we found a crude leak from the gasket of the VR4-1 fuel pump discharge relief valve.
Now my question is do you think a pressure drop occurred due to that leak?
Based on the information provided, it does not seem possible that the leak could have caused the pressure to continuously decrease as described unless the leak was very large (again--no indication of the amount of leaked LCO found in the Accessory Compartment) and the forwarding pumps could not supply the proper pressure and flow to maintain the supply pressure.

You have not described how fast the LCO pressure is decreasing once it starts to decrease. Does the LCO pressure start to decrease as soon as the unit completes the transfer to LCO is complete, or some time after that? If it's after the transfer is complete, how long after the transfer is complete does the pressure begin to decrease? You really haven't provided much in the way of actionable details/information about this pressure decrease for us to be able to understand much more than the pressure decreases and you want to know why. We need more information. We're not there on site with you.

The fuel pump discharge relief valve is to protect the high-pressure liquid fuel pump--which is a positive displacement pump (so everything that goes into the suction side of the pump MUST go out of the discharge side of the pump). A gasket leak does not seem like enough of a flow to cause a continuously decreasing pressure as described.

What you haven't told us is what is happening to the unit operation/generator load when this pressure is decreasing. Is the unit load decreasing (the electrical load on the generator)? Is it stable and not decreasing?

Has someone checked the LCO forwarding pump suction strainers to see if they are dirty ('choked')??? Is there a differential pressure gauge and/or switch on the LCO forwarding pump suction strainers? Is the differential pressure switch properly valved in? (Meaning, are the isolation valves open and any intermediate valve (on a three-valve manifold) closed?)