In a Frame 7EA, gas fuel system, simple cycle, we encountered several low trip oil pressure, that lowers to 3.4 barg from 6.4 barg for a very temporary period. Luckily the unit has not tripped, but in order to avoid any reoccurrence in future, how to eliminate such obstacle. The turbine has been in service since 12 yrs. All inspection cycles are strictly adhered to.

I'm basically a Mechanical Engineer, and I don't know if my suggestion is valid or not, can you please let provide me with your comments regard it, based on that the unit is RUNNING and following the 2oo3 logic system:

1) Flush each line of the system individually to insure cleanliness of the dunp valves.

2) inspect with boroscope probe for any scales on the ss tubings.

3) Inspecting and testing of 20TV valves as the are preceding the 20FGs.

Looking forward hearing from you.

Mohammad

 

Ain't there any input?

Looking forward seeing sthg from you experts!

 

Mohammad,

I had posted a reply, or so I thought. Sometimes, things get lost in the "bit bucket".

Basically, your suggestions are very flawed. It's not clear how Trip Oil Pressure is being measured, because on most GE-design Frame 7EA heavy duty gas turbines there is no Trip Oil Pressure system pressure transmitter; but it would appear there is on this particular unit.

Next, there is usually only one 20TV-1 solenoid, and only one 20FG-1 solenoid valve.

Finally, there are three low Gas Fuel Trip Oil Pressure Switches: 63HG-1, -2, & -3.

The Trip Oil system is basically a static pressure system. The presence of sufficient pressure (above 20 psig) will cause the respective hydraulic dump valve to move to a position that allows high pressure hydraulic oil to get to/from the hydraulic actuator of the respective device. The only time there is "flow" in a Trip Oil system is when it's being pressurized or when it's not being pressurized. So, any blockage in the piping/tubing will only affect the time it takes to establish pressure or the time it takes for pressure to drop when the system is being de-energized. (There is also flow through the respective systems when the respective solenoids are not energized--but essentially this is de-pressurizing or draining the respective Trip Oil piping/tubing.)

Now, if there were leaks in the Trip Oil piping/tubing they probably wouldn't be "intermittent", but they might contribute to problems which were set in motion by some other condition.

I would presume that the dips in Trip Oil Pressure were recorded from the Trip Oil Pressure Transmitter. I would also presume that there is only one Trip Oil Pressure Transmitter. So, my suggestion would be to verify the operation of the Trip Oil Pressure Transmitter, the interconnecting wiring, the tubing connections, etc.

Have a look at the Trip Oil P&ID (Piping Schematic). You'll also need to look at the Lube Oil and Gas Fuel drawings to get the "big picture" of how everything works. Remember: Trip Oil pressure operates on the hydraulic dump valve to allow hydraulic oil pressure to flow to/from the hydraulic actuator. And, that it's basically a "static" system.

And, this is not your mobile phone, and we're not sending text messages to each other. This is a technical forum and we should be communicating with each other with complete sentences and words.

And, when you resolve your problem please take a couple of minutes to write back to let us know how you resolved the problem--whether it was using the information provided, or if some other problem was eventually determined to be the cause. We rely heavily on feedback from the original poster to let others reading these threads, now and in the future, if the information provided was helpful or not.

Best of luck with your problem.

 

Thanks alot Mr. CSA for the valuable input, I will check the P&IDs, and absolutely, I am coming back with the feedback. Without praising, I was looking for your input, as it is usually adequately simplified for all levels.

Thx again,
Mohammad

 

Do you have a liquid fuel system also....and a gas-liquid fuel mix operation.. If mix is selected we have seen pressure going to 6 bar as the 20FL1X will be closed ( thus preventing the draining).. If it is on either gas or Liquid fuel it will be at near 3 to 4 bar...