Control.com - Nerds in Control

On a Frame 5 14MW gas turbine, is there a standard down time between runs? For example, if we run for 4 hours at 10 to 11 MW, and shut down, how long should we wait to start up again (after rotor speed is at zero)??? Thanks.

Ray,

So, did you finally synchronize the unit? What about the high spreads during start-up? One of the things which makes control.com so useful is the feedback from people who get responses to their questions. For turbine-related questions, it's pretty standard practice. And we're not afraid to tell people when they don't provide feedback. One of the early contributors used to say, "Feedback is the most important contribution." If you've been reading any of the other turbine-related threads (and you have), than you've been the beneficiary of a lot of good feedback.

Did they forget to send the Instruction Manuals to Texas?

What kind of "turning gear" or "ratchet" mechanism does the unit have? If the unit has some kind of mechanism to keep the rotor from bowing during "zero speed" after a shutdown/trip when hot, and it works, then you should be able to just re-start the unit. Of course, if the instruction manual says something different or you experience vibration problems during a start-up with a hot/warm rotor, then you'll have to consider other options. But, most GE-design heavy duty gas turbines have some kind of mechanism that either continually or periodically rotates the shaft for many hours after a hot shutdown/trip to prevent the rotor from bowing. If the unit has such a device/mechanism, and it's working, then theoretically you should be able to "mash the START button" whenever you want.

In fact, GE recommends that if a unit has been at zero speed (meaning, not on "turning gear" or "ratchet") and cool (ambient temperature), that the unit be put on "turning gear" or "ratchet" (frequently called Cooldown) for at least a couple of hours before starting it. Now, older Frame 5s don't have long compressor rotors, but the materials used back then weren't as good as they are today either (some will say). Putting the unit on Cooldown for a couple of hours prior to a run if possible if it's been truly at zero speed for a long time, is always a good idea.

Don't forget to write back now, ya' hear?

(You're the one who mentioned you were from the "Great State of Texas"!)

Thanks,

We haven't synch'd in yet due to the continual high EGT on startup. It is very odd, we usually can start the unit in the morning without getting the high EGT ESD, but starting in the afternoon is almost impossible. The outside temp has not been over 70 degrees but it just doesn't make sense.
I have been trying to get back to all replies, but have so much going on it takes a while.

We do have some manuals, the manuals we have are for a Model F and we have a Model E. Most things are the same so it doesn't seem to be a problem with the equipment.

We have a ratchet system that works very well, the new controls system (Allen-Bradley solid state) has been set up to be able to start the ratchet at will, and to start the ratchet system for 48 hours after running the unit automatically with the control system. With the manuals not being specific about the turnaround time, that is why I ask. Thanks for the reply. We usually wait about 15 to 30 minutes to try a restart after the ratchet starts, and I watch the "coast down" time after we do get up and running.

We have been trying to get up and running for a while and have been plagued with different problems. The biggest is still the high EGT. We try and run every day so the ratchet system is basically on all the time. Any comments on the high EGT will be appreciated.

We have new check valves in the nozzles, CBVs are working, some outer door are removed for observations, all burner lite off, but within a couple of seconds, some flame out, but re-lite eventually. Other comments have told me that flameout and relite may be common occurances. If we do get past the high EGT ESD, the unit runs excellent for a 1963 unit. EGT with no load is averaging 595 to 600. Wheelspace temps around 450. We have also checked or replaced all 14 T/Cs and have borescoped all cans and crossover tubes with no help.

Thanks again for any comments. And I will always try to respond.