In our Frame-V gas turbine, each compartment vent fans having pressure switch with Tag no: 63AT-1/2/3/4 & 63VG-1 & 2.

We have vent fans conditions:-
All Fan-1 selection on lead. and FAN-1 is running in all compartment.

We want to know:-

1. what will impact on running vent fan when low pressure switch will actuate. Standby fan will get start or running fan will trip.

2. We have schedule changeover of all vent fan-1 to Fan-2. If fan-1 is running and we want to change over to Fan-2 by selecting the lead for Fan-2. Fan-2 will take start or fan-1 again will start.

 

VKGUPTA,

Without being able to see the program running in the gas turbine control panel it's difficult to say for certain--and I'm not quite certain I completely understand the question(s).

In general, the logic/sequencing for redundant vent fan control will start the lag fan if the lead fan's pressure switch indicates low fan discharge pressure--regardless if the #1 fan or the #2 fan is the lead fan. I have seen both sequencing--where the lead fan's motor starter signal is left "energized," and where the lead fan's motor starter is "de-energized." (Remember, GE typically uses drop-out-to-run logic for critical fans and pumps (with the exception of liquid fuel forwarding pumps), so in this case "energized" means the normally-closed contact of the discrete output (relay output) is closed to provide a signal to start/run the motor starter.)

If I recall correctly, if the lag fan starts because the lead fan's discharge pressure switch indicated low discharge pressure the operator must select the running fan to be the lead, or re-select the currently selected lead fan to be the lead fan in order to "reset" the logic. If I recall correctly, once the lag fan is started if it's discharge pressure switch indicates low discharge pressure the operation will not automatically revert to the other (the currently selected "lead" fan).

Hope this helps--but you should consult the logic/sequencing/application code running in your Speedtronic turbine control panel to be certain of the exact operation at your site. (It's kind of confusing because the typical GE sequencing selects the "not lag" fan as the lead fan--but when you stop and think about it that's the only way the turbine control panel knows what to do when it's first powered-up--otherwise the operator would have to select the lead motor for every redundant motor fan/pump....)