hi to all
when we start the unit gas turbine frame 5 controlled by PLC allen bradley. On firing speed the flame come and go many times and after that the flame stablish and the unit go to full speed and load it successful. plze advise me about the reason for this and what the action should be take when the unit stop

note: when I MONITOR THE SRV POSITION BY INDICATOR WE NOTICE THE WHEN FLAME GO OUT THE SRV CLOSE LITTLE AND WHEN FLAME COME THE SRV OPEN

 

How long has this problem been happening? Since commissioning? Since a recent maintenance outage? After calibration of Gas Control Valve LVDT feedback?

We can't know how the programmer of your control system configured the firing sequence since we're not able to see the sequencing in the control system at your site.

As for the changes in SRV position during starting when the flame coming and going, it's probably because when there is flame there is an increase in speed and when there's not flame the speed slows down.

SRV means Stop Ratio Valve; the Ratio portion means that the valve is controlling the pressure downstream of itself and upstream of the GCV in proportion to the actual turbine speed (pressure as ratio of turbine speed). So, if the SRV was programmed in the PLC as it was programmed in a Speedtronic turbine control system, the pressure reference (and therefore the position) will change as turbine speed changes during starting. And, when the flame is coming and going, it's very likely that the turbine speed will be fluctuating slightly, which will cause the pressure reference to fluctuate slightly, which will cause the valve position to change slightly.

Every bit of troubleshooting should always begin with the question, "What has changed?" In this case, if the unit was working properly, what changed immediately prior to the problem you are experiencing? Was there a maintenance outage? Was the GCV refurbished? Were the fuel nozzles replaced? If so, are they identical to the ones which were removed, or how do the flow characteristics of the two sets compare to each other? Were the cross-fire tubes replaced? Were the gas valve LVDT feedback signals re-calibrated? If so, were they calibrated properly? What was the as-found condition of the LVDT feedback signals versus the as-left condition?

Lastly, there is a good bit of experience and knowledge here with Speedtronic turbine control systems and basic GE-design heavy duty gas turbine operation. But, when it comes to other control system packages, you won't likely find much support here (especially since you didn't identify the packager/supplier of the PLC-based system) since they can vary greatly from Speedtronic systems. You will likely need to contact the packager/supplier for support and assistance with their configuration and programming, unless you identify the PLC-based system packager/supplier and someone here has experience with their equipment.