My question is particularly with reference to GE Gas Turbine Frame 6FA mark vie.

GT is operating on base load on HSD fuel and water injection is in service. if water injection pump trips what will happen to GT especially to the GT exhaust temperature and what actions will be taken by the control system?

I want to know the detailed answer of the following;

1-Effect of water injection on GT exhaust temperature.

2-What actions are required to be taken when water injection pump trip while GT is on Base Load.

3-If water injection high flow lock out occurred while GT is on base load, what will happen to GT and actions required

 

Akhtar,

Water injection definitely has an effect on exhaust temperature, but not as much as some think. <b>When operating at Base Load</b> water injection reduces exhaust temperature slightly, which the Speedtronic interprets as a decrease in exhaust temperature versus the exhaust temperature reference, so it actually puts a little more fuel into the combustors to raise the exhaust temperature back up to the exhaust temperature reference. So, in addition to getting more power because of the increase mass flow of the water being injected into the turbine, there is also a positive effect on power output because of a slightly increased fuel flow-rate.

Should water injection suddenly trip when the unit is at Base Load, well, it is likely an exhaust overtemperature alarm will be annunciated for a brief period of time until the fuel can be reduced to bring the exhaust temperature back down to match the exhaust temperature reference. The exhaust temperature won't change by that much, in fact it will likely increase slightly (1 0r 2 deg C) while still remaining on the exhaust temperature control curve (which has a negative slope; see Section 3 of the Control Specification drawing).

However, some Speedtronic turbine control panels are programmed to reduce load in the event that water injection is not running, even to initiate a automatic shutdown. If water injection is required for emissions reduction in many parts of the world if the water injection system is not running then the turbine cannot continue to run without water injection because of the increased emissions. So, without being able to see the application code running in the Mark VIe at your site it's not possible to say for certainty if the machine would continue to run, or for how long or at what load should water injection trip and not be quickly brought back on line at the required flow-rate.

Gas turbines ran for decades without water injection without any serious ill effects. Water injection is required for permitted operation in many parts of the world, and without water injection turbines are not permitted to run except in cases of extreme emergency and probably only with written permission for that case only.

However, the combustors of many F-class turbines are designed to have water injection and so there may also be other considerations which would limit turbine operation without water injection so, again, it would be necessary to review the application code running in your Mark VIe to be certain exactly how your machine is configured/programmed to operate should water injection not be running for some reason.

Hope this helps!