Gas Turbine Exhaust frame blower


Thread Starter

Mehul Kumar

Can a Frame-VIB GE make Gas-turbine run on just one Exhaust frame blower with the other blower in stand-by mode? If yes then what will happen in case the running blower trips? will the Gas turbine unload as the stand-by blower will take some time in acquiring full speed?

According to typical control code, on GE Frame 6B gas turbines two 88TK fans should run. If one of them is stopped (the stopped state sensed by pressure switch) alarm is generated. If both fans do not provide the sufficient air flow (also confirmed by their pressure switches) turbine unload command is generated, till generator breaker is opened.

On GE Frame 9E gas turbines (125MW capacity) the principle of operation of 88TK fans is the same like on Frame 6B, also two fans should run.

One fan does not give sufficient air flow.

On GE Frame 9FA turbines (250MW capacity) design is different: only one 88TK fan remains in service, the other one is standing by. In case that for the running motor (lead motor) any defect is detected (motor's electrical overload, pressure switch does not sense the pressure or feedback from MCC contactor is missing) standing by motor starts, two motors run together for approx 5 sec then lead motor gets stop command. This procedure gives a time for lag motor to accelerate.

On frame 9..2x50% 88TK fans are installed. for base load both must be running. if one fails/stop GT will decrease the load blower does not provide sufficient air for cooling of exhaust frame..I hope similar will be on frame 6.

I guess it depends on what you are really asking.

"can a Frame 6B turbine run with only one exhaust frame blower" Technically yes, but I do not believe that was the way the system was designed. And you need to review your application code to understand how logic was configured for the loss of one or both blowers. I can't say here for sure because not all application code is the same. As far as one blower tripping and the second starting, that to is best answered by looking at you logic.

Exhaust frame blowers were installed to control the thermal expansion of the turbine shell of the gas turbine. This was done to minimize growth of the case which has effects on unit output as well as alignment of the machine and its parts. This is done on Frame machines as well as some aeroderivative units.

Your application code and operations manuals should detail the intended operation of the blowers and the way the control system will handle failure of one or both. But understand they were put there for an engineered reason. Operating the unit in a way not intended usually will produce unintended and undesired results, now or sometime in the future.
Can't we install a high capacity exhaust blowers for those turbines, so that it'll be easy to keep one fan in service and other as standby