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Why General Electric Gas Turbine 9E Has Terrible Behaved On Its Turning Rate?Why It Has No Ideal Or Constant RPM In Its Turning Mod It Turns Between 120 to 220 Turns Per minute?
Ch Amir Islam,
You seem to be describing the "slow-roll" turning gear mechanism in use on many GE-design Frame 9E heavy duty gas turbines, that uses Aux. L.O. Pump discharge pressure through the starting means torque converter as the energy to keep the turbine-generator shaft spinning when on cooldown.
However, there are many kinds of cooldown ("turning gear") mechanisms and schemes in use on GE-design Frame 9E heavy duty gas turbines, so we would need to know which type is in use on your unit to be of most help.
If it's the slow-roll type described above, the temperature of the lube oil is very influential in determining how fast the shaft turns. The warmer the L.O., the faster the shaft turns; the cooler the L.O. the slower the shaft turns. So, if the L.O. header temperature is not constant during cooldown operation the speed will usually vary.
Also, I have seen some control schemes that vary the angle of the torque converter guide vanes when on slow-roll, opening them to "maximum" to apply as much energy to the shaft as possible. And, sometimes, these schemes don't work very well or the limit switches in the torque adjustor mechanism aren't adjusted very well.
There might also be a problem with the solenoid, 20TU-2, which is causing intermittent operation if the plunger is sticking or there is some electrical problem with the coil/armature.
Again, to be of more help we would need to know a lot more about the type of cooldown mechanism in use on the turbine at your site. The more information you can provide the more help we can provide.
You seem to be describing the "slow-roll" turning gear mechanism in use on many GE-design Frame 9E heavy duty gas turbines, that uses Aux. L.O. Pump discharge pressure through the starting means torque converter as the energy to keep the turbine-generator shaft spinning when on cooldown.
However, there are many kinds of cooldown ("turning gear") mechanisms and schemes in use on GE-design Frame 9E heavy duty gas turbines, so we would need to know which type is in use on your unit to be of most help.
If it's the slow-roll type described above, the temperature of the lube oil is very influential in determining how fast the shaft turns. The warmer the L.O., the faster the shaft turns; the cooler the L.O. the slower the shaft turns. So, if the L.O. header temperature is not constant during cooldown operation the speed will usually vary.
Also, I have seen some control schemes that vary the angle of the torque converter guide vanes when on slow-roll, opening them to "maximum" to apply as much energy to the shaft as possible. And, sometimes, these schemes don't work very well or the limit switches in the torque adjustor mechanism aren't adjusted very well.
There might also be a problem with the solenoid, 20TU-2, which is causing intermittent operation if the plunger is sticking or there is some electrical problem with the coil/armature.
Again, to be of more help we would need to know a lot more about the type of cooldown mechanism in use on the turbine at your site. The more information you can provide the more help we can provide.
Ch Amir Islam,
If the turbine at your site has a turning gear coupled to the shaft via a SSS clutch <b>AND</b> the turbine exhausts into a Waste Heat Recovery Boiler (or HRSG, Heat Recovery Steam Generator) and the turbine speed is erratic shortly after the turbine is shut down but then settles down to normal rated speed, the problem could be excessive draught through the turbine, exhaust, boiler and stack.
I have seen this problem when the stack is tall and there is a large, natural draught up the stack after the turbine is shut down. Air is drawn into the axial compressor inlet, through the turbine, through the exhaust, through the HRSG and up the stack and it can result in the turbine shaft rotating faster than the turning gear can rotate it.
Since this flow of cool, ambient air through the turbine and HRSG/stack usually causes rapid cooling of the HRSG some sites have resorted to putting a roll-up metal door (as seen on storefronts or factory doors--just a heavier construction, the heaviest available) in the turbine air inlet and closing it when the turbine is on turning gear (though most of the Frame 9Es I have worked on turned at much slower speeds than 120 RPM when on cooldown).
Most sites have installed a limit switch connected to the Speedtronic turbine control panel to prevent starting the turbine unless the roll-up door is <b>FULLY</b> open (just in case an operator forgets; for while we know turbine operators--and their supervisors--never forget such trivial things, "accidents" do happen).
Again, you have not provided enough information about the site and turbine configuration to be of any further help.
If the turbine at your site has a turning gear coupled to the shaft via a SSS clutch <b>AND</b> the turbine exhausts into a Waste Heat Recovery Boiler (or HRSG, Heat Recovery Steam Generator) and the turbine speed is erratic shortly after the turbine is shut down but then settles down to normal rated speed, the problem could be excessive draught through the turbine, exhaust, boiler and stack.
I have seen this problem when the stack is tall and there is a large, natural draught up the stack after the turbine is shut down. Air is drawn into the axial compressor inlet, through the turbine, through the exhaust, through the HRSG and up the stack and it can result in the turbine shaft rotating faster than the turning gear can rotate it.
Since this flow of cool, ambient air through the turbine and HRSG/stack usually causes rapid cooling of the HRSG some sites have resorted to putting a roll-up metal door (as seen on storefronts or factory doors--just a heavier construction, the heaviest available) in the turbine air inlet and closing it when the turbine is on turning gear (though most of the Frame 9Es I have worked on turned at much slower speeds than 120 RPM when on cooldown).
Most sites have installed a limit switch connected to the Speedtronic turbine control panel to prevent starting the turbine unless the roll-up door is <b>FULLY</b> open (just in case an operator forgets; for while we know turbine operators--and their supervisors--never forget such trivial things, "accidents" do happen).
Again, you have not provided enough information about the site and turbine configuration to be of any further help.
O
otised
The preferred arrangement to stop the draught and keep the HRSG bottled up is to have a stack closure damper at the top of the HRSG stack. This also keeps precipitation out of the stack when shut down.
The damper has limit switches connected to the Speedtronic turbine control panel to prevent starting the turbine unless damper is FULLY open.
The damper has limit switches connected to the Speedtronic turbine control panel to prevent starting the turbine unless damper is FULLY open.
