J
I would like to know the coast down time for a GE HD MS7001E power generator from base load. 3600 RPM
Best Regards
jesus.ysea [at] gmail.com
Best Regards
jesus.ysea [at] gmail.com
Jesus,
I don't really understand the question. In general "coast down" refers to the time after the generator breaker is opened during a normal, fired shutdown, to the time the unit reaches cooldown or zero speed (some units use "slowroll" for cooldown and never go to zero speed; others use a ratchet mechanism and do go to zero speed at which time cooldown starts). Coast down implies the unit speed is decreasing.
Your questions asked about "coast down from Base Load", and it's not clear if you're asking how long should it take to unload the unit from Base Load to generator breaker opening, or how long should it take for the unit to go from Base Load, to breaker opening to cooldown/zero speed.
The coast down time for a GE-design heavy duty gas turbine after the generator breaker opens during a normal shutdown depends to a certain extent on the fuel being burned and the type of control system being used to control the unit.
In general, newer turbine control systems can keep the flame on during a fired shutdown (after generator breaker opening) down to approximately 20% speed, which helps reduce the thermal stresses on the hot gas path parts. This will usually result in a coast-down time from FSNL (breaker opening) to cooldown/zero speed of approximately 10 minutes, plus or minus a couple of minutes.
If the unit is burning liquid fuel, it's not usually possible to maintain flame below approximately 60% speed without a lot of white smoke coming from the exhaust (due to lack of atomizing air and incomplete combustion), so fuel is usually shut off long before the unit reaches 20% speed. This usually results in a slightly shorter coast down time from FSNL (breaker opening) to cooldown/zero speed of approximately 8-10 minutes, sometimes a little longer.
These numbers are approximate, and slightly longer or slightly shorter times are not really indicative of any problem, except maybe a problem with the "tuning" of the shutdown fuel control constants.
Now, the unloading time from Base Load to generator breaker opening can vary depending on the way the unit is being unloaded. (This isn't usually considered "coast down" because the speed isn't changing as the unit is being unloaded; only the load is changing.) If the unit is at Base Load with Base Load selected and enabled, and the operator initiates a STOP, then the typical time for unloading from Base Load to generator breaker opening (essentially FSNL), is approximately 15 minutes as typically configured from the factory. There is about a one to two minute delay when STOP is initiated and when load actually begins to decrease, and that's because of the way that GE-design heavy duty gas turbines use Droop Speed Control to load and unload the units, but from the time the unit load actually starts to decrease and the display no longer indicates 'Exhaust Temperature Control' it's usually about 12 minutes, plus or minus a couple of minutes to breaker opening. This is considered "automatic" unloading. The rate is adjustable (it's a Control Constant in a Speedtronic turbine control system, part of an array used for loading/unloading rates), and was quite often adjusted during commissioning for one reason or another (some good, most not) and so we can't say for sure what the loading/unloading rate at your site is without being able to look at the sequencing or application code running in the turbine control panel.
Manual unloading would be if the operator manually held the SPD/LOAD LOWER switch or pushbutton or continually clicked on the SPD/LOAD LOWER target on the operator interface to reduce load. In this case, the unloading rate is usually twice as fast as the automatic unloading rate, or, it takes half as long to unload the unit once the load starts dropping as automatic unloading takes.
Some units have automatic shutdowns from conditions like boiler trouble/drum level problems, or other such trouble, and the unloading rate(s) for those types of conditions can be set individually to be faster or slower. You would need to examine the sequencing or application code in the turbine control panel at your site to be sure.
Again, the question wasn't really clear, but it's hoped the information provided will be useful. If you would describe any problem or concern you are having, we could try to provide some assistance for you.
I don't really understand the question. In general "coast down" refers to the time after the generator breaker is opened during a normal, fired shutdown, to the time the unit reaches cooldown or zero speed (some units use "slowroll" for cooldown and never go to zero speed; others use a ratchet mechanism and do go to zero speed at which time cooldown starts). Coast down implies the unit speed is decreasing.
Your questions asked about "coast down from Base Load", and it's not clear if you're asking how long should it take to unload the unit from Base Load to generator breaker opening, or how long should it take for the unit to go from Base Load, to breaker opening to cooldown/zero speed.
The coast down time for a GE-design heavy duty gas turbine after the generator breaker opens during a normal shutdown depends to a certain extent on the fuel being burned and the type of control system being used to control the unit.
In general, newer turbine control systems can keep the flame on during a fired shutdown (after generator breaker opening) down to approximately 20% speed, which helps reduce the thermal stresses on the hot gas path parts. This will usually result in a coast-down time from FSNL (breaker opening) to cooldown/zero speed of approximately 10 minutes, plus or minus a couple of minutes.
If the unit is burning liquid fuel, it's not usually possible to maintain flame below approximately 60% speed without a lot of white smoke coming from the exhaust (due to lack of atomizing air and incomplete combustion), so fuel is usually shut off long before the unit reaches 20% speed. This usually results in a slightly shorter coast down time from FSNL (breaker opening) to cooldown/zero speed of approximately 8-10 minutes, sometimes a little longer.
These numbers are approximate, and slightly longer or slightly shorter times are not really indicative of any problem, except maybe a problem with the "tuning" of the shutdown fuel control constants.
Now, the unloading time from Base Load to generator breaker opening can vary depending on the way the unit is being unloaded. (This isn't usually considered "coast down" because the speed isn't changing as the unit is being unloaded; only the load is changing.) If the unit is at Base Load with Base Load selected and enabled, and the operator initiates a STOP, then the typical time for unloading from Base Load to generator breaker opening (essentially FSNL), is approximately 15 minutes as typically configured from the factory. There is about a one to two minute delay when STOP is initiated and when load actually begins to decrease, and that's because of the way that GE-design heavy duty gas turbines use Droop Speed Control to load and unload the units, but from the time the unit load actually starts to decrease and the display no longer indicates 'Exhaust Temperature Control' it's usually about 12 minutes, plus or minus a couple of minutes to breaker opening. This is considered "automatic" unloading. The rate is adjustable (it's a Control Constant in a Speedtronic turbine control system, part of an array used for loading/unloading rates), and was quite often adjusted during commissioning for one reason or another (some good, most not) and so we can't say for sure what the loading/unloading rate at your site is without being able to look at the sequencing or application code running in the turbine control panel.
Manual unloading would be if the operator manually held the SPD/LOAD LOWER switch or pushbutton or continually clicked on the SPD/LOAD LOWER target on the operator interface to reduce load. In this case, the unloading rate is usually twice as fast as the automatic unloading rate, or, it takes half as long to unload the unit once the load starts dropping as automatic unloading takes.
Some units have automatic shutdowns from conditions like boiler trouble/drum level problems, or other such trouble, and the unloading rate(s) for those types of conditions can be set individually to be faster or slower. You would need to examine the sequencing or application code in the turbine control panel at your site to be sure.
Again, the question wasn't really clear, but it's hoped the information provided will be useful. If you would describe any problem or concern you are having, we could try to provide some assistance for you.
