Gas Turbine Fuel Assy Swap

[Wolskis]

A 7FA.05 200 mega watt gas turbine. Consumes ~1800 mmbtu of NG per hour. Just a little something that had to be done this past weekend. We had a combustion issue, high C0, spreads between combustion cans and high combustion dynamics. GE central pin pointed to cans 13, 14 or 1. GE calls out the crew which consists of field engineer, supervisor, lead and several mill wrights. The day crew as exceptional. Video shows the fuel assy and forward can removed. Metal hoses are the fuel supply which happens to be NG. Work started 0900 saturday and LOTO removed and back on turning gear at 1500 Sunday. Started up at 1800 and all is well in the power plant world.

Fuel assy

Forward can looking down where fuel assy fits.

Fuel Assy with guides to carefully pass into the can

View of new fuel assy in can

Ready to go back togther

 

[3.Slow]

Damn, makes the LM2500 I worked on look like a kids toy.

 

[spectra3279]

Pretend I don't know shit about gas turbines and splainin that again.

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[Wolskis]

Damn, makes the LM2500 I worked on look like a kids toy.

The navy ship I was on had 4 of the 2500's. These are much larger in size.

 

[3.Slow]

The navy ship I was on had 4 of the 2500's. These are much larger in size.

What class of ship were you on? I was on a carrier, so we had Nuclear Power, not a whole lot of Nuclear jobs in California these days, so I ended up at a small Cogen plant.

 

[Wolskis]

What class of ship were you on? I was on a carrier, so we had Nuclear Power, not a whole lot of Nuclear jobs in California these days, so I ended up at a small Cogen plant.

USS Elliott DD 967, 4 LM 2500, 3 Allison 501k as prime movers for the generators. I've worked with nukes in the past and have one nuke bubble head here. My hats off to anyone that completed navy nuke school.

 

[Wolskis]

Pretend I don't know shit about gas turbines and splainin that again.

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These gas turbines are very similar to what you see attached to airplanes. We measure them on how many megawatts can be produced while the jets are measured on thrust. We burn natural gas, they burn liquid. The front end is the compressor, middle is combustion and the back end has the turbine. All connected on one shaft that is hollow to convey cooling air from the compressor to the hot parts in the turbine section which sees about 1100F.
The compressor has 3 rows of variable position blades then into 14 more rows of ever decreasing blade size to "compress" the air. The combustion section consists of 14 cans that are interconnected with cross fire tubes. They contain the fuel nozzle assy, forward and after cans. Cans #11, 12, 13 & 14 have the flame scanners, cans #1, 2 have the ignitors. Plus each can has dynamic monitoring. The turbine section has 4 rows with special metallurgy and coatings on rows 1 & 2 along with cooling holes at the tips and trailing edges. The hot gases hit the nozzles first then direct the gases to the blades and repeat. These blades and nozzles get larger in size to use up the energy.
The compressor end is connected to the generator. The turbine end is connected to the heat recovery steam generator (HRSG), just a fancy name for a boiler. This HRSG has 7 sections of tubes to create steam at 3 pressures, HP = 2100psig, IP = 350psig and LP = 100psig. This steam is piped to the steam turbine. The HP steam is used up and comes out of the steam turbine at a much lower pressure and now called cold reheat steam (CRH). CRH is piped back to the HRSG, connects with the IP section, heated up and now called hot reheat steam (HRH) and is piped back to the steam turbine. HRH and LP steam exhaust from the steam turbine into the condenser which is under a vacuum and changes to water. The water is treated and pumped back to the HRSG to repeat the process. The term combined cycle plant is coined for this reuse of steam and water.
Most condensers are the water cooled type where you see heat rising from them. This one is an air cooled condenser (ACC). Instead of water, ambient air is used. This one has 5 rows of 5 fans each. Fans consist of a motor connected to a reduction gear connected to the blade hub. Fans are the variable speed type so speed can be controlled based on ambient temperature and amount of steam to be condensed.
I rambled on, hope this answers some of your Q's. I'll add some pics of parts viewed thru a borescope. Let me know if you more Q's.

 

[3.Slow]

USS Elliott DD 967, 4 LM 2500, 3 Allison 501k as prime movers for the generators. I've worked with nukes in the past and have one nuke bubble head here. My hats off to anyone that completed navy nuke school.

I went through nuke school in '04, it was tough, a lot of knowledge to cram in to such a short time, but from what I understand it was a lot easier then the early days when the dropout rate was over 50%. Overall one of my better decisions in life, got me where I am today.

 

[Kaotic]

@Wolskis which plant do you work at, i manage a plant with (8) 7F gas turbines and (4) D-11 steam turbines

 

[spectra3279]

These gas turbines are very similar to what you see attached to airplanes. We measure them on how many megawatts can be produced while the jets are measured on thrust. We burn natural gas, they burn liquid. The front end is the compressor, middle is combustion and the back end has the turbine. All connected on one shaft that is hollow to convey cooling air from the compressor to the hot parts in the turbine section which sees about 1100F.
The compressor has 3 rows of variable position blades then into 14 more rows of ever decreasing blade size to "compress" the air. The combustion section consists of 14 cans that are interconnected with cross fire tubes. They contain the fuel nozzle assy, forward and after cans. Cans #11, 12, 13 & 14 have the flame scanners, cans #1, 2 have the ignitors. Plus each can has dynamic monitoring. The turbine section has 4 rows with special metallurgy and coatings on rows 1 & 2 along with cooling holes at the tips and trailing edges. The hot gases hit the nozzles first then direct the gases to the blades and repeat. These blades and nozzles get larger in size to use up the energy.
The compressor end is connected to the generator. The turbine end is connected to the heat recovery steam generator (HRSG), just a fancy name for a boiler. This HRSG has 7 sections of tubes to create steam at 3 pressures, HP = 2100psig, IP = 350psig and LP = 100psig. This steam is piped to the steam turbine. The HP steam is used up and comes out of the steam turbine at a much lower pressure and now called cold reheat steam (CRH). CRH is piped back to the HRSG, connects with the IP section, heated up and now called hot reheat steam (HRH) and is piped back to the steam turbine. HRH and LP steam exhaust from the steam turbine into the condenser which is under a vacuum and changes to water. The water is treated and pumped back to the HRSG to repeat the process. The term combined cycle plant is coined for this reuse of steam and water.
Most condensers are the water cooled type where you see heat rising from them. This one is an air cooled condenser (ACC). Instead of water, ambient air is used. This one has 5 rows of 5 fans each. Fans consist of a motor connected to a reduction gear connected to the blade hub. Fans are the variable speed type so speed can be controlled based on ambient temperature and amount of steam to be condensed.
I rambled on, hope this answers some of your Q's. I'll add some pics of parts viewed thru a borescope. Let me know if you more Q's.

Thanks. So why the gas turbine plus steam? Is the gas turbines used to heat the water also?

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[pronstar]

These gas turbines are very similar to what you see attached to airplanes. We measure them on how many megawatts can be produced while the jets are measured on thrust. We burn natural gas, they burn liquid. The front end is the compressor, middle is combustion and the back end has the turbine. All connected on one shaft that is hollow to convey cooling air from the compressor to the hot parts in the turbine section which sees about 1100F.
The compressor has 3 rows of variable position blades then into 14 more rows of ever decreasing blade size to "compress" the air. The combustion section consists of 14 cans that are interconnected with cross fire tubes. They contain the fuel nozzle assy, forward and after cans. Cans #11, 12, 13 & 14 have the flame scanners, cans #1, 2 have the ignitors. Plus each can has dynamic monitoring. The turbine section has 4 rows with special metallurgy and coatings on rows 1 & 2 along with cooling holes at the tips and trailing edges. The hot gases hit the nozzles first then direct the gases to the blades and repeat. These blades and nozzles get larger in size to use up the energy.
The compressor end is connected to the generator. The turbine end is connected to the heat recovery steam generator (HRSG), just a fancy name for a boiler. This HRSG has 7 sections of tubes to create steam at 3 pressures, HP = 2100psig, IP = 350psig and LP = 100psig. This steam is piped to the steam turbine. The HP steam is used up and comes out of the steam turbine at a much lower pressure and now called cold reheat steam (CRH). CRH is piped back to the HRSG, connects with the IP section, heated up and now called hot reheat steam (HRH) and is piped back to the steam turbine. HRH and LP steam exhaust from the steam turbine into the condenser which is under a vacuum and changes to water. The water is treated and pumped back to the HRSG to repeat the process. The term combined cycle plant is coined for this reuse of steam and water.
Most condensers are the water cooled type where you see heat rising from them. This one is an air cooled condenser (ACC). Instead of water, ambient air is used. This one has 5 rows of 5 fans each. Fans consist of a motor connected to a reduction gear connected to the blade hub. Fans are the variable speed type so speed can be controlled based on ambient temperature and amount of steam to be condensed.
I rambled on, hope this answers some of your Q's. I'll add some pics of parts viewed thru a borescope. Let me know if you more Q's.

Since you recapture/re-use so much heat that would otherwise go to waste, I wonder what the overall thermal efficiency is for the system?


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[Wolskis]

Thanks. So why the gas turbine plus steam? Is the gas turbines used to heat the water also?

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Efficiency. Gas turbine only plants are called peakers. All groups that maintain the country's transmission system are required to have about 15% of available power as backup in the form of gas turbines, pump storage, spinning reserve etc. A source of energy that can be called upon within minutes. Peakers can do this within 10 minutes but expensive to run. Put a boiler on the back end and you capture the available heat which creates the steam that feeds the steam turbine. So with 2 gas turbines that need a fuel source (cost) and a steam turbine that only needs steam (no cost) your heat rate has gone from a 10 down to say a 7.0.

 

[spectra3279]

Cool. Thanks for splaining.

Now why do we not burn the trash we produce to run boilers?

Seems this would basically be a free fuel source. I do understand you would have to shutdown periodically for clean out, but you could have a few boilers that you rotate through for this purpose.

Efficiency. Gas turbine only plants are called peakers. All groups that maintain the country's transmission system are required to have about 15% of available power as backup in the form of gas turbines, pump storage, spinning reserve etc. A source of energy that can be called upon within minutes. Peakers can do this within 10 minutes but expensive to run. Put a boiler on the back end and you capture the available heat which creates the steam that feeds the steam turbine. So with 2 gas turbines that need a fuel source (cost) and a steam turbine that only needs steam (no cost) your heat rate has gone from a 10 down to say a 7.0.

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[Wolskis]

Cool. Thanks for splaining.

Now why do we not burn the trash we produce to run boilers?

Seems this would basically be a free fuel source. I do understand you would have to shutdown periodically for clean out, but you could have a few boilers that you rotate through for this purpose.

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They exist, called waste to energy. Tire burners, not sure if any are left. Had one in CA years back but when a thousand tires caught fire and created a river of tar things went south. Logging waste burners are still around. House hold trash, never worked one but from others it’s a very smelly place and labor intensive. The problem is heat content. Imagine all the house hold trash, plastic, paper, raw material and each one burns at a different rate. The emission’s control part adds a layer of complexity to keep the neighbors happy.

 

[Wolskis]

This is a borescope pic of the 1st stage turbine blade trailing edge. The hot section of the gas turbine see's about 1150F. Holes are for cooling, the air comes from the compressor section traveling down the hollow shaft.

 

[Wolskis]

This pic is of the transition piece looking at the 1st stage nozzle section. So the hot gases exit the combustion can which is connected to the transition piece. The front end is round to match the can and this look is rectangular to fit the opening of the turbine. This rectangular section is referred to as the "picture frame".

 

[Wolskis]

The borescope inspector wanted to check on this seal. It's of a honeycomb type. The seal is in the middle of the pic and on either side is the back side of two transition pieces.

 

[Wolskis]

Each of the 14 combustion cans are connected by a cross over tube. There are 2 ignitors, cans 2 & 3 so these allow the flame to travel from one can to the next until all 14 cans have flame.

 

[Wolskis]

You are looking at the fuel nozzle tips. The black line is the borescope cord.

 

[Wolskis]

Spark ignitor

 

[monkeyswrench]

Very cool. I read the above, and added some info to my mental rolladex of weird and bizarre information. I had a primitive understanding of how the smaller CoGen systems worked. Oddly enough, one of the pools I used to work out at was heated by a methane boiler cogen system. I had always thought on power generation systems that the turbine was just a steam driven unit, not also a burner assembly for more efficient production of steam.

 

[Sleek-Jet]

Efficiency. Gas turbine only plants are called peakers. All groups that maintain the country's transmission system are required to have about 15% of available power as backup in the form of gas turbines, pump storage, spinning reserve etc. A source of energy that can be called upon within minutes. Peakers can do this within 10 minutes but expensive to run. Put a boiler on the back end and you capture the available heat which creates the steam that feeds the steam turbine. So with 2 gas turbines that need a fuel source (cost) and a steam turbine that only needs steam (no cost) your heat rate has gone from a 10 down to say a 7.0.

Not all are peaking plants, we have a base load simple cycle turbine plant on our system. I'm suprised by the combined cycle heat rate, I always thought they would be more efficient. My natural gas RICE plant is right in that neighborhood on the heat rate, though a little higher.

 

[RiverDave]

Here I was thinking about putting up some pics of me slotting some shafts to make the cotter pins go in and out easier.. LOL

Then we have Mr. Rocket Scientist over here make me feel fairly "small."

RD

 

[Deja_Vu]

Cool stuff.

I used to design the first stage turbine nozzles for Solar turbines.
The last engine program I worked on was the Titan 130. (13MW)
They later scaled that up to the Titan 250