Holtec acquires more retiring nuke plants

[OVERKILL]

Originally Posted By: john_pifer
Originally Posted By: Yah-Tah-Hey
OVERKILL: What is that shaft with the spur and helical gears? Also what is that ratchet looking gear? Wonderful,very clear photos. Your the man.


Yes! Thanks so much for all the awesome photos, guys!

I voraciously consume any and all information about power generation, transmission, distribution, etc. Really fascinating.

Any of you power plant guys ever been involved in any HVDC power transmission projects? Lots of interesting reading I've done on that. I can get lost in reading about that stuff for hours.


You and I are in the same boat. I have a particular fondness for nuclear and hydro-electric, so I tend to focus my interest on those two, but definitely watch the whole topic with a keen interest.

 

[turtlevette]

Originally Posted By: Yah-Tah-Hey
Originally Posted By: Donald
So these plants still have steam turbines in them? Are they also past useful life or can one generate steam a new way and power the turbines again? You have all the power grid attachments also.
Public Service of Colorado(PSCO) (now EXCEL) decommissioned Fort St. Vrain Generating Station in the late eighties because of the many problems of the reactor's helium cooling system. I was working at Craig Generating Station in northwestern Colorado and knew some of the employees there. I think it's fair to say they were very, very scared of that reactor. PSCO used what they could of the original plant and installed natural gas combustion turbine/generator sets. They utilized the waste heat of the combustion turbines to produce steam in steam generators to power the original steam turbine. Think Fort St. Vrain is making about 900+ megawatts.


The helium kept getting wet and reacting with the graphite core. Had they not used steam driven helium circulators, that would have been a successful plant. I crawled all around the reactor building and we didn't even wear badges because the helium doesn't activate like water.

 

[Shannow]

Originally Posted By: Yah-Tah-Hey
OVERKILL: What is that shaft with the spur and helical gears? Also what is that ratchet looking gear? Wonderful,very clear photos. Your the man.


Barring gear (GE design by the looks of it).

Turbine has to be turned slowly (barred), for 4-6 hours before run-up to get the shaft straight, and 4-5 days after coming out of service, to keep the shaft from hogging while it cools down.

The big gear is what the slow speed turning gear engages.

The ratchet is literally that. There's a hydraulic cylinder with a tooth on it that you bolt to the pedestal and stroke back and forth hydraulically if the main barring gear fails.

 

[john_pifer]

Originally Posted By: Shannow
Originally Posted By: Yah-Tah-Hey
OVERKILL: What is that shaft with the spur and helical gears? Also what is that ratchet looking gear? Wonderful,very clear photos. Your the man.


Barring gear (GE design by the looks of it).

Turbine has to be turned slowly (barred), for 4-6 hours before run-up to get the shaft straight, and 4-5 days after coming out of service, to keep the shaft from hogging while it cools down.

The big gear is what the slow speed turning gear engages.

The ratchet is literally that. There's a hydraulic cylinder with a tooth on it that you bolt to the pedestal and stroke back and forth hydraulically if the main barring gear fails.


Would you mind explaining further what you mean when you say that the turbine has to be turned slowly before run-up to get the shaft straight?

And what do you mean by "hogging"?

 

[Yah-Tah-Hey]

Originally Posted By: turtlevette
Originally Posted By: Yah-Tah-Hey
Originally Posted By: Donald
So these plants still have steam turbines in them? Are they also past useful life or can one generate steam a new way and power the turbines again? You have all the power grid attachments also.
Public Service of Colorado(PSCO) (now EXCEL) decommissioned Fort St. Vrain Generating Station in the late eighties because of the many problems of the reactor's helium cooling system. I was working at Craig Generating Station in northwestern Colorado and knew some of the employees there. I think it's fair to say they were very, very scared of that reactor. PSCO used what they could of the original plant and installed natural gas combustion turbine/generator sets. They utilized the waste heat of the combustion turbines to produce steam in steam generators to power the original steam turbine. Think Fort St. Vrain is making about 900+ megawatts.


The helium kept getting wet and reacting with the graphite core. Had they not used steam driven helium circulators, that would have been a successful plant. I crawled all around the reactor building and we didn't even wear badges because the helium doesn't activate like water.Thanks turtlevette. The last contact I had with Fort St Vrain was in the late eighties when that facility had a major fire. Their maintenance guys were trying to locate a Yarway Valve which the vendor in Denver told them we had on the shelf. I remember some discussion of our valve not having the R stamp but we shipped them what they were looking for. Apparently there was a work-around.

 

[Yah-Tah-Hey]

Originally Posted By: john_pifer
Originally Posted By: Yah-Tah-Hey
OVERKILL: What is that shaft with the spur and helical gears? Also what is that ratchet looking gear? Wonderful,very clear photos. Your the man.


Yes! Thanks so much for all the awesome photos, guys!

I voraciously consume any and all information about power generation, transmission, distribution, etc. Really fascinating.

Any of you power plant guys ever been involved in any HVDC power transmission projects? Lots of interesting reading I've done on that. I can get lost in reading about that stuff for hours.
I remember interviewing at Intermountain Power Plant near Delta,Utah in the mid eighties and their transmission lines were HVDC. Could have gone to work there but war on the mountain wanted nothing to do with moving there. Actually made Craig,Colorado look good.

 

[Yah-Tah-Hey]

Originally Posted By: john_pifer
Originally Posted By: Shannow
Originally Posted By: Yah-Tah-Hey
OVERKILL: What is that shaft with the spur and helical gears? Also what is that ratchet looking gear? Wonderful,very clear photos. Your the man.


Barring gear (GE design by the looks of it).

Turbine has to be turned slowly (barred), for 4-6 hours before run-up to get the shaft straight, and 4-5 days after coming out of service, to keep the shaft from hogging while it cools down.

The big gear is what the slow speed turning gear engages.

The ratchet is literally that. There's a hydraulic cylinder with a tooth on it that you bolt to the pedestal and stroke back and forth hydraulically if the main barring gear fails.


Would you mind explaining further what you mean when you say that the turbine has to be turned slowly before run-up to get the shaft straight?

And what do you mean by "hogging"?
The turning gear on our 420MW turbine shaft was tiny compared to that. Never heard the turning gear referred to as the "barring gear." Thanks

 

[mk378]

The clearance inside the machine is so close, that if it is not kept turning all the time, the rotor will sag down under its own weight and drag on the stationary part. Attempting to start the machine in that condition would cause severe damage.

 

[Shannow]

Originally Posted By: Yah-Tah-Hey
The turning gear on our 420MW turbine shaft was tiny compared to that. Never heard the turning gear referred to as the "barring gear." Thanks


Barring is the british term...a lot of older engines had slots in the flywheel, and a fulcrum point so that you could use a crowbar the inch the shaft around to where the compressed air starters could initiate turnover...a process called "barring"


Yes, the barring gear assembly is tiny 70 or so horsepower, but the gear that they mate to on the turbine train is typically around the end of the machine that has maximum operational torque, so has to be bigger that that shaft diameter.

BTW, they are the worst part to align, an unsupported floating dumbbell.

 

[Shannow]

Originally Posted By: john_pifer

Would you mind explaining further what you mean when you say that the turbine has to be turned slowly before run-up to get the shaft straight?

And what do you mean by "hogging"?

Internal clearances between the blades and the seal strips, and the strips on the stationary blades and the shaft is around 0.028" and 0.032", as others have said, very close for efficiency.

When the shaft has been sitting, it has sagged, and needs to be rolled slowly for hours to come good.

If the shaft is bowed, the centre of gravity of the shaft is eccentric to the centreline of the bearings, and in addition to reducing the clearances on the high side, will cause an imbalance.

As it speeds up, that imbalance will pull the high side into being further bowed (hope that makes sense), and further both the bow, and the unbalance...at the first stage critical speed (natural harmonic of the shaft...first is the skipping rope shape, second is the two skipping rope shape, with the centre of the shaft the second node/minimum, they design them to run around the second critical), the natural tendency for the shaft to really increase in vibration as it adopts the skipping rope shape is exacerbated by it already being that shape, and unbalanced in that direction...things get nasty....just a normal run-up you are wary of the critical speeds, and drive through them pretty quickly.

Hogging...if you turn the machine off hot, you end up with a temperature profile in the turbine, hot at the top, so there's a fight between the turbine's natural want to sag, and the temperature difference trying to expand the upper surface, and make it bow up...again if you roll you can get into big difficulties at the critical speeds. Not also that the casing hogs too, so you can end up with a bowed shaft in a bowed casing. The turning shaft keeps a small amount of gas flow in the casing, helping to distribute the heat evenly.

So operating manuals usually call for a minimum of 4 hours on a cold start, and a maximum measured shaft eccentricity. On a hot shutdown, must stay on barring until 150C (300F)...this protects the white metal bearings also.

 

[mk378]

Originally Posted By: turtlevette

The helium kept getting wet and reacting with the graphite core. Had they not used steam driven helium circulators, that would have been a successful plant. I crawled all around the reactor building and we didn't even wear badges because the helium doesn't activate like water.



Wow I didn't know that the US had a graphite-moderated plant running through the 1980s (even after Chernobyl). I thought that experience at Windscale had convinced Western engineers graphite is "unsafe at any speed."

 

[Yah-Tah-Hey]

Originally Posted By: mk378
Originally Posted By: turtlevette

The helium kept getting wet and reacting with the graphite core. Had they not used steam driven helium circulators, that would have been a successful plant. I crawled all around the reactor building and we didn't even wear badges because the helium doesn't activate like water.



Wow I didn't know that the US had a graphite-moderated plant running through the 1980s (even after Chernobyl). I thought that experience at Windscale had convinced Western engineers graphite is "unsafe at any speed."
There is one buried at Hallam,Nebraska. Only operated two years and AEC shut is down because of design problems. Site is now Sheldon Power Station,coal fired units.NPPD is converting one unit to burn hydrogen. Nebraska is the only state that has public power generation, no IOUs.

 

[turtlevette]

Originally Posted By: Shannow
[

So operating manuals usually call for a minimum of 4 hours on a cold start, and a maximum measured shaft eccentricity. On a hot shutdown, must stay on barring until 150C (300F)...this protects the white metal bearings also.



Yep and I keep saying that coal plants have even more operational and reliability constraints that limit their availability. Coal pulverizers are especially unreliable.

What was your record for number of days without shutdown or output restrictions.

 

[Shannow]

Originally Posted By: turtlevette
Originally Posted By: Shannow
[

So operating manuals usually call for a minimum of 4 hours on a cold start, and a maximum measured shaft eccentricity. On a hot shutdown, must stay on barring until 150C (300F)...this protects the white metal bearings also.



Yep and I keep saying that coal plants have even more operational and reliability constraints that limit their availability. Coal pulverizers are especially unreliable.

What was your record for number of days without shutdown or output restrictions.


Again, you keep saying it, but again...you are wrong. You can have your own opinions, but not your own facts. If it's from places that you worked, then I'd have to question the capabilities of the people that they employed.

One of the Units went well over a year without a shutdown of any kind. We go weeks and months without capacity restrictions due to milling

EFOF below 2% for decades in their first 20 years.

Operational range 40-105% of nameplate rating, on a daily basis. 20% to 105% in poor market conditions. (stated before you restate that they have no turndown)

 

[john_pifer]

Originally Posted By: Shannow
Originally Posted By: john_pifer

Would you mind explaining further what you mean when you say that the turbine has to be turned slowly before run-up to get the shaft straight?

And what do you mean by "hogging"?

Internal clearances between the blades and the seal strips, and the strips on the stationary blades and the shaft is around 0.028" and 0.032", as others have said, very close for efficiency.

When the shaft has been sitting, it has sagged, and needs to be rolled slowly for hours to come good.

If the shaft is bowed, the centre of gravity of the shaft is eccentric to the centreline of the bearings, and in addition to reducing the clearances on the high side, will cause an imbalance.

As it speeds up, that imbalance will pull the high side into being further bowed (hope that makes sense), and further both the bow, and the unbalance...at the first stage critical speed (natural harmonic of the shaft...first is the skipping rope shape, second is the two skipping rope shape, with the centre of the shaft the second node/minimum, they design them to run around the second critical), the natural tendency for the shaft to really increase in vibration as it adopts the skipping rope shape is exacerbated by it already being that shape, and unbalanced in that direction...things get nasty....just a normal run-up you are wary of the critical speeds, and drive through them pretty quickly.

Hogging...if you turn the machine off hot, you end up with a temperature profile in the turbine, hot at the top, so there's a fight between the turbine's natural want to sag, and the temperature difference trying to expand the upper surface, and make it bow up...again if you roll you can get into big difficulties at the critical speeds. Not also that the casing hogs too, so you can end up with a bowed shaft in a bowed casing. The turning shaft keeps a small amount of gas flow in the casing, helping to distribute the heat evenly.

So operating manuals usually call for a minimum of 4 hours on a cold start, and a maximum measured shaft eccentricity. On a hot shutdown, must stay on barring until 150C (300F)...this protects the white metal bearings also.


Pretty crazy. Is this just the mass involved? Your skipping rope analogy makes complete sense, but you would think, with the shaft being steel alloy, that it would be too rigid to sag like that.

Let's compare to a jet engine (I have more understanding of these, being an aircraft mech). Does this not occur in jet engines because the shafts are shorter and thicker?

 

[OVERKILL]

Originally Posted By: Shannow
Originally Posted By: turtlevette
Originally Posted By: Shannow
[

So operating manuals usually call for a minimum of 4 hours on a cold start, and a maximum measured shaft eccentricity. On a hot shutdown, must stay on barring until 150C (300F)...this protects the white metal bearings also.



Yep and I keep saying that coal plants have even more operational and reliability constraints that limit their availability. Coal pulverizers are especially unreliable.

What was your record for number of days without shutdown or output restrictions.


Again, you keep saying it, but again...you are wrong. You can have your own opinions, but not your own facts. If it's from places that you worked, then I'd have to question the capabilities of the people that they employed.

One of the Units went well over a year without a shutdown of any kind. We go weeks and months without capacity restrictions due to milling

EFOF below 2% for decades in their first 20 years.

Operational range 40-105% of nameplate rating, on a daily basis. 20% to 105% in poor market conditions. (stated before you restate that they have no turndown)


Not sure how this compares, but the record at Bruce (I don't see any stats from OPG on Darlington or Pickering) is for Unit 8, which in February, holds the site record at 623 days. Unit 8 is part of the newer (construction started in 1979, came online in 1987) "B" side of the site and has a current rated output of 817MW.

 

[Yah-Tah-Hey]

Originally Posted By: turtlevette
Originally Posted By: Shannow
[

So operating manuals usually call for a minimum of 4 hours on a cold start, and a maximum measured shaft eccentricity. On a hot shutdown, must stay on barring until 150C (300F)...this protects the white metal bearings also.



Yep and I keep saying that coal plants have even more operational and reliability constraints that limit their availability. Coal pulverizers are especially unreliable.

What was your record for number of days without shutdown or output restrictions.Our B&W MPS 89 coal pulverizers were very reliable and were never a problem when it came to generation. We had five installed units and could make full load with four in service. Retrofitting with ceramic wear elements made them even more reliable.

 

[Yah-Tah-Hey]

Our B&W MPS-89 coal pulverizers were very reliable and never were a problem when it came to making full load. Just as good as the old E type mills were a pain.