Steam Turbines Built Outside

[knight185]

I have worked in or visited 6 fossil power plants. Each of them have the steam turbines and generators inside large turbine rooms with roofs and overhead cranes. During a turbine training class the instructor has photos of steam turbine overhauls where the turbines are outdoors with no overhead crane.

Why would a utility build a power plant with the steam turbine and generator out in the open like that? It would seem that poor weather would delay repairs during outages.

 

[MikeHalloran]

If you consider life cycle cost, mobile cranes and temporary shelters rented as needed might be cheaper than a permanent building and bridge cranes that are used only infrequently.

I haven't seen it done that way, but I understand how the balance could work out to favor it. In a way, it's a statement about the reliability of the equipment.

The big stuff is mostly pressurized anyway. A few adaptations, and a slightly better grade of paint, and it's weatherproof.



Mike Halloran
Pembroke Pines, FL, USA

 

[byrdj]

For the utilty size steam turbines, I have always had a rail gantry crane. for CT's mobile cranes are the norm.

as for problems during maintanance, YES, there are problems, even before the abilty to get live radar on internet, the utilty would have near hourly reports especially when pulling a field

 

[ScottyUK]

I spent ten years working at a plant with no machine hall. It is a maintenance problem to say the least. Lousy weather, high winds, feezing winters, atmospheric pollution, just a few of the elements which make it a poor design.

Why would they do it? To save initial build cost, and construction program. I would be surprised that a utility would build a plant without a machine hall, but not surprised if a privately-financed plant was built this way. Much of the financial risk associated with maintaining an outdoor plant is moved to the O&M contractor so if weather results in stand-down time on a mobile crane and an outage crew then it reduces their profit. The owner is shielded from the risk because the O&M is usually based on a pre-agreed budget or fee of some form.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[knight185]

My turbine outages are done totally on T&M, but we don't use the OEM to run the outages. I am usually the project manager and I hire a few self-employed turbine engineers that my company has been using for many years. Our in-house maintenance staff does all of the disassembly and reassembly work and I bring in other contractors for sandblasting, weld repairs, etc.

Having an enclosed turbine room also makes it easy to stage all of the rotors, shells, and diaphragms. Right now my turbine deck is also being used to stage a lot of boiler tube panels.

 

[ScottyUK]

O&M [≠] OEM.

O&M = Operation & Maintenance, i.e. the guys who operate and maintain the plant on behalf of the owners.

The idea of doing a turbine overhaul in the north-east of England on a pure T&M basis, knowing the likely stand-downs due to weather-related delays would fill me with concern. With crane costs running well into 5 digits per day and stand-down on the crew in the same cost bracket, a week of wind and rain can quickly add up to a serious amount of money.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[knight185]

I know O&M and OEM are not the same thing. I was just saying that we don't use OEM field services for our turbine outages but perhaps it didn't make sense to mention that in the same sentence.

For most of the work I have done I prefer have hire the contractors on a T&M basis because most of the delays are largely under my control and I am able to better estimate their costs. Some other projects that I have worked on were fixed price for a lot of the major work but there were always countless unexpected items that popped up that were not in the original scope and had to be added to the purchase order.

 

[knight185]

I have also seen cases where fixed price contracts were not negotiated properly. A contractor may have priced it based on working 5 days per week but then in order to for us to make our deadline, the contractor would have to work 6 days per week. Depending on how much cushion the contractor put into the bid the 6 days might start eating into his profit, but our project manager doesn't want to hear that. He figured that if it was fixed price the contractor should work whatever schedule is required to get the job done when he wanted it.

 

[rmw]

Most of my past LSTG power plant experience has been along the Gulf coast in the USA where outdoor and open TG units are common. I have never seen one without a gantry crane. Is it possible Knight that the instructor's photos were shot at an angle where the crane was parked out of the view?

My more recent experience is with the type units that Scotty mentions and none of them are inside in my part of the world at least. I have seen some inside in Canada, but it is never warm there other than the 3 days of summer that they have there. (see tongue in cheek)

Most outage work is spring and fall and except for certain parts of spring, weather is not as much of a factor in the deep south other than just waiting it out when it is too bad to work. But, then, too, the weather that time of year is fast moving fronts as opposed to the dreary days of continuous rain during the winter, so it was never too long of a wait. And, work can be done under tarps and tents.

The large turbine rooms start appearing north of a line stretching between Dallas and Birmingham as I remember it. North of that, cold weather can linger well into the spring. I can think of outdoor units in Jackson, MS and a large turbine room 90 miles north in Greenville, MS.

It is the cold as much as the wet that affects productivity to my way of thinking.

Most power plant contractors in my experience in order to get people to work that type of work wanted to work 6 tens. That gave the lads one day off to do their laundry, etc. They couldn't get people to travel away from home jobs for 40 hr/wk work.

Contractors that bid fixed price work bid it on a break even basis and then hope to load it up with higher margin work for "extras". I saw one power plant operator who did all the "extras" with their own crews and denied the contractor any extra work and that contractor still moans about that job until this day.

When you go to 12 hr days, you get 10 hrs work stretched into 12 hours. And, Knight, I agree with you. When fixed price is bid, then the contractor just has to do what it takes to get it done. But that said, then they look for every excuse to blame the utility when they can't work; say like when someone else has the crane tied up so the games go on and on.

rmw

 

[knight185]

There is a picture of the Michoud plant new New Orleans on page 20 of the September 2009 edition of Power Magazine. The turbines are outdoors but there are some kind of roof structures on the turbine deck too. Can't tell if there are gantries inside or not.

For the turbines outages that I work on, I use in-house mechanics for the disassembly and reassembly work. We hire specialty contractors for the field machining, induction heating for bolting, etc. I am running into the issue of contractors not wanting to work straight time schedules and my company is not willing to pay any overtime. Some of the contractors will do it but are not happy about it. The only other way to do it is to pay them a fixed price, which they will most likely base on 60 hours. My opinion is that if a company is not willing to work less than 60 hours per week, then their rate sheet should start out at a rate that will cover 60 labors hours.

 

[rmw]

Her are three links to photos of outdoor units, the first one showing Michoud station as you mention. (I notice that they got the shot of Patterson Sta after the hurricane when NO was flooded).

Some outdoor stations will also have a gantry type shelter or tent that can be rolled over a unit to protect it from direct sun and rain but which can be rolled away so that the crane can get over the unit when it has to. Back in the old days of tight-wire alignment, uneven sun light could be a bear.

http://www.industcards.com/st-other-usa-la.htm

http://www.industcards.com/st-coal-usa-tx.htm

http://www.industcards.com/nuclear-us-south-central.htm

In the last one, you can't see that the unit is outdoor, but you can clearly see the turbine crane over the top of the building. You can clearly see it as an outdoor unit by flying Google Earth to Lat 29.994351 Lon 90.471492. If you go almost due north right across the river (follow the HV lines) you will see Little Gypsy station which is also outdoor units. There is a shelter over the Unit 3 turbine which I don't know whether it is permanent or constructed for an outage. It may be the gantry type tent I remember. I know for a fact that it is an outdoor unit as it was the first one I ever opened up. Got a good tan on that job.

rmw

 

[byrdj]

And here is an outdoor Nuclear (PWR) station (and fossil on the right)
the two yellow gantry cranes are fairly clear

 

[boilerone]

I remember reading a turbine text book so this should be the standard answer: having turbines outdoors is for SAFETY REASON.

If by chance a turbine fails, the turbine house would be immediately filled with steam and dust plus possible building collapsing because of being hit by flying turbine components all could easily kill people inside.

 

[MikeHalloran]

So, don't arrange a convention in a turbine house.


Sorry; couldn't resist.


Mike Halloran
Pembroke Pines, FL, USA

 

[rmw]

Whoever wrote that textbook ought to get out in the real world some. The vast majority of steam stations in this country have turbine halls. So much for safety.

rmw