Generator Hydrogen Cooling System

In theory it would seem possible.

However, the way most machines are built, meaning the way the internal piping for charging/purging is constructed, CO2 is chosen because of it's weight versus hydrogen and air.

Because CO2 is heavier than air it is "injected" into the bottom of the generator casing to push the hydrogen up and out the top of the generator casing.

When using air to purge the CO2 from generator casing, it is "injected" into the top and used to push the CO2 out the bottom of the generator casing.

You might also need to have different casing gas monitoring equipment for purging and charging as most monitors measure for the presence of H2 in air, or H2 in CO2, or similar. I've never seen one that measure anything in N2 or N2 in anything (for generator casings, that is).

You should study the internal piping arrangement drawings for the generator(s) at your site, and then analyze the situation to see if you could make this work. Let us know how you fare.

Hope this helps!
 
D
I attended a meeting some years back where Linde discussed using argon instead of CO2. More expensive, but vaporizes faster and therefore they claimed that both degas and regas cycles could be faster. Suggest you touch base with them if you are interested.
 
While CSA's practicality of use is right-on, I believe the top two characteristics, after economy, are the vaporization factor, and the ease of cleansing H2 of the purge-gas, if required.

Phil Corso
 
I read this article and found it very interesting. It will be great if I could know how much hydrogen (in Tons) is required for 270 MW GT cooling function and how frequently the hydrogen used in the GT need to be re-charged.
 
The answer to this kind of question depends on many factors. The size of the generator casing, including the gas-water heat exchangers, drain enlargement tanks, and associated piping. Also, the scavenging rate (the amount of gas vented from the seal drain enlargement tanks to remove entrained air) will affect the amount of hydrogen which is required to keep the pressure at or near rated.

And, scavenging rates usually increase with wear on seals or increasing shaft vibration. So scavenging rates are constant over operating periods; they will change as components wear, and are replaced.

If you have a particular generator "in mind" that will be in use at the plant, or is in use currently, you will need to find the manufacturer's or supplier's data sheets for this specific information.
 
<b>CORRECTION</b>

The sentence below from the previous post was incorrect.

> So scavenging rates are constant over operating periods; they
> will change as components wear, and are replaced.

The above sentence should have read:

So scavenging rates are <b>not</b> constant over operating periods; they will change as components wear, and are replaced.

Apologies for any confusion.
 
Get the specifications and data sheet from Siemens, or whomever manufactures the generators Siemens uses.

They are the best guidelines, unless someone here has experience, and even then you never know all of the story (leaks; piping/volume differences; scavenging rates; etc.).
 
> The problem with having a separate seal oil system is that at some point the seal oil and some of the bearing lube
> oil will eventually mix, and so I believe that's why the same medium (lube oil) is used for both bearing- and seal
> oil. Treating a portion of the lube oil is going to be costly and difficult, at best.

---- snip ----

> There are many sites around the world which have opted for on-site H2 generation. It just adds another system
> to be operated, monitored, and maintained. And in my experience, they were never operated or maintained
> properly and so most of them were soon shut down and bottled H2 was used for the generators.

what are the possible causes of oil coming out from generator water detector?
 
> what are the possible causes of oil coming out from generator water detector?

Failed or failing seals.

Poor Seal Oil Pressure regulation during purging/charging.

Poor operation or valving of Seal Drain Enlargement tank drains.

Have a look at the Seal Oil System piping drawing.
 
T
Hi I'm interested in this post as I've made a domestic computer cooling chamber that cools to about -25c. The system uses recirculated air as a cooling medium and I wish to replace this with another gaseous medium that is more effective.

While hydrogen would be appealing due to it's 10x fold increased cooling efficiency I fear it's explosive nature would not suit it for domestic use.

I was wondering if anyone has information of other gases that would be more efficient than air but safer for the domestic environment.

Many thanks.
 
T

Thomas Manaugh

Very nicely written explanation. Please answer two quick questions about the cost of keeping large generators cool during operation. Depending on the generator, where it was used, and how it was used, you might need to use hydrogen cooling. If a generator costs $100,000, what might be the estimated cost of its hydrogen cooling system in round figures? Regardless of how you cool a generator, there will be an energy cost. If a generator were to produce 100 kilowatt hours of electricity, what would be the expected range in kilowatt hours of electricity that might be needed to operate the generator's cooling system?

Thank you.
 
CSA…
I am glad this thread got bumped. That was an excellent explanation with some very good information and presentation.

One of the questions as reading through replies was the use something to prevent the need to scavenge. The LSTG units do use a vacuum treated oil system. Here is my explanation written to dispel some false assumptions on how the lube oil is used with this system.
http://www.slideshare.net/JosephFByrdJr/seal-oil-operation1

In my 3 decades, I have only passed by a few savaging units. However, if the vacuum seal oil system has a failure and untreated oil is used, the unit must be savage. Unfortunately the vacuum units are not constructed for a proper valving to do so. I wrote this paper for a customer to explain the concerns of operating for long period without vacuum treaded oil
http://www.slideshare.net/JosephFByrdJr/seal-oil-operation1

I then wrote up this paper discussing the amount of H2 expected to increase purity.
http://www.slideshare.net/JosephFByrdJr/scavagine-h2
Since I have no experience with scavenging units, do you think the rates I predicted are valid or was my assumed absorption % too high.

Last point related to cost, the pumping and reduction of cooling losses related to every % the purity is less than 99% is considerable. I believe "environmental one" has a good write up in support of their scavenging controls
 
the information helped me a lot to understand this system. thank you so much. but i still have one question. i am working on site and its siemens make hydrogen cooled generator. enlargement tank vent is connected to seal oil hydrogen side return. why is it so?? because seal oil hydrogen side return is also connected to enlargement tank. i will provide more info if you need to clear my question.
 
> I have a PowerPoint presentation I can send you but I do not know how to add
> attachments to the site, Do you know?

If you're still listening, please send a copy of your presentation to tcburger2001[at]yahoo[dot]com...
 
Dear CSA,

I am deeply impressed by your knowledge on generators and their cooling systems.

I am currently conducting a market study in this field and wanted to ask if you would be available to conduct an interview with me (remuneration would be a 75USD Amazon gift voucher for a 45min consultation).

I would very much appreciate having the chance to contact you!

Regards
Constatin Meyer
 
E

Ervin N Galera

We are currently having a lot of condensate/moisture coming from the scavenging drain lines - what would be the reason for this?

thanks
 
Ervin N Galera,

When did this problem start? After a maintenance outage? After a purge/charge event?

What kind/size of generator? Does it have stator cooling?

Have you changed hydrogen suppliers? Do you produce your own hydrogen?

Have you tested the condensate/moisture to see if it might be coming from a leaking cooler? Or stator cooling system?

Does the hydrogen have a hydrogen dryer? If so, has it been used recently?

Really, there are only so many ways for moisture to get into a pressurized vessel. Air is used to purge CO2; CO2 is used to purge air; hydrogen displaces CO2; moisture is entrained in seal oil (usually bearing lube oil); water is used to cool hydrogen; water is used to cool stator bars (in very large generators. If moisture gets introduced in any of the methods, and if the generator gas temperature gets too low then it can condense--unfortunately on generator internals. Keeping hydrogen free of moisture is very important. Most hydrogen control panels I have worked on have had moisture indicators (actually, desiccant that changed color when wet) which can indicate the presence of excessive moisture (if quickly changing colors). These are only minimally effective at removing moisture, but for most normal circumstances are adequate.

Again, moisture in air/CO2/hydrogen, and moisture from leaking coolers/stator cooling systems, and moisture entrained in seal oil are about the only suspects.

Hope this helps!
 
Ervin N Galera,

In thinking about this, has there been a drop in the cooling water temperature recently? And possibly a reduction in load since the problem started?

Both could result in condensation of moisture that was previously "suspended" in vapor in the hydrogen because the gas temperature was above the dew-point but now is below the dew-point.

Also, does the generator have a hydrogen dryer (usually electrically powered) that could be used to remove entrained moisture? If so, be sure to observe the proper purging sequences before and after use.

Write back to let us know how you fare!
 
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