2nd Class Boiler Question

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Swailfish
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2nd Class Boiler Question

Postby Swailfish » Mon Jan 07, 2008 5:33 pm

I'm studying up for my 2nd class general engineering exam, and I've come across a question about operating a boiler with seawater feed.

"At what density would a boiler be operated if salt water had to be used and what would be the result?"

I've found that the the ppm should be maintained at 125,000 and that seawater is 32,000 ppm, but I can't find what the density is.

Any help would be much appreciated, Thanks.

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TxMarEng
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Density of Salt Water

Postby TxMarEng » Tue Jan 08, 2008 1:40 pm

1.025 One however, wouldhave to be in dire straights to operate a boiler on salt water. Looks like the US isn't the only place where the inspectors don't have both oars in the water. Good luck on your exams.

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JK
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Postby JK » Tue Jan 08, 2008 8:17 pm

You can operate a scotch marine propulsion boiler on SW as a get 'er home last resort.
We contaminated our feed water with SW in some accident that I can't remember, and had severely contaminated boilers by the time we got in. You have to manage the boiler carefully with continuous bottom blowdown while steaming it.
It is a real PITA to get the boiler water back down to about 100 PPM when you get clean feed water.
All these steam questions, I regard as Scotch Marine boiler questions and answer as such.
Last edited by JK on Sun Jan 13, 2008 6:33 am, edited 1 time in total.

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TxMarEng
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Scotch Boilers

Postby TxMarEng » Wed Jan 09, 2008 11:04 am

Are there many Scotch Marine propulsion boilers left around? I agree with your recommendations however, one would think new licensees and upgraders as well would be grilled on more pertinent subject matter. :roll: Good luck with your exams! Glad I am on my final renewal of my ticket.

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JK
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Postby JK » Thu Jan 10, 2008 4:14 am

With the cost of fuel, I imagine that they have been all turned into razors long ago. However, Regulatory bodys may not realize that LOL.

dirtydan
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Postby dirtydan » Fri Jan 11, 2008 6:14 pm

Swailfish if you have Reeds Volume 3 Heat And Heat Engines there is a good description of the relation of ppm to boiler water density. It's in the chapter on boilers and combustion.

To make long story short ppm is a measure of density. In the metric system one gram of solid in one cubic meter of water is one part per million.

Swailfish
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Postby Swailfish » Sat Jan 12, 2008 9:34 am

Excelent, thanks for your help, much appreciated.

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chuck
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Postby chuck » Sat Jan 12, 2008 5:18 pm

The density of the boiler water would increase greatly with the production rate of the boiler. As the sea water flashes to steam, the solids in the water remain in the boiler, increasing the density of the water contained in the boiler. If a percentage of the water is not removed (blown out), the density increases drastically.
Compare this to a flash evaporator. If the brine water was not constantly removed, the water left in the evaporator would keep increasing in solids and become more dense.
Hopefully this will help.


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