Boilers and brackish water

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daysaver1
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Boilers and brackish water

Post by daysaver1 » Fri Aug 13, 2010 7:20 pm

I prefer to run my steam boat in fresh water. However I live in an area where the rivers slowly become brackish to the point of being entirely fresh. Added to that the fact that the 2011 NWSS meet will be just off the Columbia River in Cathlamit, WA and the water salinity is in question, I want to know if I need to use my hot well or can I merely open up the port into the river for feed water.

I realize the Tuolumne River (B&W next month) is somewhat brackish but have heard a certain amount of salinity is acceptable. I just bought a refractometer for testing salinity but question the amount of salt in water that is acceptable and not harmful to boilers. Comments?
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Re: Boilers and brackish water

Post by farmerden » Sun Aug 15, 2010 12:02 am

Salt is still salt! It's just the dilution difference! All steel parts will rust and flake off and jam in some valve somewhere,sometime. Also water with anything in will boil at a higher temperature and reduce our ability to make steam.I once had a pinhole leak in the exit line to my keel condenser.I could taste salt in the boiler water but could not find it. I ended up filling the bilge with water and pressurizing the line and sure enough there was the leak! Being a wooden boat I always have a certain amount of salt water in the bilge .The problem is your boiler will boil the fresh water away and build up a concentration of salt in your boiler and long term that would not be good.That being said I would not hesitate in using salt water to get home if I ran out of water at sea-I wouldn't like it but running with no water is not a good idea :lol: So there's my two-bits worth! Den
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Re: Boilers and brackish water

Post by artemis » Sun Aug 15, 2010 6:03 pm

daysaver1 wrote:I prefer to run my steam boat in fresh water. However I live in an area where the rivers slowly become brackish to the point of being entirely fresh. Added to that the fact that the 2011 NWSS meet will be just off the Columbia River in Cathlamit, WA and the water salinity is in question, I want to know if I need to use my hot well or can I merely open up the port into the river for feed water.

I realize the Tuolumne River (B&W next month) is somewhat brackish but have heard a certain amount of salinity is acceptable. I just bought a refractometer for testing salinity but question the amount of salt in water that is acceptable and not harmful to boilers. Comments?
The damage is not caused so much by rust - once the water has been turned to steam and leaves the boiler, it is "pure"; i.e. contains no particulates. It's the particulates that cause the damage, gluing to the inside of the heating surfaces of the boiler causing "hot spots" and tube failure.

:idea: Collect the water from your source in a clear water glass. Allow it to stand and the particulates to settle out. Surprise. If you wouldn't drink it, DON'T PUT IT IN YOUR BOILER :!:
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Re: Boilers and brackish water

Post by stevey_frac » Mon Sep 13, 2010 11:37 pm

I've often thought that it might be possible to use a small pump and a reverse osmosis system to take pretty much any water source and turn it into water that is both acceptable for drinking, and for your boiler!

Might cost you about $1000 all said and done though...

Run the pump like a boiler feedwater pump off the engine, to get the pressure required, put the brine back in the river.
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Re: Boilers and brackish water

Post by fredrosse » Tue Sep 14, 2010 1:57 am

The use of Reverse Osmosis (RO) systems as a substitute for recovering condensate for re-use in the boiler has been evaluated.

The small Reverse Osmosis (RO) systems available for drinking water have a capacity that is very much less than the feed water needs of a small steam launch. They typically store water that has passed thru the RO membrane for the user, as they cannot supply enough for a drink within a short period of time, much less supply the feedwater needs of a 1 HP (more or less) steam launch.

They could possibly supply makeup water for a condensing system that is reasonably tight and has only minor leakages. But in that case it is easier and much less expensive to bring in the makeup water rather than producing it with RO.

You can buy distilled water, but better yet, collect it from the rainwater gutters on the house. I found that this rainwater runoff was very low in Total Dissolved Solids (TDS), if about a half hour after rain had started running off the roof, the rainwater collection was initiated. The first half hour of rainfall scrubs the atmosphere of many impurities, and washes off the roof. After that, rainwater in my area had about 1 to 2 Parts per Million (PPM) dissolved solids, which is very good for feedwater. For comparison, our city drinking water has 215 PPM, and lake Nockamixon (Pennsylvania), where the steamboats meet monthly, has about 115 PPM. Either of these sources would be OK for launch boiler feed, but the rainwater, at 1 PPM is much better.

If the rainwater is acid (Ph less than 7.0), this is easily taken care of by the addition of Trisodium Phosphate to the boiler. Regardless of the source of boiler makeup, the water in the boiler should be maintained with a Ph of around 9.0 - 10.0 to minimize corrosion.
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Re: Boilers and brackish water

Post by Maltelec » Tue Sep 14, 2010 11:36 pm

The only way I would put questionable water into my boiler (if I had one) is if I moored up in nice fresh water and sailed through the questionable water and back into the fresh water when done. Then give the boiler a full blow down and fill it up with fresh water.

A bit of salt/muck isn't a big problem short term, but prolonged use of slightly salty water will cause damage. Muddy water isn't quite so bad, but a good blow down and fresh water is essential.

I would never use sea salty water though. If you were heading into salt water of that concentration, you definitely want to be condensing and take a supply of fresh with you, even if you tow it behind.

If you have differing metals in the boiler, salt will eat away at one of them. Probably the more expensive and difficult to replace one as well.
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Re: Boilers and brackish water

Post by steamboatjack » Wed Sep 15, 2010 11:46 am

Salt water feed to boilers: - all of the above are valid but assuming you have access to measuring the salinity here are the facts. A steamship engineer (water tube) would probably need medical help at anything over 10 parts per million! An auxiliary boiler and I would imagine most launch boilers could tolerate 300 PPM, at this you would be lucky to taste the salt, if you can taste it, its is way over the limit.
This does not mean you can run like this indefinitely, blow down is the best treatment for any boiler even on a fresh water lake, at the first chance blow the lot out at re fill with rain water or similar and keep the pH up as mentioned above.
As mentioned its scale formation that is the real danger not corrosion, most corrosion in launches is caused by oxygen.
I would not bother with fancy equipment, reverse osmosis I believe cannot produce boiler standard water, you need a evaporator for this, remember the salinity will multiply very quickly as you use steam, intermittent blow down would help if you cannot help running on brackish water.
The first ocean steamships used continuous blow down to help but still had to stop every few days to dig out the scale.

Regards Jack
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