I did contact the company, but it's Sunday on my side of the planet, so they wont reply until Monday.
Monotube Flash Boiler Design
- Thread starter Toymaker
- Start date
Help Support Home Model Engine Machinist Forum:
I did contact the company, but it's Sunday on my side of the planet, so they wont reply until Monday.
I am intrigued how you plan to add anti -corrosion additive to the condensate - which is pure water..?
K2
K2
I needed to verify a few old memories with a little Google research before I answered: as you mentioned, condensate is pure water and although iron will still rust in pure water, the rusting proceeds at a much slower rate. And, many water based rust inhibitors last for years after a single application, so my thinking is that soaking the motor in a good rust inhibitor will protect it from rust for quite some time, especially in pure water.
Also, pure water is a very good insulator, so no electrolysis inside the pump even if it's a "wet" pump.
K2, we're both forgetting our basic chemistry (or physics ?).
Most people living in cold climate zones know that mixing Anti-Freeze (ethylene glycol) with the water in your car's radiator will prevent the water from freezing and destroying the engine; a 50-50 mix lowers the freezing point to around -80F. But what we've both forgotten is that mixing two liquids together changes the boiling as well; a 50-50 mix of ethylene glycol and water raises the boiling point of the mixture to around 230F.
Also, more important to this discussion, if a solid is dissolved into water, like salt, when the water evaporates, the solids are left behind. But, when two or more liquids are mixed together, they all evaporate together, or very closely together.
Therefore, when a mixture of anti-freeze & water is vaporized in a boiler, and then condensed back into the liquid state, the condensate will not be pure water, but will be both the anti-freeze and water. And if the anti-freeze contains rust inhibitors, so long as they too are liquids, the rust inhibitors will also be a part of the condensate. Just need to insure none of the additives chemically break down at boiler temperatures.
I should have remembered all of this straight away,...but, I guess I'm getting old.
Last edited:
You too?
I thought AGE was an acronym for Atmospheric Gas Engine. Then I arrived at it! It's a whole new experience I am struggling to get used to. Aches all over the body, sleep screwed into a whole new life-style, Hungry, then can't eat a proper meal, Body Ballooning... Strength and endurance have gone somewhere. Motivation 1 week a month.
My brain is 37 - but with "software" levels of over 30 years ago. The processor is really slow! Memory needs de-fragmenting, and the key board is old and doesn't often type all the keys I think were pressed...
When I am on the street, or driving, my "style" is out-of-date. No-one drives as fast as I want to. No-one drives through gaps any more. (Except buses - They can get through gaps with minimal clearance!). Everyone stops at the first opportunity. Road junctions when it is their right of way or the signals are on "GO"! But they don't understand the laws of the land, Highway Code, and other things we were taught as kids. Then walking the pavement, they are all pushing to get past me, or in my face expecting me to get out of their way because they have their heads n eyes in their phones, their ears plugged full of plastic, and brains stuffed full of stuff I cannot imagine! With thumbs that have some sort of insane disease that causes them to tap their phones at a random high speed. Then after knocking one out of the way, call "sorry" and continue without looking to see if they really have put you on the floor. They even look at you strangely when you offer to pay for something with MONEY! As if my having held the stuff will kill them if they touch it? Or their machine "doesn't do Money". As if being in the same space as "an old person" will give them some contagious disease? - Well, I have learned they are right. That disease is called "AGE"!
An don't "Old people" sometimes just "go on a bit"?
K2
I thought AGE was an acronym for Atmospheric Gas Engine. Then I arrived at it! It's a whole new experience I am struggling to get used to. Aches all over the body, sleep screwed into a whole new life-style, Hungry, then can't eat a proper meal, Body Ballooning... Strength and endurance have gone somewhere. Motivation 1 week a month.
My brain is 37 - but with "software" levels of over 30 years ago. The processor is really slow! Memory needs de-fragmenting, and the key board is old and doesn't often type all the keys I think were pressed...
When I am on the street, or driving, my "style" is out-of-date. No-one drives as fast as I want to. No-one drives through gaps any more. (Except buses - They can get through gaps with minimal clearance!). Everyone stops at the first opportunity. Road junctions when it is their right of way or the signals are on "GO"! But they don't understand the laws of the land, Highway Code, and other things we were taught as kids. Then walking the pavement, they are all pushing to get past me, or in my face expecting me to get out of their way because they have their heads n eyes in their phones, their ears plugged full of plastic, and brains stuffed full of stuff I cannot imagine! With thumbs that have some sort of insane disease that causes them to tap their phones at a random high speed. Then after knocking one out of the way, call "sorry" and continue without looking to see if they really have put you on the floor. They even look at you strangely when you offer to pay for something with MONEY! As if my having held the stuff will kill them if they touch it? Or their machine "doesn't do Money". As if being in the same space as "an old person" will give them some contagious disease? - Well, I have learned they are right. That disease is called "AGE"!
An don't "Old people" sometimes just "go on a bit"?
K2
Sorry, I hogged your thread. I can delete it if you wish...
K2
K2
Toymaker, I think that many inhibitors change the PH, or tie-up Oxygen ions with heavier elements, metals or whatever, which precipitate as solids when the water boils-off.... But I am not a chemist, so do not really know what happens. I agree that miscible liquids can boil at a "mutual boiling point" as you describe, but I don't really understand this at all? e.g. salt raises the boiling point of water... but: surely Distillation is the removal of the lower boiling point "fraction" from the mix? Otherwise how would fractional distillation work? - Different temperatures to boil-off different fractions of the mix? Anyone with a Still knows to control the temperature to boil-off the Ethanol, while not boiling-off the methanol, and water, when removing the spirit from the fermented mash. Of course, in your flash boiler, you are exceeding the boiling point of all the various fractions I guess, if using an inhibitor, so everything is passed to the condenser to mix again.
K2
K2
Don't you dare delete it,...it's priceless and soooooo true.
If these little pumps work as well as I hope they do, I'm willing to diss-assemble them, coat the rust vulnerable parts with high temperature paint, then re-assemble. If I destroy the case during this process, I'll make a new case. These pumps are the perfect fit for my feed pump needs, so I'm willing to go the extra mile to make them work.
cdn flyr
Member
cdn flyr
Member
Why not try an automotive windshield washer pump? They force a pretty good flow thru the washer jets so they might have enough pressure. Certainly suitable for water.
cdn flyr
Member
Forget above windshield washer suggestion. I did some further research and think the following is closer to your requirement. I do not know how to post a link but Google Amazon.com and enter in Amazon search "12v car washer pump kit' . They claim 135 or more psi and 80 to 100 watts and 1 to 5 litre per min flows. Alibaba should have similar. There are two types: one has a 135 psi cutoff switch and the other does not.
Thanks for the suggestion cdn flyr. Using a pressure washer (aka, car washer) was one of my first thoughts,...they certainly look good in the adds, and I purchase one of these nearly a year ago:
The label on the pump states:
Flow: 8LPM
Pressure (protected): 1mpa
But what the label (and the sales adds) are not telling you is that you will only get 8 LPM flow rate at zero psi, as soon as pressure builds, the flow rate quickly slows. Also, the stated pressure is rather miss-leading. It looks like the pump will supply 1 mpa (145 psi), but what it really states is that the pump is somehow "protected" at 1 mpa. When I tested this pump, I could never get more than about 50 psi, and at a very low flow rate.
Pure water is an acid. It is given a non technical name aggressive water because it is so corrosive. It is quite conductive because of its free ions. Oxygen is usually removed with a deareator (open feedwater heater) Solids entrained in the water will require blow-down. The single tube boiler design will be especially vulnerable to total dissolved solids since there will be no drum to keep them under control. The water can be forced on the alkaline side with various chemicals. The higher the operating pressure the more stringent the demand on quality will be. A rust inhibitor will not work on your pump as there is no way to keep it on the metal. Your water treatment scheme will be a research project in itself. As a matter of history in the first development of water treatment they used potatoes thrown in the drum. Rust or oxidation can proceed at a very fast rate in pure water of that fact I can assure you. You will need to control the oxygen level, the total solids, ph and depending on pressure if its high enough silicon.
For corrosion resistance:
re: "If these little pumps work as well as I hope they do, I'm willing to diss-assemble them, coat the rust vulnerable parts with high temperature paint, then re-assemble.":-
I would seriously consider electro-plating stuff. Or hot-tinning with an electrical solder.... (and wipe while molten to the tinning is thin). Tin is an excellent corrosion inhibitor, as is lead, and a soft-solder wetting the chemically clean surface of steel provides a pretty good protection. As does electroplating of steel (or anodising of aluminium). For steel parts, screw a bolt in a thread and suspend the component in the electroplating solution by the bolt. That way the outside of the component is plated without pin-holes where the part contacted the electrical connection. Even Copper plating works better than nothing. Plate with a small torch battery (1.5V) - Not a 12V car battery!
Plenty of U-tubes on that I guess...
K2
re: "If these little pumps work as well as I hope they do, I'm willing to diss-assemble them, coat the rust vulnerable parts with high temperature paint, then re-assemble.":-
I would seriously consider electro-plating stuff. Or hot-tinning with an electrical solder.... (and wipe while molten to the tinning is thin). Tin is an excellent corrosion inhibitor, as is lead, and a soft-solder wetting the chemically clean surface of steel provides a pretty good protection. As does electroplating of steel (or anodising of aluminium). For steel parts, screw a bolt in a thread and suspend the component in the electroplating solution by the bolt. That way the outside of the component is plated without pin-holes where the part contacted the electrical connection. Even Copper plating works better than nothing. Plate with a small torch battery (1.5V) - Not a 12V car battery!
Plenty of U-tubes on that I guess...
K2
Last edited:
Actually, pure water is neither an acid nor a base - it has a neutral pH. It also has a very low conductivity/high resistivity due to it's extremely low ionic strength. That said, it is a very good solvent.
Corrosion in steam systems is mostly due to the presence of oxygen, which will react with metals to form oxides and cause pitting. Deaerators are used to reduce the oxygen in the feedwater. To combat the effects of residual oxygen, anti-corrosion additives are often added to the boiler feedwater - sodium sulfite, filming amines, etc. , as well as using caustic soda to raise the pH of the boiler water. Depending on the quality of the raw makeup water, pretreatment may be required to reduce/remove contaminants (total hardness due to calcium & magnesium, silica, etc.) that can also contribute to scaling and corrosion. The higher the pressure/temperature, the more critical this is.
All good suggestions, and with a bit of luck, I wont need to use any of them.
I still have an unanswered request for more information into the manufacturer; I'm hoping these pumps have been designed such that pumping water wont be a problem.
Boil water 3 times (an electric kettle works) - and you'll start to hear it "knock" as it begins to boil. That is de-aeriated water. Not good for Coffee, or tea, but better for your boiler. Of course, rain water, melted ice from the inside of the freezer etc. is better than ground water (full of minerals!) for any boiler generating steam. (Including my Wife's hand iron!).
K2
K2
I plan to use a sealed system, and will start with de-ionized, highly filtered water. I don't see any way for the water to become contaminated with anything besides copper ions leached off from the boiler.
Am I missing something ??
Tim Taylor, is the sodium sulfite dissolved into the feed water, or is it placed into filter-like containers which the feed water is pumped through?
