The 844 thread got me thinking about water treatment and I thought I would start a new thread with some basic points on water treatment.

All oxygen should be gone and most boiler chemistry people agree that 15-30 PPM of oxygen scavenger should be present. It is better to go over than under, 100 PPM of scavenger will not hurt the boiler, it will cost extra money but not as much as the damage from oxygen pitting.

Boiler water pH should be above 8.5 but below about 10.5. The P alkalinity should be maintained above 350PPM and the M alkalinity should be around 500PPM. This is where the water is going to be least aggressive.

Total dissolved solids is a general measurement of the junk in your water. The problem is when the TDS "cycle up". To explain this think of your incoming water as having 10 parts of anything present, once that first boiler worth of water has been evaporated and replaced, another 10 parts of that impurity will have been added with that water. The first 10 parts are still there because they are solid and don't leave with the steam. The second 10 parts now give you a total of 20 parts of solids. This is 2 cycles, as it continues we 'cycle up" the boiler water. This could be anything; iron, calcium, silica, etc... The problem is different solids will not stay in solution and end up on your heating surface. Silica or calcium are often first things that will plate out onto your heating surface. The more TDS in your water the more readily it will conduct electricity. Keeping the TDS in check is as simple as using the blowdown to keep the conductivity below 3,000 micromho as measured by a conductivity meter.

Hard water and solids are not really as bad as they sound. For a 300 PSI boiler the evaporates 200 GPM and runs 24/7 I would use a softener and not go any other way. For a locomotive that runs once a week I would probably deal with the hardness with chemical treatment. If the boiler is blown down, drained/washed monthly, chemically treated, and only run a few days per month the water will never cycle up enough for the hardness to be a problem. The polymers available will bind up the bad guys and keep them from sticking to your heating surface.

Soft water is actually aggressive as water is a solvent and likes to have a solute on board. If you can deal with the solute (iron, silica, magnesium, calcium, etc... ) by binding them up with polymers you are probably better off (not everyone might agree with me on this). Softened water, in it's quest to find a solute will leech metal from everything it is in contact with to gain that solute. Untreated this can cause another whole set of problems but can be remedied by adding yet more chemicals to the treatment program. You will have to test and adjust the polymer treatment according to the manufacturers instructions (there are several programs available).

This is just a quick overview. Forgive me for any typos. I have been working with boilers for 30 years and know this stuff pretty good. I teach boiler operation/maintenance for a living and do private boiler training and consulting as well. If anyone would like more information I am always happy to help out a steam operator with no charge.

I ran a program treating with oxygen scavenger (after presoftening hard feedwater on its way into the storage tank) and altering the blowdown schedule and duration based on frequent boiler water test results. Apart from the scavenger, the only treatment required ON THAT LINE WITH THAT WATER was an addative to keep scale in suspension. I'd not wish to base any traditional treatment program on an ything other than test results, but........

Nontraditionally, the Porta water treatment program seems to offer some advantages. I don't know if anybody in the US has adopted it as of yet, but it seems to have met with success in other countries.

dave

[quote="tomgears"]
All oxygen should be gone and most boiler chemistry people agree that 15-30 PPM of oxygen scavenger should be present. It is better to go over than under, 100 PPM of scavenger will not hurt the boiler, it will cost extra money but not as much as the damage from oxygen pitting.

Tom,
Agree in principle and generally in practice with everything you stated except the above. Most commercial water treaters are not trained, nor do they have a program that is appropriate for steam locomotive conditions.

Oxygen scavengers have their place in marine ( if you can find one ), industrial and utility boiler systems, where there is a deaerating feed tank. These typically reduce the dissolved oxygen level to 40 Parts Per Billion ( PPB ). Cold water holds 7 to 8 Parts Per Million ( PPM ). Injectors and feedwater heaters are incapable of deaeration . We are still cold feeding our boilers, for chemistry purposes, with them.

The common oxygen scavenger is Sodium Sulfite, catalyzed with Cobalt Sulfate, ( SS Cat ), preferrably in easily dissolved crystalline form. Some suppliers provide the SS Cat in an acidic liquid solution of about 33%. The advantage to this is that personnel are not subjected to the hazardous dust evolving from handling the dry form.

Operationally, sulfite is highly electrically charged. This contributes not only to Total Dissolved Solids, but disproportionately moreso to electrical conductivity and the tendency for promoting Galvanic Corrosion between dissimilar metals. Being a sulfur compound, it reacts with calcium present in boiler water which arrived as water hardness ( Calcium and Magnesium Carbonates ). The nasty product is Calcium Sulfate, which is Gypsum, the binder in concrete. This converts a somewhat benign soft and chalky sludge that would have been easily washed out into a hard honeycomb scale that helps other deposits to hide-out.

The uptake on this is that it is futile to attempt to protect a cold fed, oxygen laden feedwater supplied boiler with chemical oxygen scavengers. Don't even think about hydrazine or octodecylamine !

The best protection, IMHO, is to maintain proper ( chemically basic ) boiler water chemistry, with limits on alkalinity to avoid embrittlement. An absolute must, in conjunction with this, is to either use nitrogen blanketing or keep the boiler at or above 220 F and vent off the dissolved gases after adding feedwater. A boiler that has a protective film of Magnetite Hydroxide on all water side steel will not be attacked by 40 PPB dissolved oxygen. Magnetite hydroxide is the natural result of religiously maintaining that basic chemistry.

My background, navy submarine nuclear power, industrial and utility power generation operations and maintenance. Have been at that for 40 years. Have been a steam power fan a few years longer.

Regards, Jim

Well said Jim. I don't disagree with you at all. I am always up for learning more. I worry a little when I hear about steam operators using soft water because I'm not sure everyone understands how aggressive it can be. I did forget to mention about keeping the water above 220 degrees and the nitrogen blanket. The main this is there are a lot of options and the best thing is to figure out what works and keep doing it.

Greetings,
It is such a joy to have a civil and productive discussion on boiler preservation, preventive maintenance and water treatment ! As we all know, this can be a highly charged ( no pun intended ) topic.

Tom covered the concepts of TDS and cycling of water contaminant concentrations very well. I'd like to shine the light onto the topic of Chlorides. The chloride ion comes from dissolved salts, Sodium chloride, magnesium chloride, calcium chloride are some of the more prevalent species, and they vary in concentration and relative proportion from region to region. The really bad thing about chlorides is that they corrode the living daylights out of boiler steel. They attack the hottest parts most; the firebox and tubes. They cause pitting and form Ferrochlorides. This is a particularly fast acting destruction. In a scaled boiler, both oxygen pitting and chloride pitting will progress under scale deposits and in crevices, where there is a concentration cell. This is an electrically driven process. Some treatments programs are capable of producing very clean metal surfaces combined with a micro- thin organic film that is non-conductive. Obviously, this will protect the boiler metal much better than a program that leaves behind a porous and moisture-holding scale.

What are the common sources of chlorides ? They are naturally present in groundwater at a low level. They are increasing in freeze prone areas at an alarming rate due to the use of ice melting agents, particularly calcium and magnesium chloride brines on the highways in winter. I have personally been monitoring a 10 fold increase in ground water chloride levels along US 30 in Lancaster County, PA over the past 15 years.

If you use a water softener, be sure the waste salt is not re-entering your water supply. Also, an incorrectly operating control valve might not be rinsing all the regenerating salt out of the unit at the end of the regeneration cycle. A test kit to check this is available for $ 50 or less. I know of some traction engine folks who, knowing half the story and had enough knowledge to be dangerous, did a bad do-do in their own canteen and learned the hard way.

If you have a high chloride level water source, the chlorides can be removed by Reverse Osmosis . As Tom mentioned, pure water is highly corrosive, so it must be stored properly and must have some treatment applied to make it neutral. It isn't complicated, but it takes a water treater who fully understands the needs and operating conditions of a steam locomotive and tender.

Salts dissociate, or separate into positively and negatively charged ions in water. As Tom said, these electrically charged ions conduct electricity and the more of them there are, the easier the electricity flows. This is conductivity, the inverse of resistance. The old traditional unit is Mho, or Ohm spelled backwards. Now the international unit is MicroSiemens per centimeter2. The units for TDS is Parts Per Million ( PPM ). Anyway, a simple conductivity or TDS tester is available pocket sized and battery powered. Simply, you can measure, monitor, track, predict and prevent significant boiler water carryover into the steam.

Why would we want to do this ? Every drop of boiler water is carrying dissolved and suspended minerals, along with abrasive scale and rust. This junk is going through your throttle and engine valves, rings and cylinder walls. On the way it is sandblasting steam lines, superheater bends and valve seats. It is embedding itself into rod packings, making them into coarse abrasive. Oh, yes, it is also chill shocking superheater tubes and leaving caustic corrosion deposits as the water evaporated to dryness in the superheaters. The pH goes infinitely high in micro cracks and crevices, leading to caustic stress corrosion cracking. Have a high chrome alloy ?
Chlorides also concentrate in these crevices, leading to chloride stress corrosion cracking.

Is all gloom and doom ? No, simply know your enemy !

Boilers don't have to be loaded with crud, scale and corrosion products.
If you want to be " traditional " and do things the 1890's to 1920's way, you are resigning yourself to this. If you choose to ignore boiler water chemistry, you had better love to spend lots of time and money on heavy mechanical repairs. In contrast, a little bit of routine care and some appropriate knowledge will save you a bundle.

Regards, Jim

Some great thoughts Jim. Below is a link to the industry standard conductivity meter by Mryon-L. These little meters cost a couple of hundred buck and are found in tens of thousands of boiler rooms. I still like to use Mho, I know I am stuck in the past doing doing so, I seem to be there with steam locomotives too.

http://www.myronl.com/products/DS_pDS.htm

The Myronl meters are a little more than a couple of hundred but no matter, they are worth every penny.

You can sometimes find these on EBAY at reduced prices.

http://www.myronl.com/products/DS_pDS.htm[/quote]

Would it make sense to use distilled water in a boiler if you could get it dirt cheap?

Disclaimer: Non-expert reply here.

Yikes. I think distilled water would eat at everything.

Steve

Distilled water would be a good starting point...
However, untreated, it would be like filling a boiler with acid.
As I state in my boiler preservation spiel at Rough and Tumble,
water alone is not ' boiler friendly '.

In shop talk, pure water is hungry. It will dissolve whatever is handy.
If it happens to be your pride and joy's boiler or water tank,
they will soon be holed-through, or too thin to be useful.

Much better to deliberately put something into the water that will
both satisfy that hunger and be friendly to the steel. Also...
what is friendly under cold storage conditions must also be friendly
under steaming conditions.

Alkalinity is a good thing, within limits. It comes in two ranges , based
upon the easy and common chemical test indicators. Learn this:
it is possible to have some alkalinity present, even though the water pH
is slightly acidic. The chemical indicator for this is commonly Methyl Orange.
If we add a few drops of this to a fairly clear water, the color will change
to orange if there is some Bi-carbonate present. This would roughly correspond to a pH of 8.4. If we add some known concentration dilute sulfuric acid, we neutralize the
bi-carbonate alkalinity, and the color changes from orange to clear. This is called the Methy Orange alkalinity, or simply M alk. More on this later...

Comparing roughly to pH, the next common indicator for alkalinity is Phenolphthalein.
In this one, we add the P, and the water sample turns a brilliant scarlet red.
Again, we titrate as above until the red or pink disappears to clear. The result is calculated as Phenolphthalein alkalinity, or P alk.

We can have a strong base dissolved in water, and that will give us a certain pH.
Think of the difference between a flag pole and a pyramid. The overall height would be the pH. Yes, we can have a nice pH of 9.5 in our boiler water. However, if there is not enough M alkalinity to support it, like the base of the pyramid, that P alkalinity and the resulting beneficial pH that is protecting our steel, is easily knocked over, like the flagpole in a high wind. In contrast, if there is some M alkalinity, it Buffers the combined solution. Without a buffer, simply having a high pH is like riding a bicycle on a pickett fence; nice trick, but the fall is ugly.

Related to this is the major reason why we need to control and limit the P alkalinity in our boiler water, Caustic Stress Corrosion. Where there is good circulation of water,
there is a constant dilution of alkalinity where boiling is happening. Remember, a boiler is a concentrating mechanism. This is true on the large overall scale of the boiler as a whole, and it is also true on a microscopic level, where the tiny steam ( nucleate ) bubbles are formed. We may take a water sample, say from a lower try cock directly on the boiler shell, and assume that it is a representative average of all of the water in the boiler. If there is decent circulation, this is true. However, if there is a crevice, narrow spot, weeping rivet, staybolt, mechanical mounting stud or pipe thread joint, we have a location where boiling or concentrating is occuring, and there is no dilution. The extreme failure would be a catastrophic joint failure, like a rivet seam or front course. When we see star cracking around a hole, it is this same mechanism, only it hasn't progressed to the point of failure. If I want to split masonry or rock, I drill a row of holes, then place expansion wedges or feathers in them. It doesn't take much for the micro-cracks to line up and grow into a cleavage line.

How to avoid this ? Limit the P alkalinity to 350 Parts Per Million ( PPM ). I go super-conservative with the old steam tractors, and recommend 150 for riveted construction. Welded construction is, theoretically, not as great a concern.
However, a zero-tolerance policy for leaks and weeps is ideal.

Another way to avoid the caustic stress corrosion hazard is to not use an alkaline treatment. Whoa ! Down Brakes ! What was that ?

Not all bases are alkalis. An alkali leaves that white cement-like deposit when it is boiled to dryness. This is the same stuff that builds up in crevices, cracks and weeping joints. This is the stuff that wedges apart the joints and micro cracks, leading to star cracking and caustic stress corrosion cracking. Amines, Ammonia related compounds, can be boiled to dryness without leaving an alkaline, caustic, cement-like deposit. We can get an ideal pH to protect the steel, and it can be self regulating. Some of the ammonia boils off into the steam, this increasing the pH in the steam lines and condensate, protecting piping and superheaters along the way. A few PPM of ammonia in the exhaust is nothing compared to the nitrogen the farmers and lawn care folks are applying. The amine is dosed into the feedwater, so the incoming supply of treatment is fairly constant. It starts working as a cleaner as soon as the heat is applied, so feedwater injectors and check valves stay clean.

Did I mention before that dissolved oxygen control is essential ?

Amines and the beneficial Magnetite Hydroxide film on boiler water side surfaces can be overcome, destroyed, wiped out, by too much dissolved oxygen in a boiler in cold wet layup. This is why industry and utilities use either nitrogen blanketing or dry layup. No cold, wet, non-protected B.S. I have worked in plants where a boiler must be kept full and ready to start on a 1 hour notice. Water at starting level, chemistry is spot-on, simply secure the nitrogen and open the vent. Ready to go, light the fire.

The little live steamers, steam boats, automobiles, now even traction engines, and there are tens of thousands of them all together, are performing warm blowdowns to dryness after they get their boilers cleaned up.