Has anyone experienced either a boiler tube or firebox sheet problem in the last 5 to 10 years that they felt was premature for the length of time the material has been in service? I have had conversations with a number of operators who are experiencing this issue and would like to see if more cases exist to see if this is an issue that we as an industry should be addressing as a whole(through education) rather than each operator doing his own thing, or someone ignoring the problem, with a volunteer/employee getting injured or worse and the regulators step in and change the rules for all of us. From what I have heard, it seems we might need to adjust our boiler wet lay up practices to prevent rapid excessive corrosion. No need to use names or locations, just the facts. If you are not comfortable with posting your information, please email it to me.(Use the button below the post for email).
Thanks in advance for your cooperation,
Mike Tillger

Just one - and I believe it was an engineering issue rather than a material failure. Two sheets of vastly differing thickness were welded at 90 degree angle, the thinner sheet suffered a crack just at the edge of the weld fillet - FTS (1") joining crown (3/8").

dave

Ideally, for minimum corrosion, boiler water should have a pH of 10. Remember, the pH scale runs from 1 to 14, less than 7 is increasingly acidic, 7 is neutral, and above 7 is increasingly basic. Neutral water, like we drink, is like an acid to boiler steel.

The traditional way of achieving this is to add an alkaline chemical ( base ),
such as Sodium Carbonate ( Soda Ash ) or a form of Phosphate.
It is imperative to monitor and control the water conditions in the boiler frequently.
Daily monitoring of an operating boiler is ideal. Also, and ATSF found this and documented it well, buffering the water with a nitrate to help prevent Caustic Embrittlement of riveted joints is also best practice.

In this era, there are tried and true treatments that are available, among them some
modern treatments that are easy to use, do not require the handling of hazardous chemicals and do not require frequent blowdowns, wasting water, fuel and treatment chemical. The tests that should be performed on boiler water are simple. They are no more complicated than making instant coffee or reading a digital thermometer. A person does not have to be a chemist nowadays, simply follow 5 or 6 easy steps.

When it comes to dry layup, the best available practice is to clean and dry a boiler, then close it back up with a nitrogen atmosphere inside.

For wet layup, a nitrogen blanket on top of the normal steaming water level in the boiler is best practice. This is standard procedure in the power generating, marine propulsion, and refinery and general industrial steam generating field. This is valved in before the boiler cools down and the steam condenses. This way, the boiler draws in nitrogen rather than air, which is 21% oxygen. Also, cold water at 70 F holds more than 200,000 times more oxygen than steaming water at 220 F.

The use of sulfite oxygen scavengers is futile on boilers fed from a cold water source.
Sulfite does have it's place, and that is with preheated and deaerated feedwater in a stationary or marine installation. I have yet to see a locomotive with a deaerator. A feedwater heater or injector is not a deaerator. Furthermore, sulfite is documented to actually promote corrosion when cold, and it makes ordinary calcium carbonate scale into tenacious calcium sulfate gypsum, the binder in concrete.

If you are going to start using nitrogen blankets in a boiler, maybe it is a bit obvious but still worthy of note, make sure that you clearly have a tag or labeling system in place especially above the steam dome in case during restoration some one decides to say climb inside and work on the locomotive. A lot of volunteer restoration projects I have seen can have guys coming and going and not always being informed of what some one else did the other day other than to see it got done. Nitrogen in a boiler isn't something you will see to easily. In the power industrial boiler side of things I have heard a few stories of men climbing into drums while under nitrogen blanket and not returning.

I also think if I am not mistaken that even thou it is 80% of air it is still a bit heavier than an air oxygen mix so if you drained it from the boiler and were over an inspection pit, I could see hopping into there with out good ventilation may be an issue too. Am I wrong?

Most small railroad operations I've been to in their restoration shops follow what I would consider good common sense rules of restoration but more often than not I can't say they are OSHA compliant. I don't know how many locomotive shops out there do a proper confined space sniffing before hopping in but if you are going to get started with nitrogen blankets and no sniffing I would think that having some sort of fan system in place would be prudent.

Adam

I interpret the original post as not concerned with corrosion, but with material quality. Am I wrong?

Mark and all,
The original concerns come from premature failures of new (last 10 or so years) boiler material (tubes & sheets) that have excessive corrosion developing, while the "original" boiler materials remain unaffected. An example is where a new firebox patch has been installed and welded to the "original" sheet, and the new patch needs to be replaced yet the old sheet is still acceptable for reuse. Another example is the premature failure of 2" tubes by excessive pitting, randomly down the length of the tube, while the rest of the tube was unaffected. Yet another locomotive experienced premature failure with pitting only on the top longitudinal surface. Just looking for more info and to see if this is affecting others in the industry.
Mike Tillger

Mike, I have seen this rapid loss of metal on a number of boilers. One door sheet section I saw was reduced to minimum thickness in places after 700 days of service, over a 10 year period. I have done some research into this, and will offer these points.

First off is makeup water and water treatment, I believe there can be a fine line between success, less than idea success.

Oxygen in the water, bad, very bad.

Excessive copper levels in the steel, under certain condition cause rapid metal loss.

New steel may also contribute to the rapid loss of metal, I spoke to our pal D S Young about this and he has indicated that new steel is very clean. Meaning the intergrainular boundaries are also clean, so that if corrosion begins the grain boundaries will not impeed the corrosion. As opposed to wrought iron, which is quite corrosion reistant.

Also, there is an acellerator in oxygen scavenger chemicals that may contribute to corrosion, under certain conditions.

I believe that water treatment must be done in a scientific and deliberate manner if it is to be benificial.

As for wet lay-ups, probably not a good idea especially if there is disolved oxygen in the water.

Sacrificial anodes may also have their place.

Any one of the above points may not be disasterus to your boiler, but the right combination can be. I pitty the new boiler owners who may not have a handle on water treatment, will they have have a nice boat anchor in 15 years?


My thoughts...

Robert Yuill

Is this something that the application of Apexior to cleaned surfaces (both new and old boiler steel) would allieviate?

Some disturbing "reports from the field" here.

Howard P.

OK....I'll go out on the limb here:

Galvanic Corrosion?

I know we're talking about similar metals, not dissimilar metals, but are they dissimilar enough???

Related to what Hogger and Robert said, the oxygen content of water can be reduced by bubbling nitrogen up through it (we used to call it "sparging" but I don't know if that's standard nomenclature). I've seen it done on stored steam plant feedwater but it should work for a boiler just as well.

Vent the boiler and admit nitrogen to the wet boiler through a blowdown valve so that the nitrogen bubbles up through the water. After doing that for a reasonable time, close the vent which leaves a nitrogen blanket on the water. That would be a good way to do a wet layup if anyone has to do it that way.

Greetings:
A couple of quick comments:

Howard mentioned APEXIOR No. 1, an excellent product which I have used for about 40 years on various boilers in my care. Both of our locos. here at the Valley have been so treated and you can still see the brush marks. Zero scale on the boiler interior. But, it has to be painted onto freshly sandblasted surfaces, which leaves out virtually all of the firebox. I have heard of painting tubes & flues but have never tried it myself. Note: I do not own stock in the Dampney Co.

What we have done for the tubes and flues has been to passivate them after installation using DEHA as our oxygen scavenger for the first week of operation. I would use DEHA on a regular basis except that the steam smells funny and it is rather expensive (being a rather penuriouos sort, that is a major factor).

I was surprised to learn from a post in this thread that sulfite doesn't work as an oxygen scavenger. Depending on the water characteristics and available funds, I have found sulfite to be the most effective (results & cost) oxygen scavanger available. We have used nothing else during my time here at the Valley (23 years, but whos' coounting). I invite any of you to drop by during annual instections and check our tubes for active oxygen pitting. Wayne retubed our No. 97 in 1996 and we haven't touched a tube since. It has 87 (but whos' counting) FRA "Service Days" left to run before it will be due for its' next 1472 day inspection.

I understand the concerns that some people have with "modern/new" steel, but, in my opinion, if the correct, certified steel is chosen, it is properly prepared prior to installation (anneal tube ends, etc.), properly installed (tubes properly fit to holes and not over rolled), the boiler properly handled (slow fire ups and cool downs, leave firedoor closed except to add coal, etc., etc.) AND a water treatment program is conducted which addresses a minimum of free oxygen, Ph, and TDS/conductivity which is monitored and adjusted to suit ON A DAILY BASIS; then I wouldn't worry too much about the steel.

J.David

I wish the experiments with Porta water treatment, whivch have now been under way long enough to establish a track record, would be described in this thread. Anybody working on it got your ears on?

dave

You responded to your own statement, coating the I.D. of the barrel is fine, but coating heat transfer surfaces is Nix Nix, IMHO. It's on a par with painting your vehicle's brake drums then descending a steep mountain road with lots of switchbacks. Paint kills heat transfer.

Passivating with DEHA is more than scavenging the oxygen, if you read the MSDS, note that the pH is in the 11 range. Having a moderately basic water is also important in achieving passivation of steel. Here is a webpage comparing various oxygen scavengers, it is obviously pro DEHA; http://www.arkema-inc.com/literature/pdf/346.pdf

Please don't jump to Sulfite not working as an oxygen scavenger. I should have made myself clearer, the disadvantages can outweigh the advantages. There are many variables, chiefly a.) the proportion of time that a boiler is in cold wet layup vs. steaming. b.) the amount of blowdown the boiler is given, and the resulting Total Dissolved Solids ( TDS ). Sulfite is a strongly electrically charged ion, and it takes 8 parts of Sulfite to remove 1 part of oxygen, plus maintain a 20 Part Per Million ( PPM ) residual. Add to this that there is a constant intake of oxygen from feedwater. The result is that boiler water TDS can get to the point of carryover, and in more severe cases, foaming, by having too high a TDS.

There have been some very good additional comments regarding nitrogen blanketing, especially with regard to safety and confined space atmosphere. I would like to point out that the most economical application of nitrogen blanketing is with the vacuum breaker and 2 stage regulator. Nitrogen is only flowing as the boiler is cooling,and at 11 inches of water pressure, then it can be shutoff, $aving dollar$.

I have to come down on the side of old steel being more resistant to corrosion than new steel. I base this opinion on what I have seen over the years where you can see the differences in the same boiler. On our #89 for instance, we replaced the entire length of both side sheets at the mudring because of grooving. The sheets, and of course the staybolts (About 450) were replaced and first put in service in the late 80s. In addition to the sheets being grooved, we replaced about 40 additional staybolts besides the ones that were removed because of the grooving. The reason for that was while inspecting the surrounding areas; we noticed tremendous corrosion on the bottom sides of some of the bolts along with the usual stress corrosion. With the corrosion on the bottom side, that tells you that it was caused when the boiler was emptied and the water hung on the bottom side and started the corrosion process. The top side had next to no corrosion. What really got our attention was that only some of the bolts were that way. Even though they were put in at the same time, not all of them were from the same “batch”. Some were old stock and some were bought new. Going by memory, we ascertained that the majority of the bolts put in during the late 80s were old stock, and the vast majority of the bolts were fine. We had one of each tested and found the bolts that were severely corroded had a higher percentage of copper in them. The other mostly uncorroded bolts were lower carbon and much lower copper. Does that mean the high copper content set up a dissimilar metals scenario within the bolt itself?

I have seen pitting on one flue and no corrosion on the one beside it after several years of service. There were put in new and were all the same heat number.

We visited a large boiler company a couple of years ago and I asked them what a normal life expectancy of their boilers was. I was told that 15 years was it. You throw it out and get another new one. It didn’t used to be that way.

I’m not a chemist or a metallurgist and I don’t play one on TV.

In a traction engine boiler, I have seen the bottom side of staybolts nearly cut through by corrosion right next to the firebox, with the balance of the bolt fine. My assessment was liberated oxygen from steam bubbles formed at the firebox sheets streaming upward, and this oxygen attacking the staybolt which was "in the way" of the bubbles path. I welcome any comments or insight on this type of corrosion attack.


Yes, I see that all the time in my work.