Rotted boiler sections

Ray Binder

Exactly four years ago I replaced a customers steam boiler with a new Dunkirk 400MBTU steam boiler. Did everything by the book, and it ran perfect from day one. Yesterday the customer called me and said there was water pouring out from the bottom of the boiler. Sure enough as soon as the boiler ran for about three minutes, water started drenching the burners below. I also noted that the burners had rust deposits on them across three quarters of the boiler. I separated the sections and couldn’t believe my eyes.. Section one, nearest the makeup water was rotted out about two inches above the water line across fifty percent of the section. Section two, a little less, Section three had a hole the size of a quarter, and section four had a small hole in it as well. All above the water line, within two inches from the top of the section. My first thought was a broken return line causing the boiler to constantly make up water. But there are no underground returns, and everything is tight. Dunkirk says its the PH of the water, but the boiler I replaced lived there for over twenty years. Anybody have any thoughts?

EBEBRATT_2

What about stem leaks in n undetected location? You could lose a lot of water that way.

Robert O'Connor_7

Judge Wopner../

Did the previous install include an auto feeder perhaps? Why did the last boiler fail? Without more info, the wrong PH and excessive make up would certainly be high on my list. Find out why it failed and fix it before another one bites the dust before its time. If you still want to use an auto feeder, get one with a meter and adjust your PH as well...Robert O'Connor/NJ

James Macnab

Dunkirk Boiler

I could only guess a bad casting if the old unit lasted over 20 years Did Dunkirk ask for a water sample which may have changed over time. The real question is, did Dunkirk make good on the warranty? including labor I was told these had the best warranty in the busineess and I am about to replace my existing boiler (55 years old) with a Dunkirk. I realize this is a selfish request but I would really appreciate your comments as a profesional about this company and product.
Jim Macnab
23 Beech St
Franklin, NH

Unknown

There's more to it......

Speaking for all boiler manufacturers in general, it is more than just excessive makeup water. Here is a list of things that can simply kill boilers. Why it didn't happen with the older boilers has a lot to do with the physical size of the sections, water volume, time it took to make steam and the fact that those old castings were much thicker with a lot less effeciency.

Uninsulated Steam Mains (The OLD boiler usually still had the insulation on the mains.....all be it Asbestos though.)

Insufficient or non-functioning Main Vents (Slow venting combined with uninsulated mains will put combine unvented CO2 with excessive condensate producing Carbonic Acid and altering the PH of the boiler water.)

Near Boiler Piping Methods

Near Boiler Piping Materials (Copper can cause a Galvanic Reaction if electrolytic conditions are just so)

Steam Leaks in System or Radiators (Remember that they may not be visible at room temperature....a mirror or cold water bottle will bring those leaks to life)

PH of Water

Softened Water

Excessive Makeup Water

There are other things but these are the ones that always seem to rear their ugly head at times like this. They are NOT boiler problems at all.....they are System problems and have to be dealt with. The reaction I usually get in cases like this is that the older boiler lasted 20-30 years and that it will cost more to replace the insulation than it does to replace the boiler. The latter may be true but it has to be dealt with. Hope this helps.

Glenn Stanton

Burnham Hydronics

Steve Ebels_3

Glenn

I have never heard a good explanation as to why softened water is death for a steam boiler. Does this also hold true for a process steamer where all heated water is lost? Please enlighten my troubled mind.

Unknown

Steve

I don't claim to be the brightest bulb on the tree when it comes to chemistry, but from what I am told by those that are it has to do with the protective layer or skin that the natural minerals in water provide on the inside of the boiler. As far as processing boilers go, doesn't heated water tend to remain more deoxygenated? Maybe someone else can add some more scientific detail to this.

Glenn Stanton

Manager of Training

Al_19

Glenn---Wouldn't mineral buildup in the boiler be a bad thing--decreased heat transfer or hot spots in the cast iron? Also, a softener exchanges sodium or potassium for the calcium in the water, but it doesn't reduce the total dissolved solids. I would think that deionized or r.o. water would be bad because the minerals have been removed, but not so with softened water. Also, wouldn't excess minerals, especially calcium which is more prone to scaling out, create more problems in feeders/prv's strainers?

Unknown

Al

Like I said....I don't profess to be an ace in water chemistry. I am going by what I am told that softened water is not neccessarily a good thing for a steam boiler. Neither is water with excessive mineral content. That is why we would like to keep makeup water to a real minimum. That brings us back to the issue of checking the integrity of the system to keep makeup water to a minimum. Although auto water feeders may be a neccessity for some installations due to older occupants or absentee landlords, they tend to act as a Bandaid for leaking systems and a Canker Sore for the boiler. Water usage does still need to be monitored. Companies such as HydroLevel can be praised for their work in trying to accomplish this.


Glenn Stanton

Manager of Training

Burnham Hydronics

Ken_8

Read what he wrote again...

ALL CORROSION, DAMAGE AND LEAKS ARE ABOVE THE WATER LINE!

That's an essential and critical aspect of information IMHO.

It is also the most puzzling.

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tim smith

rotted boiler sections

The last one I found like this was a V9 boiler. It rotted the upper 1/4 of a few sections. I am pretty sure it was that the boiler when assembled on site by (installer) was never totally tight. You could see evidence of steam leaking inside flue collector and it showed to be rotting from outside in. Just FYI, good luck. Tim

Tony Conner_2

Boiler Corrosion...

... and deposits can be a real spiderweb of interlocking factors. pH related corrosion is typically a general, all over, wasting of the metal below the water line. Oxygen corrosion shows up as localized pitting. I think if acid condensate (carbonic acid) was a issue here, you'd see grooved-out condensate piping. Anything I've seen regarding condensate lines in little domestic steam heating systems shows the classic oxygen related carbuncles & pitting, rather the grooving typically seen in industrial or institutional systems. You CAN get a bit of CO2 forming from air pulled in from steam system vents, but the great bulk of the problem stems from alkalinity in make-up water breaking down into CO2 under boiler conditions, being carried out with the steam (it's not enough to be noticed, or make any difference - yet), then dissolving into the condensate. This will typically give you condensate about the same pH as soda pop. This is bad news for the condensate system.

The corrosion 2" above the water line sounds like oxygen pitting, occuring on start-up. As steam boilers fire-up, the water level "swells" due to steam bubbles forming in the boiler water. (These bubbles take up a lot more space than the water from which they were formed, so the level goes up.) If there's any dissolved oxygen present in the upper water level, then it will tend to be driven-out as the boiler comes up to operating temp. If this is the case, though, there should also be some oxygen pitting evident along the water line when the boiler is sitting cold. Pictures would really help.

Softeners should be kind of a non-issue with boilers like this. If you have so much make-up water that a softener is being considered to deal with scaling problems, then you'll kill the boiler in short order with dissolved oxygen corrosion anyway.

And I've gotta ask - any COPPER return lines in this system? Dissolved copper being dumped back into a boiler can cause corrosion that looks very much like oxygen pitting. I absolutely hate to see copper piping for condensate service, for exactly this reason. I'd use stainless steel before I ever considered copper for steam condensate service.

The attachments are from the "Betz Handbook Of Industrial Water Conditioning".

Jim Davis_3

boiler rotting

Having been on hundreds of commercial and industrial steam boilers, I have never seen a water softener be the cause of boiler corrosion, not to say it can't, just haven't seen it.
Electrolysis can be a possibility because of dissimilar metals but usually this appears close to where the pipes are connected. I have seen where old black iron piping actually changes its properties and becomes disimilar. Running a good ground to the piping can eliminate this. I have seen cast iron boilers rot from the outside in from flue gases condensing from venting issues and even less than 4 years. Flue gas condensate is just as acidic as steam condensate and might explain why the corrosion is above the water line. If there is a lot of water or steam leaks there would also be excessive scale buildup on the inside of the boiler which would cause outlet flue temperatures to be excessive.