Any water treatment gurus? Leaking steam boiler expert?

RayWohlfarth

I have a customer with a vertical fire tube steam boiler that developed a leaking tube after only 2 years. They pulled the tube out and I was hoping someone would look at the tube and see if you know the cause. It was right at the water level. I believe it is caused by oxygen pitting. Let me know what you think.The customer said water treatment was done.
Thanks
Ray

EBEBRATT-Ed

Is this high pressure steam, like a laundry or something? Do they get all the condensate back or is their a lot of make up water?

Do they have a deiaireator?

RayWohlfarth

Ebebratt Low pressure steam all condensate is returned and no dearator

hot_rod

What I have been learning about water quality over the past several years is the TDS both on steam and hot water boilers is often the cause of problems like that.

But a water quality expert should know that especially if the deal with steam specifically.

Good info here. These folks know steam

http://www.spiraxsarco.com/Resources/Pages/Steam-Engineering-Tutorials/the-boiler-house/controlling-tds-in-the-boiler-water.aspx

nicholas bonham-carter

What sort of "treatment was done"? In a non leaking system, with very low makeup water, the oxygen should have been driven from the system. Chemical analysis of the feed water might show some impurities which could be to blame, and in this case, a purifying filter would help.
Maybe it was the medication which killed the patient, and not the disease!
Large fluctuations in water level, while operating, caused by improper piping, could also thermally stress the metal.-NBC

RayWohlfarth

Hot Rod Thanks Spirax Sarco has some really good info on steam. I use it for research. I know the customer have had some issues with elevated TDS. They are seeing lots of junk from the system being flushed back.

Nicholas, they are using a combination water treatment which uses sulfite as the oxygen scavenger. The owner is upset that a two year old boiler leaked. The water treatment "expert" is throwing the boiler manufacturer and me as the rep under the bus. I think the oxygen scavenger was too low.
Thanks

nicholas bonham-carter

Where in the system could the oxygen have reentered once it has been boiled off? Are there significant leaks, and an auto feeder?
Could there be any chemicals stored nearby, whose volatile fumes could have been sucked into the burner?
An analysis of the feed water may show some bad components of the water as well.--NBC

hot_rod

For corrosion to happen you need the fluid, (water), and O2. Look for wherever O2 could be entering on an ongoing basis.

Once water in a closed system is heated for a few days all the O2 is consumed in the corrosion process. It will rust or oxidize ferrous componets in that process. After that it is considered "dead" water or O2 free water.

The classes example of O2 ingress is non barrier pex used in hydronics. Under favorable conditions, like high temperatures enough O2 can enter to start pin holing expansion tanks and corroding the system, sometimes within a year. That was the case with high temperature fin tube systems connected with the early non barrier rubber hydronic tube products.

I suspect you have two things going on, insufficient chemical balance and high TDS water, and the high TDS could be chlorides which makes things even worse. Also low levels of O2 scavengers can cause even more aggressive corrosion attack as some metals are not sufficiently protected, while some are. Does the conditioner also have a film provider component?

The water should be sampled at the time the problem was discovered. The evidence may be gone by now.

I doubt that is normal for a boiler that young.

A good lab can usually reverse engineer the cause of the failure.

jumper

Usually condensate lines rot out long before boiler tubes. If it's only one tube then most obvious suspect is the tube rather than water. Also may be coincidence that failure is near waterline. Could be a local metallurgical defect?

Sometimes a commercial water heater lasts much longer than others of the same kind under same conditions. Metal was somehow better on that tank bottom? Manufacturers have long known that longevity statistics are a bell curve. So maybe that tube came from left side?

When it costs you money,you want to know. But honest answer is you don't.