If I owned a steam boiler

hot_rod

I've been doing more fluid quality research for my fall training schedule, the topic comes up more than any other.

I pulled out a Rhomar training manual form a number of years back, some interesting info on steam boiler water quality. Well written, easy to understand lingo. A few statements presented here with permission.
Rhomar hopes to will make updated electronic versions of the manual available soon.

* Steam boilers may require more treatment and attention compared to hydronic boilers due to their tendency to take on more fill water, and much higher operating temperatures.
* Corrosion rate in water solutions tends to double for every 18- 27° temperature increase
* O2 treatment is the most critical part of a steam system treatment.
* Maintain Ph in alkalinity range
* Scale inhibitors bond the minerals in the water making them less likely to plate out
* Sludge is a result of the bonding and settling of the minerals in the water
* Dispersants help prevent sludge by keeping minerals in suspension
* Amines assure that protection moves thru the system with the steam, many chemicals stay in the water and don't protect the piping and radiators.

Seeing pics across the www of failed steam boilers only a few years old, makes me wonder if it is not the boiler brand or models fault, always.

RayWohlfarth

Bob I believe there are some other things to consider when thinking about steam boilers.
Steam boilers require more care as they are constantly exposed to air each time the boiler shuts off.
Corrosion does rise with the elevated temperatures but most steam pipes look brand new when opened after decades of service. The real corrosion seems to be in the return piping. I was taught as a yound boiler guy to alwasy use schedule 80 pipe onthe return because of the corrosion.
You are correct about the O2 concern because of the presence of air. Most chemical treatement I have seen is an all inclusive which has contains an oxygen scavenger, alkalyne, and phosphate. The biggest problem I see is the near boiler piping is incorrect and the system has carryover. When the water goes out into the system, the oxygen scavenger is consumed and that is what is being checked. It causes bouncing water levels because of the excess phosphate and alkalyne.
Amines are rarely used on smaller boiler systems. I see them on larger commercial units
Hope this helps
Ray

Steamhead

And a lot depends on the incoming water supply. Here in Baltimore, it's good enough that cast-iron boilers do not generally need treatment. Steel boilers may, but again it depends on the circumstances of their use.

Boilers that fail quickly are almost always taking on a lot of make-up water. Using water treatment under these conditions is like putting a Band-Aid on a stab wound. Fix the leaks out in the system and the boiler will last.

hot_rod

All good points, Ray. Obviously Rhomar position is to prevent as much air (O2) as possible, and maintain scavengers, and other components to deal with ingress. They suggest monthly testing, compared to yearly on hydronic.

Some suggest phosphates are "old school" and newer polymers and organic inhibitors are better blends?

From what I read amines can be neutralizing or film forming.
Neutralizing to react with carbonic acid formed in the condensate, again due to air ingress. Film forming evaporate with steam to plate out and protect steam piping.

When the steam cools and CO2 is absorbed to form carbonic acid in the condensate, ph drops, possibly into the 4's so the condensate lines take the hit.

I believe the Rhomar 903 includes all these ingredients. Certainly a steam treatment expert would test and blend a treatment to a specific condition, if needed.

Remembering what Tony Conner wrote here back in 2000
"Get all the condensate back that you reasonably can, and you are way ahead in the chemical/ water treatment game"

Assuming as you noted the system is piped properly to allow all this to work correctly.

I imagine, like hydronics there are many opinions on how best to treat stem systems. Or not
Is there much tap water out there that is acceptable steam boiler feed water, without some intervention?

Canucker

It sounds like that set of instructions was written with process steam in mind, more so than residential. That can use a lot of make up water and you definitely need to have a chemical treatment regimen. I think it would be good to have O2 scavenging in any boiler but how much oxygen gets in an idled steam boiler system?

RayWohlfarth

I had a steel fire tube fail after only two years and they found it was chlorine in the water which caused it and they had not treatment. A steel water tube failed in only a year from the same cause.

Steamhead

RayWohlfarth said:

I had a steel fire tube fail after only two years and they found it was chlorine in the water which caused it and they had not treatment. A steel water tube failed in only a year from the same cause.

Obviously, in that case they did not test the water supply until after the fact.

Was this for a process or heating application?

Jamie Hall

It is well to remember that there are really three classes of steam boiler, with very different conditions and treatment regimes. These are process steam; generally moderate pressures and corresponding temperatures (say up to 200 psig), but usually a lot of makeup water to replace lost process steam. Then there are power boilers, which may quite commonly run up to a thousand psi -- and back down to a near complete vacuum -- but which use, relatively speaking, very little makeup water and are completely isolated from the atmosphere while running (cold layup of a power boiler is a completely different animal). Then there are heating only boilers (the ones we usually talk about here) which run with very low pressure and almost negligible variation in pressure across the system, and which -- like power boilers -- should use almost now makeup water. Unlike power boilers, they may allow some oxygen into the piping but not the boiler or boiler water to any significant degree.

A water treatment regime suitable for any one of those three will not be suitable for the other two.

RayWohlfarth

@Steamhead It was for space heating. The site was in WV and there is speculation it could have been that chemical that was released a few years ago which shut down the county for a week

Steamhead

This one?

https://en.wikipedia.org/wiki/2014_Elk_River_chemical_spill

GBart

I also think there is something wrong with the castings, could be a combination of thinning them for more profit and changing the mix in the foundry, again to increase profit, because boilers made in 1900 are still around with no treatment or care.

WWII was the catalyst for steel and foundry innovations, to make more with less.

RayWohlfarth

@Steamhead That was the one Yes. It was so weird seeing a whole city shut down, like somthing from a movie.
@GBart I had often wondered that

GBart

Aye, well in the late 80's I believe I noticed a certain brand got incredibly lighter, I thought I got stronger until I compared the weights, they dropped 100lbs, that's a lot of metal and they started having failures.

Did they save anything? make more money? I doubt it but I'm sure they had a pie chart that proved they did.

RayWohlfarth

@GBart I bet the weight loss helped with heat transfer and efficiency

AMservices

I'd like to ask a question.
Why can't boiler manufacturers make a stainless steel steam boiler?
It wouldn't have to be as thick as cast, so heat transfer would be quick.

If the people in charge of designing boilers, put a little more effort into developing a new steam boiler, A lot of these problems would go away.

For instance,
Not putting a crap pressuretrol, set to ten psi on a packaged boiler.
How about cleaning the metal shavings and oil out before putting the jacket on.
Maybe insisting that the installer uses 2 risers and pay more attention to what exit velocity is.


If manufacturers put half the effort they do dreaming up hot water boilers into a steam system, There would be automatic Drain valves that would Activate from a maintenance timer and then fill it self backup.
If a steam boiler was made out of stainless steel, Too much feed water wouldn't be a problem and they would probably Find a way to make them whole house humidifiers.
There would be fully modulating burners operating on ounces of pressure.
Vacuum system that could run steam at lower temperatures.

If I had a steam system, there would be nothing stopping me.

GBart

RayWohlfarth said:

@GBart I bet the weight loss helped with heat transfer and efficiency

customers and contractors weren't impressed with the cracked blocks and they use AFUE which is a lie for Eff, people are still replacing these blocks