boiler lay-up question

[Deleted User]

boiler for the past year..so far so good tho..we like the 4'' tappings..we like the push nipples..

[Deleted User]

the dunkirk 247 steam boiler

recommends in their installation instructions to entirely fill the steam boiler with water during the summer months to exclude air...does anyone else do this? what are the pro's & cons of this practice...we've always just left the boilers in a standby condition throughout summer....any thoughts would be appreciated.

Boilerpro_3

I've read that elsewhere too...

sounds like a good idea. It would put that corrosion point at the water line up in the piping. I'd just try to make sure that that piping was easy to replace. I am installing a 247 steamer with CSD-1. What's been you experience been with his boiler, Gerry? Someone posted awhile back they were having problems with the burner controls cuttting out on the CSD-1. Nice wide sections with lots of water and two big 4 inch tappings (on the side though).

Boilerpro

Tony Conner

That's One Way...

... to lay-up a steam boiler. You really should check it periodically though. If a drain valve leaks, the water level will slowly drop. The top layer of water will absorb oxygen from the atmosphere, and you'll suffer oxygen pitting at the water line. If the water level drops so it's down in the boiler, that's where the pitting will occur.

I think a better way is to drain the boiler completely, open up any inspection handholes, etc. and flush it out with a hose. Leave everything open, and the make-up water source off, with the union broken so there's no way water can get into the boiler. There is no periodic maintenance required with this method. Close-up and refill the boiler in the fall. As soon as it's filled, fire it just enough to make some steam, even if there's no call for heat. This will drive off the dissolved oxygen that arrived with the fill water.

[Deleted User]

thanks tony- question tho

I think i like your method better..is there anything in writing anywhere that says thats an accepted practice tho? reason i ask, is the homeowner will naturally want to follow the installation instruction booklet which is calling to fill the system..i figure that anything is better than just leaving the boiler idle, half full..i would think its absorbing air from the open air vents?..if i remember right, in the navy, our boilers were never left idle with water in them,,they either were pressed up with nitrogen, or drained and open like you said...since i'm putting in a new boiler for the customer i want to get the thing off to its best start with correct maintenance and layup.

Bob_19

Boiler Layup

There are 2 methods for laying up boilers, wet and dry.
The duration and type of boiler material will determine the method.
Anything less than 3 months should be layed-up wet, and if it's cast that's more of a reason for this method, here's why.
Cast being a more pourous metal than steel will retain some moisture when drained. When a boiler is emptied an absorbant, say lime, should be put into the boiler to remove any stray moisture, and replaced on a regular basis, this is the prefered method for long term(dry) lay-up. But this is not practical for a homeowner.
If any moisture is left behind and not treated fore it will cause undo corrosion.
It would be advisable to use the wet method for seasonal shut-down.
At the end of the season drain and clean internal surfaces, then refill above gauge glass, after boiler is filled close headers and open vent, then steam some of the water off, this will help to remove any excess 02 and mix chemicals into water, shutdown boiler, if traps are used then watch for vacuum build-up, vent as needed, and at beginning of season just empty, refill and steam away.

[Deleted User]

ah-okay, I think i understand now

why the manual calls to lay it up wet..thanks Bobby

Steamhead

BP, that job is shaping up nicely

love to see a pic when it's done!

Side steam tappings aren't so bad. On Columbia gas steamers, we hook them up the same way you did there, except we install the tee with the run horizontal. This not only lets us use it as a skim tapping, but we can also stick a hose thru that run if we need to power-flush the boiler.

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Tony Conner

Corrosion Of Cast Iron Vs Steel

I was curious, so I dug through a pile of books, and I can't find any reference anywhere that mentions the porosity of cast iron vs steel, let alone one specifically dealing with corrosion. The only info I can locate is in the "Mechanical Engineers' Handbook" (1916) by Marks, and "Marks' Standard Handbook For Mechanical Engineers" (1979). (This is the 1st edition and the 8th edition of this book.) The wording is identical - "Under similar conditons, iron and steel corrode at practically the same rate. Steel, however, corrodes more uniformly than iron."

With a wet lay-up, you've just gotta periodically check the water level in the boiler, if nothing else. I've seen big boilers under wet lay-up where the blow down valves leaked by, and the water level gradually dropped down into the boiler proper, over the summer. Nobody was checking it - it got lost in the summer vacation shuffle in a plant that was shorthanded at the best of times.

Wet lay-ups ARE the best - IF you've got somebody to fire the boiler weekly, test the sulfite level, and make sure it stays FULL of water. If you haven't got the resources to do that, then go dry lay-up. Dry lay-up = zero maintenance.

Is there a specific instruction on this subject from the boiler manufacturer(s)? If there is, then it should be followed.

[Deleted User]

thanks tony

whats does the sulfite do anyways? all we ever check is the ph..these are residential boilers by the way..

Tony Conner

Sulfite...

...is an oxygen scavenger. It'll grab the dissolved oxygen and hold it, so it can't pit the boiler. Testing for oxygen requires a bunch of equipment, and is pretty involved. Testing for sulfite is relatively easy. (Just a wet chemistry colour change.) In industrial boilers, the water (condensate and make-up) gets sent to a deaerator that mechanically strips dissolved gases (oxygen is the biggie) out of the water. No DA is 100% effective, so sulfite is added to tidy-up. If you've got 30 - 50 parts per million (typical levels) of sulfite on your test, then you're sure that there's no dissolved oxygen running around, pitting things. For an industrial boiler on wet-lay up, the sulfite levels are usually jacked-up to about double the norm. Residential boilers won't likely get into stuff like this. They should be getting almost 100% of the steam they send out back as condensate. If you're getting all of the condensate back, chemical treatment isn't much, if anything. Make-up water is bad news, unless you're in a big steam plant that's got the equipment to deal with it. And even there, get all of the condensate back that you reasonably can. It's already soft, it's already almost deaerated (because it's hot), and ... it's HOT. Nice running start for the boiler to turn it into steam again. Plus, the more chemicals you add, the more you have to blowdown the boiler, so more hot water is lost in that process too. Dealing with make-up water is expensive, for a whole bunch of reasons. Get that condensate back - it really matters.

Bob_19

I Probably

should have clarified pourous as not meaning absorbing.
Cast boiler sections have a texture( rough ) surface and will hold water and not allow quick sheading of it, it stays there and increases rust formation.
Most residential users probably don't treat for oxidation, and 1 other concern is if they run fire weekly they are adding more raw water. Now if we have a boiler on stand-by, then yes it is keeped in a ready state by running on a more frequent schedule, and treated.
In a industrial setting a boiler is usually never layed-up wet, either it's on stand-by, or taken completely off-line and opened for inspection. On residential and commercial wet lay-up is the prefered method, but if not watched then any system will fail in time.

Gerry: Sodium Sulfite is for the removal of free oxygen,sulfite mixes with 02 and forms sulfate, test by checking for residual sulfite levels in the boiler level to ensure constant protection from oxidation, fyi: sulfite works better on a firing boiler.

Boilerpro_3

Side tappings really do make inspection possible.

I always love it when a boiler manufacturer says to flush the sections out with a strong steam from a hose, but leave you no way to do it because it only has large tapings on the top! This was my first install with one of these, so I still haven't got the best piping layout for it yet. Dunkirk also changed the tappings, without changing the installation instructions, so I was unprepared for some aspects of the installation. Maybe I'll just pull that elbow apart and turn it. I was planning on leaving a hose connection on the bottom for a nice long steady skim, but ended up putting a 1 1/2 inch skim valve on the other side that is going to go directly to the floor drain.

Boilerpro

neilc2

wet layup / weekly fire?

> I was curious, so I dug through a pile of books,

> and I can't find any reference anywhere that

> mentions the porosity of cast iron vs steel, let

> alone one specifically dealing with corrosion.

> The only info I can locate is in the "Mechanical

> Engineers' Handbook" (1916) by Marks, and "Marks'

> Standard Handbook For Mechanical Engineers"

> (1979). (This is the 1st edition and the 8th

> edition of this book.) The wording is identical -

> "Under similar conditons, iron and steel corrode

> at practically the same rate. Steel, however,

> corrodes more uniformly than iron."

>

> With a

> wet lay-up, you've just gotta periodically check

> the water level in the boiler, if nothing else.

> I've seen big boilers under wet lay-up where the

> blow down valves leaked by, and the water level

> gradually dropped down into the boiler proper,

> over the summer. Nobody was checking it - it got

> lost in the summer vacation shuffle in a plant

> that was shorthanded at the best of times.

> Wet lay-ups ARE the best - IF you've got somebody

> to fire the boiler weekly, test the sulfite

> level, and make sure it stays FULL of water. If

> you haven't got the resources to do that, then go

> dry lay-up. Dry lay-up = zero maintenance.

>

> Is

> there a specific instruction on this subject from

> the boiler manufacturer(s)? If there is, then it

> should be followed.



> I was curious, so I dug through a pile of books,

> and I can't find any reference anywhere that

> mentions the porosity of cast iron vs steel, let

> alone one specifically dealing with corrosion.

> The only info I can locate is in the "Mechanical

> Engineers' Handbook" (1916) by Marks, and "Marks'

> Standard Handbook For Mechanical Engineers"

> (1979). (This is the 1st edition and the 8th

> edition of this book.) The wording is identical -

> "Under similar conditons, iron and steel corrode

> at practically the same rate. Steel, however,

> corrodes more uniformly than iron."

>

> With a

> wet lay-up, you've just gotta periodically check

> the water level in the boiler, if nothing else.

> I've seen big boilers under wet lay-up where the

> blow down valves leaked by, and the water level

> gradually dropped down into the boiler proper,

> over the summer. Nobody was checking it - it got

> lost in the summer vacation shuffle in a plant

> that was shorthanded at the best of times.

> Wet lay-ups ARE the best - IF you've got somebody

> to fire the boiler weekly, test the sulfite

> level, and make sure it stays FULL of water. If

> you haven't got the resources to do that, then go

> dry lay-up. Dry lay-up = zero maintenance.

>

> Is

> there a specific instruction on this subject from

> the boiler manufacturer(s)? If there is, then it

> should be followed.

neilc2

wet layup / weekly fire?

Quote:
"Wet lay-ups ARE the best - IF you've got somebody to fire the boiler weekly, test the sulfite level, and make sure it stays FULL of water. If ..."

I understand firing to drive off the O2, but we're not building pressure right?, and keeping the water above the vessel? just building the heat up, right? to what temp? and how to tell temp or duration,
OR...
flood it and forget it, just keep checking it's flooded
thanx for too many q's neil

Tony Conner

You Only...

...need to fire 'em up just enough to boil the water a little. For boilers with extra sulfite added (which will likely only be the bigger ones anyway - not residential), it'll circulate the water, and mix things up. Then you can be pretty sure you're getting a representative sample of the boiler water when running the test. Big boilers are filled with water right to the stop & check valve. A separate vent line handles the air. I don't think any small residential boilers are piped like that, so they'd be filled so the water level is up, and out of the boiler. There will still be corrosion at the water line, but now it's on a nipple, or piece of pipe that's a lot cheaper and easier to change than the whole boiler. Chemical addition aside, I can't imagine residential boilers being handled like this, though. Few people would pay to have it done, and fewer still could do it themselves. The lay-up water level won't get checked even once all summer on one boiler in a thousand, let alone on every boiler, every week.

I think in the old days, residential steam boilers were the source of domestic hot water as well as heating, so they got fired regularly all summer. Lay-ups weren't an issue. That's not the case anymore. There's usually a separate water heater, so the boiler just sits there for months at a time, with the water at the basement air temp, absorbing oxygen, and quietly corroding at the water line - which is usually IN the boiler.

Mark Eatherton1

The last time I tried to lay up a boiler...

I threw out my back, broke a ladder, destroyed the glass back board and totaled the hardwood floor on the court.

Swore I'd never try to do a lay up with another boiler ever again...Huh? Oh, THAT kind of lay up...

NEVAH mind:-) Happy Labor Day Hydronicing!!

ME

Bob_19

Added Info

I found my books from " Steingress & Frost " c1986, It's been about 14 yrs since I left school so I had to look this up to be absolutly sure on this point.
Dry Lay-Up vs Wet Lay-Up.
If you are going to use a dry method you have to keep in mind of the room conditions, high humidity will cause havoc to the internal surfaces, fire and water side. The method recommends to avoid this by use of an absorbant, most homeowners won't. A de-humidifier will help a little.
Also one other issue are the gaskets on a cast-iron sec will dry out and become brittle much quicker in a dry environment, no the humidity will not help here.
The issue of leaks are always a concern, they show up at the strangest time, that is a issue that needs to be addressed.
On a cast-iron sectional I believe that the wet-layup method is the lesser of two evils IMO.
When I was doing commercial boiler tending this was what we used, but I always made it a point to check the boilers at least once a day during off-season. I believe a homeowner/operator in the interest of saving money should make it a habit, it only takes 5 minutes.

[Deleted User]

thanks everyone

the info helps alot..thanks again

Tony Conner

If The Boiler...

...is just sitting out of service for a period of time, you can get fireside corrosion whether or not there's water in it. (This type of corrosion will happen in hot water boilers as well, and forced air furnaces for that matter.) This is normally much more of a problem with fuels that leave a lot of soot in the boiler - coal or bunker oil. Moisture from the air dampens any soot or ash deposits, and triggers some nice sulphur based corrorsion. (Low sulphur fuels help a lot.) I've seen bunker oil soot absorb enough moisture from the air that it pretty much turned into a paste.

I agree that the gaskets between the sections of some boilers could dry out, and leak when refilled. They shouldn't, but that doesn't mean that they won't. Speaking for myself, I'd risk a gasket leak over oxygen corrosion. I don't think you'll ever see more than very small percentage of homeowners maintain the lay-up water level. A lot of people can't even get around to getting the oil in their cars changed every 3 months.