Commercial hot water boiler tank - sediment accumulation

[zeppy]

for a 16 section cast iron hot water boiler, is there accumulation of sediment in the boiler tank

should the sediment be removed via blowdown?

ok to leave sediment in tank for several yrs?

[phbsales]

Even if the make up water supply to the boiler is softened, solids like silica are not removed in that process. The boiler will require periodic blow-down to remove those solids. If those solids are permitted to remain in the bottom of the tank, the heat transfer efficiency becomes diminished as new solids fall on top of those solids that are already there.

[zeppy]

what happens if sediment remains at bottom of boiler?

does it contribute to corrosion of boiler tank and section seals.

no water treatment in the system

[phbsales]

what happens if sediment remains at bottom of boiler?
Boiler sections could overheat and crack due to the heat from the burners not being able to effectively heat the water from the bottom of the sections to the top (heat rises, you know)

does it contribute to corrosion of boiler tank and section seals.
Possibly.

[ascj]

Even if the make up water supply to the boiler is softened, solids like silica are not removed in that process. The boiler will require periodic blow-down to remove those solids. If those solids are permitted to remain in the bottom of the tank, the heat transfer efficiency becomes diminished as new solids fall on top of those solids that are already there.

So how often is someone to blowdown their hot water boiler?

There should be no makeup water being used....unless there is a leak. I tell my customer to not blown down their hot water boilers. I'll check the water quality and safeties. Am I wrong?

[929rc51]

So how often is someone to blowdown their hot water boiler?

There should be no makeup water being used....unless there is a leak. I tell my customer to not blown down their hot water boilers. I'll check the water quality and safeties. Am I wrong?

Blow down rate is going to depend on water quality. There will still be some make up do to evaporation of the water even there isn't a leak. How smart is your customer? Most of my customers wouldn't think about it, unless its a maintenance man... In which case depending on their knowledge you may not want them touching it either:grin2:. What you don't want however is a maintenance man/customer thinking they can service the boiler... That is when you start finding pilot valves adjusted, operating and high limit ranges way out of wack, ect, ect....

[ascj]

Blow down rate is going to depend on water quality. There will still be some make up do to evaporation of the water even there isn't a leak. How smart is your customer? Most of my customers wouldn't think about it, unless its a maintenance man... In which case depending on their knowledge you may not want them touching it either:grin2:. What you don't want however is a maintenance man/customer thinking they can service the boiler... That is when you start finding pilot valves adjusted, operating and high limit ranges way out of wack, ect, ect....

How does water evaporate in a closed hot water loop?

And the customer's I'm referring to are in house boiler operators.....they also go by custodians.:whistle:

[flange]

most places require you to open up water side every two years at most to clean and inspect. if not, too much sediment can cause poor heattransfer from fire to water sides, and over time can cause cracking and leaky boilers.

[ascj]

most places require you to open up water side every two years at most to clean and inspect. if not, too much sediment can cause poor heattransfer from fire to water sides, and over time can cause cracking and leaky boilers.

That's not blown down. That's routine boiler boiler inspection, done by your boiler company.

[zeppy]

i believe whats being said is that the hot water boiler tank should be blown down very infrequently to purge accumulated sediment on bottom of tank.

if water is not treated there may be more sediment that accumulates

annual inspections done by insurance cos. (h art ford steem boiler co) are worthless as they really dont do much except a very superficial inspection

[flange]

In general, closed loop systems, if flushed properly, and treated do not require daily or weekly blowdown. they are however required to be opened and cleaned every two years. steam boilers on the other hand are a wholly different animal.

[zeppy]

when you say opened and cleaned every 2 yrs, you mean a good waterside cleaning.

the boiler in question is certain sectional boiler that is tough to do a good waterside cleaning due to access limitations (so what do you do?).

i guess a good waterside cleaning includes washing/flushing out the interior of tank and inspecting the internal surfaces for any problems/excessive scaling/corrosion.

[fxb80]

annual inspections done by insurance cos. (h art ford steem boiler co) are worthless as they really dont do much except a very superficial inspection

When I did steam boiler work, the Hartford inspectors would suit up and crawl in the dry and the wet sides and search earnestly for more work for me. And I knew they would prove all safeties, inspect wiring, and scrutinize the water report. That's not what I would call superficial, so your experience is not universal.

[supertek65]

closed system hot water boiler.
stay on top of your chemicals!
no blow down needed!
SECTIONALS are very difficult to descale or clean! Or to even see inside to know if they are scaled up!
I just replaced the middle section of a boiler a couple weeks ago!
It is about 10-12 years old. The 6 sections I removed to get to my section all looked really good and all the push nipples were good as new!

[zeppy]

thanks supertek65

whats your guess as to why a 10 yr old 16 section boiler would start leaking (leak is in the middle)

i guess diagnosing the leak, which is not streaming from sides but slowly leaking from underneath (visable from both sides) will be a real challenge.

in light of no chemical treatment and maybe not doing blowdown to eliminate sediment once a yr i guess, what could cause the small leak? is it water treatment related or possible corrosion caused by sulfuric acid condensation?

and whats the guarantee leak will be resolved, once one section starts leaking, others may soon follow - have heard it may be a good time to invest in 2 smaller boilers vs having one lone bigger boiler.

[supertek65]

zep

i will not do any brand bashing, but let's just say a BLUE boiler has a class action law suit against them right now!

The push nipples leak!

You will get good at changing them! I have!

Thermal expansion is all you could guess except poor manufacturing!

I would guess poor manufacturing?

there are some great boiler guys on here that only do boilers and may have some better input?









thanks supertek65

whats your guess as to why a 10 yr old 16 section boiler would start leaking (leak is in the middle)

i guess diagnosing the leak, which is not streaming from sides but slowly leaking from underneath (visable from both sides) will be a real challenge.

in light of no chemical treatment and maybe not doing blowdown to eliminate sediment once a yr i guess, what could cause the small leak? is it water treatment related or possible corrosion caused by sulfuric acid condensation?

and whats the guarantee leak will be resolved, once one section starts leaking, others may soon follow - have heard it may be a good time to invest in 2 smaller boilers vs having one lone bigger boiler.

[supertek65]

of course 2 boilers would be better!

before you make any decisions
first pull it apart and inspect it!

remember when you fill it back up after you change the section to

fill it with room temp water and let it sit for a day
then bring it up reallllllllllllllll sllllllllllllllloooooooooooooooooow!

someone already mentioned
dirty boiler poor conductivity and way too hot boiler!!!!!!!!!!!

you will know once it is apart!

[929rc51]

How does water evaporate in a closed hot water loop?

And the customer's I'm referring to are in house boiler operators.....they also go by custodians.:whistle:

Yeah, I guess your right. It would be like a refrigeration system at that point if it was tight huh? Sorry about the knuckle head comment.

Yep I know the type!

Just some other thoughts I'll throw out there, is it leaking directly above the pilot? Was the boiler cold @ the time you noticed the leak?

[ascj]

One other thing, I'll throw out there. Sectional cast iron boiler need to have a none settling base under the sections. Concrete pads are great and all, but they don't stay level. You should have some steel under those sections. I can't count how many sections I have found fail due to improper installation.

[929rc51]

One other thing, I'll throw out there. Sectional cast iron boiler need to have a none settling base under the sections. Concrete pads are great and all, but they don't stay level. You should have some steel under those sections. I can't count how many sections I have found fail due to improper installation.

Great advice! Thank you for that.

[waterworld]

If you are leaking somewhere in the loop, then the sediment is likely mineral deposits from the makeup along with oxidized iron from the pipe walls from the introduction of oxygen.

If you are not making up, then it is likely corrosion product from either a galvanic problem or just low pH iron corrosion.

I would add Sodium Nitrite and Borate. The nitrite will give you good protection on the mild steel and the borate will raise the pH. You want to add until the pH is between 8.5 and 10.

In a truly tight loop, you never need to blow down because there is no accumulation of mineral deposits. But... you have to get chemical in there. From my experience, once a loop begins to have leaking problems, it never is the same again.

Oh, and NEVER NEVER NEVER add soft water to a closed loop. Soft water is extremely corrosive. Hardness inside a closed loop acts as an alkaline barier and keeps the pH up. When a softener removes the hardness and introduces sodium you lose alot of the protection that calcium gives.