Cast Iron boiler leaking again after repairs

elfie

have a 15 section HB Smith cast iron hot water boiler (12 yrs old) that began leaking in the mid area (on both sides) last yr.  it was repaired by replacing some gaskets (no sign of a crack)



and now its leaking again (a slow leak)



started chemical treatment after the repair (not chemically treated since installation, and lots of new water has found its way into system when system pipe repairs done)



does water temp effect rate of leak (ie. keeping boiler hotter vs less hot)



and now the question is what to do?

jumper

what do mean some?

Some gaskets? You'd think that when pulling apart a boiler....

elfie

pulled sections apart

they pulled the sections apart and replaced gaskets for a couple sections

kcopp

Yes temperature....

can and does effect leaks...especially w/ gaskets. Tell us more about the system. Having a boiler leak in less than 1 year is odd. Is it going through thermal stress? How is it piped? If it gets a big slug of cold water back to a hot boiler  after a night of set back it will stress it.

M Lane

Keep it as hot

as you can, expansion is related to temperature. But the leak likely won't stop. A boiler that big is a big job, it looks like you need to ride it out to Spring if you can. The big problem is constant fresh water, it will introduce O2 into the system and start corroding things. Might try dumping Hercules Boiler Solder in, it might buy you some time.

If the water starts dumping on the burners though, that is very bad. Call someone in asap. Some contractors have portable boiler trailers they can rig up to heat your building while repairs/replacement commence. Good luck.

elfie

what went wrong

so did they do a bad gasket repair job??



this is crazy to have another leak

nicholas bonham-carter

Short-lived repair

Maybe it's leaking from another joint, and not the one which was repaired.

If it must be replaced, then a trio of boilers could take its place.

Stop leak is more effective on hot water boilers than steam.--NBC

SWEI

15 sections

A 28-15 burns enough fuel that you really should consider your options carefully.  Perhaps a pairing of a mod/con or three (ganged 399's work quite well) with a smaller cast iron (2MM BTU comes to mind) lag boiler for the really cold days.  This is not a "call the plumber" replacement -- you need a real pro (and probably an engineer's stamp.)



I'd recommend a full system evaluation and re-commissioning regardless of what you decide.

jumper

not a boilerman

I'm not a boiler repair technician. I presume that when somebody pulls apart a boiler; he replaces all gaskets,nipples,stays and nuts.

EBEBRATT-Ed

repair

It is common with that type of boiler to only repair what is leaking. I had one once that leaked after we repaired it with new gaskets. It leaked after the repair.

I called Smith in. We found the sections cracked (and others cracked that weren't leaking) due to the original installer not using a torque wrench and over tightening the sections.

They had hairline cracks that couldn't be seen with the naked eye.

You can go to a welding supply and get spray cans, penetrate, developer and cleaner to spray near nipple ports and look for cracks.

Unknown

gasketed boiler sections

How can you overtight a gasketed boiler sections is beyond me.

M Lane

Chemical treatment

might have flushed out some crud that was sealing another leak. I've never been enthusiastic about using chemical flushes on old systems.

elfie

use of chemical

so possibly, introduction of chemicals could have cleaned out crud that was acting to seal a leak.



so maybe after not using chemical treatment for a 12 yrs, we may now be exposing an existing crack due to chemicals? 



i wasn't present to watch the repair, quite possibly, they missed a cracked and simply were hoping that a new gasket would solve the problem. 



how possible is it that the source of leak was missed when they did the repair?????



i suspect that this may lead to replacement of boiler which is oversized by 50%+ (but inefficiency due to an oversized hot water boiler I dont believe is that serious (a steam boiler yes, but not so much for hot water)  - ie. hard to justify scrapping an oversized hot water boiler.

nicholas bonham-carter

The silver lining

If the boiler must be replaced, then a good heat-loss on the building, and some analysys of your climate could lead to an asymmetric boiler setup (thanks SWEI) to save you a lot of fuel in the future.

It would be wise to do a thorough examination of the system to determine why it failed-eg low return temps/thermal shock etc.--NBC

SWEI

Oversized hot water boilers

short-cycle quite nicely.  I've seen reductions of 50% or more in fuel usage when replacing them with mod/cons.  If you've done a heat loss and the boiler is 1,000,000 BTUs too big, you have a no-brainer ROI on your hands.  If the utility won't help with the cost, a bank or a leasing company probably will.

EBEBRATT-Ed

sections

If the boiler is oversized remove the leaking sections and leave them out. Down fire or replace the burner. On a hot water system I'll bet the sections are not crudded up. Is the return water piped correctly? I think Smith wants both rear tappings used if I remember correctly. Check delta t on water across boiler supply and return. You need to find out why it is cracked/leaking or the repaired or replacement boiler will do the same thing

elfie

removing bad sections

i like removing section vs replacing



burner is set on the low side already,



if a downsized burner is added, it may make getting a new boiler more attractive (and at that point, might as well remove several sections)

nicholas bonham-carter

Perils of down firing?

If that is an atmospheric boiler, and down fired too much, then the burner heat output will be uneven, and contribute to an unequal heating of all the sections, which may have caused some of the problem.--NBC

SWEI

Down firing

pretty sure it's a gas gun.

Mark Eatherton

It would have to be a gas gun...

If you've ever tried running an atmospheric burner at 1" W.C., then you discover what burner aspiration is all about,,, Fire at the orifice is NOT a normal consideration and produces a LOT co carbon monoxide… You also learn about delayed ignition, which WILL get your attention with fire coming from every possible source that it can...



Sounds like you have the condensation issue under control with a boiler turbulator pump.



ME

icesailor

Over torqued draw rods:

It's easy. Don't own or ever use a torque wrench.

Use the "Shade Tree Mechanic" Torque Wrench. Two long 1 1/4" box end wrenches, don't use never seize on the nuts and bolts, and tighten it as tight as you can get it or until the mill scale on the draw rods start to flake off. It's just right then.

Bob Gagnon plumbing and heating

Its A Good

Reason to use a boiler with Cast Iron push nipple instead of rubber gaskets, if you are using a cast iron boiler.



Thanks, Bob Gagnon

Weezbo

pull the skins off of it,

and cop a visual.

then open the clean outs and do the same .

if you have some nylon brushes see if any of the sections have grey wet stuff coming back on the brush .



when you find the leak take a picture .



could be a lot of things, however , it might be something as simple as tightening up some nuts that are not snug enough ..



with the skins off it might only leak when it is hot at a certain temp and that would probably be something that sprays out as the crack enlargens due to heat.



it would take some time to bring it back up i like to run boilers up gradually in like 30 degree rises aand then give them a few mins to dissipate some of the heat after the burner shuts down .. like if you shut it down at 70 and then again at 100 and again at 140 , they should rise another 7 or 10 degrees each time then i fire them again ..

keep an eye open for at what temp it starts leaking .

SWEI

Slow rises

make for happy iron.  It's a modulating burner, so if it's controlled properly there should not be problems.  Keep it hot all winter.