HELP! Cracked hot water housing

GaryG

I came home yesterday to a few inches of water in my basement, coming from my 60+ year old American Standard steam boiler. After getting rid of most of the water i located the leak at the rear of the boiler. There is a bolted on cast iron domestic hot water coil section that has a 4" by 6" hole in it where it cracked. I have a Rinnai instantaneous hot water heater for my domestic hot water and dont use the boiler for hot water at all in my house. Can I take out the 20 or so bolts holding this section on, remove the whole thing and use some kind of block off plate to contain the water in my boiler and get some heat back in my home?



Any help would be appreciated.

Thanks

Gary

Brad White

Get a pro.

If I read the situation correctly, the head of the domestic HW insert coil has cracked (and what is up with THAT?)..



That location, the gasket surface, is a pressure boundary. You would need a new fitted flange (called a blind flange- solid with no taps), new gasket and bolts.

A presumption here is that the mating surface and bolt holes are also in suitable condition.



I have no idea what caused the crack, (freeze? Thermal shock?), so any such repair is a risk as it may have also affected the boiler casing to which it is bolted.



But because this is a boiler, a fired pressure vessel even at low pressure, the repair has to be done by a professional. Depending on our area, they may need to have an ASME "H" stamp to certify the repair.



If your boiler is 60 years old though, it may be time to stand back and look at a replacement.  That boiler is at twice the expected life-span of today's boilers and at the outside of what I would expect it to be for one installed before the Korean War. You got your money's worth out of it.

GaryG

Gotta give it a shot.

I got the hot water insert removed( i did crack the housing in half in the process). It is in 2 pieces but suitable for some sort of template to make a blank block off plate on the back of the boiler. I have to give this a shot before i spend hundreds or thousands(in my area there are only about 5 licensed plumbers who will all pound me to do this repair). Does the plate need to be cast iron? or will steel do? the old flange was almost 1/2 inch thick. the mating surface is smooth and undamaged.  do you think a hi temp silicone gasket will suffice? this only has to last me 2 months. I was ripping the whole system out right after heating season anyway.



thanks again

BobC

It ain't kosher but it might just work

Necessity is the mother of invention.



i assume there are many bolts that held the old one on. As long as you can get all the bolts in I would just make one out of heavy steel and use the high temp RTV as a gasket. Leave a little room on the holes because the expansion rate will be a little different and you don't want to damage the boiler casting.



Make sure the boiler operates at no more than 2 PSI and send all the women to the inlaws.



good luck,



Bob

nicholas bonham-carter

hi-temp silicone

is there a time for the silicone to cure before putting the final turn on the bolts holding the plate to the block?

i have seen sheets of rubber sold for making gaskets. that might be better as far as having an even thickbess.--nbc

Brad White

I am down with that...

meaning, it is worth a shot on your dime, you are on your own.

Glad to see the mating surfaces appear clean. I understand your dilemma.



Steel should be fine, even mild steel and as Nicholas and Bob said, whatever gasket you use, let it cure (follow the directions, basically).  Low pressure.



And yes, your wife and kids never visit grandma nearly often enough

BobC

Silicone rubber sheets

McMaster Carr does sell silicone rubber sheets, this is for a 12X12 3/32" sheet - just choose the hardness you want.



http://www.mcmaster.com/#silicone-rubber-sheets/=b3rh6e



Bob

GaryG

so before i fire this beast.......

ok here it is.  went out and got 1/2" thick steel plate, drilled all 20 holes then test fitted and reamed 3 so it would fit. (thats the abbreviated version). just bolted it up over a nice bead of 700 degree high temp silicone. will let cure for 2-3 hours before refilling and hopefully firing it up.



i understand that if this crazy fix isnt right that it will obviously leak, but is there any danger of something more severe happening?

Brad White

It may not

leak and may get you through.

Are you sure that 2 to 3 hours is enough cure time? I have seen 24 hours, not 2 to 3.



Hate to see your efforts (drilling twenty freaking holes in half-inch plate?), go for naught because the gasket was not cured.



If your LWCO and relief valve are in working order, that will take care of the obvious things. A leak may well scald you even at under a pound, but you should both see and hear it at those lower temperatures/pressures.  I would stay with it through a few cycles and do not be afraid to trip the red plate switch.

Mike Kusiak_2

Cure time

RTV cure time is a function of temperature. If you gently warm up the boiler without actually building any pressure, it will accelerate the curing. I would wait at least several hours until the silicone skins over before actually trying to steam. Warming up the boiler to below boiling temperature should be ok to speed up the process.



I have done emergency repairs of large circulator pumps using silicone RTV instead of gaskets, and put them back in service immediately without waiting to cure. Even under 20 PSI pressure, they never leaked, and several years later are still in service.

Brad White

That is good to know, Mike

I have used Permatex blue and red for gaskets, but went by the instructions. Do you use a different brand?



Regardless, it is probably the same RTV silicone and your success is encouraging.

Mike Kusiak_2

All pretty much the same?

 I use what ever RTV I have on hand at the time. Aside from the very high temperature automotive silicones, they all seem pretty much alike in composition and performance. Originally used the Permatex types, but then found no real difference between them and general purpose Silicone RTVs



 Actually my current favorite is GE "window and door" silicone caulk, available in the 14 oz gun cartridges. Good to 400F and much less expensive than the 3 oz tubes of "specialized" sealants. Been using it for years for all types of sealing applications with excellent results. Typically, I apply a thin coating to both sealing surfaces and let it set up for a few minutes before fastening the parts together.



I have a feeling that there is a lot of marketing hype involved with the multitude of silicone sealants available.

BobC

RTV's

I spent decades designing high voltage systems for military use. We used silicone RTV (silastic) to insulate high voltage connections that were not inside the potting material.



The clear RTV will pretty much attach anything to anything else but it out-gasses ascetic acid as it cures so it can be problematic in HV work. It takes a week or more for the stuff to fully out-gas. The white RTV's (Most door and window 100% silicone caulks) does not give off ascetic acid as it cures but it's not as sticky either.



I've never used them as a gasket on steam but I can't think of a reason why they wouldn't both work well, just make sure they are 100% silicone.



Bob

Mike Kusiak_2

Different types

GE sells both  types of RTV as "window and door". GE Silicone I is the traditional acetic acid cure type, while Silicone II is the newer non-outgassing type. Both seem to work well as general purpose sealants and I use them pretty much interchangeably.



Type I seems to have somewhat better shelf life, as I have had some problems with opened tubes of type II failing to cure properly when near the expiration date.



Ge also sells the black Silicone II in small tubes calling it "gasket and seal". Bought a tube once and compared it to the black Silicone II "window and door". Never really found any discernable difference.



My background is also in electronics, and I remember using Dow-Corning electronic grade RTV for sealing circuit assemblies. Didn't outgas, but as I recall it took forever to cure.



http://www.caulkyourhome.com/ge-silicone-I-window-and-door.php



http://www.caulkyourhome.com/ge-silicone-II-window-and-door.php



http://www.caulkyourhome.com/ge-silicone-II-gasket-and-seal.php