Slant/Fin boiler door crack

DanRegienus

I have a Slant/Fin Liberty boiler and the front burner mounting plate door has a small crack running from one of the bolt holes into the observation door hole. The front door is no longer available from Slant/Fin so I will have to have it repaired, my question is, should it be welded or brazed? I have seen a lot of debate on what process is the best solution but I have yet to see why one method might be better than the other. The door itself is cast iron and the crack is extremely thin, the only way you can really see it is if it were backlit from behind. Please let me know if there is any advantage/disadvantage between the two possible repairs (weld vs braze)

DanRegienus

Does anyone happen to know how hot that burner mounting plate door might get? I just talked to a guy about brazing the crack and he was concerned the braze wouldn't hold up to the heat and might melt out. He also said that if he was to try and weld it, it might create more cracks and make the situation worse. The local HVAC company told me if I can't get a new door than the boiler is junk and needs to be replaced. But on the other hand I've seen posts on other forums where people say they can or have welded/brazed a similar type of crack and everything was fine and it was a good durable repair. I'm not sure what to believe, the rest of the boiler is in good shape and I can't afford to replace it at this point and time. Anyone that has had success in this type of repair please chime in.

STEVEusaPA

You should've put these questions in your other thread.

Grallert

You can have it brazed.or silver soldered. The casting wont get hot enough to melt the repair it will cause the two different metals to move at a different rate maybe causing the repair to fail at some point in the future. I'd have it repaired be a good welder, explaining whats going on.
From your other post it looks like that honeywell control have been cooked from the back pressure coming from the inspection door. Something to keep in mind.

DanRegienus

This is a different boiler, the other thread i started i was asking about the boiler in my house, this boiler with the cracked door is in my tenants apartment. I realize they are both the same make and model but they are two physically different boilers with two different problems.

STEVEusaPA

Ah...thanks for the clarification.

DanRegienus

That honywell control on my other boiler got a bit exposed to some heat 6 or 7 years ago when the boiler was run for a while with the observation door not shut all the way.

DanRegienus

Could anyone give me a ballpark number as far as how hot the burner mounting plate door gets. The guy I talked to about brazing the crack seems to be uncomfortable/hesitant of doing the job until he knows how hot it gets.

SuperTech

If your guy can't weld it don't let him mess with it. He will just make it worse.

Just go to your rental property and take the temperature of the other boiler.

Jamie Hall

On welding cast iron. It can be done and the result can be very strong. That is... if the welding is done with the entire door brought to a good high heat (at least red, and hotter is better), then welded, then cooled slowly. You are trying to stress relieve the part. Otherwise, it will crack again, with the only questions being when and where...

DanRegienus

I would go ahead and check the temp of the boiler but I don't have an IR thermometer or any other temp gauge to check it, that's why I was hoping maybe someone might know a ballpark temp estimate.

DanRegienus

Has anyone ever tried these muggy weld brand welding electrodes?

77 Electrode: Non-Cracking Cast Iron Welding Rod

77 is a premium cast iron welding rod that produces welds which are high strength, crack resistant, and porosity free when applied to a wide variety of cast irons. The special tri-metal core wire has a high current carrying capacity and the specially designed coating converts the impurities of the base metal into slag instead of being trapped in the deposit. The high deposition rate creates an extremely narrow heat affected zone– a feature suitable for all weldable cast irons requiring post weld machining.

77 cast iron welding electrodes are softer than nickel rods, and have unique properties that allow the cast iron welds to stretch and elongate up to 300 percent more than other rods, which helps prevent the base metal and weld from cracking in the process.

Key Features:

High efficiency weld metal transfer eliminates electrode overheating
Crack-resistant formula eliminates the need for pre-heating or special cooling
Ideal for heavy machinery, trucking, bus lines, automotive, marine, and RVs
Repair cast iron exhaust manifolds, engine blocks, industrial machines and more

DanRegienus

They also make this for dirty or contaminated cast iron if that's a factor, seeing how a boiler door would be subject to a lot of heat, soot, and other possible contaminants.

72 is a nickel-iron non-conductive electrode formulated to join dirty and contaminated cast irons. This universal electrode can be used to weld a wide variety of malleable, ductile, and nodular cast irons. In addition, it is ideally suited for the repair of defective or cracked malleable iron castings.

There are occasions in industry where exceedingly dirty cast iron is encountered. 77, which bonds well to most cast iron does have a limitation. Since 77 has controlled penetration, which is ideal for non-cracking and machinability, it may not be able to bond exceptionally dirty cast iron. 72 should be used for this application. It has a high penetration, can anchor deep into the subsurface of dirty cast iron, and seals in porosity generating contaminates prior to finish welding with 77. 72 is used for a cladding operation, then the weld is completed with 77.

Key Features:

Flux coating does not side arc even after being heated
Extremely strong arc drive penetrates surface contaminates
Special slag composition can be welded over without creating porosity
Extra nickel content insures crack resistance machinable weld

EBEBRATT-Ed

@DanRegienus

Sounds like that will work. Or you could use bronze brazing rod comes with flux on it plenty strong.

If your guy is reluctant take the door off and bring it to a good welding shop they will know what to do. If your guy screws it up you will be screwed.

Cast iron is touchy you have to preheat it and use caution with the right amount of heat.

The temperature of the front plate is not an issue. It has room air on one side and the other side is insulated so any braze or weld will be fine

A good fabricator could probably make you a new door out of steel if need be but you should be able to save that one

DanRegienus

EBEBRATT-ed - thanks for the info

DanRegienus

I have talked to half a dozen welding shops in my area and it seems like no one can or wants to do any cast iron welding repair.

SuperTech

> @DanRegienus said:
> I have talked to half a dozen welding shops in my area and it seems like no one can or wants to do any cast iron welding repair.

That's not good. It looks like your only options are letting your buddy take a crack at it or bite the bullet and replace it.

DanRegienus

Slant/Fin no longer makes the part i need and I can't track down a new or used one anywhere.

EBEBRATT-Ed

What about cutting a pc of say 1/8 or 3/16 steel plate. Cut it so it will span across the crack and drill and tap and put a bunch of screws and bolts across it

DanRegienus

EBEBRATT-ed
I was thinking of that method also but was afraid it could possibly do more damage. (I will look into this method a little more in depth) I don't want to further weaken the door and promote additional cracking. I think that welding or brazing is a solid solution, it's just a matter of finding someone that is willing to do it.

DanRegienus

Maybe a combination of brazing and plating could be an acceptable solution.

EBEBRATT-Ed

Don't know how popular Slant Fin is in your area. We don't see many around here.

Maybe a trip to a boiler scrap yard and you will get lucky.

Post on here under "buy, sell, barter" maybe you will get lucky

DanRegienus

EBEBRATT-ed
Thanks for the advice