Epoxy for leaking boiler

[DougButtimer]

Hi,
I have a leaking Trianco boiler water jacket. I welded it up successfully about 12 years ago , but it has started leaking again . I have now re-welded it and thought that it was OK ... but it started leaking AGAIN AGAIN Having done some research on the web, it turns out that welding cast iron tends to create cracks due to the temperatures involved. So I tried some Furnox LS - this appeared to work at first , but the leak has started again (not massive, but still worrying that it might increase) . I have used Araldite epoxy resin for a whole host of jobs with great success, and I see that Araldite 2014 is spec'd to 120 degrees C . Has anybody had any experience of such a repair - what did you use and where did you get it from ? Many thanks !

 

[Bahco]

You have had your moneys worth out of the boiler if it is over 12 yrs old.
Time to dig deep and buy a new one

 

[Agile]

I am not much of an expert on welding techniques but wonder if brazing with the right flux is perhaps a better solution on c.i. ?

As far as araldite is concerned, I have seen several repairs done with it, not always successful but sometimes it is.

My experience is that using araldite to glue a small steel plate over the leak is best. Its necessary to clean down to bare metal and have the parts totally dry and clean.

I had a cracked car water pump in Turkey after getting stuck in a snowstorm. I managed to repair it with araldite and drive back to England ok !!! Similar or worse operating conditions but that was alloy.

Tony

 

[DougButtimer]

I am not much of an expert on welding techniques but wonder if brazing with the right flux is perhaps a better solution on c.i. ?

As far as araldite is concerned, I have seen several repairs done with it, not always successful but sometimes it is.

My experience is that using araldite to glue a small steel plate over the leak is best. Its necessary to clean down to bare metal and have the parts totally dry and clean.

I had a cracked car water pump in Turkey after getting stuck in a snowstorm. I managed to repair it with araldite and drive back to England ok !!! Similar or worse operating conditions but that was alloy.

Tony

Hi Tony, Thanks for the reply ! The technique/material is not the problem according to what I read - it is the effect of expansion/contraction
of the surrounding material - although pre-heating and controlled cooling can get round this, it is clearly impractical for a private individual to do this with a domestic CH boiler !!! Like you suggested, I had already had it in mind to use a small plate to effectively enlarge the seal area. I have now found that RS stock Araldite 2014 (£8.70 for 50 ml. + applicator for £13.80) - I just wondered if anyone else had tried this type of "solution" !

 

[Agile]

Ah, but the difference is that brazing is at a lower temperature than welding !!!

 

[ChrisR]

One technique employed with cast iron is to preheat the area as best you can with oxyacetylene, then arc (stick or mig) weld the crack. Then cover it in insulation (eg hot sand) and leave to cool as slowly as possible.
An issue with brazed repairs can be the difference in expansion rates of the metals on heating/cooling cyles, though 120º or so isn't hot at all as far as these materials are concerned. Depends on the shapes of course.
It's better to grind say a 4mm slot and fill it with braze metal than run the same stuff into a crack, because the surfaces will be so much better. Some alloys are designed for the purpose as fillers.

 

[DougButtimer]

Yea, unfortunately I only have electric, no oxy !! Also my brazing kit hit the dust many years ago and I haven't replaced it. Anyhow, the epoxy "solution" is attractive because the chances of curing the leak first time are that much higher and I don't have to move the boiler out into the garage (to do the welding) !!! I just wonder whether it will last ?? (and will IT cope with the expansion/contraction of heating cycles ??)