heating crown on boiler

[falisitas]

Hi need some advice to be able to get the crown inside the firebox up to temp for silver soldering 8off 6mm copper stays that I have had to  put in due to a bad desing on the top stays boiler was made about 60 years ago and has never been used my boiler inspector siad i need to do it but cant now get the crown hot enough any help would be appreciated.

[johnd]

Hi,
A couple of suggestions first if you are a member of a club, ask for help. There will be many that will, it always amazes me at the generosity of fellow members, i also try to give back whenever i can.
If you are unable to take on the above.
1) use heat reflecting blocks to form a heat reflecting wall, broken bit of block inside a firebox to reflect heat to a certain area.
2) use a second heat source, such as a hand held canister torch with high temp gas.
Not sure of your equipment but the bigger the better.
Good luck

[JonL]

I think this needs a bit more background info, we need as much information as possible really to make sure we give you the exact information you need. As John has said, this is probably best provided in person by your fellow club members or the boiler inspector himself. Reworking older designs can be a bit of a minefield, especially to me as a novice.

[John Baguley]

What sort of burner are you trying to use? If using only propane then you are really going to need a cyclone burner. An ordinary Sievert type burner will just keep blowing out in such an enclosed space due to lack of air. Also, as already suggested, plenty of insulation around the outside of the boiler to conserve as much heat as possible. I would advise putting some insulation on the firebox tubeplate as well to protect the ends of the tubes and their soldered joints. It's very easy to burn the tube ends and/or remelt the existing soldered joints leading to even more problems.

John

[ettingtonliam]

If the boiler is 60 years old, how were the other stays fitted? Practice of around 1960 tended to be threaded stays, nutted on the inside and sealed with soft solder/Comsol. If this is what they are it would be a mistake to try silver soldering the crown stays as the heat will overheat and destroy the solder on nearby stays.

[John Baguley]

Sept 28, 2021 7:20:14 GMT ettingtonliam said:

If the boiler is 60 years old, how were the other stays fitted? Practice of around 1960 tended to be threaded stays, nutted on the inside and sealed with soft solder/Comsol. If this is what they are it would be a mistake to try silver soldering the crown stays as the heat will overheat and destroy the solder on nearby stays.

Good point

John

[falisitas]

Hi thanks for the advice  I packed clay bricks around the firebox and covered the tube in a insulating blanket and used a sivet 25mm blover and a 19mm blower that i managed to point into the regulator hole and got the bigger torch going in the firebox this got the crown realy hot and the silver solder flowed going to hydrolic test tody. i just want to clartfy that i had to drill and tap the rods threw the top of the boiler into the firebox and tapping the firebox side do the silver solder was to seal in the copper stays in yhe firebox and on top of the boiler . the positioning of the stays whent through the origional stays which were on top of the crown but were not of the correct desing and collapsed under the pressure test thus the crown pushed down into the firebox the boiler inspector wants this done before he will pass it.I live in south africa and the hobby is a bit of a chalange as we dont have the supply stores for model making as in the uk 

[JonL]

Ah, I've no idea what the regulations are in South Africa, so it's hard to say what will pass and what wont!

Best of luck regardless.