Insulation for sil soldering

[cwr]

Hi Folks,
Just wondering what people are using for insulation while silver soldering copper boilers?
Last big boiler I did was a 7 1/4 Edward Thomas and I used rockwool. It worked well in terms of insulation, ease of use and you can happily play the flame on it etc.
However I, was becoming more and more concerned that over time a fine and slightly irritating dust was being produced. Don't know if there are any health concerns over this, but I'd rather not risk it.






Thanks
Chris

[simplyloco]

May 23, 2020 13:43:46 GMT cwr said:

Hi Folks,
Just wondering what people are using for insulation while silver soldering copper boilers?
Last big boiler I did was a 7 1/4 Edward Thomas and I used rockwool. It worked well in terms of insulation, ease of use and you can happily play the flame on it etc.
However I, was becoming more and more concerned that over time a fine and slightly irritating dust was being produced. Don't know if there are any health concerns over this, but I'd rather not risk it.

SNIP
Thanks
Chris

Vermiculite blocks. Durable and effective.
John

[uuu]

Yes - that's what Steve and I used on his Brit boiler - see this thread: Steve's Brit boiler

Wilf

[ettingtonliam]

I use vermiculite blocks from the builders merchant for the hearth and to be an adjustable wall to the sides and back of the hearth, and thermal blanket from Cupalloy to wrap around the parts of the boiler I'm not actually operating on.

[cwr]

Thanks for the replies folks.

I hadn't realised that the firebricks used in modern stoves are mostly vermiculite blocks, so easy enough to get hold of. Got some coming in the post to experiment with.

I see that the cupalloys blanket is kaolin wool. There's plenty of alternative ceramic fibre insulation with apparently equal properties available on eBay, Amazon etc. I wonder if they are worth trying. I do like the idea of a material flexible enough to closely wrap round the boiler.

[springcrocus]

My twopennorth-worth: the blocks that are generally found in builders yards, the lightweight ones, are NOT vermiculite. They are reconstituted from the ash produced in modern-day power stations where high-temperature burning of pulverised coal produces this fine ash. They get marketed under various names including Thermolite and Celcon.

In earlier times, builders blocks used to be made from the cinders of normal coal-fired power stations and these were generally called Breeze blocks, both heavier and denser than modern wall blocks.

Vermiculite is a silicate of magnesium, aluminium and iron and is similar in weight and structure to pumice, a volcanic rock with high water and gas content. It usually comes in granular form but can be mixed with clays to form blocks. Great for gardeners (in pellet form) but expensive for model engineers.

Different again are fire bricks, as used for making kilns and fireplace backs, which are clays with a high silica content, kaolin (or china clay) being a good example. In brick form, they are usually called refractory bricks.

Night storage heater bricks are another different animal, being a mixture of fire clay and Feolite, an iron oxide added to the mix to increase the ability to retain heat. It is this component that makes them so damn heavy, I've lifted hundreds, if not thousands of the things over the years. They take in a lot of heat and release it over a long time.

Fibreglass blankets are the modern form of asbestos blankets and are generally pretty useless. At silver-soldering temperatures they scorch and break down quite quickly although they seem to last a long while at soft-soldering temperatures.

To protect your bench and reflect the heat back into the component, use Celcon/Thermolite blocks - really cheap and can be cut with a wood saw. Easy to shape around the component.

If you need to soak heat into a component, or bring the temperature down really slowly, put the item on a pre-heated night store heater block, then cover with Celcons of a fibreglass blanket.

Fire bricks are great if you want to build a permanent kiln but are quite expensive and break easily. They don't degrade like Celcon blocks do.

Breeze blocks are only any good for building walls with.

Just my take on a few items.

Regards, Steve

[Roger]

Any of the aerated concrete blocks will do the job. Thermalite or Toplite are two but there are many others. Any decent sized DIY will have them. You can saw them with a wood saw to make any shapes you like.

[daveburrage]

I've usually used firebrick combined with some sort of lagging. As regards lagging I got some scrap diesel engine exhaust lagging from where I used to work - maybe you can also buy it from engine or exhaust dealers. It had a stiff outer and a tough inner insulation core. I'm still using it. I've also used the lagging from pottery kilns (I live near stoke on trent) I bought it from a kiln supplier. It worked well but was a bit weak and fluffy - it tended to break up after a lot of use.

regards

Dave Burrage

[Roger]

Out of interest, you don't need any insulation to silver solder a boiler if you have a large propane torch and you use oxy acetylene.

[ettingtonliam]

True, but I don't, so I use lagging. Apart from anything else, covering parts of a boiler with lagging reduces the amount of heat reflecting back to the operator.

[Roger]

Just another observation... I'm surprised you can get it hot enough with that torch, it doesn't look very big. When Paul Silver Soldered mine with his Oxy-Acetylene, we preheated the whole boiler with two Propane torches that were about twice that size and got it all beyone the point of flushing colours before starting.

I draped a Fire Blanket over it to retain the heat, but he normally doesn't bother.

[cwr]

Hi Roger
Yes that's a fair observation. The propane torch was used to heat up as much as possible and then oxy acetylene. Even then only had just enough heat to do a satisfactory job.

[Roger]

Jun 9, 2020 9:09:44 GMT cwr said:

Hi Roger
Yes that's a fair observation. The propane torch was used to heat up as much as possible and then oxy acetylene. Even then only had just enough heat to do a satisfactory job.

I think Paul only spent maybe three or four minutes with the oxy-acetylene before we got back on the propane torches again. He didn't want to add more local heat than absolutely necessary.