Silver soldering percent

[Jyman]

I was just wondering what percentage of silver solder does everyone use when making a boiler. Hydro tested to 80 and running under 40 psi steam pressure.

 

[lennardhme]

40.
Leonard

 

[GWRdriver]

40% would do the job but the most commonly used and available alloy (at least in the USA) is 45%.

 

[Jyman]

Ok I just read an article on boiler making and it says that you can use solder that doesn't melt below 350F if its not exposed to the flames.

That would just be regular plumbers solder then.

Here the article

http://www.1920-30.com/toys/things-to-make/model-boilers.html

 

[RonGinger]

[I would not use plain tin-lead solder on any kind of boiler, model or otherwise. The linked articles says

Joints not exposed directly to the furnace flames may be soldered with a solder melting not below 350 degrees Fahr.

This is not true- on a small boiler like this it is all going to be about the same temperature, so distinguishing flame area from other is not important. It is also important to understand that solder becomes very weak and plastic long before it melts. A solder melting at 350 is probably just about mush at anything over about 250 or 300.

There is over 100 years of experience in making model boilers and just about everything written says to use silver solder. I would use it.

 

[KBC]

Ok I just read an article on boiler making and it says that you can use solder that doesn't melt below 350F if its not exposed to the flames.

That would just be regular plumbers solder then.

Here the article

http://www.1920-30.com/toys/things-to-make/model-boilers.html

If you look at the date of the article that you posted, it's dated 1920-1930.

In those days people made boilers with no thought of safety but in today's climate of litigation and for insurance purposes soft solder is a No-No.

Any boiler Inspector with knowledge of the code of practice for Model Steam boilers would refuse a Hydraulic test Certificate for a soft soldered boiler, I know that I would.

As Ron says " use silver solder " and he gives the reason why, don't be put off, Silver Soldering is easy as long as you have plenty of heat.

George,

 

[Jyman]

I know the boiler codes for my area because I am a Power Engineer (Stationary Engineer in other parts of the world) and take care of 89 hot water and steam boilers, and I wouldn't dream of doing anything unsafe.

I have only attempted to make one boiler so far and that was using 75% silver solder. Which ended up taking a couple tries to get it sealed up and hydro tested to 80 psi. As was a nightmare to solder probably because i was border line on the heat.


Has anyone tried the silver solder paste it's at 56% silver and has a melt point of 1050F and a bonding strength of over 85,000 psi?

 

[abby]

Mamod boilers are soft soldered , and were/are heated by direct heat from the burner onto the barrel , also they are made of brass so incorporate all the features that you will be advised against
older boilers running at 80 psi + were often rivetted and soft soldered.
For your own private use you can do whatever you like , you do not need certificates etc but for safety sake an annual hydraulic test should be carried out.
Silver solder paste is no better or worse than rod but much more expensive. On the plus side a small amount can be pre-placed in a joint which can be very handy with awkward jobs.

 

[KBC]

For your own private use you can do whatever you like , you do not need certificates etc but for safety sake an annual hydraulic test should be carried out.
Silver solder paste is no better or worse than rod but much more expensive. On the plus side a small amount can be pre-placed in a joint which can be very handy with awkward jobs.

[/QUOTE]

abby,
You are quite correct in your post regarding private use
but in the case of Mamod and other small brass boilers that are only working at 10- 15 p.s.i.
not the 40 p.s.i. that Jyman is contemplating and that the boilers built in the past using riveting and soft soldering up to 80 p.s.i you don't know how many failures there were as at that time there was no control on what you could build.
Can you imagine the things that happened with the big roaring paraffin burners working under pressure did to soft soldered boilers.?

Jyman,

As I don't know where you live but appreciate your experience with pressure vessels and codes of practice but full size codes of practice are not the same as the model boiler code of practice that we use in the U.K.
I would still strongly advise you to use Silver Solder with the 42% silver as advised, Paste is very good for small jobs but would be very expensive to use if doing a boiler, it's expensive enough using the S/s sticks.
Don't be put off building a boiler and if you don't require insurance you can use what you like.
Have you thought of Copper to Copper as the rods are so much cheaper than S/solder.

George.

 

[gus]

I did use soft lead solder for my first two 2" O.D. boilers and solid parafin wax to heat boilers
to raise steam for oscillating engines. All these boilers fell apart when boiler was about to run dry or totally dry.:hDe:

Read books by Tubal Cain on silver soldering and seek professional advice from air conditioning contractors,plus a good friend who has good working experience with gas welding from using steel rods,brass rods and silver solder rods. His advice was most beginners use gas torches with insufficient heating power.The torches powered by small camping gas canisters will not provide the heating power.Bought Mapp Gas torches that comes with two burners and even three burners and these torches gave me enough brazing power. For bigger jobs,I use two Mapp Gas Torches.
Next advice was pickle,sand and clean up joint surface and apply Easy Flow Silver Solder Flux
and slowly heat till paste dries up before applying full power to dull red heat which is just after the flux liquidifies. Do not overheat.Dip rod into flux and prehit before plunging into joint. Do ensure you put in sufficient solder and with sufficient heat,the solder will flow by itself. Do not overheat.

There will be failures but if one persist, good silver soldering will happen after a few goofs.Gus had too many goofs.
For beginners , please practice on copper to copper. Copper to brass or steel is another game.
Practice makes perfect.

 

[Jyman]

no your totally right I would not need a pressure certificate unless its has over 1 m2 of heating surface. which is still a fair size boiler. I live in Canada and as far as I know there is no model engine club around me.

I haven't really put much thought into copper brazing, I guess I'm going to have to look into it.