Compression fitting or solder?

[rangerssteamtoys]

For my big boiler that I'm building I have to cut 10' sections of 5/8" OD copper tubing, fill them with sand and coil them. Then get the sand out and connect them back together.

My question is, How do I connect them? With a compression fitting, or a 45 degree copper fitting which I solder together. I have solder that melts at 430F, its the highest temp I could find. I just dont know what to do, solder or compression fitting. Other suggestions are welcome

 

[chuck foster]

i have never seen compression fittings used for steam or any other high pressure applications, you might want to us silver solder, it has a much higher melting point.

chuck

 

[Powder keg]

I would use the solder.

Wes

 

[Bogstandard]

Ranger,

The joint for safety's sake, has to be be done with a hight temp silver solder with a rigid outer support sleeve. Your hi temp soft solder is OK for plumbing, not boilers.

John

 

[Stan]

I don't know anything about steam service, but for air conditioning, at higher pressures than you will be running, they don't use a fitting.

Any A/C supply store should have a punch like object that you hammer into the end of the tube to expand it so that the next section slides inside. You then solder with some form of silver solder. On A/C they usually use Silfos (brand name) in 5, 10 or 15% silver. This is about the same price per pound as per ounce of 55% silver solder.

 

[Mcgyver]

what John said soft solder is occasionally used to fill pin holes leaks (personally that doesn't appeal as then things get contaminated) but not as a primary joining material. The tensile strength difference is one reason, about a 10:1 difference, and operating temps are the other. At 150 psi, your water is a 359F - does that seem like a good idea with 430F solder? iirc, the strength of the solder is not linear as it approaches the melting point. This needs to be brazed (which is what SS is) not soldered.

With a boiler, because there is so much potential energy that can be released if it fails (however one believe that actually takes place lol
) a high safety factor is used. 8:1 comes to mind. The boiler and fittings need to both be within this. So if you talking an operating pressure of say 125 psi, everything should be made to have a burst strength of 1000 psi or greater. This includes the dia & wall thickness of the cooper tube and fittings.

 

[rangerssteamtoys]

Ok, so I dont want to go with a compression fitting but with silver solder. I dont know where to get higher temp braizing type silver solder, the stuff I found was at Homedepot :

Maybe at a welding supply store?

 

[Mcgyver]

home despot is for guys to whom the pinnacle of diy technological achievement is a deck ;D

It serves its function I guess but you'll go mental viewing them as a supplier to our hobby. Welding supply, HVAC suppliers, the big industrial catalogue houses and even the model engineering suppliers should have silver solder.

 

[rangerssteamtoys]

Ok, I figured that a welding supply stor would have so high temp stuff.

As for the rest of the plumbing, I plan to use 1/2" galvinized steel pipe, its cheap, easy and I have a connector to go on the boiler. Will the pipe hold the pressure? I imagine it would, it holds 150 psi of air pressure.

 

[applescotty]

You could request a free sample kit from this guy:
http://www.practicalmachinist.com/vb/showthread.php?t=160675

Scott

 

[rangerssteamtoys]

You could request a free sample kit from this guy:
http://www.practicalmachinist.com/vb/showthread.php?t=160675

Scott

Thanks for the link, I just sent the guy an Email

 

[te_gui]

Every boiler refurb I have been involved with, which has been inspected by State boiler board folks requires black Schedule 80 pipe at least to the first valve. They get pretty worked up about galvanized anything for whatever reason. I have heard some people state that the galvanizing process weakens the material, I have no evidence to support either point of view, just passing along the "official" stance up here in the Northwest.

Brian

 

[GailInNM]

Galvanized pipe is not permitted in most places for any gas transmission. be it air,steam or natural gas. The reason often stated is that the galvanize can flake off on the inside and plug up a safety valve or wedge in the seat of a pressure regulator holding it open. Most plumbing suppliers will have black pipe available, particularly in areas where natural gas is commonly used. I don't know about any of the other safety considerations or specifications of using pipe for steam.
Gail in NM,USA

 

[BMyers]

Another reason galvanized pipe is a bad idea: porosity. The mill starts out making all pipe as black iron, any pipe with pin holes is galvanized for water pipe, if the holes are too large to be water tight it is sold as rigid conduit.

 

[rangerssteamtoys]

Well then I'm going to use balck iron pipe. Does black iron pipe come in small lengths, the stuff I have seen is very long.

 

[zeusrekning]

Just sticking mynose in. Is it supposed to be seamless pipe or does it matter?

 

[rangerssteamtoys]

I have acquired the solder, its safety silv 45. Its 45% brazing solder, which from what I read on another topic is just enough. I have tried to solder with it, and it takes alot of heat. My propane torch had a run for its money, but later it just flowed into the joint.