Crazy idea?

[SDBob]

SS tubing fittings are pricey. On a quest to save money, I'm going to attempt to silver solder 3/4 tubing into a 1/2" NPT female fitting. I cut some 1/2" NPT threads into the tubing easily, altough they're shallow and will never seal. But I can thread the tubing in, in fact, I cut the threads long enough to bottom the tubing out in the female fitting, leaving no threads inside for bugs.
I picked up some liquid flux and food grade solder, and I'm hoping I can silver solder the shallow threads to the female fitting.
If this works not only will I save hundreds on compression fittings, but I can eliminate 99% if not all of the threaded surfaces normally left exposed in the inside of an NPT connection.
The tubing is cheap at just over a buck a foot, and I can polish the inside of 4' sections with a dremel bit I welded to a 2' x 3/16 metal rod.
The tubing also bends easily enough with my 1//2" EMT bender.
I'm thinking this technique will leave me as close to a sanitary install as I can get without welding.
My "it's too good to be true" and "why can't I find anyone else who's tried this" radars are sounding loudly, but I can't wait to get back to the shop tonight to give it a go.

 

[Rhumbline]

Are you talking about using conduit?

 

[SDBob]

No. Stainless tubing. It's od is slightly larger than 1/2 emt, and less than 1/2 rigid. 15/16 maybe? I saw it in the remnants pile at the metal supply. It's welded tubing, relatively clean inside, and polishes up nicely. I'll throw calipers on it when I get back to the shop, I'm not at all familiar with tubing sizes.

 

[Rhumbline]

Without knowing what it had been used for or anything else about it. I'd pass.

How much would you be saving over copper or new SS?

 

[SDBob]

Here's a pic I took of it at the shop last night, you can see the shallow threads...
https://drive.google.com/file/d/0B4vXJz1SOThZUU5ZUThMLWVpVWM/view?usp=docslist_api

 

[SDBob]

It's new. 316

 

[SDBob]

https://drive.google.com/file/d/0B4vXJz1SOThZZlN0S0k4a09QMlU/view?usp=docslist_api

A picture of the wall thickness and inside condition before polishing.
Sorry for the picture quality.
My camera lens is cracked on my phone, but if you have 3 beers, close one eye, and tilt your head slightly it clears up. A little. Lol

 

[SilverZero]

After having taken up silver soldering on my rig, I'd say go for it. I'm in love with the process. I think some people avoid it because it's really not well-known outside of the one or two threads here on HBT that talk about it (I've been here for a few years and only found them a couple of months ago). Everybody assumes you either get weldless fittings and try to leak-proof it all, or you get a pro welder to do the job for you and hope you can get away without losing your shirt on the deal. I'd never heard of "silver solder" until I stumbled across Bobby's thread. Even then, I looked at the price for silver solder and balked until I found the $10 kits at AirGas that were plenty to do all my fittings.

It's really easy to do. I actually enjoy it.

 

[SDBob]

It silver soldered up just fine. I don't know what I was thinking about threading it further into the fitting to get rid of threads. The female threads are tapered. But those threads were going to be exposed regardless.

But... it soldered easily. The only draw back I see is weakness at the joint due to the wall thickness where the threads are cut. Easily mitigated by a $1.00 clamp by the joint. I man-handled it in the vice and I couldn't crack it.

I'm going for it. No compression fittings for me. That knocks off a ton of extra hardware.

 

[SilverZero]

It silver soldered up just fine. I don't know what I was thinking about threading it further into the fitting to get rid of threads. The female threads are tapered. But those threads were going to be exposed regardless.

But... it soldered easily. The only draw back I see is weakness at the joint due to the wall thickness where the threads are cut. Easily mitigated by a $1.00 clamp by the joint. I man-handled it in the vice and I couldn't crack it.

I'm going for it. No compression fittings for me. That knocks off a ton of extra hardware.

When I built my first HERMS kettle last year I was using an aluminum coil with brass fittings. When the compression just wouldn't stop leaking I tore it apart and salvaged the female parts on either end, and sealed them up with JB Weld. Worked perfectly. It was then that I realized I needed to start thinking of my own solutions instead of relying on what everybody else does. You're there now.

 

[SDBob]

When I built my first HERMS kettle last year I was using an aluminum coil with brass fittings. When the compression just wouldn't stop leaking I tore it apart and salvaged the female parts on either end, and sealed them up with JB Weld. Worked perfectly. It was then that I realized I needed to start thinking of my own solutions instead of relying on what everybody else does. You're there now.

Amen, and God bless JB Weld.

 

[Calfj60]

Do you have a picture with the fitting on? I'm trying to picture what you are making. Sorry I'm a visual learner

 

[crane]

I say go for it. I'm about to do something similar. I bought some Chinese solenoid valves that are supposed to be 1/2" npt, but no matter how much Teflon tape I put on a fitting it will still bottom out and leak. I hate how some of the Chinese stuff doesn't have real tapered npt threads. Anyway when I get some time I am going to take it all apart and solder the fittings in it so I can get a good seal.

 

[SDBob]

https://drive.google.com/open?id=0B4vXJz1SOThZSDR1UTcwcFNvQVk

OK, so when you look at this picture, understand that it was a test fitting. I initially threaded it with the normal length threads, stopping the die as the last tooth exited the end of the pipe, or tubing, lol. I got my normal pipe depth into the female NPT, but noticed there were still about 5 threads showing inside the 3 piece valve. Thinking I could eliminate these threads by over-threading, I put more turns on my threader. It didn't work, obviously. But given it was a test fitting, I soldered it up anyway. I was nervous but it soldered easier than I thought. I think I can make the others look much better.

With respect to the diminished wall thickness of the tubing, it's my belief after some stress testing involving a bench vice and a sledge hammer that the silver solder restores the tubing to it's original strength. I may be wrong, but I slapped that joint like a step child and it didn't crack.

Visualize the silver solder getting pulled up and over each thread inside that fitting, and you'll understand why I believe this connection is superior to many other solutions available. And it doesn't cost $10.00.

I'd still like to find a way to eliminate the threaded surface left behind in the interior of the valve, but it's not a critical problem at this point.

I'm still looking for a flaw in this solution, so I welcome all views.

 

[SDBob]

By the way, again, that's 3/4" stainless tubing with 1/2" NPT threads. The tubing can be bought in 4' sections, and I'm polishing the insides with a dremel bit I welded to a 24" piece of 3/16 steel rod. Hit it from each end before bending and threading. Doesn't take that long to get a nice shiny interior surface.
A 1/2" hand bender designed for electrical conduit is inexpensive and easy to learn to use. The bend radius is about 5-3/8", which is a bit bigger than I'd like but it's workable.
I'm not saying I'm going to be anywhere close to sanitary standards with this method, but I think it's my best available solution. And given the fact that $500.00 of Swagelok fittings may have become unnecessary, stainless piping is affordable.

 

[Calfj60]

By the way, again, that's 3/4" stainless tubing with 1/2" NPT threads. The tubing can be bought in 4' sections, and I'm polishing the insides with a dremel bit I welded to a 24" piece of 3/16 steel rod. Hit it from each end before bending and threading. Doesn't take that long to get a nice shiny interior surface.
A 1/2" hand bender designed for electrical conduit is inexpensive and easy to learn to use. The bend radius is about 5-3/8", which is a bit bigger than I'd like but it's workable.
I'm not saying I'm going to be anywhere close to sanitary standards with this method, but I think it's my best available solution. And given the fact that $500.00 of Swagelok fittings may have become unnecessary, stainless piping is affordable.

Where are you buying the stainless steel? What are you planning on using this for if you don't believe its sanitary?

 

[SDBob]

A local metal supply company.
A "sanitary" installation means no exposed threads anywhere, ie. tri clamp. Welding sanitary tubing is an art I'm not prepared to attempt right now, so my 3 piece valves all have threaded hubs. Regular cleaning handles the thread issues.

 

[IslandLizard]

I really like the ideas here. And is "sanitary" always needed?

Whatever gets boiled doesn't need to be assembled in a sanitary way. Threads and puckery welds are still acceptable.

Anything that comes in contact with chilled wort can be sterilized by placing in a 250-300°F oven for an hour. Just make sure there are no plastic or low temp parts (e.g., PTFE valve seals) attached. Whoever uses a plate chiller can testify to that technique.

Camlocks can be used to break down larger runs.

 

[Calfj60]

I was just curious, because someday I want to replace the silicone for hard line. I'm using tri-clamps already. Thank you very much for posting this.

 

[Beernip]

The only thing I've found soldering my brew kettle is that the strength of the joint isn't near that of welding and using a long piece and some leverage you could break the solder.

If these are fixed lines on a brew system I think it should be fine as they won't get much stress on the joints. Even when my fittings do break they are easy enough to fix.

 

[SDBob]

I've got about 5/8" screwed in wrench tight. When I get back to the shop I'm gonna rig a torque wrench and find the breaking point. Any guesses?
I say it holds at least 50 ftlb lateral pressure.

 

[SDBob]

Well, I was able to get over 75 ft.lbs. on it before the end of the tubing deformed to the point where the test jig I threw together would slip out. The picture shows 73.3, but that was as much as I could do with one hand and take the picture. The 2nd blurry picture shows the tubing deformation and that the bolt wasn't deeper than the end of the threads.

I'm not going to be standing on these pipes, and they'll be stronger when they're threaded properly, so as far as I'm concerned I'm good to go.

https://drive.google.com/open?id=0B4vXJz1SOThZUWxDQUZqRENjdUE
https://drive.google.com/open?id=0B4vXJz1SOThZeFNUYlpsZmc5ZE0