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Adding bottom drain to boiler using flange on triclamp elbow

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Adding bottom drain to boiler using flange on triclamp elbow

Postby Crackpot » Sun Dec 13, 2015 3:55 pm

Hi there, I've been working on my boiler (55 gal stainless drum), I'd like to add a bottom drain and I'd like some fabrication advice.

I want to take a triclamp elbow and use the flange as a silver-solderable mounting surface. It seems to me that the wider flange would give a much stronger connection vs just using a ferrule. This would be covering a pre-cut hole near the rim.

I'll be using steam injection (will have its own thread) so the bottom drain won't get in the way of a burner or anything. The drain is large because it'll be matching the (new) garbage disposer I'll be using as a pump/grinder.

Also, is it worth soldering the inner seam on the bottom of the drum where it's folded over into the rim? It looks like a prime spot to get crap stuck in that'd be difficult to get off.
I'm thinking of fluxing the area (Harris flux), placing a silver solder ring in it and heating up the area with my mapp torch from the outside until the solder melts and flows into the seam. It'd leak-proof the area too.

Thoughts?

Sorry this is in the "welcome" area, don't have access to the rest of the site yet.
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby varocketry » Sun Dec 13, 2015 4:52 pm

Crackpot:

Cool idea. Certainly more bonding area. You could make a ring of the Harris Safety silv 56 and put it in the ring in the tri-clamp flange. It'll move a tiny bit when the hard solder melts, maybe.

I like the idea. I guess your barrel bottom is flat, right?.
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby zedzedtop » Sun Dec 13, 2015 6:21 pm

I've had ferrule solder seams fail after prolonged exposure to hot wash. Harris 56%Ag stuff. If you MUST solder I'd pass four or five small machine screws through as a mechanical backup. Otherwise I'd take it to a shop and have somebody TIG it.
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby Crackpot » Sun Dec 13, 2015 8:22 pm

varocketry wrote:I like the idea. I guess your barrel bottom is flat, right?.

Yeah, but I've been considering taking a 2x2x36, sanding the edges round, and slightly rounding the bottom with a rubber mallet or the like.

Zed; was the ferrule just "edge" soldered like a normal ferrule, or with a wide flange like I'm thinking of?
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby zedzedtop » Sun Dec 13, 2015 9:01 pm

It was a 1/2'' npt nut. It was pretty obvious that a small crevice formed and that this propagated across the whole face. If it had been a large flange, it would have failed as well. The repeated stress of heating and chilling with an acidic crevice that never got cleaned was likely the cause. I wouldn't use the method again for a critical joint. Wouldn't want 50gal of boiling wash suddenly coming out of a 3'' hole when you aren't expecting it. Is your flange 3''? It looks like it, or a bit larger.
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby Crackpot » Sun Dec 13, 2015 10:30 pm

It's 3 inches to match the pump/grinder inlet size. I like the idea of a mechanical attachment, but I'm hesitant to drill a hole all the way through it for attachment bolts because of possible future leaks.

I've also got a 4" triclamp butterfly valve that I can't use for its original purpose. I could attach it to the bottom instead, the valve body is beefy enough that I could drill and tap mount holes in it without going all the way through the flange. Then I'd reduce down to 3" to match the grinder inlet size.

It's also avoid having so much wash down in the elbow.

I've got a little mig welder, it wouldn't be as pretty but I could probably weld the flange on - If I don't burn through the thin stainless of the barrel. I've never welded thin stainless before.

Or I could braze it on..
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby Rebel_Yell » Tue Dec 15, 2015 6:20 pm

Have access mate. Moved the topic here for more discussion.
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby acfixer69 » Fri Dec 18, 2015 8:31 pm

With good internal purge gas and a Tig or Mig you won't go wrong. How ever a good sweat joint would work as well for a drain. The large contact area is a plus. In the boiler top where temperature differences will raise fast and expansion of the dissimilar metals could cause a cracking. Building a very similar boiler so very interested in how it works.

AC
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby zedzedtop » Sat Dec 19, 2015 3:13 am

I highly recommend you don't braze this joint. The melting temp is plenty to sensitize the stainless, and the large fitting will necessitate more heat to the area. In short, sensitizing stainless refers to a loss of the alloy's corrosion resistance. You're then going to expose the joint to a hot, acidic environment for hours on end. There will be stress on the fitting. Theory, my own experience, and the severe risks involved are banking against you. I understand the allure of wanting to diy. If you look into having a shop TIG it for you, you could prepare everything in advance and have a bunch of other fittings/ferrules ready for them to do too. Often shops charge and hour minimum, which could be a lot of ferrules if they are prepped in advance.
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Re: Adding bottom drain to boiler using flange on triclamp e

Postby zedzedtop » Sat Dec 19, 2015 3:27 am

The fitting that failed on me did not fail catastrophically. I noticed some discolouration around the perimeter of the braze. I used the boiler several more times. Eventually it became obvious that some wash was actually leaking through and 'carmelizing' outside. In another use or two there were obvious beads/balls appearing. At this point I stopped using the kettle/boiler. Some months later I donated the boiler to a mate. Unsure of the braze, I gave it a gentle to medium tug with a ball valve attached. It popped right off. The braze was meticulously prepared with abrasives and a good wipe with isopropyl alcohol. I used the harris 56% solder with the borax based flux they sell that is recommended for the alloy. MAPP torch for heat.
'Bubble cap plates are better for batch distillation than perforated plates' - Benjamin Franklin

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