JB Weld as a sealant

[Cliff Rohrabacher]

Application:
1.) micro levels of food contact at the edge of the M-&-F thread intersection line
2.) 212 F degrees is the duty temperature.
3.) Used to join and seal SST half inch pipe threads
4.) Ph of the contact fluid is about 5.2

It's a goofy way to get a bulkhead pass through into a pot of boiling fluid.
A nut that threads onto the pipe threads, an O ring, a coupler, and a nipple.
The coupler and nut and O ring go on the inside of the vessel where they effect a seal. It's the bulkhead fitting package sold & in the picture here:
http://www.bargainfittings.com/index.php?route=information/information&information_id=7

I thought that it might be a real bonafide bulkhead fitting just from China. But it's not, it's just a jerry rig, using plumbing parts.

Anyway I have some of them and I can't quite get my head around how it seals. Yah I get the O-ring against the vessel wall, but as to the threads?

Lots of other people use these things. I've read their posts in brewing forums. They claim the fittings produce a leak free junction.

Yet when I dry fit it all together I find that there are "issues" obtaining full thread engagement. So I'm thinking instead of Teflon tape what about JB Weld?

Looking at the picture knowing what I just described what do you think?

[Jim Koepke]

When you do the dry fit is it in place where it will be used?

The silicon O-ring needs to compress in order for the seal to be made.


Yet when I dry fit it all together I find that there are "issues" obtaining full thread engagement. So I'm thinking instead of Teflon tape what about JB Weld?

From the information I can not determine if the threads are not tight or do not reach fully into the coupling or if there is not a tight fit in the vessel where it is being installed.

Many things like this are put together by entrepreneurs to fill a need. Often, it will not fit every case. It is also possible a part got mixed in that does not meet specifications.

For such an installation, I would avoid something as permanent as JB Weld, not only for the permanence, but for what it could do to the flavor or quality of anything with which it comes into contact.

Pictures showing your installation with details of the problem encountered will help in developing a solution.

jim

[Dan Hintz]

I take it you're worried about the fluid seeping by the threads without some form of sealant in there? If so, I wouldn't worry about it once the nut is snugged up. If the pot was under pressure I would see it as a problem, but at atmo you're fine. If you want to be extra comfortable, find a food-grade grease and put a bit on the threads before cranking it down.

[Cliff Rohrabacher]

From the information I can not determine if the threads are not tight or do not reach fully into the coupling or if there is not a tight fit in the vessel where it is being installed.

I said: "there are "issues" obtaining full thread engagement."
On a pipe thread, that means in, this instance, that the metal to metal engagement of the male & female threads is not happening fully. Metal pipe threads are supposed to interfere with each other such that the metal deforms under the force of engagement creating a seal. Pipe dope and teflon tape are just for those micro-size cracks in the metal to metal joint that don't fully engage.


I take it you're worried about the fluid seeping by the threads without some form of sealant in there?

Yah, That's correct. There's two places inside the vessel where a seal is paramount: First its the threads between the nipple and the coupler. Then there's the O-ring .

If the O-ring seal leaks it'll let fluid leak out of the vessel.
That is not a sanitary problem it's just messy.

If the thread fails to seal it'll mean that fluids passing through the bulkhead fitting are able to exchange with the fluid in the vessel. That is a sanitary problem as it'd be leaking coolant which will flow through those bulkhead fittings, through my Swagelok fittings, and through the SST thinwall pipe that I have made into coils. The coolant may end up being plain tap water or chilled and pumped mineral oil. Either way I can't have the coolant making it past any of the junctions.


If you want to be extra comfortable, find a food-grade grease and put a bit on the threads before cranking it down.Well if the threads are not going to fully engage the actual "fit" will be a tad sloppy. This means it can work it's way loose.
ERGO: my wondering about JB Weld instead of teflon tape.

[Cliff Rohrabacher]

This is what I mean by the leak pathways
158738

There is no seal between the coupler and the nut.
The engagement of the threads between the coupler and nipple won't have much force to hold 'em together.

When Dry fitted there is only 0.075" left between the nut and coupler to obtain a seal by tightening the coupler onto the nipple.

I'd braze the nut to the coupler but I don't want brazing rod in my beer.

[Mitchell Andrus]

...beer.

Food contact. I'd have a look and see what JB Weld is made of and if there's a danger of a leaching a contaminant. Even if it isn't hazardous, it might interfere with process or storage.
.

[Cliff Rohrabacher]

I found this stuff:
MicroFlame No.3105 Silver brazing rods pack of 4
MicroFlame No.3103 - Silver Solder Flux
Silver content is high with no zinc or cadmium That might do the trick.

[Myk Rian]

Don't melt the O-ring when soldering.
I don't see why teflon tape wouldn't work. It's used on pots and pans. Shouldn't be a problem in this application. Use scissors to slice the tape thin.

[Jerry Bruette]

I suppose you could take the coupling and shorten the end that goes onto the nipple in the valve. That would put the nipple threads further into the taper of the coupling threads.

[Cliff Rohrabacher]

I suppose you could take the coupling and shorten the end that goes onto the nipple in the valve. That would put the nipple threads further into the taper of the coupling threads.

That's something I have considered. I could pop them on my lathe and trim a hundred thousandths or so off.

[Jerry Bruette]

Got thinking about that nipple at work today. I'd double check to make sure it has real NPT threads on it. It might be straight threads with the same pitch as NPT...of course those will never seal in the coupling with NPT in it.

The nut that compresses the o-ring goes pretty far up the threads. Either it's over size or your nipple has straight threads on it.

Good Luck
Jerry

[Cliff Rohrabacher]

I'd double check to make sure it has real NPT threads on it.

It is.



The nut that compresses the o-ring goes pretty far up the threads. Either it's over size or your nipple has straight threads on it.

The nut is pretty thick and beefy. The nipple is standard NPT.

I'm leaning more and more toward locking it all together with cadmium free silver braze. That is taking the coupler the nipple and the Nut and making one unitary That'll close up the places where I siimply can not bring myself to believe the notion that the O-Ring will hug the threaded section such that it will stop leaks from getting past the threads. No O-Ring can do that. O-Rings don't seal Threads.

[Bill Cunningham]

There are several thicknesses of teflon tape available. I have used a tape that was about .005 thick, and a couple of wraps of that, will seal anything. We were working with pressures of 5000 psi plus..