[jaso]

Hello everyone,

I'm using the stock regulators that came with my Millermatic 220 on both 75/25 and 100% argon tanks (it's the same model regulator for both). I've gone through a few 75/25 tanks with no observed issues, but I'm having issues with leaks where the regulator hooks up to the tank on my 100% argon tank(s). On this tank it was audible and I was able to confirm the leak location using soapy water. I've cranked down on the fitting as much as I'm comfortable doing with a wrench. I'm not 100% sure if I had a leak with the previous argon tank, but I think that it did in retrospect (tank emptied faster that I expected and gauges would be at 0 the next time I went to use the machine).

I crack the cylinder before hooking up the regulator and am careful not to cross threads. I took the regulator off and noticed a lot of debris (soft and dusty - kind of like corrosion) in the threads on this tank. I cleaned both the regulator threads and the tank threads with a brass brush. I don't see any thread damage. That slowed the leak considerably, but has not stopped it.

Any sage advice here?

Thanks,

j

[VA-Sawyer]

Not sure where you are located, but here in the US, the threads don't do any sealing. They just hold the two faces of the cone together. The seal is the two metal faces, sometimes with an Oring on the Male side. Make sure those faces are smooth and free of burrs.

[Oscar]

If the cone from the regulator has scratches you can lightly buff them out with some red or gray "scotchbrite" or similar. If it has a very deep scratch, toss it in the trash can. A basic flowmeter regulator is $35.

[LtBadd]

You can also buy replacement parts

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[jaso]

Thanks a lot for all of the replies. Doesn't sound like there is anything special I need to be watching out for - likely just a bad or damaged regulator nipple.

Replacement part sounds like a good idea if I can't find any obvious damage to the nipple, though I've been itching to look into a flow meter...

[snoeproe]

Don’t start buying parts. The threads are supposed to seal. They are pipe threads. Pipe threads are supposed to seal. The problem is the valve on the bottle.
The last argon bottle I had didn’t seal with my regular/flow meter. I ended up taping the regular threads with Teflon tape/pipe thread tape. It made the seal and stopped the leak.
I just replaced my argon bottle again, this one seals fine with my regulator without Teflon tape. No leaks.

[VA-Sawyer]

Sorry, but the threads into the valve on the bottle, are NOT pipe threads. Pipe threads are tapered, and bind as they are threaded together. The decrease in clearance provides the seal in pipe threads.
The threads into the valve are straight threads, like a nut on a bolt. Their purpose is to provide force, to hold the stem against the cone. The seal is at the cone.
Inspect the nipple and the cone for scratches, cracks, dents, etc. A quick polish with Scotchbrite can sometimes help.

[noddybrian]

I agree the threads only create a clamping force on the cone seat so any blemish on either side of the seat can cause a leak but I doubt scotchbrite will help - it really only polishes the brass shiny - any damage will still be there - regulators mostly leak only when they've been dropped & have a deeper mark caused by the surface they made contact with - the best way I've found if you don't have machining facilities is to remove the stem from the regulator & spin it in a drill chuck against some fine emery cloth on a wooden block - on a side note the threads are pipe threads - usually 5/8" BSP ( which is where the 580 designation originates ) - pipe threads can be parallel or tapered according to they're intended use / pressure which is why you can have a tapered thread on say schedule40 pipe for something like 10 bar water & the same thread but parallel on the same size pipe with conical seats for hydraulic service pressures - if anyone is thinking of changing a regulator stem check out the new style which has a small groove with an " O " ring in to achieve better sealing with minimal torque on the nut - these will mostly seal even if the cylinder valve face is marked - obviously if you own a lathe you can adapt an old solid style to do the same.

[VA-Sawyer]

Sorry again, but the thread is not 5/8 BSP. It is defined as .965-14 NGO. A 5/8 BSP is a .905-14 thread.

I agree the Scotchbrite doesn't correct deformed metal, but it will remove corrosion, tape debris, plumber's putty, and other foreign matter. I have come across all of these in the last 40 years on cylinders. I am careful with my regulators, so don't have problems with the nipples. If it won't seal after hitting it with Scotchbrite, I take it back for exchange. Another thing the Scotchbrite does, is make it easier to see any dents, scratches or cracks in the cone.

I also agree that the O-ring style of nipple is an improvement. If I have to replace any of my nipples, I will get the O-ring style, as they will probably pay for themselves in gas savings.

[noddybrian]

@ VA-Sawyer - my bad - sorry for the confusion - it's weird how it's possible to be so sure in the mind yet wrong on something in reality - the reason I say it's BSP is over the years I've made various fittings to adapt cylinders or regulators & keep taps & dies in 5/8" BSP - I thought that's what I'd used - either I completely forgot & have the thread you stated or in the UK they don't use the same threads - likewise regulator outlets here are always BSP - either 1/4" or 3/8" but I assume stateside you have NPT which is kinda similar but not the same - I believe 1/2" is close enough to interchange but it gets progressively more difference on sizes either side of it - maybe some things are not quite the same across the pond - I sometimes forget that the majority of active members on the forum live in the land of the free & while we have a handful of members dotted across the globe most of the discussion centers around the states hence is more specific to your products - some things seem the same other aspects are very different between counties = I meant no offense questioning your post.

[Arno]

Tank connections are almost a per-country variation on thread type, left or right handed thread, male/female, sealing construction, etc. etc. etc.

Here in the netherlands a regular 200 bar (2900psi) argon cylinder has a Whitworth 21,8 x 1/14″ thread (figures.. ) and uses a flat nylon sealing washer inside.

Actually each major gas type/class (oxidising, combustible, noble, toxic, etc. etc.) has it's own thread and connection here so you can never attach the 'wrong' regulator/connection to a bottle.

I guess as bottles are so long-lived and surrounded by so many rules, regulations and approvals everywhere around the world, old-skool regional/local standards like these not just survive bu are continuing as it would just be too much effort and cost to go to a more unified standard.

Bye, Arno.

[VA-Sawyer]

Noddybrian,

I wasn't offended, sorry if I sounded that way. I spent hours doing research on the 580 standard before my last post. The AGO is a defined thread from the AGA, but I'm not going to spend $500 to get a copy of the standard from them. I was just interested in what the thread profile was.
This thread got me interested in just what the 580 standard really was. I sometimes make my own fittings for things, and was looking for the required specs. It all turned into a deep rabbit hole.

[Lightning]

It all turned into a deep rabbit hole.

Ain't the internet great?

[VA-Sawyer]

Actually, it really is. I learn new stuff every day from the net. You need to have a pretty good BS filter, but there is a lot of good infomation available.
I was suprised that I couldn't find a drawing with the NGO thread specs. It appears that the AGA keeps a very tight leash on that info. I found the specs for BSP threads. Wentworth 55 degree profile, etc. No such luck on AGA thread shape. It happens sometimes.
Still, even with the 'deep rabbit holes, I end up learning things.