Acetylene tank/regulator seal concerns

As I mentioned previously, I have two acetylene tanks, 145 CF and 397 CF.
So I bought some O/A kit that includes a regulator, among other
things.
Here's something that concerns me: the 397 CF tank, seems to leak acetylene from the seal between regulator and tank. The symptom of it is that the high pressure gauge shows pressure that declines relatively rapidly if I close the tank valve. I would say most pressure is lost in one minute. This makes me concerned since acetylene is explosive.
Here's my findings:
1) Quick pressure loss with tank valve opened and then closed, happens on the 297 CF tank
2) it does not happen with the 145 CF tank, or at least it is extremely slow
3) The rate of loss on 397 CF tank seems to depend from how tightly I tighten the connecting nut. The tighter, the slower is the leak. I am not sure how hard I can push that brass nut, but my guess is not too hard. I used perhaps 50 Ft/lbs or so of force.
Any thinking on this. Thanks.
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Yeah, five minutes with a canfull of water, a few drops of dishsoap, and a chip brush should be pretty evident.
Might your gas supplier give you credit for a mostly full tank when you exchange it? My first instinct in this situation is to make it someone else's problem... trying to fix it on your own is likely to only lead to madness or injury. --Glenn Lyford
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Try tightening the packing nut on the cylinder valve. Checking for leaks with a soap solution is a good idea. I use 409 cleaner in the spray bottle. Engineman

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"erngineman" wrote: Try tightening the packing nut on the cylinder valve. Checking for leaks with a soap solution is a good idea. ^^^^^^^^^^^^^^^^^^^^^ Chances are it's in the cylinder-to-regulator connection, since the OP says the tighter he makes the connestion the slower it leaks. Now, to determine whether it is the regulator or the tank valve, swap the regulators to the opposite tanks. If the big tank still leaks, it should go back to the dealer. If the leak moves to the smaller tank, the regulator needs help.
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Leo, it is the tank end for sure. When I move the same regulator to the small tank, no leaks. I will try to clean it inside with scotchbrite or something like that.
i
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In an ideal world, it shouldn't leak at all with just good snugging. Spray some Windex on there, and that will tell you a LOT. Then look at everything. If you can't see anything that's obviously deformed or dinged, take it to the shop. Maybe someone before you really reefed it down and distorted it. It could be just a little distorted enough to leak, but appear good. Fix it. It might be as easy as getting a new nipple and shaft. (that sounds weird, doesn't it?) That's a good place for a fire to start. I've heard that stuff is flammable. ;-)
Steve
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SteveB wrote:

Not to mention that if you over tighten your regulator to fit, then you'll distort _it_.
I can't see a decent welding shop _not_ wanting to make good on this.
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Tim Wescott
Wescott Design Services
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Ignoramus14646 wrote:

Don't assume you know where the leak is, use dishwashing soap and a brush to wipe it here and there and find the exact leak location. It is very easy. It could be the main valve fitting, the pipe to the regulator, the regulator diaphragm, the low-pressure side, or even the tank valve stem.

Oh, no, we go quite a bit higher than that. Some tank valves have mars on the sealing surface that close up if you crank down tighter. Is this a rental cylinder? If it leaks, make them swap it out for a good cylinder. Also, it could be your regulator fitting that is marred. Inspect visually, you can replace the fitting pretty easily.
Jon
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