Removing acetylene low-side gauge?

[rossow (mn)]

I posted an earlier question about a dead acetylene low-pressure gauge. After trying the suggested fixes (thanks for them), I concluded it was gone for good. I bought a replacement gauge, but ... the original doesn't want to break loose. (It's almost surely a 1/8 pipe thread.) A 9/16 open end fits a tiny bit loosely, and I haven't tried with metric open-ends but fear they still wouldn't fit well enough to get the gauge to budge. Maybe it was factory-installed with permanent thread locker?

Anyway, my question is this: If I remove the whole gauge assembly from the tank, do I dare use a pencil-point butane flame to try to get things loose? As you know, heat is a great wrench, but I don't know if there's a danger in heating up the gauge's square head on the threads. I don't want to use excessive force and round off the square corners. Your thoughts on a tiny butane flame? Thanks now as with your earlier suggestions about the gauge.

 

[Phill Tibbetts]

Get a good quality wrench, It will come out. If you heat it you will probably ruin it unless it has an extension on the gauge.

 

[rossow (mn)]

Get a good quality wrench, It will come out. If you heat it you will probably ruin it unless it has an extension on the gauge.

I've test-fitted USA-made Craftsman, Mac, SK and a couple of others, and all seem equally a tiny bit loose. (I don't own Snap-On.) When you say heat might ruin it, do you mean the gauge itself (already no good) or the complete oxy and acet unit that has the hoses and screws onto the tank? I don't care about the dead gauge, but I don't want to harm the larger A and O gauge assembly.

If I have no luck plucking the 2" acetylene gauge off of the unit, I suppose I'll remove the hoses and take the whole assembly to my OA guy when I swap my nearly empty oxy tank soon. He does repairs so knows how safely aggressive to get with such problems.

I'll give an update when I get one. Thanks again. (Does anything ever go smoothly?)

 

[stevieb49829]

As you can see in the pic, the surrounding brass is fairly thin. And there's nothing nearby to be destroyed by a little heat. I'd unscrew the black cap off where the regulator handle is, and remove any plastic/rubber parts out of there first, and then heat it a bit. But do it quickly. Brass tends to migrate the heat away rapidly. If you take the two screws out of the back of the gauge, you should be able to take the surround off the mechanism, and that may give you a better purchase with a wrench. You may have to remove the lens also to accomplish this.

 

[joeysmith]

Tried a good adjustable wrench?
I wouldn't be afraid of a little heat but I wouldn't do it while its on the tank zn dont go all pyromaniac heating it

 

[wh]

I would not use heat. Would not risk the internals of regulator. Either use a longer wrench, or take a hammer and hit the end of wrench you are using to jar it loose. Oxy/acetylene regulators are not to be trifled with in my opinion.

 

[RedMF40]

You should just go FULL RAMBO on the gauge. Twist its little head off to get a better bite on the square nut. In the process of putting a wrench on the gauge itself, it may decide to break loose and start to unscrew. I would put my biggest pair of channel locks on it and wear eye protection to shield against flying glass.

USE NO OIL

You can be more gentle on reassembly.

 

[matthies]

Try tightening it first, then loosen. Sounds goofy but works on pipe thread.

 

[Eman85]

How old is the regulator? I'd can it and get a new regulator if it's old.

 

[Jim.ME]

They start hard. If a 9/16 wrench fits the square, the thread is likely 1/4" NPT, not 1/8.

NO heat.

 

[caterpillar guy]

No heat you can burn the diaphragm in there and then you would need to send it in for repair or replacement. Look closely they sometimes have a different size slightly on one side that would seem loose and then a quarter turn the square will fit right for the wrench you are using. The gauge can have a bit of a step on one side use the quarter turn and it will come out. And yes sometimes just getting it to move tighter just move not a half turn or anything and it will come out easier then.

 

[Ark68SS]

Might try a 14mm wrench, it’s a bit smaller than 9/16”.
BillL

 

[MarkB_MI]

The old gauge can be sacrificed. As RedMF said, go Rambo on the gauge but try not to damage the regulator. If you break the gauge off its nipple you can get a bigger wrench on it. A large Crescent should do the trick. Or a small pipe wrench.

I think if you apply enough heat to have any effect, it's likely to damage the regulator.

 

[jimg.allentown]

The regulator has a diaphragm and a needle/seat in it, both of which can be damaged by heat. I would strongly recommend AGAINST using heat. If the gauge is that stuck, you might want to consider replacing the regulator.
My opinion.

 

[teddy52food]

I would heat it with a carbon & quench it with water, then try to loosen it.

 

[Eric in IL]

I posted an earlier question about a dead acetylene low-pressure gauge. After trying the suggested fixes (thanks for them), I concluded it was gone for good. I bought a replacement gauge, but ... the original doesn't want to break loose. (It's almost surely a 1/8 pipe thread.) A 9/16 open end fits a tiny bit loosely, and I haven't tried with metric open-ends but fear they still wouldn't fit well enough to get the gauge to budge. Maybe it was factory-installed with permanent thread locker?

Anyway, my question is this: If I remove the whole gauge assembly from the tank, do I dare use a pencil-point butane flame to try to get things loose? As you know, heat is a great wrench, but I don't know if there's a danger in heating up the gauge's square head on the threads. I don't want to use excessive force and round off the square corners. Your thoughts on a tiny butane flame? Thanks now as with your earlier suggestions about the gauge.

If you decide to wreck the gauge so you can access the nipple, don't forget the 8 point socket rolling around in your tool stash that you haven't used in the last 30 years. It might be time for it to shine.

 

[miangus]

They unscrew hard. I use an adjustable wrench. I have one that locks like vise grips. I would not heat it might damage the regulator.

 

[FarrviewSouth]

For what it is worth if you have an extra feeler gauge use it to shim the wrench so that it fits tight on the nut. It might be enough to keep it from rounding.

 

[Powered By IH]

Suprised nobody mentioned that it might be left-handed thread...if that's the case it would turn out the opposite of normal.

 

[Jim.ME]

Suprised nobody mentioned that it might be left-handed thread...if that's the case it would turn out the opposite of normal.

Because they are not left hand thread.