Acetylene Reg leak/bleed-off, not sure which???

[timdhawk]

I picked up an older (i assume) Vicotor SR-260 A acetylene regulator. When i close the tank valve the tank pressure gauge will not hold the pressure reading and will leak/bleed-off over a couple hours from 150 down to 0. The hose side holds the pressure just fine without any drop.
Its just the tank pressure gauge.
Are these regs meant to bleed off when the tanks are closed, or do i have a leak somehwere between the tank and the guage?

thanx
tim

[MR.57]

It might be leaking at the fitting to the tank. Even when the fittings are tight they can sometimes leak a little bit that isn't noticeable unless you do a "bubble check".

I use a spray bottle full of water with a couple drops of dishwashing liquid added to check for leaks at the fittings every time I install any fuel gas regulator. It only takes about 30 seconds and is cheap insurance.

Lesson learned-
I once had a regulator fire caused by a leaking acetylene fitting lit by a stray grinding spark. I only noticed the small flame when I went to shut the cylinder off and the knob was hot. It was only the size of a candle flame and caused no damage, but I've been paranoid about leaks ever since. It had probably been burning for at least ten minutes. The fitting was properly tightened, but it was unseated just enough for a small amount of gas to leak out and one grinder spark was enough to provide ignition. It could have been a disaster.

Safety note- make sure whatever you use as a bubble check solution contains no animal fats or oil (don't use regular soap) because fat/oils are a spontaneous ignition hazard with pure 02

[DSW]

X2 on a bubble check. It could be leaking where the nipple enters the reg, at the tank valve/nipple conection, or thru the reg itself, say a pin hole leak in the diaphram.

[timdhawk]

thanx for the fast replies. What are my options if its at the tank/reg connection? I assume its a reg rebuild if its the diaphragm, right? If the bubble test shows nothing at the fitting, do i assume its within the reg?

[MR.57]

Diaphragm leaks on single stage regulators are usually audible. A torn rubber diaphragm will make a high pitched "fart" noise when pressurized that's hard not to notice. If you look at the front of any regulator around the handle you'll usually see 6-8 small holes approx. 1/8" in diameter around the circumference of the face. The holes are there so one side of the diaphragm is referenced to ambient pressure and can move freely. The gas will escape from these small holes if you have a bad diaphragm. Since you obviously don't want to get liquid inside your regulator, the only real practical method for checking them is to place your ear very close to the vent holes and listen carefully if you suspect a leak.

thanx for the fast replies. What are my options if its at the tank/reg connection? I assume its a reg rebuild if its the diaphragm, right? If the bubble test shows nothing at the fitting, do i assume its within the reg?

Disassemble the fitting and inspect the nipple where it seats in the cylinder valve. If your regulator was ever handled carelessly while off the tank, you may notice some dings in the brass cone where it seats. If it looks bad, get a new nipple (only $3 or $4 at your LWS) for your regulator. Also inspect the seat area inside the tank valve and look for corrosion/debris. I've seen exchange tanks that were stored with no cap have all kinds of stuff in there- dead bugs included!

If everything looks good, but you're still getting bubbles. Try tightening and loosening the fitting a couple times. Sometimes there's just a high spot on the brass that takes a little extra "oomph" to get seated.