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Acetylene line pressure increases overnight


I have an acetylene take with two pressure gauges. Recently, the
left hand gauge (which I believe monitors the pressure in the line
to the handpiece) gradually increases the pressure reading
overnight. I bleed the line each time I’m done for the day, dial
down the pressure valve, and have checked for leaks.

Initially the pressure would only go up a bit. Today it was almost
at full pressure (into the red) from evening to this morning. I
rebled the line. There was a slight odor of the gas, but not like
when the tank is full on.

Any thoughts on what is going on? And what I should do for safety?
The tank is in my garage–it does get cool at night here. then warms
up in the day.

I would appreciate any advice. Thank you.
Jamie Tuohy

Jamie, I had exactly the same problem with my acetylene tank. Mine is
a B Tank. I have a prestolite torch, only one gauge. No matter how
tight I tightened the key at the top of the tank, the pressure would
slowly creepup and by morning the gauge would register "full.
Pressure–in the red. There was no odor of gas, but just to be safe
I checked for leaks and found none. However, being a cautious person,
I called the company which supplies my tanks, and they said it was a
problem with the tank, and they immediately came out and replaced
the one I had with another one. According to what I understand, there
is a ring inside the tank that acts as a seal. If it is not seated
correctly, or is worn, the gas will seep out, causing the pressure
in the gauge to rise. At least that is what I was told

My advice is to call the company that refills your tank (or brings a
new one in exchange for the empty one), and get a new tank.

Alma Rands

You most likely have a regulator leak. Have it checked by your local
welding shop.

John Dach

Sounds like you have a leaking regulator. Do you turn the tanks off
when you leave the shop at night?.. Teddy


Couple of questions.

  1. How old is regulator?
  2. How old are your hoses?
  3. did you perform a full leak test around the square nozzle of your

My guess is that you have malfunctioning regulator. I saw this once
on my propane tank.

Swap out the regulators, borrow a friends if you can and see if the
problem persists. If it does it is the tank. If it does not, then it
is the regulator.

One question. When you bleed the line, do you completely unscrew the
T valve to the regulator? If not, you are maintaining pressure on the
interior diaphragm of the regulator and thus weakening its integrity
to effectively read line pressure.

Hope this helps!
Karen Christians

The B tanks are the most abused tanks of any next to MC’s. It is the
valve tank seal or seat that is starting to leak. take it back to
the LWS and they should exchange it. The valve stem can be slightly
bent, since a lot of people feel it is necessary to use a 12" inch
adjustable wrench when closing the tank, when finished with the tank
for the day.

And just for some fun, The B designator stands for the original use
of that sized tank. Pre electric lights it was used to power the
lights on Buses. The MC designator with the angled valve was used om
motorcycles as it fit on the crossbar.


Hi Jamie,

I had the same problem and found it went away after I took the gauge
off of the tank, cleaned the connections by wiping with a clean
brush and paper towel. NO OIL! Then I put it all back together and it
has not leaked in six months. Try this before spending any money.

Nel Bringsjord

I agree with Glen that it is the valve tank seal or seat that is
leaking. I had the same thing happen with one of the B tanks I had.
It was not a problem with my gauge, or regulator. I phoned the
company which provides my acetylene and they made the same diagnosis
as did Glen. The problem was with the seal. They immediately sent
out a replacement tank, and took back the defective one.



You may have two problems. Try this if you haven’t already. Turn
your tank valve completely off. Leave the pressure adjusting screw at
your normal use setting and open the torch valve to drain the line.
This should result in both gauges reading zero.

Now turn the pressure adjusting screw to the left until it turns
freely. This is what you should be doing at the end of each workday
as it gives you three barriers to a gas leak: the tank valve, the
closed line pressure diaphragm, and the torch handle valve.

Let it sit overnight. In the morning if the tank gauge shows pressure
then you have a tank valve seal problem. If the line gauge also reads
a pressure then you also have a malfunctioning diaphragm in the
regulator which is much more serious than the tank valve seal. If the
latter, this situation will only get worse with time until you cannot
control your line pressure at all. This is a very dangerous
malfunction both during use and non-use periods. This should be
attended to immediately by a qualified repairman or replacement of
the regulator.

Les Brown
L F Brown Goldwork, Inc