Also, I was told by my welding supplier that one should open the
top of the tank almost completely; meaning several full turns
rather than the half turn that I have been exposed to in my ten
years in jewelry workshops.
The advise you received about backing out the adjustment knobs on
your oxy & gas regulators when finished welding is right on.
However, there appears to be a little confusion about opening the
tanks. The oxy tank should be open COMPLETELY. Oxy tanks are
typically under about 2000 psi. pressure when completely filled. In
order to prevent oxy from leaking around the valve stem when the
valve is open, oxy valves have 2 seats. The lower one is used when
the valve is closed. The upper one is used when the valve is open.
The only way to assure that oxy does not leak at the valve stem is to
completely open the valve until it can’t be turned any more.
The fuel gas tank on the other hand need only be opened a quarter
turn or so. Fuel gases are typically under much less pressure & the
packing around the valve stem can contain the pressure. Another
reason for only opening the fuel gas valve a little has to do with
safety. If an accident were to happen, say a gas hose came off or
began to leak badly, the gas supply should be shut off as fast as
possible. A partially opened valve makes this much faster. There is
really no need for a fully open gas valve, all that’s needed is a
sufficient volume of gas to keep the torch orifice filled.
The proper shut down procedure for a oxy/acet torch is to: 1. Turn the
gas of 1st, then the oxy. 2. Close the valves on the tanks, gas 1st,
then oxy. 3. Open the torch valves one at a time (oxy 1st, then acet),
watch the gauges on the tanks, both gauges should go to zero. 4. When
both oxy gauges have gone to zero, the acet torch valve can be opened
& the line cleared. Wait until both gauges go to zero. The torch
valves can be left open. 5. Unscrew both oxy & acet regulator
adjusting knobs until they turn freely.