Oxy in a refillable cylinder is stored at approximately 2000 lbs.
per sq inch. That pressure makes it impossible to make a valve that
won’t leak if only opened partially.
The valves on oxygen tanks have 2 seats on them. One is used for the
closed position & the other is used for the full open position. To
prevent oxy from leaking out when the valve is open the valve must be
opened all the way.
Acetylene is stored at a much lower pressure & the odds of it
leaking are not very great. Therefore the valve only needs to be
Another point to consider is that if an accident happens will the
torch is lit & the flame needs to be extinguished quickly only the
fuel needs to be removed to put out the flame. There’s oxy in the
air so there’s no way the oxy part of the flame could not be removed
by turning off the oxy valve.