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Prestolite torch shutting down procedure

I have a Prestolite torch—with one regulator. The recommended
setting is the B setting, which works just fine for me.

However, I am puzzled as to what to do when shutting down the torch
for the day. I checked two sources on the Internet. Both referred to
my specific type of prestolite. However the instructions are

One source told me to shut off the gas from the tank. Then to open
the torch valve to bleed all the gas from the hose, and then to shut
the torch valve. This same source says to leave the regulator at the
B setting. This is the procedure I have been following for years.

The other source has me follow the same procedure except that when
shutting down for the day I should " Back out the pressure adjusting
screw on the regulator."

I am not sure which procedure to follow. Also, I don’t know what
they mean by “backing out the pressure adjusting screw on the
regulator.” Is one to turn it clockwise, or counter clockwise?.

For years I have just been leaving it on the B setting, but I was
told that this will wear out the diaphram and that I should Back it

Alma Rands

Hi Alma

I remember wondering what it meant to back out the screw also. Here
is what I do now every time I am finished for the day.

  1. Turn off the tank with the hex wrench

  2. Bleed the line

  3. Back out the screw- for me it is counterclockwise until it feels
    wiggly loose.

  4. Turn off the torch handle with the little screw.

Then if the pressure creeps up during the night you have missed one
of the items above, or the tank has a goofy value and if it does
exchange it for a different one. Those B tanks used for welding are
really abused by the welders. I remember worrying about the same

Jean Menden


The second method you posted is correct. You back out the regulator
screw by turning counter clockwise until it spins freely. This
completely shuts down gas to the line so if there were a leak in
your valve seal the gas would still be stopped in the regulator
rather than re-pressurizing the line. It also means that when you
next open the tank valve the diaphragm and line aren’t forcibly
pressurized at whatever setting you left it at - also not good on
your equipment and a potential safety hazard.

This procedure will lower wear on your regulator and give you a
triple barrier to overnight line leaks: tank valve closed, diaphragm
pressure screw all the way out, torch valves closed.

In the morning check the torch valve to be sure it is closed; open
the tank valve one quarter turn; set the line pressure to the desired
position; and you’re good to go.

L F Brown Goldwork, Inc

The practice of not leaving the regulator gas flow adjusting
screw/knob turned in when the torch isn’t in use is to get the
pressure off of the diaphragm and spring, in the regulator that
controls the gas flow. as some of the gauges show the tank pressure
and not the pressure being used at the torch tip.

The marks either numbers or letters or some other means of adjust
the gas flow for the tip size. (consumption) in cu ft per hour. The
only chart I have handy is for the Turbotorch brand prest-o-lite
air/acetylene torch handles. For S-1 or S1QD tips either the
standard or quick disconnect handles is .53 to .89 Cu Ft per hour. to
the S-6/S6QD 8.8-14.8 Cu-Ft per hour.

The pressure of the coming out of the torch is between 5 psi to 14
psi. As at 15psi acetylene gas becomes highly unstable in free air.
That is why it is dissolved in the acetone liquid inside a porous
filler material in the tank. In the old days it was asbestos and or a
cement mix. now a days it is a assortment of spaceage materials.

The chances are you have an old school tank, There are some that
have been around and really have been used on a bus,truck as a light

With a full new tank having the regulator set and opening the tank
valve is when you have the best chance of having a regulator
failure. As most people open the tank valve more the 1/4 open first
thing and then wind the valve back to the 1/4 open position.

The purpose of which is to make it faster to close if their is a

“Those B tanks used for welding are really abused by the welders. I
remember worrying about the same thing! Jean Menden”

Welders generally don’t use a B tank, as there are 20 cu ft
acetylene and oxygen back pack tanks that don’t require as refilling
as often. if they need to take a small rig up a ladder etc. Welding
and cutting use more gas per hour.

The B tanks and the smaller MC tanks are used by plumbers for
soldering the most, followed by Heating,AC/refrige repair and
install. The largest user group for these tanks are the hobbyist of
all kinds.

And the biggest problem is the people that will not use the correct
valve wrench on the square stem valve. I think that they are around
a buck at the LWS. But use vicegrips,crescent wrenches or almost
close open end wrenches. There is a reason that the proper wrench is
a square closed end.

The second group is the sacred people because of the stories that
they have heard and so they crank the valve tight. Which causes
problems when they go to open it the next time, which will lead to
leaking seats in the valves.

The last bit of advice is don’t let the tank hang around your work
area unsecured make sure that it can’t fall over. If the valve snaps
off, the tank will tank off like a rocket with catastrophic results.

Hope this helps.