Hi all, I have been following the recent discussion of acetylene
safety. I am always interested in learning more about safer handling
of compressed gases. I use both oxygen and acetylene in my shop. This
morning I was reading some different safety regarding the
use of Teflon tape on threaded fittings to help prevent leaks. It was
recommended by some and strongly discouraged by other safety sites.
Seems it is not unusual to use it with propane tanks and I saw Teflon
tape being sold by some propane suppliers. I also saw that they make
not only the white Teflon tape but also a yellow tape for use with
gas fittings of some sort. One of the sources that discouraged its
use with compressed gases said that it could bend or stretch the
threads in the fitting, possibly causing a leak. Another source said
that the Teflon tape could become finely powdered and get caught on
the regulator poppet, causing full pressure downtstream. That is
technically a bit over my head but doesn’t sound good.
I have used Teflon tape sparingly in the past when connecting a
regulator to a tank. Seemed to really help get a good seal. But this
may have been a very dangerous mistake in procedure that I shouldn’t
repeat. Although looking in the archives I see that I am not the
only one to have used tape. What are your thoughts on this?
Also, how far apart should I keep an oxygen tank from an acetylene
tank? I use a Little Torch that of course connects to both tanks. So
that limits how far apart they can be. Maybe the recommendations I
was reading about keeping tanks apart was referring to storing tanks
not in use. Thanks for any and all advice. - Carrie Nunes @t-pnunes
In regards to Teflon tape in a pipe joint… Start wrapping the
tape 2 threads back from the end of the fitting and only put on a
single or double layer. You have to wrap it in the proper direction
as well, so when you screw it in it doesn’t unwrap. You just need to
make sure that no fragments get into the line, if it starts back from
the end by 2 threads, it won’t get in and gum anything up yet makes a
great seal.
I was taught how to apply it in an airframes and powerplants course
(aircraft) way back when… (I have a pretty strange backround…
computers, electronics, biomedical equipment, and aircraft
maintenance)
If properly used it can be used in any pipe thread that I am aware
of.
Almost all fittings DO NOT require or need Teflon tape or other pipe
sealer.
These fittings take place with a male/female metal to metal seal.
The threads only pull the seal together and are not part of the seal.
If there were a leak in the metal to metal seal, it would leak
through regardless of the tape on the threads.
The only time Teflon tape should be used is on the regulator gauge
threaded into the regulator.
Any other use of Teflon tape could result in a plugged line (or
torch!) if fragments of the tape are sucked into the gas line.
Teflon tape is designed to act as a lubricant on pipe threads where
the seal is developed on the thread not the face of the joint this
is the type of joint used in plumbing and natural gas lines or
propane lines in a house for example.
Do no use teflon tape on any fittings for standard regulators, hoses
or torches. all of these fittings are designed for a metal to metal
seal. If you look at both halves of a fitting you will see one side
has a conical or hemispherical shape and the other side of the
fitting will have the negative form of that shape. These are the
sealing surfaces of the fitting they are designed to be brought
together in firm contact by the threads on the fasteners. If either
of those faces is scratched up or distorted in any way then they
will not seal properly. Adding teflon tape to the threads will not
improve the ability to seal as the threads are not what creates the
seal and it is likely you will get some teflon between the sealing
surfaces and make it impossible to get the metal to metal seal. It
is also very possible that over time as the joint is taken apart and
put back together that some teflon will get into the inner parts of
the hoses and regulator which could cause operational problems with
the regulator . If you can’t get a seal on these type of fittings
there is a problem, take it to your gas supplier and ask them to
check it out for you. Acetylene and oxygen tanks are often used on
construction or industrial sites where they are not very well
treated and can often have damaged sealing surfaces on the valves
due to rough treatment. So inspect the sealing surface when you
receive the tank from your supplier if it looks damaged don’t accept
it or send it back.
My gas supplier just told me to quit using the teflon tape. It
doesn’t make a tight fit. I followed his advice and I’m no longer
plagued with gas leak problems.