Question concerning O Rings for repairing oxy/acet torch used for
I have an airco torch that needs new o-rings in the valves.
If I go to the hardware store in the o-ring box and get o-rings that are
black and have the same dimensions as the old ones should be, is there a
difference between Mr. Hardware's o-rings and the special replacement
parts from Concoa (if I could get them) ?
Thanks in advance.
Can't give you real advise, but there are about 3 or 4 different "O" ring
materials. Some are more compatible with the materials that they are seal
against that others. Silicone is petty resistant to heat, but is pretty soft
and will blow out at high pressure. Nitrile is reasonablely good as a
general rule but I'm not sure how compatible it is with oxygen & acetylene.
Most bearing shops sell "O" rings so you might call on one and ask the sales
bloke about which ones to use.
you want fluorocarbon o-rings , some places call them viton , they will hold
up much better than
nitrile or buna-n , some torches use pure silicone o-rings ,
you can tell if your old ones are viton or nitrile by holding them up to a
cigarette lighter , nitrile burns quickly and readily while viton will only
smolder and char
Can't find the original reference but I've read somemewhere that
severely overheated Viton rings degrade to some pretty unpleasant
fluorine compounds that are dangerous to inhale or handle. Perhaps
some of our chemist friends can comment.
One of the local welding supply places here has various torch o-ring
seals on the shelf, kind of surprised me when I saw them, they're the
kind of outfit that wants to do your repairs for you. Have you tried
any place local? I know the Victor torch I've got uses some pretty
dinky seals that I couldn't possibly find at the local hardware joints.
With pure oxygen, you really don't want to take chances, the wrong
material is apt to take off in flames. Most hardware store o-rings
I've seen have been Buna-N or neoprene, they're intended for plumbing
use, not oxygen. If you're hard up for it, the MSC catalog has o-rings
in a lot of different materials. I'd think a flourocarbon or silicone
seal would probably be best for oxygen, not sure about acetylene.
Nitrile: Most common elastomer in o-rings. Aka
Buna-N, NBR, acrylonitrile-butadiene copolymer. Excellent resistance to
petroleum products, silicone greases and oils, and water. Good
compression set resistance, cold flow, tear, and abrasion resistance.
Poor resistance to ozone, sunlight, or weather. Temperature range
(depending on compound composition) -65F to +300F. Typically 90 Shore A
Silicone: Although this elastomer is not commonly found in scuba
o-rings, I have listed it because many divers mistakenly refer to the
amber-colored o-ring in some valve faces as silicone when in fact it is
polyurethane. Silicone has poor tensile strength, abrasion and tear
resistance, but has excellent flexibility properties over a wide range
of temperatures. The temperature range is -80F to +450F.
Fluorocarbon: A copolymer of vinylidene fluoride and
hexafluoropropylene, fluorocarbon elastomers are highly resistant to
deterioration when exposed to many fluids and gases. It also exhibits
low compression set, and is highly resistant to heat; it is this
property that makes it a common elastomer in Nitrox applications. It is
most widely known as Viton, which is a registered trade name of the
DuPont Dow Chemical Company. The temperature range is -20F to +450F.
Aka FKM or FPM.
Polyurethane: Polyurethane, or urethane, is highly resistant to
petroleum products, ozone, and oxidation. It exhibits high tensile
strength and is very abrasion resistant. This is the amber-colored
o-ring found in the valve face of some cylinder valves. The temperature
range is -65F to +200F.
Ethylene Propylene: Commonly referred to as EP or EPDM (ethylene
propylene diene monomer), it is a copolymer of ethylene and propylene.
It has excellent resistance to ozone and sunlight, compression set, and
most solvents. It is non-compatible with petroleum fluids and oils. It
is considered inert in the presence of oxygen, and has become
increasingly the elastomer of choice for EAN/Nitrox applications. The
temperature range is -65F to +300F.
Also used: Neoprene aka CR.