Hi all,
Question concerning O Rings for repairing oxy/acet torch used for METALWORKING.
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.
"Machinery's Handbook" has good design guidelines for sizing glands to the O ring.
J&L Industrial
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.
Tom
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
Ya. Viton is the type I couldn't think of. They are the best all rounders when you don't want to take a chance. Probably cost an extra 20 cents but what the hell!
Ah, better not to do that. The combustion by-products from viton are kinda nasty I think.
Jim
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.
Jim
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.
Stan
yes , yes they are , don't smoke viton o-rings
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 hardness ("durometer").
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.
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