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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Propane tanks
I have decided to make a bbq cooker out of a propane tank if I can find one
of the appropriate size. A friend of mine owns a supply house, and I believe they will have a dead one or two I can cut up and use. I was going to make a brick one in the back yard, and then a guy at my church wants me to cook up some stuff for July 18th. One on wheels would do what I need, and be available for others, too. I know to flush, fill with water, etc, to cut it. How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? ??? Steve |
#2
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Propane tanks
On 2012-06-17, Steve B wrote:
I have decided to make a bbq cooker out of a propane tank if I can find one of the appropriate size. A friend of mine owns a supply house, and I believe they will have a dead one or two I can cut up and use. I was going to make a brick one in the back yard, and then a guy at my church wants me to cook up some stuff for July 18th. One on wheels would do what I need, and be available for others, too. I know to flush, fill with water, etc, to cut it. How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? I heard that Clorox works. I am sure that a good fire will also kill that smell. i |
#3
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Propane tanks / odorant
On Sun, 17 Jun 2012 13:15:46 -0700, Steve B wrote:
I have decided to make a bbq cooker out of a propane tank [snip] How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? It might make no difference in smell removal, but according to http://en.wikipedia.org/wiki/Liquefied_petroleum_gas the odorant in use nowadays is ethanethiol. Wikipedia says "In the United States, tetrahydrothiophene (thiophane) or amyl mercaptan are also approved odorants, although neither is currently being utilized." This doesn't agree with http://www.msdshazcom.com/MSDS/E/exxon/wcd002fe.htm or http://www.suhresgas.com/help/LP_GAS_ORORIZATION_INFO.html. The former says "Exxon, like many other propane marketers, uses ethyl mercaptan as the odorant, adding it in a ratio of 1.5 lb per 10,000 gallons of propane..." and the latter says "In order to detect presence and prevent an explosion from a buildup of propane gas, odorant (almost always ethyl mercaptan) is added to liquid LP-Gas. Ethyl mercaptan has a distinctive order and has a high odor impact. To familiarize yourself with this type of odor you can request €śScratch and Sniff€ť leaflets from the National Propane Gas Association..." Does anyone here know for certain what's used now? -- jiw |
#4
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Propane tanks / odorant
Ethyl mercaptan is the old common name (along with mercaptoethanol) for the
more IUPAC-correct ethanethiol. Same compound, structurally CH3CH2SH, ethanol with the oxygen replaced with sulfur. Never tried to wash it out but I have to think that bleach followed by fire should do the trick :-). ----- Regards, Carl Ijames "James Waldby" wrote in message ... On Sun, 17 Jun 2012 13:15:46 -0700, Steve B wrote: I have decided to make a bbq cooker out of a propane tank [snip] How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? It might make no difference in smell removal, but according to http://en.wikipedia.org/wiki/Liquefied_petroleum_gas the odorant in use nowadays is ethanethiol. Wikipedia says "In the United States, tetrahydrothiophene (thiophane) or amyl mercaptan are also approved odorants, although neither is currently being utilized." This doesn't agree with http://www.msdshazcom.com/MSDS/E/exxon/wcd002fe.htm or http://www.suhresgas.com/help/LP_GAS_ORORIZATION_INFO.html. The former says "Exxon, like many other propane marketers, uses ethyl mercaptan as the odorant, adding it in a ratio of 1.5 lb per 10,000 gallons of propane..." and the latter says "In order to detect presence and prevent an explosion from a buildup of propane gas, odorant (almost always ethyl mercaptan) is added to liquid LP-Gas. Ethyl mercaptan has a distinctive order and has a high odor impact. To familiarize yourself with this type of odor you can request "Scratch and Sniff" leaflets from the National Propane Gas Association..." Does anyone here know for certain what's used now? -- jiw |
#5
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Propane tanks / odorant
"James Waldby" wrote in message ... On Sun, 17 Jun 2012 13:15:46 -0700, Steve B wrote: I have decided to make a bbq cooker out of a propane tank [snip] How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? It might make no difference in smell removal, but according to http://en.wikipedia.org/wiki/Liquefied_petroleum_gas the odorant in use nowadays is ethanethiol. Wikipedia says "In the United States, tetrahydrothiophene (thiophane) or amyl mercaptan are also approved odorants, although neither is currently being utilized." This doesn't agree with http://www.msdshazcom.com/MSDS/E/exxon/wcd002fe.htm or http://www.suhresgas.com/help/LP_GAS_ORORIZATION_INFO.html. The former says "Exxon, like many other propane marketers, uses ethyl mercaptan as the odorant, adding it in a ratio of 1.5 lb per 10,000 gallons of propane..." and the latter says "In order to detect presence and prevent an explosion from a buildup of propane gas, odorant (almost always ethyl mercaptan) is added to liquid LP-Gas. Ethyl mercaptan has a distinctive order and has a high odor impact. To familiarize yourself with this type of odor you can request "Scratch and Sniff" leaflets from the National Propane Gas Association..." Does anyone here know for certain what's used now? -- jiw Or how to remove it when it is undesirable? Is there an echo in here, or is it just me? Steve |
#6
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Propane tanks
"Steve B" wrote in message ... I have decided to make a bbq cooker out of a propane tank if I can find one of the appropriate size. A friend of mine owns a supply house, and I believe they will have a dead one or two I can cut up and use. I was going to make a brick one in the back yard, and then a guy at my church wants me to cook up some stuff for July 18th. One on wheels would do what I need, and be available for others, too. I know to flush, fill with water, etc, to cut it. How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? ??? Steve Steaming for about 4 hours will get rid of about 80% of the smell. The rest can be neutralised with a wash down with potassium permanganate 10% solution, then steam again. Its likely that the smell will recur as it really does get into the metal. |
#7
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Propane tanks
Steve B wrote:
I have decided to make a bbq cooker out of a propane tank if I can find one of the appropriate size. A friend of mine owns a supply house, and I believe they will have a dead one or two I can cut up and use. I was going to make a brick one in the back yard, and then a guy at my church wants me to cook up some stuff for July 18th. One on wheels would do what I need, and be available for others, too. I know to flush, fill with water, etc, to cut it. How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? ??? Steve BEFORE you open it dump in a gallon of clorox and 10 gallons of water. Roll it around and let it set a while. Then let it drain. Now cut it open. Use a solution of 10% potassium permanganate and spray it down. If you plan on splitting it and using hinges on parts of the top weld angle strips around the cut areas before you cut. That way the cut areas are reinforced and all you need to do add the hinges. -- Steve W. |
#8
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Propane tanks
Steve B wrote:
... I know to flush, fill with water, etc, to cut it. TOTALLY unnecessary! Just cut it - there's no oxygen in the tank to support combustion and no pressure to force anything but tiny amounts of gas out. I have done it many times. How about removing the mercaptan smell? ... As others have said: bleach. Forget the potassium permanganate - you'll have a devil of a time finding it and it's unnecessary (use a burn-in fire to remove residual oil, etc & Bob's your uncle). Not your uncle, Bob |
#9
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Propane tanks
Bob Engelhardt fired this volley in
: As others have said: bleach. Forget the potassium permanganate - you'll have a devil of a time finding it and it's unnecessary (use a burn-in fire to remove residual oil, etc & Bob's your uncle). Bleach converts mercaptans just fine, but Bob, you must be living wrong if you have trouble finding potassium permanganate! It's _everywhere_ as "green sand" recharging material for iron-removal water filters. It's not cheap, and bleach is perfectly acceptable. Any strong oxidizer will work -- even hydrogen peroxide, if you have enough money! I differ with you on the idea of cutting into an "unknown" propane tank, though. You can't know if someone has introduced air into it. If they did, you have a bomb on your hands (and "bombs are us", since I'm in that business). It's a minor bit of safety practice to yank the valve and properly purge the tank. It's certainly less expensive than a stay in the emergency room. Lloyd |
#10
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Propane tanks
Lloyd E. Sponenburgh wrote:
Bob Engelhardt fired this volley in : Bleach converts mercaptans just fine, but Bob, you must be living wrong if you have trouble finding potassium permanganate! It's _everywhere_ as "green sand" recharging material for iron-removal water filters. ... Oh yeah, I remember using it for that. Easy enough to get, but awful to work with - I also remember the indelible purple stains G. I differ with you on the idea of cutting into an "unknown" propane tank, though. You can't know if someone has introduced air into it. If they did, you have a bomb on your hands (and "bombs are us", since I'm in that business). .... Introduced air in the tank cannot create a bomb condition. A good old whoosh for sure, but not a bomb. Pure oxygen would have to be added for that. Bob |
#11
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Propane tanks
Bob Engelhardt wrote:
.... Introduced air in the tank cannot create a bomb condition. A good old whoosh for sure, but not a bomb. Pure oxygen would have to be added for that. Oh ... that reminds me of one caveat: do NOT cut open an unpurged tank with oxy-fuel. That oxygen can create a problem. Bob |
#12
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Propane tanks
Propane plus air, under pressure. That's explosive mix, if the proportions
are right. I'd not want to chance it. The risk of failure is too terrifying. Christopher A. Young Learn more about Jesus www.lds.org .. "Bob Engelhardt" wrote in message ... Bob Engelhardt wrote: .... Introduced air in the tank cannot create a bomb condition. A good old whoosh for sure, but not a bomb. Pure oxygen would have to be added for that. Oh ... that reminds me of one caveat: do NOT cut open an unpurged tank with oxy-fuel. That oxygen can create a problem. Bob |
#13
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Propane tanks
Bob Engelhardt fired this volley in
: Introduced air in the tank cannot create a bomb condition. A good old whoosh for sure, but not a bomb. Pure oxygen would have to be added for that. Bob, please take this from someone who knows something about explosive mixtures -- Approximately any mixture of air and propane that would create a good blue flame will constitute a mixture that will explode with force sufficient to fragment the tank. I'm not guessing or theorizing. I do this for a living -- making explosives (and machines to make explosives) for stage and film. Propane is one of our "staple" items. I have experience (deliberately) creating both flame and explosion effects with propane. The lower and upper explosive limits of propane/air mixtures are pretty broad. It doesn't have to be stoichiometric mixture to explode. (acetone is worse... look it up) One machine I designed mixes pure oxygen and propane under PLC control to create "tuned" explosions for noise-making, with differing mixtures for differing noise levels. Another less expensive system (in terms of expendables) does the same thing with compressed air. The difference is one of total acoustic pressure -- oxygen being the more "efficient", since the entire mass of mixture is explosive, where with air only about 30% of it is (the rest being nitrogen and trace gasses). You seem to be working from the stance of "it hasn't killed me yet", which is a fatal flaw in blasters, fireworkers, and stage pyrotechnicians. We (who still survive) work from the posture of "what I don't know will kill me." You're welcome to cut into all the propane tanks you want, and I wish you no harm when you do. Please don't recommend this practice to others who might not end up as lucky as you. LLoyd |
#14
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Propane tanks
Lloyd E. Sponenburgh wrote:
Bob Engelhardt wrote: Introduced air in the tank cannot create a bomb condition. A good old whoosh for sure, but not a bomb. Pure oxygen would have to be added for that. Bob, please take this from someone who knows something about explosive mixtures -- Approximately any mixture of air and propane that would create a good blue flame will constitute a mixture that will explode with force sufficient to fragment the tank. I'm not guessing or theorizing. I do this for a living -- making explosives (and machines to make explosives) for stage and film. Propane is one of our "staple" items. I have experience (deliberately) creating both flame and explosion effects with propane. The lower and upper explosive limits of propane/air mixtures are pretty broad. It doesn't have to be stoichiometric mixture to explode. (acetone is worse... look it up) You don't say what your experience is regarding adding air to a propane tank, so I assume that you are extrapolating and not speaking from direct experience with tanks. I have added air to a propane tank, attempting a stoichiometric mixture, and igniting it. I did get a good whoosh. I'm not saying the mixture won't "explode". I'm saying that the explosion won't have much force. An empty tank just doesn't have enough propane in it and a lot of it has to be displaced by air to get an explosive mix. ...[oxygen] where with air only about 30% of it is ... about 20% You seem to be working from the stance of "it hasn't killed me yet", which is a fatal flaw in blasters, fireworkers, and stage pyrotechnicians. We (who still survive) work from the posture of "what I don't know will kill me." Let's turn to chemistry: _Chemical analysis of propane combustion in a closed container_ Take the term "analysis" with a grain of salt - I'm no chemist and it's been a long time since freshman chemistry. So, if the logic is wrong, let me know. And if there are 2nd order effects that I haven't taken into account (and are significant (10%)), those too. The approach here is to determine the amount of heat generated/released by ideal/stoichiometric propane-air combustion and then calculate the effect of that heat on the temperature and pressure in a closed container. The propane combustion reaction: C3H8 + 5O2 - 3CO2 + 4H2O One mole of propane reacts with 5 moles of oxygen. After burning, the reaction produces 3mol CO2 and 4mol H2O vapor (steam). The heat produced: the (net) Heat of Combustion of propane is 2043 kJ/mole, i.e., the combustion of 1 mole of propane produces 2043kJ of heat. How much will this heat raise the temperature of the gases? First, it's just not propane and oxygen involved, but the nitrogen that's in the air with the oxygen. Air is 21% oxygen and 78% nitrogen by volume, so for each mole of oxygen (O2) in the air, there are 78/21 = 3.71mol nitrogen (N2). And our mixture has 5mol O2, so there are also 18.6mol N2 in our mixture. (I'll ignore the other 1% of atmospheric gases and any atmospheric water vapor.) Assume that all the heat of combustion goes to raising the temperature of the gases in the container (none lost). The specific heat is the heat it takes to raise a unit mass 1 degree (J/g-degree). For our (resultant) gases the specific heats* (constant volume values) a CO2: 0.63 steam: 1.76 N2: 0.71 Since mass = # moles * molecular weight, the contents have these masses: CO2: 3mol * 44 = 132g H2O vapor: 4mol * 18 = 72g N2: 18.6mol * 28 = 520.8g For a temperature raise of delT, the heat required would be: delT * specific heat * mass Then the total heat is: (delT * 0.63 * 132) + (delT * 1.76 * 72) + (delT * 0.71 * 520.8) = 2043kJ reduces to: delT = 2,043,000/580 = 3,525K and the final temperature, T is: T = start + raise = 293 + 3525 = 3,818K For a constant volume, pressure is proportional to temperatu P2/P1 = T2/T1 P2 = P1 * T2/T1 = 14.7 psia * 3818 / 293 = 191 psia (176 psig) So, the peak pressure in a closed container with a stoichiometric mixture of propane and air would be (only) 191psi. Seems low? ... consider that 64% of the heat went to raising the temperature of the nitrogen in the air! Note that I didn't base the calculations on a particular tank size, because the temperature and pressure results would be the same with any volume (the amounts of gases would be proportional to the volume). 20# propane tanks are rated as follows: Working pressu 240psi Pressure relief: 375psi Test pressu 480psi Design burst pressu 960psi Observed burst pressures: 1200 - 2000psi ( not a "rating", I know) So our calculated peak pressure is 23% below the working pressure and only 19% of the design burst pressure. Also, this is worst case: it is a stoichiometric mixture in a sealed container. It's hard for me to see the risk. * - Specific heats from Engineering Toolbox web site: http://www.engineeringtoolbox.com/sp...ses-d_159.html That for steam is for 150 psig, 360 - 600F, which is probably conservative (increases with temperature and pressure). You're welcome to cut into all the propane tanks you want, and I wish you no harm when you do. Please don't recommend this practice to others who might not end up as lucky as you. I don't think that luck has anything to do with it. Bob |
#15
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Propane tanks
In article ,
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote: Bob Engelhardt fired this volley in : As others have said: bleach. Forget the potassium permanganate - you'll have a devil of a time finding it and it's unnecessary (use a burn-in fire to remove residual oil, etc & Bob's your uncle). Bleach converts mercaptans just fine, but Bob, you must be living wrong if you have trouble finding potassium permanganate! It's _everywhere_ as "green sand" recharging material for iron-removal water filters. It's not cheap, and bleach is perfectly acceptable. Any strong oxidizer will work -- even hydrogen peroxide, if you have enough money! I differ with you on the idea of cutting into an "unknown" propane tank, though. You can't know if someone has introduced air into it. If they did, you have a bomb on your hands (and "bombs are us", since I'm in that business). It's a minor bit of safety practice to yank the valve and properly purge the tank. It's certainly less expensive than a stay in the emergency room. Lloyd A little OT here, but just the other day I ran across a most interesting YouTube video involving potassium permanganate and hydrogen peroxide... http://www.youtube.com/watch?v=OLUyeCC-2Ko Be patient, the cool part is the 'accidental' fast reaction towards the end. Erik |
#16
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Propane tanks
Erik wrote:
A little OT here, but just the other day I ran across a most interesting YouTube video involving potassium permanganate and hydrogen peroxide... http://www.youtube.com/watch?v=OLUyeCC-2Ko Be patient, the cool part is the 'accidental' fast reaction towards the end. Skip down to 4:20 for the cool part. |
#17
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Propane tanks
On 6/17/2012 4:15 PM, Steve B wrote:
I have decided to make a bbq cooker out of a propane tank if I can find one of the appropriate size. A friend of mine owns a supply house, and I believe they will have a dead one or two I can cut up and use. I was going to make a brick one in the back yard, and then a guy at my church wants me to cook up some stuff for July 18th. One on wheels would do what I need, and be available for others, too. I know to flush, fill with water, etc, to cut it. How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? ??? Steve YES, wirebrushing! THAT'S the ticket! |
#18
Posted to rec.crafts.metalworking
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Propane tanks
In article ,
"Steve B" wrote: I have decided to make a bbq cooker out of a propane tank if I can find one of the appropriate size. A friend of mine owns a supply house, and I believe they will have a dead one or two I can cut up and use. I was going to make a brick one in the back yard, and then a guy at my church wants me to cook up some stuff for July 18th. One on wheels would do what I need, and be available for others, too. I know to flush, fill with water, etc, to cut it. How about removing the mercaptan smell? Once I get it open, what should I do to kill that smell, or will heating it up with charcoal for the first time do the trick? Electric wirebrushing? Scrubbing with some type of cleaner? ??? Steve Bite the bullet and go buy yourself a Webber 22 1/2" [1] charcoal BBQ. You'll never look back. They work really well, and will put big smiles on your face till your a little old man. Had mine since the early 80's... probably used it once a week average, and it's still going strong. Replacement parts are available (but I've yet to need any). http://www.weber.com/explore/grills/...ch-silver-22-1 http://www.amazon.com/Weber-741001-2...er/dp/B00004RA LU/ref=sr_1_4?ie=UTF8&qid=1340000982&sr=8-4&keywords=webber+22.5+gold Even used from Craigs list they're great, long as the porcelain isn't chipped, there are no missing parts and corrosion/rust of legs and grates is reasonable. They make other charcoal models with any bell/whistle imaginable... but the basic ones are more than satisfactory. Erik [1] If just cooking for 2 or 3, go for the 18 1/2" model. http://www.weber.com/explore/grills/...ch-silver-18-1 http://www.amazon.com/Weber-441001-1...dp/B00004RALW/ ref=sr_1_3?s=lawn-garden&ie=UTF8&qid=1340001070&sr=1-3&keywords=webber+18 ..5 |
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