Panache
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Galvanised Iron LPG tank
I have this large LPG (liquified petroleum gas i believe) cylinder that i welded legs to (yes it was empty and had been water rinsed several times).
The problem i have is that the smell of the short-chain mercaptan the gas company dopes their LPG with is seemingly unremovable. I have filled it with
some 20 L of water and boiled it for an eternity but the smell lingers. Is there a way to remove this. I know they only dope it in ppm.
Any ideas? It would make a nice cheap steam pressure vessel for me if only i can get it clean.
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woelen
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Treat the tank with a mix of some NaHCO3 and dilute H2O2 (1%) and vinegar. This works very well for removing bad smells in most instances and does not
corrode the material on the inside of the tank if you leave it in the tank for an hour or so.
Do not use mineral acids instead of the vinegar. If you use those, you certainly will get some corrosion, especially if you leave it in the tank for
many hours.
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12AX7
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I've heard bleach works well, which I suppose is just about the same thing.
You'll have to get that hydro tested and certified to use as a steam boiler. (No complaints, the pressure doesn't matter: they require certification
on steam boilers for a very good reason!)
Tim
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not_important
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Were you just boiling, or allowing free venting of the steam?
Slightly alkaline peroxide is a decent bet, but rinse will afterwards. Chlorides really promote corrosion of ferrous metals so I'd avoid that.
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Mr. Wizard
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Let me give word of caution to anyone who would weld or solder or apply flame to ANY sort of tank or enclosed container. They can and do blow up,
even when 'empty'. Rinsing them with water may give you a false sense of safety, but it doesn't prevent explosions. The problem lies with the very
thin plastic coatings, paint, light oils, and combustible residues inside most containers. LPG containers often contain a smelly waxy oily residue
that can cause this problem. I have a propane carburetor on a vehicle, and during maintenance have seen this in the oily looking stuff. Almost any
piece of metal you may have has some oil, coating, or paint on it, and when heated will smoke to a certain extent. This smoke can burn. This is a
minor thing in the open air, but in a tank it just has to reach a combustible concentration, then when ignited by your welder, torch flame, or
grinder, even a slow burning flame will raise the tank pressure to several bar, shooting molten metal, flames, and possible tank parts. I have seen
55 gallon drums fly 75 feet when being cut by a man with an abrasive wheel. Everyone insisted the drum was empty, but he was seriously burned in the
face as the flame shot out of the hole he had just created. Often the less volatile oils, paints and residues are more problematic, as people don't
recognize them as potential fuel. Once the LEL (Lower Explosive Limit) is reached in any part of the tank it can start burning. A gram or two of
material is all it takes. The LEL for diesel fuel is 0.6% for example. That means only 6 parts per thousand diesel vapor in air can burn. It can
ignite at less than 500 degrees F (257 C).
If you have to drill, grind, solder, cut, or weld on an enclosed tank, take precautions. Fill the tank with an inert gas such as nitrogen N2 or
carbon dioxide CO2, steam or water. I used to use freon until it was removed from the market. Keep the inert gas flowing while you work. This is not
meant to be a primer on how to work on tanks, just a warning to adventurous amateurs. We don't need any more one eyed, one handed chemists, with
ruptured ear drums.
Not that there's anything wrong with that ;-)
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12AX7
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Another excellent point. Ironically, by flushing it with water, you increased your danger by allowing oxygen in. If you merely had removed the valve
(thus ensuring no pressure remaining or able to build up) before working, it would always be saturated with flammable gas and the worst thing that
could happen is a candle-like flame from the valve hole.
Tim
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chemrox
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It doesn't sound like he wants to use it for pressurized material anymore or am I reading in? One drop of oil in a gas cylinder that is being filled
can kill everyone in the room. A mechanic I know lost an employee that way. Moral: If you're using it for gas let the vendor do the cleaning and
filling. By welding an empty tank heat is created inside that makes a vacuum when cooled. That could draw moisture, oil, many things ... to be
avoided. So, once the legs were welded on, it stopped being a gas cylinder IMHO.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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YT2095
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fill it with sand before welding, that should prevent anything catastophic happening.
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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12AX7
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And how do you get the slag off internally?
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YT2095
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it`s only for boiling water, it doesn`t really matter does it?
but you could tumble some grit in there after if you Really wanted it perfect.
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Mr. Wizard
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I think the sand idea is a good one. Why didn't I think of that?  I wouldn't be
afraid to try that, even with a lot of oily residue or fuel inside. Handling a large tank filled with sand can get unwieldy rather quickly unless you
have a lot of sand and a lot of strength or equipment. Tumbling a tank to remove slag and rust works. I repaired a rusty gasoline tank for my son in
law by putting it in a cement mixer after wrapping it with a blanket to hold it in the mixer. Wood blocks,foam chunks. old carpet or padding can also
be used. I put a rag and duct tape over the openings and put in a handful of iron nuts, bolts, and washers inside the tank. The mixer was positioned
in the dump position, (horizontal), to allow the metal to be evenly cleaned. An hour of this very noisy operation left me with a pile of dusty rust
and a very clean tank. In fact it exposed a few pin hole leaks that were then soldered up. Use safe procedures to solder tanks, if you don't
understand what you are doing, don't attempt this as you can be very seriously injured.
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YT2095
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it`s the way I used to do it when repairing old diesel tanks for canal boats, fill them ordinary builders sand, do the welding, hoist the thing up
with a block and tackle, tap around the welds, and then blow the sand out with an airline.
never once had a problem during or after, and the tanks were NOT entirely dry of diesel either.
I should think an LPG bottle would be much different really.
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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12AX7
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| Quote: | Originally posted by YT2095
it`s only for boiling water, it doesn`t really matter does it? |
That depends what kind of water you're boiling. If it's not going to be used for more than a few PSI -- and has a safety release valve (or burst
disk, etc.) sized accordingly, it would be okay. If you're boiling it for the purpose of steam pressure...that's a significantly more troublesome
prospect.
If you do want high pressure steam, a flash boiler is much safer -- it has less internal volume.
Tim
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Panache
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Firstly thank-you all for your concern. I must say an admirable quality of this site is the genuine concern members have when situations of potential
(yet unrecognised) danger may be suggested.
Secondly thank-you for the responses to the cleaning issue, i have just cleaned and rinsed the vessel with the peroxide acetic mix (did i mention it
was aluminium?? lol just kidding) and am letting water rinse out inside it for some time. I presently have no use for it, it originally was intended
to be the boiler for a batchwise water-still but soon after i finished it and couldn't get it clean i relegated it and converted a beer keg for the
same role (using epoxy though as i am too crap at welding to weld fittings). I never actually welded legs directly to it rather made a stand for it, i
hate welding galvanised things, being a crappy enough welder under ideal conditions.
I only asked the question as i had a clean out and was considering turfing it but now that it appears clean i will keep it until i have need for it.
Finally the steam coming out of it still smells like a locker-room shower bay, is that some sort of galvanised iron pipe hot water steam thing. Does
anyone know what i'm talking about? Is that just the smell of steam? Hmm maybe silly questions.
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PHILOU Zrealone
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| Quote: | Originally posted by Panache
Firstly thank-you all for your concern. I must say an admirable quality of this site is the genuine concern members have when situations of potential
(yet unrecognised) danger may be suggested.
Secondly thank-you for the responses to the cleaning issue, i have just cleaned and rinsed the vessel with the peroxide acetic mix (did i mention it
was aluminium?? lol just kidding) and am letting water rinse out inside it for some time. I presently have no use for it, it originally was intended
to be the boiler for a batchwise water-still but soon after i finished it and couldn't get it clean i relegated it and converted a beer keg for the
same role (using epoxy though as i am too crap at welding to weld fittings). I never actually welded legs directly to it rather made a stand for it, i
hate welding galvanised things, being a crappy enough welder under ideal conditions.
I only asked the question as i had a clean out and was considering turfing it but now that it appears clean i will keep it until i have need for it.
Finally the steam coming out of it still smells like a locker-room shower bay, is that some sort of galvanised iron pipe hot water steam thing. Does
anyone know what i'm talking about? Is that just the smell of steam? Hmm maybe silly questions. |
I had the problem with a destilation setup I made with such a tank for alcohol.
Even with long distillations with alcohol, water boiling or NaOH boiling, I wasn't able to get rid of the pollution inside. The smel had disappeared
but the ethanol from my 10% fermentation juice kept on having a very bad taste...the 90-95% ethanol I was able to distil turned from transparent to
orange brown upon addition of NaOH...I stil don't know precisely what caused this but it was only good for burning( even with a very good vigreux
collumn for the distillation).
There is some porous rubber plastic coating on the inside (at least we found this out when cuting the tank in two) that adsorbed a hurge quantity of
sulfurated compounds (organic sulfides, disulfides, thiofens and the likes).
After that discovery, we abandonned this, like you did, for an inox beer tank...that made good drinkable alcohol 95%  (yes I was able to drink that when I was younger ... although the first lap was a bit
hard ). Unfortunately those tanks are less common to find and cost a little more
to get; but it is a good investment  Hips
[Edited on 5-3-2008 by PHILOU Zrealone]
PH Z (PHILOU Zrealone)
"Physic is all what never works; Chemistry is all what stinks and explodes!"-"Life that deadly disease, sexually transmitted."(W.Allen)
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Saerynide
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| Quote: | Originally posted by Panache
Finally the steam coming out of it still smells like a locker-room shower bay, is that some sort of galvanised iron pipe hot water steam thing. Does
anyone know what i'm talking about? Is that just the smell of steam? Hmm maybe silly questions. |
For some reason, the steam lines in the undergraduate labs (not the research labs) always smelled god awful like a mixture of metal and I dunno what.
I think its the metal in the piping and probably the stuff growing in said piping.
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