Simple idea for 55 gal fuel tank w/ sight glass

[bschwartz]

Bob obviously has money to burn.... 

[mbryner]

ronmar, I meant the injector pump.  Bad choice of words on my part.  So, that means I have to install the fuel the tank horizontal to keep it above the injector pump.   Ceiling isn't high enough to install it vertical.

mobile_bob, I think used propane tanks aren't that bad to work with.  It's just the residual stink that's aweful like you said.  Once the tank is open to the atmosphere, filled and emptied of water to evacuate any residual, then it can be easily welded on or drilled.   I have a used propane tank muffler.   Some people have expressed concerned about residual propane in the tank walls, but I can't see any science to that.   Anyway, I have a free 55 gal drum, but not a free propane tank that large, so I'll stick w/ the drum.

[AdeV]

If it were my  money, I'd get that "justrite" gauge with the wee pop-up widget. Then I could rig a microswitch above, and make my own audible "full" alarm, if I needed it (e.g. if filling the tank from afar).

Of course, it doesn't help with reading a low fuel level...

[mobile_bob]

Marcus

there is nothing wrong with free as long as it is safe and effective and doesn't end up costing more to use in the end.

a 55 gallon drum is a thing of beauty, a very versatile piece of our industrial life, they can be used for containing everything from
oil to making a wood burning furnace.

and are available everywhere for at most, what?  25 bucks?

hard to beat that, i just mentioned the larger propane tanks because of the relative easy to work with, and their inclusion of a decent
fuel gauge, however they are expensive as compared to a 55 gallon drum.

as for the stinky oil, i once tried a 200 pound used tank, and found it to have over 2 gallons of the stuff in the bottom of the tank
that was one hell of a mess to contend with.

why it had that much in the tank is beyond me, i only mention the stuff as a problem in a used tank, because it is nearly impossible to tell how much is in there before you buy the tank and take it home.

to me it is worth the premium to just buy a new tank and not have to deal with that crap every again.  i had to have spent nearly 6 hours, 20 bucks at the car wash using hot soapy water, after first draining and flushing with a garden hose and 2 bottles of dawn dish soap, and having my hands smell like death for what i recall as being several weeks after the fun.

fwiw, just an option and an observation from a guy that routinely thinks he can save a buck doing it himself only to find it costs more in the end and takes vastly more time and effort than he anticipated.

btw, be sure to provide some means of draining the very bottom of your drum periodically, it will collect water over time, settle to the seam and evenually rust out the drum otherwise.  i have seen that happen surprisingly fast on drums that might have already been rusted before i got them. its really hard to see down in there well enough to tell what the condition of the drum is, right down in the seam.

thats another advantage of the propane tank, the bottom is shaped convex just like the top, and has no seam to leak, this dome can
be drilled in the center and a suitable T or elbow along with extension pipe can be fitted to make a very nice drain that will make it easy to remove water that settles to that very lowest part of the tank.

bob g

[BioHazard]

btw, be sure to provide some means of draining the very bottom of your drum periodically, it will collect water over time, settle to the seam and evenually rust out the drum otherwise.  i have seen that happen surprisingly fast on drums that might have already been rusted before i got them. its really hard to see down in there well enough to tell what the condition of the drum is, right down in the seam.

Maybe it would be a good idea to use some of that epoxy sealer meant for rusty old gas tanks in cars?

I think sometimes oil is added to larger propane tanks, to help keep the inside from rusting. (not sure how that would happen?) I imagine the oil soaks up the stink and becomes disgusting over time. I've never found that kind of stuff in "mobile" tanks though, only permanent mount type. I love makin' stuff out of propane tanks!

[billswan]

Marcus and forum

You wrote

"Some people have expressed concerned about residual propane in the tank walls, but I can't see any science to that."

Well there may not be any science in it but from my personal experience I once filled an I believe 100 pound cylinder full of water and then lowered the water level to a few inches below where i wanted to start a cut with a torch and guess what . Yes there was a pop not a large explosion but a pop that definitely got my attention. I guess it might be that onion oil bob spoke of in his post. It probably coats the inside as the water floats it out then it turns to a burnable mix as the cutting torch gets the metal up to cutting temp. At least that is my view for what it is worth............

Billswan

[cognos]

The "stenchant" added to propane is a chemical called "ethyl mercaptan". It made by mixing the pure chemical with 55% toluene, and that liquid is added to propane at the rate of 1 lb/1000barrels of propane - it's powerful, stinky stuff. It smells like skunk, for a good reason - skunk smell is butyl mercaptan.

Ethyl mercaptan is detectable by the human nose as a disagreeable odour at 1ppm - or less!

There should *never* be liquid accumulation of mercaptan in a consumer tank. I've never heard of it. Bob, your experience is very unusual. Think of it - the stuff is supposed to dissolve and vapourize with the propane, not remain in the vessel. Even if it did, you'd have to run 1000 barrels - that's 159,000 litres or 42,063 US gallons - of propane through that tank in order to collect a pound of the stuff....

It can be very effectively neutralized, and the smell made to disappear.

Mix 50 grams of lye/sodium hydroxide per gallon warm water, fill the propane tank, let sit for a couple of hours. Pour out the liquid into a suitable container, and add vinegar (or any other weak acid, HCl can be used, be careful) to bring the pH to 7 - then the liquid can be disposed of - it will be salty water.

Repeat if necessary - time and temperature are your friend here.

Propane absolutely can "sink into" the metal in the container, and be released back into the vapour space later, to form an explosive mixture. One needs to steam a container for a bit to ensure it will be gas free, and work on it right after the steam-out. Using a cold water flush can not guarantee the container will be gas-free.

Propane is a small molecule, and can become incorporated into the crystalline structure of the steel in the container, released by heat.

[mbryner]

    I stand corrected.    Thank you cognos.   Still can't see how it would come back out of the metal in enough quantity and fast enough to cause problems.

[Crofter]

Well here is the science Marcus. The propane is quite volatile and easy to blow out but there may be oil and other stuff not soluble in water so you are only temporarily displacing the gaseous volume by filling with water and emptying. The sneaky danger is oil accumulations that may be in a puddle, spread over the walls in a film or loosely held in lap seam construction of some tanks. Most now are butt welded seams both lengthwise and headers but lots of lapped jointed tanks still around. Even painted and internal corrosion treated surfaces can become dangerous when heated. Dont consider an old air receiver to be non explosive either. I saw the aftermath of a truck drive shaft that exploded because of the internal cardboard sound deadening tube. A long stretch from a propane tank but shows that it is not always the obvious that can get you.

Applying welding heat can vaporize oil or paint into an explosive mixture if you do not maintain an inert gas purge or keep it swept excessively lean by continuous air blast (that works but is not approved procedure)
Another problem is that the gases from the secondary combustion of an oxy-acetylene flame (either cutting or welding) can get forced into the tank and go poof. The oxygen cutting jet also can enrichen any oil vapours to an explosive level that would not otherwise be in the volatile range.

There have been lots of very poorly supported methods used to do hot work on vessels but they often depend more on luck than science. Popular support for some of them can be found all over the internet.

Edit; I see that Cognos was listening and replied while I was typing. I think that liquid propane sometimes contains a bit of oil that gets left behind when the tank is used for gaseous withdrawal. After many fills it could accumulate.

[mobile_bob]

another point that cannot be overstated is the dangers of using an oxy/acet torch to cut holes in or to weld to an enclosed
tank or drum of any kind, regardless of whether or not there is any flammable residue inside lurking around.

it is easy to have a blowout of the flame while cutting a hole in anything, more so for the inexperienced
it takes a remarkably small amount of acetylene gas to turn a drum or or tank into a very potent explosive device.

the results can be deadly, many folks have been seriously injured or killed cutting and welding on drums and tanks.

i really don't want to hear of anyone here being hurt or worse, so please guys don't cut of weld on a tank or drum
unless you know its clean, is either filled with water, or filled with an inert gas such as CO2, and even then use a hole saw
rather than a torch to cut holes, limit your exposure to possible bad outcomes.

bob g

[Apogee]

I've always been fairly amused by all of the folks welding on propane tanks.  Honestly, I've been waiting to hear of someone who has been really hurt by a serious tank huff.

Filling with water is not the best solution.  The problem is, unless the tank is completely full (making it hard to weld), the water will concentrate the vapors into the confined air space.  The net result is a more combustible air mix than would have otherwise been present.

Better to buy a couple of pounds of dry ice, put it in the tank and then add a cup or two of warm water.  The dry ice will "activate" (bubble) and it will displace the air in the tank.

As Crofter also mentioned, using a continuous stream of air in the tank also works.

If you've ever had a tank huff on you while working on it, it will get your attention in a hurry.

Please be safe and don't take any shortcuts!  Yeah, it's likely a hassle to go get dry ice.  TAKE THE TIME so you don't end up in the hospital.

Your local welding supply likely has dry ice or will know where to get it if you call and ask.  I know Airgas stocks it because I recently purchased some for a used gas tank I was reworking.

USE YOUR HEAD AND BE SAFE!  (And no, I'm not being a nanny...)

Steve

[vdubnut62]

The Guy at the propane store here told me that the ethyl mercaptan precipitates out of the liquid propane.
He ALSO said I could burn it out!!! Really!  (I'm up for a used 500 gal tank)
I'm figuring that would be a "Here, hold my beer" moment.
Guess I better use a camera with a heck of a zoom lens for the YouTube video. (kidding!)
Really, I DO know better. I'm a edumacated Redneck.
Ron

[Crofter]

Bob, I never thought you would try to emulate a lawyer!

I might add that you never really "know that a tank is clean". If you are using a purge you should have a helper to ensure it remains continuous and that the dog has not knocked it out of the hole etc., while your attention is busy elsewheres.

Yes Acet. is a bad cat; has one of the highest ranges of explosability of any gas, roughly 2% to 90% and also one of the sharpest deflagration rates.

[Tom Reed]

In the past I've done an air purge on fuel tanks while welding and brazing. The theory being that flammable concentrations of vapors can't collect. And I ain't ded yet. Just lucky, maybe.

However I have a motorcycle fuel tank that needs brazing and I'm thinking about running the exhaust from a small engine into it and starting brazing after the tank is fully warm. Any options on the safety of this method?

[Crofter]

Sitting open for a long period of time would not do much for oil trapped in lap seams. The propane gas itself is the easiest part to deal with. The gasses you create when you start welding the tank is the rare thing that can get you. Cognos is right about the steaming. First part of every recognized procedure!

A fellow I know, shall we say, combines the method of the air hose and pushing the tank into a bonfire to give it a good toasting. Not something you could handily do in the city though, and it wont get the Popes blessing either. Not hard to pick some holes in it.

The only approved procedure is steaming for a prescribed length of time, then using CO2 or Nitrogen in a continuous purge flow while monitoring with an explosibility sensor. I have gone through the procedure a number of times in industrial settings  but when you can control all the parameters yourself and are risking mostly your own neck you could choose to eliminate some of the layers of redundancy. You better be confidant though that you know what each risk issue really is and that you have it covered.