What Is This Stuff?

A "used 40-pound LPG tank" should have been a warning.

An oily substance does not support combustion in a LPG burner.

The oily stuff is some type of oil and it came from some oily source.

Maybe someone used it as a compressed air tank.

Vent the gas, take all the fittings off and wash the tank with some solvent. Twice.

Blow all the lines out from the burner back, or replace them.

Let this be a lesson to you. "E Pluribus Unum" Clean the tank first.

I've never had this problem, but I did stay in a Holiday Inn Express last year.

A "used 40-pound LPG tank" should have been a warning.

Well, to be fair (and in light of my having no prior experience with used - or new - LPG tanks), it's a bit hard by looking at the outside of the tank (it's in great shape) to tell what's inside the tank (not so great). And Those El Cheapo X-ray glasses I ordered once, when I was a kid and believed that crap on the back of cereal boxes (I recall paying the standard 'two boxtops and 50 cents')?

They're still in the city dump shop, so can I borrow yours next time? You know, to read used 40-pound tank warnings?

I think I'll just get my money back and buy a new tank from Amerigas. All things considered the tanks are not very expensive and certainly a lot cheaper than rebuilding my furnace. I'm taking the lines and regulator down to Amerigas tomorrow to see what they say. I rather suspect the stuff could foul a pressure regulator as well. This might explain why I had no heat last night even though the tank is nearly full and with good pressure. I just don't want to risk damaging my furnace, mainly, and I do like to be toasty-warm. It's getting cold here very quickly at this elevation (well over a mile).

Just unscrew the top fitting and look inside. You may need to strike a match for light.

Amerigas will tell you it's too late and they will have to clean everything and maybe replace the entire RV because of oil contamination. That'll only cost you $80,000.00 USD.

Seriously, blow the lines out and try a fresh tank of gas.

Good luck!

_{(I don't really have a clue, again)}

Tried that. How do you think I got to Colorado from Texas? Flew? (Well, yes actually, but that's besides the point; I really wanted to go to Hawaii but landed here, so what would you recommend next time? A bigger used tank? )

A boat.

A new tank. All LPG tanks have "best before" or "expiry" dates. The dates are there for a reason. Or, you may get rid of it at a tank exchange station (if you can find one that takes that size), where instead of filling your tank, you just give them yours and you take another one, which, should be up to par.

you just give them yours and you take another one, which, should be up to par.

Think about this Kevin,

that is unethical as well as immature.

Unethical how?

The tank exchange programs are designed for two three things:

1) User convenience: No need to spend the time or effort to refill the tank you have, just swap out an empty for a full.

2) Equipment safety: Using the 'swap' system, older tanks are collected and disposed of/recycled for their metal while newer tanks are introduced into the 'network.' This method allowed for the phase-out of the older fill valve styles (identified by the classic 'cookie with six bites' handle) and introduce the newer safety valves (identified by the 'circle cut into a blunted triangle' handle). A fouled/old/corroded/unsafe tank would be accepted as readily as a new-model tank, as well as a tank with a competitor's brand on the shrink sleeve. All tanks collected are inspected and the bad ones removed from service, while the good ones are cleaned/repainted/re-branded and refilled to do another cycle in the 'cylinder exchange network.'

3) User safety: (forgot this one at first) By doing an exchange instead of an in-front-of-the-user refill, the user is not exposed to the potential hazards of filling an LNG tank (risk of fire, risk of tank rupture, risk of inhalation of vaporised LNG). Yes they're exposed to these same risks when USING the LNG tank, but why 'roll the dice' more often than you have to, when you only need to roll snake eyes ONCE to lose?

I wasn't aware of the deposable aspect that that was one of their responsibility, and I don't believe it is, just due with to the back in 2002 the replacement of tanks because of the Over Fill Device safety valve requirement.

To trade in a known defective tank on the other hand, and try passing it on to become some else's problem or costs is my point. That in my view is unethical.

Remember that next time you buy something used, who may have had it before you.

I own my own tanks. I insist that I get my tanks back and watch the refilling process.

All of these tanks have a finite life, after which they are just scrapped. I expect to buy news ones when needed and I expect to always have my own.

I also believe that you must own/purchase a tank to exchange before the renting process is allowed. Never done it myself.

On the exchange, the ones I been to, After you pay, a Door that's empty opens, you have to put your empty tank in, (don't know if they have a sensor that says there's a tank in there.

And after you close it, another door opens that has a full tank in.

I have a 40 lb tank, but the smaller one, but back in the 90's they had fill stations that I used. Now, I use the exchange just due to the convenience.

One thing about it, a while back, you had a label on it, where you send it in to get a rebate, because the gas company that was selling it, had reached a court settlement because they were not filling the tanks up.

The gas company still made a hefty profit, just because you needed a receipt to get your rebate.

Well, every 'tank exchange system' that I've seen has been run by a major LNG supplier, Either AmeriGas or Blue Rhino. Every tank they sell has an overwrap with their logo on it, and there are NO refill stations at the site. So there must be a truck that goes around, collecting the empties and restocking the fulls, and then taking the empties to a central location.

From there, it would follow that every tank is inspected prior to refilling. You have the same thing happening at water bottling plants, every 3-5 gallon water bottle that is returned gets cleaned, inspected and sterilized before it is refilled. The plants don't care where the bottle came from, or who's brand is on it, because they'll simply re-brand it when they fill it. That's why most water cooler bottles have no printing on the side, and the branding is all on the cap.

The Central Refilling locations would have the inspection procedures in place, as well as the connections for having old/damaged/contaminated/etc tanks either refurbished to 'like new' condition or scavenged for their usable parts and materials.

I would never purchase an LPG tank (or any compressed gas tank) from a 'third party,' it would be either direct from the supplier or through an official distributor. I also would never sell a 'used' tank at a flea market or other casual venue. If someone were in the market for a fresh LNG tank and I had an empty one I was no longer using, I would sell them the empty tank ON THE CONDITION that they immediately take it to a 'tank exchange vendor' and exchange it for a fresh tank.

As an aside, I was volunteering with the Scout Troop my dad is involved in, and I noticed that one of the LNG tanks they had in the troop trailer was the old-style valve. I informed them that that tank is no longer considered safe for refilling, and that they should use it up and get it exchanged for a new tank ASAP. I had only spotted it on the last day of the work weekend (it's a big trailer, and the cleaning and reorganizing of the trailer was done after all the campsite maintenance was done) and the cooking had all been done with the smaller 'hand grenade' LNG canisters, so there wasn't much I could do at the time but give my 'professional opinion as a Safety Engineer.' I'll see how things have progressed next spring when I'm up for the next pre-summer camp work weekend.

This is off topic, but it is interesting.

And yes, the tank exchanges I've used is run by a major LNG supplier.

Procedures was not the point,

The point is, id it expectable to whatever entity that is running the gas exchange, for a person to exchange a known faulty tank for a new one by rotating it into the stock.

I don't know this? I am only referring to when the Over Fill Valve issue was, And these tanks, for the most part had to be disposed of by the owner expense.

I also like to add, good for you on your volunteering. Very commendable.

Those 'use by' dates are there to compel either a retest (for pressure) or to replace it if not re-tested. Has nothing to do with the age of the gas in the tank. I too had such a condition in a plumbers tank, 20 lb, with a vertical fitting to directly support a buener and pot, I can only assume it is a breakdown of the gas. I still used it until it ran out. By that time, it was about 7 years out of date. Didn't bother re testing it, I just took the valve out, flooded it and cut the bottom out, then installed a weldolet so I could use the top to support the burner and fed it from a different tank. (More time than money, ya know.)

This is a common occurrence, you need to drain the tank and flush the lines, and probably change the regulator....as to where it comes from, there are several theories from residue from the gas itself, to the added odor substance that is added....but you should go ahead and learn how to clean the system out and maybe add a filter, cause that appears to be regular maintenance for these systems...

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/23677889/print/true.cfm

My question is: what is this oily stuff and where did it come from? Does LPG decompose into other compounds over time? How did this oil (or whatever it is) get inside the tank? Did it form there?

Considering it was a used tank, your asking the wrong people.

Maybe Moisture got into the tank is my only guess.

The used tank is costing more than a new one.

A new tank is not always the answer, but at times it is, problem is, you only find out about the savings after a bad experience.

With the other responses, I hope it works out for you

Thanks, Similar here for refilling,

where did this come from?

If your supply system is same as I have described then it is not your duty to clean the condensate.

The only difference is on a new cylinder, it always should be purged before filling for the first time, which is done at the refilling station.

A lot are waste products like Butane which is left over from the process of making rubber from natural gas.

Sounds more like Natural Gas but still possible. especially with your practical experience with it.

I had forgotten that it is the foundation of other products including fertilizers.

Natural gas is mostly methane and it takes a lot more pressure to liquefy. There are other gases in natural gas like propane and butane. They are usually separated out in cleaning up methane for home use. In that process other contaminates gets processed out into the LPG if it is done poorly. Which is some of the oily stuff in question. There are also a couple of LPG grades. Some of which in their use the contaminates are not an issue.

Some people will substitute a lesser grade because of price or availability issues . Which the end user usually pays for in equipment failures.

Thanks, that I didn't know.

Tank snot. That's exactly what this stuff looks like: snot.

Not necessarily related, but I use the "tank trade in service" from my local gas supplier. I traded an empty tank, for a full one last summer, and when I connected it up and opened the tank valve I heard a hiss! Upon further inspection, I found that the gasket inside the tank connector was all cracked...man I'm glad I didn't have an ignition source near when I opened that valve! Took the tank back and reamed the manager out for not replacing the gasket like they are supposed to do, and got a replacement full tank.

Seems be a similar post, only with new cylinders

As noted in #18, the liquids in propane, (C₃H₈), are not condensates or polymerizations of the compound propane. Propane is a short chain saturated aliphatic chemical with no double bonds, any polar components and nothing but carbon and hydrogen. These low molecular weight materials, methane, ethane, propane, etc. are difficult to react with or polymerize to themselves. The oily compounds are much higher molecular weight materials as seen by their liquid states.

https://en.wikipedia.org/wiki/Aliphatic_compound

Only an extremely small portion of these are due to extractions from the hoses or other equipment used for propane transferring, parts per billion.

Again, these oils are caused by carry throughs of the components of the equipment used to purify and process the propane. An example is the oil used to operate the compressors.

Good Luck, Old Salt

I certainly asked on the right forum. I've hit the motherlode. Lordy, just look at the replies! Hell, I've learnt more about propane/LPG/natural gas than I thought possible. Thanks everyone!

Old Salt, do regular propane dealerships sell these 'dirt legs'? I'd ask the local guy but he's closed til Thursday (death in the family) and the airhead answering the phones knows how to paint her nails but not much else.

What is their technical name so I know what to look up?

Thanks

Just in case Old Salt doesn't get back to you in a timely fashion.

You can create your own dirt leg (correct name by the way) by installing a tee piece vertically in the gas line, bring the gas in via the top port, and out via the centre port.

Fit about 6 inches of pipe to the lower port and cap it off. The theory is that the gas has to make a turn to exit the tee, and so drops its junk on the way.

I'm not convinced that they are all that effective, they do rid the gas of the heavier particulates, but much of the rubbish, especially phthalates which are colloidal with the gas still gets into regulators etc.

A Y strainer of sorts.

Excellent idea. Put a longer pipe, or suitable pressure container, into the strainer drain leg outlet to collect the liquids. The strainer removes "chunk junk" and the liquids collect in the leg/container. Use a propane rated valve on the drain from this (with a cap/plug after the valve) to facilitate removal of the junk/oil. A fancy and more effective dirt leg.

Good Luck, Old Salt

Would either (or both) of you mind elaborating on this idea a bit more, for the uninitiated (ie, yours truly)?

I'm a bit jockey, basically, and an electron-pusher, meaning that such esoterica as propane plumbing & accessories is bit beyond my experience. And, given that propane is highly flammable (so are computers, btw but you have to work harder at it), any detailed guidance you can offer will be greatly appreciated.

Thanks!

Thanks!

As a matter of interest, if you were to install that device that I pictured upside down in the water line, it provides a pretty effective water hammer arrestor.

Air trapped in the top pocket compresses and decompresses to limit the knocking when taps are turned on and off

RE: Drip legs. Even with natural gas every time I installed a line to power an appliance I always addes a drip leg. Don't need them too much now, but in 'the old days' natural gas also had a lot of condensate issues.

When in charge of an LP gas plant we used to test the cylinders that came in for refilling. Remove the valves, check the inside for rust (visually) and put new valves in. These were then filled (by weight) and checked for leaks. Since these were transported by sea and road (and for other obvious reasons) no leakage could be tolerated. We never found any kind of sludge, oil or anything else in the bottles. Here in Australia (well in Victoria anyway) gas bottles must be tested every ten years and date stamped as tested. I would suggest that the bottle (or tank) had been used for some other purpose sometime in its later life. Possibly oil from a repaired pump or line was injected to the gas line when filling the bottle. Some good possible remedies have been suggested by others. At the risk of stating the obvious, do not look for leaks with an open flame. I have seen it done and can only tell the tale because the operator was on the ball.

LPG has a tendency to leach certain chemicals out of the transporting mediums such as rubber hoses. There are a couple of phthalates, commonly used as plasticisers in rubber hoses and plastic fittings, which are regular contributors to a build up of gunk in much used LPG bottles, in gas regulators, heating appliances and vehicle gas injector systems (the very reason that the mounting of the gas converter and delivery piping in these vehicle must be such as to allow flushing of these contaminants from the system).

LPG also contains, among other things, Paraffinic Naptha, pump oils and other lubricants, which can separate out of the gas in small quantities at the point of evaporation (in the bottle), and which build up in that bottle over time. Naptha residue commonly has a brown colouring.

Some oil companies use common delivery pipelines for LPG and for other petroleum products which can cause minor cross contamination.

Current rules allow up to 500 ppm of oily residues in LPG (in Australia, may be different elsewhere). At the high end this equates to roughly 4.5 ml per fill of a 40lb bottle, that's sufficient to cause a significant collection with subsequent refills, and if the tank has been upended at some point, it can collect in the valve and be ejected.

Olefins such as Propene (another plasticiser) can be in quite significant quantities in various LPG mixes, it has a lower boiling point than propane and can also leach out of LPG and form gummy deposits under certain conditions.

Thanks for the heads up, though I have never seen this before myself.

My thoughts are:-

1) Could have come from the last filling station

2) Could be simply a sign of age

3) Why not add one of those compressed air water/oil remover like this one, which might even be a good idea anyway, for all gas cylinders:-

from here:-

In-line 1/4 Compressed Air Oil / Water Separator Filter For Compressor Tools

You may need to make some sort of adapter to allow it to be fitted, but you can at least use up the rest of the gas and prevent the regulator getting fouled with the oil.

Then get the cylinder flushed before re-using.....

Andy,

You casually ask "Why not add one of those compressed air water/oil remover like this one, which might even be a good idea anyway, for all gas cylinders:.

Let me tell you why not:
1) It's a very bad idea and you may kill or injure yourself, or somebody else, or a large group of people. The bodies of most compressed-air water separators (including the one you illustrate) are molded from polycarbonate plastic. If you do even a cursory check for the chemical resistance of polycarbonate against butane and propane, you will discover polycarbonate is severely affected. Here is a useful compatibility checker:
http://www.coleparmer.com/Chemical-Resistance

2) It is irresponsible to add such a device to a gas line and breaches every gasfitting code in the land.
DO NOT EVEN THINK ABOUT DOING IT! YOU WILL HURT PEOPLE!

Agreed! These ARE NOT for flammable gas.

OK. Understood.

You did notice that I had never done this before? I had written:-

Thanks for the heads up, though I have never seen this before myself.

My thoughts are:-

It was not the high command you took it for!!! So be cool Guy/Gal!! [CR4 ADMIN: deleted potentially offensive content.]

So how about one made of metal?

The pressure will be somewhere between 100 and 200 PSI for propane.....so the pressure will not be a problem....

Is there something that you know of along the line of a filter?

Can you offer a working alternative idea?

Old Salt mentioned in Post #18 a kind of filter/separator used with propane.

Andy, no need to take offense at others' reactions to your suggestion (to the point of your posting then removing Admin-delete-worthy comments? Really, Andy, your skin is much too thin for an engineering forum - and this one is about as tame as they get). I suspect their comments were not directed at *you, personally,* so much as they were reactions to the *danger* to some unwitting soul following your suggestion and getting hurt or killed. An implicit "DO NOT DO THIS, DEAR READER!" That's the way I took it, anyway.

Look at it another way: you can take offence if you want to - it's your option of course - but which is better? Your feelings getting hurt by someone's stern warning, or someone else getting hurt or killed through its absence?

It's not about you. It's not at all.

I found a whitish waxy substance in all of my BBQ valves and regulator stopping it from working properly. Since cleaning that stuff out I have always turned the gas off at the bottle whilst leaving the burner on, emptying the lines. I no longer get that waxy sh!t. I surmised that the deposit was due to long periods of standing without use. Your situation may be the same.

I have not had that problem again for over 20yrs.

Jim

This stuff isn't waxy. It's more like ... mm ... snot? I can't think of anything it's more like, actually. Next time you blow your nose, look in your hanky: that's exactly what is in this tank - Tank Snot^®.

Speaking of finding waxy compounds in things and wondering how they got there, a bloke who graduated from my high school years before went on to college and got a degree in Chemistry. Later, whilst working at a chemical company back east, he was trying to make new kind of chlorofluorocarbon refrigerant (somewhat unsuccessfully I might add). Turns out the tetrafluoroethylene gas in its steel pressure bottle stopped flowing before the bottle's weight had dropped to the point signaling 'empty.' Since he was measuring the amount of gas-used by weighing the bottle, he became curious as to the source of the weight, and finally resorted to sawing the bottle apart.

When he did, he found the bottle's interior coated with a waxy white material that was oddly slippery. Analysis showed that it was polymerized perfluoroethylene, with the iron from the inside of the container having acted as a catalyst at high pressure. His company patented the new material in 1941 and registered the Teflon^® trademark in 1945. My older brother dated his granddaughter.

Sure. I would still guess that if the tank snot were left for some time, as was the case with my BBQ, it would end up being the same stuff. Clearly different country, different gas. But the upshot is; if you are about to leave the gas unused for some time empty the line first. Friends/family who use/d their BBQ regularly don't have the problem but those who don't, do have the same problem. I have cleaned a few regulators and valves for friends/family.

Jim

Are you actually sure, the "used 40-pound LPG tank" was not one half of a two component tank system for wall foam? It would be a laugh if it was, but your gas lines would either smell of polyurethane not polymerised, or stink like cyanide or something, which in that case could be really hazardous.

If indeed it contained LPG, the oily stuff probably comes from the processing plant or a compressor used in making propane into liquid.

Lol. I'm pretty sure it's not that. I've used those two-part urethane foam setups. It's pretty cool stuff but stinks to high heavens. We used to use it years ago to pack sensitive electronics assemblies in shipping crates. We'd spray a bit in the bottom of the crate, place clear plastic wrap over the foam whilst it was still soft and push the assembly halfway into it, then place plastic wrap over that and hit it with more foam. Made great 'clamshell' packaging and we never lost an assembly due to rough handling. Yeah, cyanide would certainly solve all my problems, but not quite in the way I might prefer?

With all that crud in that tank it's more likely the previous owner used it *as* one of those 'dirt leg' thingies Old Salt describes?