LP tank valve removal UPDATE

I realized last night there was still some liquid left in the tanks. I bled that off, and left the valves open overnight.
Note: Don't get that liquid on your skin. Not so much for the obvious frost bite hazards, but because of that nasty ethyl mercaptain odorant that is in the gas that will absorb into your skin. My wife was not happy with me last night. My hands still wreak.
This morning, I chained the tank to a solid post, and used a load binder to tighten it up so it wouldn't move. I lucked out in that I managed to find a combination of links that allowed me to get the chain very tight, but not to the point of crushing the tank.
I closed the valves, and used a propane torch to heat the bung until it was too hot to touch.
I leaned on the handle of a 24" pipe wrench, and the valves backed out easily. (they are RIGHT handed, by the way)
There is a thread seal dope on the threads that hardens as it cures. As many people have told me, this makes the valves virtually impossible to remove. Heat softens the dope, and makes it easy to remove the valves.
Now, before I get flamed for applying heat to the tanks, let me explain some logic here.
First, although the tanks were full of LP vapor, there was no liquid, and there was no pressure in the tanks.
Second, the valves were closed, so no gas was escaping and available to ignite.
Third, the inside of the tank contained 100% LP vapor. This is not explosive. The explosive limits for LP gas is between 1% and 10% in air. Had a fracture occurred, the flame would not have burned into the tank. The flame would have only occurred where the escaping gas was mixing with air.
I got advice from people saying to pressurize the tank with air, and bleed it off a couple of times. This could have easily left me with an explosive mixture inside the tank. Leaving it full of 100% LP vapor was MUCH safer.
Fourth, this was a 100 pound LP tank. Heating the bung is not going to heat the gas inside to any significant amount, and certainly not enough to risk a pressure explosion. In fact, when the valve was removed, there was barely any hiss of gas escaping.
Dave
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You were lucky Your arguement about it being 100% vapor sucks wind after leaving the valves open overnight. Next time before we read about pieces of you being found elsewhere quit screwing around and fill the tanks with water.
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On 26 Nov 2003 15:07:50 -0800, snipped-for-privacy@localnet.com (Beecrofter) wrote:

Luck had nothing to do with it.
First, LP gas is more dense than air. It isn't going to leave the tank of it's own free will.
Second, even if some air had managed to get drawn back into the tank, it certainly wouldn't achieve the 90% air required to make the mixture explosive.
Third, how would you fill a propane tank with water with the valve still in it?
Dave
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David A. Webb writes:

You need to learn about diffusion.
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On Thu, 27 Nov 2003 03:42:08 -0600, Richard J Kinch

Okay, I'll concede that if I left the tank valve open long enough, air would eventually replace ALL of the gas through diffusion. Between now and that point in time, there would be a point where the mixture would be explosive. However, the passageway through the valve is pretty small, and as I stated before , LP vapor is heavier than air. With the tank all but sealed, and no real movement of the vapor inside the tank, the diffusion would even slower than if something was stirring up the gas inside. Overall, the diffusion would be a very slow process.
I will also concede that based on this, odds are the gas inside the tank wasn't 100% LP vapor as argued by a previous post. So was it 99.9%? 95%? As stated, the LP vapor has to get down to 10% before it is explosive.
So in reality, how long would it take for air to diffuse into the tank through the tiny valve opening, and replace 90% of the LP vapor?
Maybe in my lifetime, but certainly not overnight.
Dave
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On Thu, 27 Nov 2003 14:04:21 GMT, David A. Webb

How exactly did you determine it was at the concentration level you stated? Visit my website: http://www.frugalmachinist.com Opinions expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.
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On Thu, 27 Nov 2003 16:23:29 GMT, snipped-for-privacy@hotmail.com (Roy) wrote:

Which concentration level? I initially stated that it was 100% LP vapor.
Then someone argued that because the valve was left open overnight, it couldn't have been 100% LP vapor. So I conceeded that the LP vapor concentration in the tank might have been slightly less than 100%, but not much. Regardless of what it actually was, there was no way it could have been down to the explosive range.
My initial statement was based on the fact that there was liquid LP (I know it is redundant) and any tiny bit of air that might have been in the tank with the liquid would have been purged when I vented the tanks.
Once the liquid was evaporated, and the pressure inside the tank dropped to zero, it is safe to assume the only thing left in the tank is LP vapor.
Had there not been any liquified gas in the tank, I wouldn't have had any way of knowing what kind of mixture was in the tank, and I wouldn't have attempted to heat the bung before doing something to make the situation safer.
Dave
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If you let the LP vapor bubble out thru a jug of water, if there is any suck back it will be water.
--
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On Thu, 27 Nov 2003 14:04:21 GMT, David A. Webb

.............................. snip..................................

...........................very, very wrong..........................
Dave. I am not trying to be sarcastic but you really need to educate yourself about LPG before you kill your self. Google up the word "BLEVE" and I think you will see some of your premises are not true. I have worked in a big chemical refinery for the last 30 years, and deal with huge quantities of propanes, butanes, methanes,ect. and can assure you that I know what I am talking about. I have seen bleves and and have known people who were killed when they went up. I have seen little things as you have done become really bad, really quick. Yes, hot taps are made, but these are done under special conditions that are too lengthy to describe here, and with trained personel. Knowing what I know about LPGs I wouldn't have done what you did for a million dollars. I would have gotten a very big wrench, like the propane companies do, and taken the valve off. Ask your local fire chief as to his opinion, or better yet , email the Texas A & M fire school and query the chief instructor. Stay safe..........................
Kent

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wrote:

Kent,
BLEVE... Boiling Liquid Expanding Vapour Explosion
Do you see how this fails to apply to my situation?
I said I removed ALL of the liquid first, so there is no "BL"
Second, The internal pressure of the tank was at atmospheric pressure. So there is no "EVE".
SO I am not at risk for BLEVE.
And before I would ask my local fire chief, I am reminded of the chief my Dad worked for 20 years ago, who talked about how dangerous it was to hydro-test their SCBA tanks. According to him, tanks were tested under water to help contain an explosion if the tanks failed. Super dangerous because under that pressure, if a tank burst, shrapnel would kill everyone if it wasn't for the tank of water used to slow down the explosion. Duh.
So, as far as I'm concerned, being a fire chief doesn't make a person the final authority on risks of tank explosions.
Dave
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C'mon, people, it's a done deal.
He got lucky.
He did it right.
He should have been killed.
Perhaps all of these are true. Perhaps none of them are. That isn't important. What is important is that he got it done, and, regardless of how or why, he got it done without getting hemself damaged or dead in the process.
No amount of Monday-morning quarterbacking changes that fact.
Sure, it was insanely dangerous. Sure, he could have blown himself to hell. He might have even taken half the neighborhood with him in the process.
BUT HE DIDN'T.
Task is completed, results satisfy the person who wanted it done. Can't we move on to something a little more constructive than fancily phrased "You were a stupid fool that got lucky once, here's what you should have done, dummy"???
Think about it, people - the horse is dead, the crows have picked it down to clean bones, and even the bad smell is gone.
Let it rest already!
--
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Funny, you are doing EXACTLY what you are criticizing others for.
I posted only to explain how I did it, and why I consider it safe.
I encourage people to criticize, and give reasons why they consider it dangerous. As far as I can tell, many people agree it was relatively safe. And those that said it was dangerous didn't really support their opinion.
If you think it was so terribly dangerous, please explain why.
Dave
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"David A. Webb" wrote:

Indeed!
Good luck. I've posted about my experiences with empty propane tanks and ALWAYS get a lot of baloney about how dangerous they are without any explanation, or even anecdotal evidence. There's a common psychological model at work here: If you've always heard that something is true, and it seems reasonable, then it must be true. In this case, the belief creates a fear of investigating whether it really is true.
I've been meaning to do the chemistry to show that there simply is not enough energy from the propane in an empty tank to do any harm. But I haven't gotten around to it (what else is new?).
Bob
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....>

when a 500 or 1000 gal residential tank vents it scares ten years out of you. all the folks i knew in the NM volunteer fire dept's said that if you didn't get a hose on it early, you had to just leave it alone and stand clear. but worse danger is an overfill that vents, the valve does not close until the tank is empty. you need to stay a _long_ way away from that one.

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That would match... The first question after "Is anybody inside?" was "Any propane bulk tanks? Where?" ("Yes, out back, big pig, about 500 gallons, maybe half full, I think")
First place the hoses went was back to the pig, about 20, maybe 25 feet from the back wall. The back wall of the house (in fact, it was the section of bathroom wall that I mentioned was the only thing left standing in the end) was the only part that wasn't actively burning at that point, although everything inside, and the entire front, was blazing away merrily. They put a man with a handline on it, and there he, or someone like him, stayed for the next 6 hours or so, until the final bits that were left of the house finally collapsed into the basement.
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In my opinion, what is important is that people realize the fact that he got away with it doesn't in and of itself make it a good idea, or safe. Without getting into the specifics of the valve removal this can be discussed as a matter of philosophy. i.e. doing something risky and getting away with it for a while doesn't make it either safe or a good idea. Its good to be lucky, but it isn't a good idea to depend on it over the long term.
They flew the shuttles with burnt O-rings that were not supposed to burn for quite a long time before they lost the Challenger. They flew with 11 times the foam falling off, when none at all was supposed to fall off, after they changed the adhesive that they used to have for several years before they lost the Columbia. In both cases the logic was that because it worked a few times it was safe. History has shown, with tragic outcomes, the flaw in that logic, though it seems to be a lesson that is very hard to learn.
The deal is that a contemplated course of action should be shown to be safe, or have acceptable risk vs payback, or one doesn't proceed. One does not have to show something to be unsafe to avoid proceeding. The difference is profound.
Doing risky things and getting away with it is a matter of chance. Do it once, you have a better chance of dying from other causes than if you do that same risky act a lot. People pass over the yellow line and may get away with it. People cut in and out of traffic on freeways at high speeds and get away with it. People who do these things a lot usually don't. There are similarities.
Shop safety is much the same. I file on the lathe by holding my right arm over the work with the file handle in my left hand to avoid having my arm over the chuck. Most folks I know do it the other way. I suspect this is probably because they are right handed and want the file handle in their right hand. I'm right handed, but with practice it doesn't matter. The chuck, in my experience, is more likely to be able to grab the arm or clothes because:
a) its bigger in diameter and closer to the arm than most of the work on the lathe
b) it can have grabby things sticking up like chuck jaw ends that are usually not there on the work. They can be, in which case maybe the chuck end is safer in that instance, but usually the work where the right arm is smooth.
Similarly, when using a lathe dog between centers, I don't want my arm over it, even if it is the "safety" type with a recessed setscrew. People file with their arm over the chuck a lot, but I don't think it is as safe as doing it the other way.
Its called risk management. Its a personal choice.
You pick your pony, you take your ride.
Fitch
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Now there's a revelation... (please imagine my eyes rolling)
The guy never claimed his method to be "safe". In fact, it seem to me that he was worried that it might not be safe, so he was taking umtpy-four different precautions. In the end, he claimed it got the job done.
Look, NOTHING is "safe". Getting out of bed in the mornign has been proven to be fatal in certain situations. Risk assessment (and acceptance) is something we all do every day. I KNOW I can get in my car to head for work only to wake up in the hospital (or not wake up at all...) because SOMETHING (I won't even make a feeble attempt to enumerate all the "somethings that are possible) went wrong. Maybe I was driving too fast. Or too slow. Maybe there's a drunk heading for me around the next bend. Maybe the wheels fly off the car and I go into the drink - whatever! I accept that there's an element of risk to *EVERY STINKING THING I DO*, and it's not for you or anyone else to tell me I may or may not do something because *YOU* think the risk is too high. Ony I can make that decision as to how much risk is too much, so I'd thank you and your cronies who are intent on protectng me from myself to keep your nose in your own business.

Likewise, as I just said, *I* decide what risk is acceptable for *ME*, regardless of what you or anybody else thinks. Yours is to assess *YOUR* risk and act on that assessment. Yours *IS NOT* to to assess my risk and tell me "you can't".

And then here, you come into 100% full agreement with me. Yet you still try to preach that your decision regarding a risky activity is the only one that's right. Come on, guy, which is it? Is it my decision, but only if *YOU* think the risk is low enough? And where's the boundary between "You go ahead and make your choice" and "Oh, no you don't! That's too dangerous!"?

Interesting analogy, since I'm primarily a horseman. And I agree... *YOU* pick *YOUR* pony and *YOU* take *YOUR* ride. *I* pick *MY* pony, and *I* take *MY* ride.
So long as you don't try telling me "That one's too dangerous for you" (or vice-versa) we'll both get along just fine.
The instant you start trying to "pick my pony" for me, we're going to be at odds.
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Whoa.
I don't mind the argument, but lets keep the emotions down a little.
I don't think he was trying to tell you whether or not you could do anything. He was just saying that in his opinion, my ability to accept risk is greater than his. My argument is that it isn't, because I don't believe the risk is truely present.
I considered the whole "it is not safe to drive to work" issue, but I thought it was better to stick to the issue. "If what I did was risky, please explain how"
Maybe people will develop a better understanding of how risky this really was. Heck, I might even learn something.
Dave
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I never said anything about your choices anyplace. I specifically said I wasn't going to discuss the valve removal - I agree its been discussed to death. I don't know anything about the chemistry of that stuff, and I didn't discuss it. I don't see that I had a decision in that posting anyplace other than the discussion of how I use a lathe file, and why, which you can do with as you please.
What I said, as a matter of philosophy, applies regardless of circumstance. The physics of risk taking are pretty simple - if you do something that is risky enough, often enough, it will have a bad outcome. The corollary to that is that the fact that if one took a chance, committed a risky act, and didn't have a bad outcome, doesn't make the act safe. The fact that a person took a chance and it didn't have a bad outcome isn't the important lesson. The important lesson is that the lack of a bad outcome doesn't make an act safe. My intention was to make that point. I provided examples to illustrate it.
The bottom line is that taking a risk, assessing a risk, is a personal decision. The outcome depends on chance. Nothing I wrote is inconsistent with that.
Fitch
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.Apparently:.........................
Yours is not to reason. Why?
Welcome back Fitch. <VBG>
XXXXXXXXXXXXXXXXXXXXXXXXXXXX

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