LP tank valve removal UPDATE

Only if we are skipping dangerous and moving directly to stupid!

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...........................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

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

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!

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

Are you sure?

And just because the tank was at atmospheric, there was NO hydrocarbon vapor in it?

So you hope.

We are not talking hydrotesting, we are talking putting heat to a vessel that has hydrocarbons in it

Maybe not, but I gave you directions to the people wrote the book on the subject. But I can see that nothing is going to change your mind that what you did is perfectly safe, so I can see I am wasting my time. Maybe some one else reading this exchange will learn a little from it

Regards, Kent

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

Hmmmm... I had the tank inverted until all of the liquid was purged, and I then left the valve open all night... yep, pretty sure there is no liquid left, and hence nothing left to boil. Hence, no "boiling liquid" part of the BLEVE equation.

Why are you having such difficulty with this?

On the contrary, I was hoping there was 100% hydrocarbon vapor in it.

With 100% hydrocarbon vapor, there is zero risk of explosion. Propane will not burn or explode (as in a fuel/air explosion) without the oxygen in air.

Hope has nothing to do with it. Explain why you think there is risk?

True, I am talking about putting heat to a vessel that has hydrocarbons in it. However, YOU were talking about putting heat to a vessel which has a LIQUID in it. That changes everything. Lets stay on the same page, shall we.

The vapor inside my tank isn't going to spontaneously ignite. It can't, without oxygen. So again, where is the risk?

I know that most firemen are extremely over reactive to people asking questions about fire. Their passion sometimes gets in their way of logic. I don't know any firemen with a degree in physics or chemistry, probably because anyone with a degree in physics or chemistry would be in a different career. Maybe forensics investigator, or something of the sort, but not fire chief.

Not to mention the fact that for liability reasons alone, no fire chief is going to admit that what I did was safe. For that matter, I never claimed it was safe (again, for liability reasons). But if you can tell me where the risk is, I'd love to hear it.

Dave

The reason I pointed you toward bleve is to see the result of a vapor explosion.

And what happens if you just happen to burn a little bitty hole in the tank with your torch?

Changes nothing. You still have the vapor and the vapor is what is going to ignite first if you happen to put a hole in that thin tank with a torch.

The little bitty hole and a heat source such as your torch will sure do it.

I know lots of them. Degreed chemical and mechanical engineers compose part of our plants' fire crews and other refineries in this area. Let's not get elitist here..

The torch and the vapor is the risk

Regards, Kent

You get a little bitty amount of propane oozing out (it's not under any pressure) and burning _outside_ the tank (remember there's NO AIR in the tank).

Wrong - 1. vapor won't ignite without oxygen, 2. There's nothing "thin" about a 100# tank.

Dave:

Braaahh! Wrong again! A little bitty hole will not introduce air into the tank. Using an OA torch to cut a tank can introduce oxygen depending upon the mix, but Dave was using a propane torch - there's no way that's going to put a hole, "little bitty" or otherwise, in the tank.

Bob

As I said before, you can't have a vapor explosion without a proper fuel/air mixture. The gas inside the tank is far from explosive, hence a vapor explosion is far from possible.

Okay, for the sake of argument, lets assume for a second that my Bernz-O-Matic propane torch could somehow burn a hole in the propane tank. Now I have a spot where gas could exit, or flame could enter.

We are right back to where I stated the fact that 100% propane gas is not explosive. Heck, it isn't even flammable if there is no oxygen present. If the flame tried to travel inside the tank, it would extinguish as soon as it ran out of oxygen. The smaller the hole, the faster this would occur. The flame would never reach the inside of the tank, because there is no oxygen to support combustion.

Since I am very slightly heating the tank, it is more likely that some of the gas would be forced out of this pinhole. If it caught on fire, it would burn. But with very little pressure and gas flow, it would be pretty uneventful.

If it was a pinhole, the flow of gas *could* be pretty fast coming out of the hole, in which case it is unlikely the gas could even ignite. Ever try to light a propane torch with too much gas flow? Can't do it.

Do you honestly think a tiny hole in the tank is going to instantly allow enough air into the tank to replace 90% of the internal volume? That is what would have to happen in order to have the gas inside explode.

Or, are you concerned with the tiny hole allowing gas to escape and catch fire? It isn't going to be much gas, since I said there was no pressure in the tank.

Are you one of these people who believe lighting hair spray on fire as it exits a can is dangerous, because the flame can travel through the nozzle, and inside the can, causing the contents to explode? You have the pinhole (nozzle being depressed), you have the fuel, you have the fire..... but the flame can't travel into the nozzle.

Lighting hair spray on fire as it exits the can is dangerous for many reasons, but not that one.

Dave

Our local junk-yard cut up the old PL tanks everyday... They take a hammer and bust off the old valve and light the escaping gas and start the cutting immediately... So far no problems... I watched them do this... I would not like to do it...

Dave, let me put it this way and then I am ending my part in this thread. . I hate to see folks get hurt/burned/killed by taking chances they did not have have to. I have known people who were maimed or killed by doing just that. And in my opinion, you took a pretty scary chance and I think you were lucky the conditions weren't right to have an accident. They could have been real easily. As I said, I would have gotten a big wrench or if push came to shove and I could not have taken the valve out. I would have filled the tank with water through the valve to eliminate the vapor space then used the torch. I wouldn't have stuck even a match to it until that vapor space was gone. Why take the chance???? As far as the hairspray thing. I'll say this. I work with hydrocarbon reactions using super high pressures and elevated temperatures every day. I know the physics. I know the math. I also know what can happen if one little thing goes wrong.

Regards, Kent

The Has mat manager of a local large county near here is a personal friend. He gets full tanks all of the time. Lots of partials.

People move out - can't take them with them so they have to turn them in somewhere.

Martin

I respect that. However, my opinion was that there was very little risk involved. And it seems that more and more people are coming up with examples where people deal with similar situations in every day life, where it is not only considered safe, but also routine.

Because someone else would probably argue that there will always be a chance that you *thought* the tank was full of water, but really wasn't.

You know the math and physics, but what about the chemistry? I've seen first hand how chemical reactions can become explosive. If the temperature is wrong. If the chemical ratios are wrong. If the pressure is wrong. etc. I agree, one little thing going wrong can cause major problems.

But we are comparing apples and oranges. I wasn't dealing with high pressures. I didn't have high temperatures. The propane wasn't going to react with anything inside the tank.

I certainly wouldn't try this with an acetylene tank, because acetylene is not very stable by itself, and can detonate violently with no oxygen present.

Dave

No, because you at least eliminated most of the vapor space.

Know the chemistry very well. Worked a propylene oxide unit for 5 years. Used direct oxygenation of hydrocarbons in the process. Have been working oxo-alcohols and plastisizers units for the last 25 years. Chemistry is a part of my every day job.

I didn't say it would. But it certainly might have reacted with a spark or a flame, which is the point of this dialog.

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

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...

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.