LP tank valve removal UPDATE

On Tue, 02 Dec 2003 00:05:26 GMT, David A. Webb


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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Kent Fowler wrote:

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 02 Dec 2003 01:55:24 GMT, David A. Webb

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 02 Dec 2003 07:27:20 -0600, David A. Webb

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.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Kent Fowler wrote:

Inside a petro chem plant which are generally held together with bubble gum and bailing wire.
A PC plant is not a 100 pound cylinder.
Kent , your impressing me that your the type of person who no one else can be right or you can't be wrong, no matter what.
--
Mark

N.E. Ohio
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Been in a lot of petrochem plants and refineries, have you? Do you actually work in one?

A 100 pound cylinder can get you burned or dead.

Nope, I've been wrong on lots of occasions. My wife usually proves me wrong at least once a day and I admit it. . But I will never, ever change my opinion on this one. I think you need to go back and re-read all the posts. I suggested he query the chief instructor at the Texas A and M fire school as to his opinion. Does this sound like I think I am right all the time? Or his local fire chief. Again, does this sound like I think I am the only one who is right?? The response I got was:
1. Fire Chiefs don't know shit about tanks and vessels with hydrocarbons in them and he wouldn't ask a fire chief about anything.
2 Firemen don't know shit be cause they like to err on the side of caution and really don't understand because they don't have a physics or a chemical engineering degree and would do something else beside be a fireman if they had said degrees.
3 And obviously believes that only degreed people have the mental capacity to understand the fire triangle.
And you accuse ME of being block headed? I think you must have us mixed up. I' m the guy who won't take a torch to a propane tank with out it being cleared first.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Wow, you sound pretty sure of yourself. Care to back it up? What are your qualifications?
You seem to be pretty proud of yourself for working in a petrochemical plant, but I have yet to hear what you actually do. For all I know, you are a custodian. (or maybe a fireman?)
What is your education? Do you have an associates degree? How many chemistry, math, or physics classes have you taken?
Even though you can't back up your opinions about the LP tank, you should be able to back up your statement of general knowledge.
Dave
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Kent Fowler wrote:

And what kind of idiot will blow down a tank in the presence of an ignition source?
--
Mark

N.E. Ohio
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I've seem a few that would, fortunately they didn't make their probation period.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 02 Dec 2003 00:05:26 GMT, David A. Webb
......and in reply I say!:

Did you leave the tank inverted all night? I do not know how much explosive stuff would be left, but that would sure alter the LPG-Air ratio from leaving it upright.
**************************************************** sorry remove ns from my header address to reply via email
Imagine a _world_ where Nature's lights are obscured by man's. There would be nowhere to go. Or wait a while. Then you won't have to imagine.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

No. As soon as all of the liquid was purged, I sat the tanks upright. (and left the valves open)
Dave
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 04 Dec 2003 07:46:21 -0600, David A. Webb
......and in reply I say!:

Being a bit sarky here, but the _exact_ following requirement holds very true here, if reasonable safety is to be assured.
Now that was a part of the procedure that needed clarification. So was "warmed".
My point is that if filling the beasty with water, after purging a couple of times, or some other method can make it _obviously_ safe (within the limits of going to work on the Clapham Omnibus), then your way could be dangerous if any of the steps was not carefuly described and understood, then followed to the letter. I do NOT know the math of how dangerous the result could be, I admit, but if any liquid were left, or if "warm" was too hot, then there could be problems. **************************************************** sorry remove ns from my header address to reply via email
Imagine a _world_ where Nature's lights are obscured by man's. There would be nowhere to go. Or wait a while. Then you won't have to imagine.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hey Beecrofter,
And leave the valve closed? Now that IS scary. The steam pressure will kill him long before there is enough heat applied to loosen core. Or the core loosening will cause the steam to blow it out!
Take care.
Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXXX On 26 Nov 2003 15:07:50 -0800, snipped-for-privacy@localnet.com (Beecrofter) wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Only if we are skipping dangerous and moving directly to stupid!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Better you than me, I already went through having a pressurized -non-flamable container go off on me, and certainly would not want to even consider a container that held propane no matter how small of ratio of gas to air it had. Its certainly not worth my life or limb to take such a chance.
I have taken them out before and have never used heat. Visit my website: http://www.frugalmachinist.com Opinions expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 27 Nov 2003 02:13:31 GMT, snipped-for-privacy@hotmail.com (Roy) wrote:

How can you compare the danger of a pressurized container to a non-pressurized container?
How dangerous would a non-pressurized container be, if it's contents were not explosive?
Dave
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just make sure you wash it out with Chlorine (Chlorox) to kill most of the ethel mercaptan (stink) or you'll smell it for a very long time.
Also ethel settles out , there could be a pool in the bottom of an old tank. It should be dumped before washing. Don't spill it or you could be sorry.
--
Mark

N.E. Ohio
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I turned the tanks upside down and vented off the last bit of liquid LP... and got the stink all over myself in the process.
So... bleach will kill the odor?
Dave
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.