Cutting a propane tank

Date 07-10-2010 02:31

I hate to even get involved in one of these threads about cutting propane tanks. First off stop useing the exhaust off a gas engine your loading the tank with unburnt fuel. A diesal truck is a lot better way to go, nitrogen being the safest option.

Your going to get a lot of comments from so called experts, about how they have been filling them with water and cutting on them for years and nothing has happened.

I know people who do it this way, I have done it that way, and people have died doing it that way so i would never suggest that some one attempt to purge a propane tank with water.

Purging the tank with nitrogen 4 times the cubic feet per hour IMHO is the safest way to attempt a cut out. Diesal is another common method but you will still from time to time get the "flash".

A gas engine especially over 2000 rpms is expelling unburnt fuel that you will light with a torch!!!!

I heard two guys burnt to death cutting on an old pressure vessal in marlow ok this week, at a salvage yard were they cut on them all the time and have never had an accident. So it's alway better to take every precation available, it's better to save your life than save time and money by taking short cuts

By awspartb (***)

Date 07-10-2010 02:42 Edited 07-10-2010 02:47

Do a google search first. There are graveyards full of people who've welded and flame cut on propane tanks making grills. Some even filled them with WATER and were killed when the thing exploded.

Stop listening to the toothless, redneck wonders on this thread who have done it dozens of times and are cooking up some fatback and catfish right now on a nasty old propane tank grill. These same toothless, chaw spitters also like to make AIR COMPRESSORS out of old propane tanks to save a few bucks. You are going to get KILLED! Why do you think all these old propane tanks are FREE? It's because they are deadly and they cost money to dispose of properly!

Seriously, buy an old piece of large diameter pipe and use that instead.

By Cactusthewelder (*****)

Date 07-10-2010 03:12

There you go with that Redneck thing again.

By Rig Hand (***)

Date 07-11-2010 18:05

Dad-gum, we's just try'n ta cook us up some possum bellys. Spit.

By 52lincoln (***)

Date 07-10-2010 17:16

man im glad someone asked this question.im just trying to figure out exactly what your saying by purging 4 times the cubic feet of the tank.i have a 250gallon tank.

By low_hydrogen (**)

Date 07-11-2010 16:11

http://www.balloonlife.com/publications/balloon_life/9801/9907/shipping9907.htm

By dbigkahunna (****)

Date 07-12-2010 00:35

It no make no nevermind,
purge the tank 4 times or 40 times, you do NOT cut into the tank until it has been tested with a calibrated LEL monitor and reads 0.
You can wash it with soap, dish washing liquid or scrubbed by pygmy warriors, you do NOT cut into the tank until it has been tested with a calibrated,LEL monitor and reads 0.
Let me see if I can explain it another way...........................................Nope
You want to keep your butt attached to your backbone? You do NOT cut into the tank until it has been tested with a calibrated LEL monitor and reads 0.

By RonG

Date 07-12-2010 15:29 Edited 07-12-2010 15:32

Oh shucks, just open all valves and vents put it out in 40-acre field (uninhabited) and throw Hand grenades and Molotov cocktails at it until you can't throw no more (if you got a hand held Rocket launcher try that too). Then if its still in one piece give some homeless person a bottle of cheap wine and a Hack saw to cut it open.

By rcwelding (***)

Date 07-12-2010 18:16

Well I got the bottle of wine and a hack saw with a new blade and an old blade... So when did you say you were free to come cut it for me..??? Start with the old blade first it makes smaller sparks..!!! LOL

Sorry I had to give you a little heck...

There is a safe way to do it RonG Im just trying to find out what that is.. LOL

RC

By RonG

Date 07-12-2010 20:24

No sweat, I ask for it.

It sure seems to me if it was full of water there could not be flash or explosion. I know I have welded on full Diesel tanks and they make hot taps on gas lines all the time.

My understanding of the hot tap is that there is no O2 and the gas volume is great enough to carry away the heat before it can ignite the gas. I may be wrong (usually am) but I think filling it with water would have the same effect.

Back a long time ago I cut in to a hydraulic shock absorber while laying under an armored personnel carrier and that was educational enough to put the fear of cylinders in to me.

By Tyler1970 (***)

Date 07-10-2010 03:18

why such a long stack? you gonna put a joake brake on that thing?

By rcwelding (***)

Date 07-10-2010 14:22

I was hoping to sell it to Shad and I didn't want the smoke to blow in his face... LOL

I built it that tall to make it draw better... It lets you have a smaller vent hole and cooks really slow... That pit went 9hr at 250 degrees before I had to put more wood in it... I caught so much hell over its height from friends that now I make them shorter but they don't cook quite as well... I can only get about 6hr out of the new ones before I have to re-load them...

RC

By weldwade (***)

Date 07-12-2010 15:48

I worked in a semi tanker shop for several years. We repaired and built new semi tankers, testing and inspection. The process we used to de-gas a tank was the use steam for a period of time depending on the layout and size of the tank or compartment. After steaming a calibrated 4 gas monitor was used to sniff the tank in every nook and cranny, only after passing this test would the tanker be allowed in the shop. We mainly worked on crude oil and refined tankers. On several occasions I worked on propane tankers and I can tell you this from my experience. Every one of them spent about 4 days on the steam rack put through many cycles of heating and cooling before the monitor would read ZERO! Keep this in mind it is very hard to de-gas a propane tank.

Just a suggestion but you can orange peel a pipe or rolled plate and get the same look as a head on a propane tank...

By dbigkahunna (****)

Date 07-12-2010 17:17

I was surprised the first time I used dishwashing soap to de-gas a tank. Be sure it is diluted as the water is the key. 1-5 is a good ratio using Dawn. The solution needs to be soapy to make a lot of bubbles. If you can fine and use a eductor to arieate the solution the better. It will work when steam will not. Also, do not use hot water. It needs to be cold. This stuff has even worked on sludge in a gasoline tank.

By weldwade (***)

Date 07-12-2010 19:46

Thats why I like this place you can learn something new every time you log on! I will give the soap a try for sure the next time I do a steel tank. I made an eductor a long time ago to pump out a sump I was working in but it is rather large and would not work for a gas or propane tank. I'd have to make a smaller model for that job! Is it that the hot water or steam opens the pores of the steel?

By dbigkahunna (****)

Date 07-12-2010 23:03

No. The dish washing soap has a de-greaser and surfactant that is designed to work with water temps below 130 degrees. And the key is the bubbles. You want almost foam going in the tank. There are other things you can use like standard de-greasers, but Dawn is available and cheap.

By rcwelding (***)

Date 07-12-2010 18:02

I don't care about the look so much... You can make a good looking smoker out of just plate or many other things... I can pick these tanks up for $40 and get as many as I want... You can't get a 6ft to 8ft long 24 or 32 inch pipe 1/4 in wall for anywhere near that...

I sell them for 2k and by the time I get axles tires grates and all the other stuff on them plus time Im cutting it close to make any money...

I just need to find a 99.9% safe way of cutting them... Nothing in life is 100% I just want to be as safe as possible then get after it...

Plus I enjoy building and cooking on them..... All you guys who haven't had a chance to eat slow cooked Brisket or ribs from a BBQ pit, you are really missing something... Call us Redneck or Hillbilly or whatever else you want but dang it we can cook some good food..!!!

I just have to figure out how to do it safely now.. LOL..!!!

RC

By dbigkahunna (****)

Date 07-12-2010 23:08

RC that scare me. You are willing to take a risk with your life for how much?$$$
If nothing else take a 3 inch hole saw and cut a hoe opposite of where you are going to make your initial cut.
It is not that hard to do it right.
Good luck.

By DaveBoyer (*****)

Date 07-10-2010 03:39

I don't know if a tank that size is strong enough to withstand it, but I think I would hook My vacuum pump to it and pull a deep [29"] vacuum on it for an hour or two.

If You still have a tank when You are done with that, and not a crumpled chunk of scrap, let the air in, and cut away.

From what I remember, the procedure for preping a small aircraft fuel tank involved purging with steam. I think a tank the size You are working on woukld require a larger steam source than My Steam Jenny steam cleaner, but I don't know what You might have.

Propane is heavier than air, keep that in mind when You are trying to get it out of the tank.

If there is any oily residual crap in the tank, You still run the risk of turning that into a flamible vapor from the heat of cutting. The only propane tank I ever cut had no such residual crap, just stank like hell.

By 803056

Date 07-10-2010 03:48

Darwin is alive and at work.

Al

By DaveBoyer (*****)

Date 07-10-2010 04:26

You don't think the vacuum will work?

By raftergwelding (*****)

Date 07-10-2010 07:46

i do not weld or cut on propane tanks

By rcwelding (***)

Date 07-10-2010 14:28

The 150gal tanks have a 24in diameter buy 6ft long... Some go up to 7ft long and the 250gal tanks have a 32in diameter by 8ft long...

I have seen the wall thickness range from 3/16 5/16 depending on the tank... They all seem to be different..

RC

By DNukem Date 03-15-2019 06:17 Edited 04-16-2019 02:36

Cutting into an LP/Propane tank has HUGE RISK! There is a thread from RCWelding (07-10-2010) with much discussion on this subject.
I did not find any of the following important information in that discussion. Using Dawn soap is discussed in his thread & is warranted.

The question is: What will work best to displace Gasified Propane?
Something to consider in trying to displace Gasified Propane.
Molecular Weights of the fuels/gasses in RCWelding's discussion by lightest to heaviest.
CO (Pure Carbon Monoxide) 28.011
CO (Exhaust/Impure CO)    28.011+ = (unknown wt.)
N3 (Nitrogen) 28.013
Air (common blend of gasses)    28.966
AR (Argon)    39.948
CO2 (Carbon Dioxide)    44.010
C3H8 (Gasified Propane) 44.097

As you can see the Gasified (Vaporized) Propane is the heaviest of all of them with CO being the lightest.
If you are trying to displace the propane vapor, the tank openings MUST BE ON THE BOTTOM to allow the volatile gasses to escape.
If you are purging the tank and the openings are anywhere other than on the bottom you are asking for serious trouble!
None of the lighter gasses can blend with or move the very HEAVY Vaporized Propane uphill to an opening above the bottom.

YES - CO2 will mix fairly well with the vaporized Propane but only to an UNKNOWN dilution at best. Don't chance it!
CO & N3 will "push" the vaporized Propane out a tank bottom better than any of the others as they are the lightest.
However CO (Carbon Monoxide) is very flammable in air mixture concentrations of 12.5% to 74%...
A much wider explosivity range than air mixtures of Propane at 2.15% - 9.6% - a lower explosive limit than CO requiring less material (propane) to achieve said concentration.
Using "Exhaust" (impure) CO is even more hazardous as it has additional unburned oxygen/fuel components from incomplete combustion within the "Impure" Carbon Monoxide, producing a truly unknown explosivity range.
Only INERT Gasses shall be utilized. Anything with an oxidizing component shall be avoided.
Accordingly - N3 (Nitrogen) is the best purging gas as it is very light and has NO OXYGEN or Fuel component! BUT, the tank openings MUST be facing down!

Sources: http://www.stadealer.com/uploads/1/8/4/1/18412059/coalarminstallationheight.pdf
Propane Research and Education Council – www.propane.com

By dbigkahunna (****)

Date 07-10-2010 12:45

Take all the valves off and let the vessel de-gas for 2-3 WEEKS.
Get a calibrated 4 gas monitor and someone who knows how to use it and test the tank. If the LEL's are 0 it is safe to cut.
Using dish washing soap to help de-gas the tank will work. Use 2 cups per 5 gallons of water. Use a pump up sprayer to put the soap in the tank. Use a nozzle to put air in the solution to get bubbles. Spray where the solution gets on the tank walls. Let the solution set for a few days.
Again, never cut into a tank that has held any flammable liquid material unless the tank has been tested with a calibrated monitor.
This can be done safely, but using your nose as the calibrated detector will result in a lot of paperwork on your survivors.

By Joseph P. Kane (****)

Date 07-10-2010 14:24

dbigkahuna

Excellent technique. Sound advice.

I would add a three other caveats;
-Another poster suggested using exhaust gas. This is bad, because carbon monoxide is also a flammable gas in the right combination.
-As you suggested, use blowing compressed air.
-Do not leave any spaces where gas can accumulate, such as might be caused by tipping the vessel on it's side.

Joe Kane

By bozaktwo1 (***)

Date 07-12-2010 16:53

And if the tank has a coating, consider the potential problems with outgassing. Just sayin'. :)

By dbigkahunna (****)

Date 07-12-2010 03:11

READ THIS BROTHERS & SISTERS
http://www.csb.gov/assets/news/document/CSB_Hot_Work_Safety_Bulletin_EMBARGOED_until_10_a_m__3_4_101.pdf

By rcwelding (***)

Date 07-12-2010 14:39

Well it looks like the Good Lord has protected me through my ignorance.... I was told the truck exhaust would displace the oxygen thus making the tank safe to cut...

The exhaust must have done something because when I would separate the two halves I would get a pretty good flash.. Some of those old tanks had a half inch of sludge in them and even after they were cut open and I scraped all the crap out It would still burn when I was welding on them... I just figured that if it could not get compression it would just burn and not explode...

I am going to read up more on hot work and the best way to purge these tanks... I have four of them laying in my yard that I was going to work on this winter....

Just because I have been lucky so far doesn't mean I am going to continue using the same process...

Thanks for the advice and information... I wont be cutting anymore tanks till how do they say it in redneck terms..??? ( Till I get some more learnen )

Thanks everyone... And I am still open to more advice or Ideas on how to go about this safely...!!!

RC

By Lawrence (*****)

Date 07-12-2010 14:54

Wisdom!

Now that you said that.... Those are really nice lookin grills!

I hope you can come up with a safe system to zero out the Lel and cut them...

By Tommyjoking (****)

Date 07-12-2010 17:53

Well it is a touchy subject....

Nice looking work!!! I have been approached to do this before...have not yet. I have welded up a few fuel tanks large and small tho....not gonna get into how I went about it...but I always had my fingers crossed no matter how sure I was. I think propane tanks may have a nastier reputation..... I do not have much to say bout it...great advice has been given already. BUT as far as purging goes, dry ice can make for a cheap oxygen remover, definitely not fool proof.

By rcwelding (***)

Date 07-12-2010 18:07

Never thought of dry Ice... I can get as much of that as I want..!!! I mite have to research that a bit...

RC

By awspartb (***)

Date 07-13-2010 01:41 Edited 07-13-2010 01:43

I was working just down the road from the 2001 Motiva acid tank explosion in the link you provided. The poor guy who was killed was disolved in the acid. There were no remains to bury from what we were told.

By Austin-T (*)

Date 07-12-2010 21:54

For what its worth your BBQ Pits & trailer look great. Id like it if you could post more pics and dimensions/sizes of the trailer/tanks, etc. These are good projects to get people more interested in learning how to weld and exercise caution. Keep up the good work and be safe.

By Austin-T (*)

Date 07-13-2010 00:17

By FixaLinc (****)

Date 07-13-2010 00:45

Steam steam steam steam steam for days & balls. Old welding shop in town here did many of them for years to convert to molasses, water or diesel tanks putting new fittings in. They got too old sold the shop & died of old age not from a tank accident.

By DNukem Date 03-15-2019 06:18 Edited 04-16-2019 02:39