Large propane tank purging

[lightman]

Not to hi-jack the thread but I've seen those larger tanks cut up and used for some useful things. Our Scout troop had an end cut from one that we used as a base for fires. A farmer buddy has one that we use to cook Crawfish in. I expect a cut off one smaller than 1000 gallon would make a good smelting pot. Once the ends are cut off they make good culverts. Sorry for the hi-jack!

[Hossfly]

That’s ok I saw a 250# tank repurposed for a bar b q commercial and was mounted on a trailer axle , nice and portable. On my large tank , after extensive leak testing, hooked up vacuum pump with long water hose for exhaust. Good so far, 12:00, 5 hours later returned to only find down to 10’’ Hg, upon further evaluation found the large fill valve that wouldn’t leak @ 100 psi was sucking in air. Used some 515 by Locktite gasket eliminator and some tight fitting dust caps, sealed and restarted evacuation again this morning, we will see.

[Hossfly]

Good news, got all input valves sealed with gasket sealer and dust caps and teflon tape pulled 7 hrs vacuum down to 29+ on gauge set. Noticed liquid H20 at hose fitting @ pump discharge, oil very cloudy when changing oil in pump. Will let set and check pressure in am. Have to get my old wet bulb device out and test to see if dry.

[Down South]

If you find propane at $1.00 a gallon, you do well. They had a price war here in September and the best I could do was $1.75 per gallon. I filled up a 500 gal and a 120 gal tank.

Oh, BTW, I wish that I had a 1000 gal tank.

[Hossfly]

Next time they call with that price i will have the capacity to say filler up.

[samari46]

maybe I'm overly cautious but would remove all fittings like guages and stuff that will not be used for a water test. Introduce the water from the bottom of the tank and when filled keep it running to make sure you are getting a good overfill.Then when satisfied that the tank is/gas been completely filled drain out the water and use compressed air to remove any water clinging on the sides and bottom. After that a good visual inspection with a high powered light source to check on the internal condition of the tank should be performed. Frank

[Hossfly]

Up date; pulled vacuum for 2 days and am sure all trace of water and gas is gone. Hurray, hooked up 100# tank with regulator and took about 1 hr. To bring pressure up to above atmospheric. So now ready to clean and paint install skids and get set up in area of other tanks, fixin to get cool next week.

[.429&H110]

Break the vac with propane. Just right. The air is gone and might be some moisture clinging on but the propane will absorb it. The other way is put in five gallons of propane, and flare it off, three times. The air rises to the top and escapes with the bad smell. This purge idea will not get all the air out, but it works. Boss has to buy 15 gallons of propane for each tank, and a gallon of methanol and an hour of my time. Vac a new dry tank, and life is good. Same idea is used for refrigeration. The steam tables are your friend.

[Hossfly]

.429&H110 that’s what I’ve been doing for last 45 years Heavy ref. Large chillers and skid boilers so been evacuating large vessels. This is first propane tank this large I’ve had to deal with tho. Looked inside when had valves off didn’t see any liquid water inside, some trash like substance in very bottom, not much tho. Got valves tight and pressured to 100# all good, took 2 days to get to point i thought was good vacuum few bubbles out pump exhaust. Now setting with a little pressure to keep anything getting in.

[.429&H110]

The trash in the bottom is odorant mixed with junk that tried to seal the delivery truck plumbing. Thread goop, teflon tape, lost o-rings, grease from the hose reel. I have found cigarette butts, rust, pop-tops, mice, dirt... Junk can stop up the liquid withdrawal valve and cause a very long day. Taking vapor from the top leaves all that in the bottom.

[Hossfly]

Update on large propane tank. Been a while since I started this thread, so got the 1,000 gallon used tank leak tested, evacuated, pressurized to
15# and let sit over 3 months. Still at 15# dragged to area of intended operation, cleaned up pretty and painted silver. Piped into system manifold. Called around for price’s locally, in August prices ranged from high of $2.59 to low of $1.45, bring it on. Bought 300 gallons first time waited till September and price still low bought 300 more, I wanted to make sure all was working before getting a lot. Now have enough to last till next August, with this large tank and the 250 gallon as reserve, the 150 gallon tank is now sitting at old shop for melting WW and sheet lead. Now I can fill my small tanks from large one at lower cost. Thanks for all your input on this project Hossfly

[10x]

The whole point of purging is to get oxygen and moisture out of the tank so that when you fill the tank you have undiluted propane Filling a propane tank and mixing with air (21% oxygen) under pressure creates a potential problem.
O2 also rusts the inside of the steel tank.

Sometimes the internet is helpful
https://www.google.com/search?q=Purg...hrome&ie=UTF-8

[dg31872]

I would find a propane guy that you can work with and follow his recommendations for testing it.
We use a lot of propane on our farm. We buy transports loads at a time. Just got a load last week at .745 per gallon laid-in. A transport is around 9,000 gallons. It is going up.
Normally, best time to fill it is the first of July.
The fact that it was still pressurized is good. Means no rust on the inside.
I think you said it was setting on the ground? Might do a thickness test for the bottom. If it has been on the ground for awhile, there will be rust pits on the outside bottom.
Not real expensive and then you will know for sure. Propane guy can set that up for you.
We bought a 12,000 gal tank couple years ago that had been open. I requested a hydro test (they fill it almost competely full of water then pump air in to the max pressure) and a thickness test. The tank passed both tests, so I could sleep close to it with our worriyng.
Better to spend a couple extra bucks and be safe.

[Froogal]

At one time my propane supplier would not fill a tank they did not own. That company is now under new management so it may have changed.

[Hossfly]

This tank had good paint, rolled it over and found no pits. Cleaned with wire wheel grinder, wiped down with thinner and painted silver. After filling with first 300 gallons, checked temp/pressure , during 100’+ days pressure would get to around 160# in August with sun on it. Now at night and colder weather pressure down around 80#. Dropping thru primary regulator to 9-10 psi. Then secondary regulators to 14” at gen. Set and boilers for 2 greenhouses. Been running great thru generator and boilers flames look good and blue, no hiccups so far,also have 250 gallon in reserve. Also tank is elevated on concrete blocks and level so we can access for cleaning and maintenance. The liquid valve does leak when operated, have it tight right now, and blocked in, when this tank gets real low will pump out vapors with recovery pump and replace.

[drac0nic]

I used to work at a propane plant. You have 2 options:

1-Vacuum purge is how the factory did it when we were getting new tanks in. Totally valid way to go.
2-We would pressurize the tank with LPG then release it 3-5 times. If you have a burn off stack or some other way of getting rid of the propane vapor this isn't a bad way to go.

That said if you had a couple psi in there you're probably okay. I will say that there is somewhat of a controversy in the industry around "odor fade" although I've personally experienced it as well as being able to ingnore the smell. You're not supposed to see either really.

Look for any black crap around the valves and along the welds. If it's got a leak there you'll probably see spots. You can rub your hand on them a bit and you'll smell the oil if it is. The bottom plugs weren't that unusual to have leaking a bit and the gauges were another fairly common spot.. If it's leaking on a weld you can take a punch around the pin hole and "peen" it shut. Seen it done a few times.

ED:whoops way behind the curve reading this morning. Sounds like it got settled out. The liquid valves are indeed leak prone at times. If it has one with the pipe going in to the bottom you should replace it with the "spreader" type when you do. They tend to fill the tank easier because they cool it as they fill.

[MT Gianni]

One local company will not fill a personally owned, non white tank. They require a white finish as identification. That is the only way to find one friends house. If his tank were green you would never see the place. I think you did good, though a 500 gallon tank only gets me from August to February with out a refill.

[Hossfly]

Update on large tank. Started heating season with 600 gallons of propane, and 250 gallon tank at 60%, large tank is down to 10% and will switch over to smaller one tomorrow. Tonight will get to about 29’ and both greenhouses will pull quite a bit of gas. This last storm that took out power for general area and gen set ran for 30 hrs. So that took quite a bit of gas. Called my propane supplier for price and got delivery set up for 100 gallons to be delivered on Monday for $1.50 per gallon. Trying to make it till summer and will buy more. Waiting for pressure to drop so I can change out the liquid recovery valve. I do have a pump out unit to pull out the remaining gas.

[drac0nic]

holy smokes it's 1.50 a gallon in winter? I remember when it was 2.50+ back some 15 years ago!

[Hossfly]

I was surprised also thought they would be at least $2.50. If $1.50 is winter price maybe it’ll get down even lower by summer. Here in Louisiana the winters aren’t very severe. That’s why I bought the 1000 gal. Tank so could buy in summer when it was cheaper.