Transferring Lp Gas

wasn't sure where to post this but figured this sub forum was a good place. This is probably a advanced skill.
In some parts of the world LP is used as a refrigerant. I fill 20 lbs, 30 lbs, 40 lbs and 100 lbs cylinders.

I've been working with lp gas since I was a kid. We ran our sawmill on it. I have a hand pump to transfer lp gas from a big tank to a small tank.

But there is another way. LP gas is flammable, explosive in certain conditions and can cause frost bite. I wear leather gloves and safety glasses when transferring. I don't smoke but I guess it should be mentioned not to have a flame when transferring.

Most LP gas bulk tanks have what's called a liquid retrieval line AKA wet leg. Liquid is transferred through this line using a hose, pol and a valve. It's a differential in pressure process.

here's the start. A valve and nipple is screwed into the wet leg port. The nipple pushes a seat open and LP is available at the valve. A hose and pol is run to a tank and tank filled to 80%



I sometimes use a scale, LP tanks are filled to 80 percent. This photo shows a 80% bleeder screw. When the gas is being transferred, vapor comes from the bleeder, when it turns to liquid, it is 80% full. Shut the supply line off and tighten the screw. It;s done.

 

I am an AC tech among other things. I have worked on freezers that use propane as the refrigerant. They are usually medical freezers that are operating WAY below Zero.

I have also worked on a lot of LP/propane refrigerators that require no electric power to operate. In rural places, LP is the way to go for heating and cooking. I've even owned a truck that had two big propane tanks in the back and would run on either the gasoline or flip a switch and run on propane. The propane made for very clean engines and injectors.

Most bottled gases that I have delt with can be used in either gas or liquid form. For small swops like 30lb container to one pound containers you just flip the 30 pound can upside down. Bigger tanks have a dip tube in the tank and a wet line. We used to make dry ice with a tank of CO2 with a liquid line from a dip tube. When you squirt liquid CO2 into a wooden mold it goes from liquid to solid as the liquid expands. You definatlywear gloves anytime that you are handling liquid gasses that you are allowing to change state. It is that change of state that is what makes refrigration work.

 

Appreciate the information . I am going to investigate LP gas farther for refrigeration . Iv got an future off grid house in mind .

 

Very nice, thanks randyt. The pics really help.

Can you provide more details on the pol fittings (are these standard sizes/threads on the 500 gallon tanks, or do they vary by manufacturer?) you're using and connection to the wet-leg on the bulk 500 gallon tanks. I'd like to build a couple of these transfer hoses to mate the most common 500 gallon wet leg connectors to a standard 20 pound tank, mostly for SHTF use. Any details on the end-to-end hose/adapters/fittings for constructing these would be much appreciated.

 

My equipment is rudimentary. I think the hose may be a hydraulic hose, not sure it could be a reefer hose from a place my granddad worked at. The POL is a standard POL. There are POLs available with a hand wheel, I used what I had.

The upper photo shows a blue handled valve. This valve was screwed into the wet leg with a nipple. The nipple pushed the seat open, the valve kept the gas off. It really wasn't the correct valve. I changed it out when I got the correct one.

Some tanks have a tapping at the bottom. It works the same way, a nipple and valve pushes the seat open then a hose is attached.

the lower photo shows the filling process. Right under the handle of the tank there is some frost, the screw can be seen too.

I also have a hand pump that can be used to fill tanks. It is used with a scale, the 80 percent bleeder is not used.

I have been in the HVAC trade for 35 years and as a kid we ran our equipment on propane, forklifts, trucks and such.

 

Thanks again. Found I have different style wet legs (or "liquid withdrawal excess flow valves") on each of the two house tanks. Looks like $60-70 for an adapter and valve for the newer tank, plus the high pressure hose. The rest of the fittings/adapters to mate it to a 20 pound tank I should already have. The bad news is that even my newer tank is still using an older style wet leg fitting, the new "standard" seems to be 7590U fittings (maybe) and are apparently much more common and less expensive.

The second, even older, tank is still a mystery and requires more research, the valve is under 3 coats of paint and the manufacturers info plate on the tank itself is tarnished so bad it's unreadable. Still need to check what the third tank at the bunkhouse has. It's a newer style so hopefully the same as the newer one at the house, if not the newest 7590U type.

 

This thread seems to be not very valuable to anyone other than a refrigeration technician ... UNTIL I realized that, in a post-SHTF scenario, such knowledge might come in handy if i ran across a deserted commercial- or industrial-size LP tank just as my own 20-lb tanks are getting dry. I have two tanks for my RV, two for my barbecue, and three more for the torches around the farm.

On the other hand, maybe it'd make more sense if I got my own large tank to keep just for such emergencies. I ought to price one out!

 

That was my thought as well, many people in my area use propane. We use it for refrigeration, kitchen stoves, lighting, and one of our generators. Three 500 gallon tanks, two 100 pound tanks, and about eight 20 pound tanks. Being able to fill the 100 and 20 pounders off the big tanks would be a big advantage if the SHTF, including trade/barter for selling or buying it, or providing it as a service to others that wanted to trade but didn't have the know-how or the equipment to transfer it between their tanks.

Problem I'm finding is each of my 3 big tanks has a different excess flow check valve (wet leg), requiring a different adapter to open the valve. Seems there never was any real standard for these valves, and even those sold by the same company (e.g., RegO which is a popular one) have changed over the years and are not compatible. You'd need to get something like this semi-standard Chek-Lok valve:



and then adapters for the bottom that matched the specific type of excess flow valve on your big tank. One of mine would use a RegO 7572-14A adapter and another would need a Squibb Taylor PA5138 adapter for connection to that Chek-Lok above. The third tank I'm still not sure of, but it's different from either of the other two so a third adapter required. Since I have 3 tanks and 3 different types, guessing there are lots of different styles in use.

I'm hoping I'm wrong and these adapters aren't so specific, like any fitting of the same size and thread will open the valve on the tank, but not sure. Unless randyt or someone else here has any advice I may join a LPG/propane forum and ask there.

 

I have never accessed a wet leg with anything but a valve and a 3/4 inch nipple.

 

my tank is hooked to absolutely nothing. I have the lp supplier bring a load now and then. They asked me what I use it for and I tell them for boiling maple sap in the spring.

I have gotten free gas from folks that switched to nat gas from LP. Their supplier would not give them much or anything for the gas left in their tank so they let me take it. I fill up my various cylinders.

 

Want to add another important point. LP gas delivered to bulk tank is much cheaper than having mall tanks filled at a filling place. Probably half price if you fill them yourself from your bulk tank.

 

Think the difference may be in the tank design, either yours is what some refer to as a "nurse tank" or maybe it was manufactured prior to 1961. "ASME containers built prior to 1961 can be evacuated through the filler valve in the top of the tank since they have dip tubes installed which extend to the bottom of the tank to evacuate liquid through the filler valve." (page 79 of the doc here: https://www.ncpcm.org/assets/Technical_Spport/om handbook.pdf).

Mine have only vapor valves under the tank hood, and a separate Actuated Liquid Withdrawal Excess Flow Valve off to one side (opposite side from the relief valve on the right side of your tank) that has the wet leg/dip tube. "A transfer valve with a machined adapter must be used to evacuate a tank through a liquid evacuation valve" and "Use the machined adapter supplied by the evacuation valve manufacturer" (page 80-81 in that doc above).

Going to have a chat with the propane guy the next time I get my tanks filled, the delivery guys are usually much more willing to talk than the people in the office. And I'll be watching for any valves and fittings at farm/yard sales, my minimal experience (and supplies) are on the low pressure vapor side of the regulator.

If you can write up some info on your hand pump and the transfer process when using it that'd be great.

 

A month or two ago I tossed out an old BBQ but not before taking the hose and fittings for later use on a project. This could be a worthy one.

I forget who but one guy in a war zone talked about filling 1# propane cylinders with a 20# tank upside down and using these as trading stock. People would bring him their empties and he would give them back full. I have the adaptor and have filled several for myself.

After so many refills the 1# tank valve can start leak so having a torch head to screw on, if it starts leaking, is handy.

https://www.amazon.com/Propane-Adapter-Cylinder-Coupler-camping/dp/B0745CNJYL/ref=sr_1_5?crid=3BGGWFNV3NN10&keywords=propane+fuel+cylinder+adapter&qid=1560026002&s=hi&sprefix=propane+fuel+cylinder+a,tools,245&sr=1-5

 

In the event of a severe or prolonged SHTF event (or series of events), I would also be thinking of concealing large propane tanks to help protect it from thieves. Easier said than done!

That propane would be more valuable than gold.

One thought that came to mind: Paint it with a dark rust colored paint to remove the tell-tale white "flag" that screams "propane." Then hide the tank in plain sight with a junk or trash pile around and over it. Park an old junked car or two near it, broken appliances, lawnmowers, and maybe a brush pile here and there...


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Stacking firewood around the tanks would help hide them, and give them protection from gun fire. Maybe not the best solution in the event of a forest fire however which is why I don't do it now, but considered it for post-SHTF.

 

That is a thought, but if propane is gold, then firewood would be like silver... My plans for firewood is not to stack them but to hide it in a similar way. Along that line of thought, Silky brand saws would be more valuable than noisy chainsaws so as to not attract trouble during prolonged SHTF events.

(Sanford & Son, move over...you gots competition, lol.)


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The thunk of metal on wood is pretty loud! Even a woodpecker's bill stabbing a tree can be heard at a distance.

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An axe has a distinctive sound that can be heard quite a ways but far quieter than a GAS chainsaw. I have an electric saw but that won't work for long if I don't have a way to charge the batteries.

I was thinking about getting a 1000# tank and making a flat spot on my property where I have a slope. Put up a retaining wall to hide the tank and then build a woodshed over it. If you poured a concrete floor in the shed it should be fire proof

 

Not if you put all your eggs in the same basket. The tanks are lifted or drug into place and then filled. The propane truck has a hose, much like an oil truck.

 

LMAO. You are half right. I have pavement to the front door but I still need 4-wheel drive to get home.