place propane tank upside-down as liquid service tank?

[pulaunias]

Dear members,

I have been frequently visiting this forum and learned a lot from you guys.

Now I am having a problem and hopefully some experienced members can help me get things straight.

We have a DJ 2700 in our lab (a university lab); we recently purchased a propane vaporizer (Algas-SDI) for this system because the common way of drawing gaseous propane from a cylinder (which relies on the natural vaporization of compressed liquid propane) cannot sustain the flame. The 2700 torch requires quite a large volume of propane gas per minute, so the natural vaporization can only suppor the flame for several minutes, then it flames out.

A surprising problem in the place where I stay is that it is obscenely hard to find liquid-service propane cylinders, which has a "dip tube" inserted deeply into the interior of the cylinder to draw luquid propane out and feed to the vaporizer.

After repeated failure to find this type of cylinder, it came to my mind that: is it possible to simply turn a regular propane cylinder upside down (or not completely vertically upside-down, but just downwardly slant with the copper outlet valve pointing to the ground). At this position, the liquid propane in the cylinder should submerge the valve; then when I (super-carefully) open the valve, liquid propane should come out and flow into the tube that is connected to the vaporizer. Suppose we have good plumbing.

So I will appreciate it if any one can help me figure out if there are any safety concerns associated with this "abnormal" cylinder position. I know it is an absolutely No No for LPG tank to be used in this position with a regular furnance or stove, because liquid LPG comes out and turns into a large volume of gaseous LPG, potentially produce explosion in the furnace/stove. Here my situation is a tad different; I have a vaporizer that is designed to interface with a cylinder outputing liquid proane. However, I still need more advise on the safety issues, as I am not a truly experienced person in gas cylinders, and I think it is always good to know more when dealing with gas cylinders.

Thanks gain.


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PS: This idea came to my mind because I ever worked in a factory where I was trained to collect dry ice from a CO2 cylinder by placing it horizontal (or slightly slant with valve pointing down) and open the valve widely. Liquid CO2 comes out and soon becomes dry ice (I don't know exactly how), which is collected in a bag placed over the valve. So I though a propane cylinder should work the same, just requiring much more caution.

[Stephen Booth]

pulaunias
Sounds dangerous, have you contacted the supplier of the Vaporizer?

What is the percentage of the Propane in the LPG you are using? What pressure are you supplying the propane to the DJ?

[pulaunias]

Sounds dangerous, have you contacted the supplier of the Vaporizer?

What is the percentage of the Propane in the LPG you are using? What pressure are you supplying the propane to the DJ?
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I agree, that is why I am cautious and would like to hear more before going ahead. No have not contacted them.

I try everything to get >95% propane; In my place the nasty thing is that I was told some suppliers sell LPG (~50% propane) as propane; the pressure is the level specified in the DJ manual (the number off my mind at this moment). I am curious how is the quality of propane in Indonesia? Also curious why you describe it as LPG (you use that for your HVOF? DJ? Does it work OK?)?

[Stephen Booth]

Yes you are correct, I was using LPG term as I was following your term, LPG in the last paragraph of your posting.

LPG is a commercial gas in Indonesia, with a target of 60 propane, and 40 Butane (lower vapor pressure). At one time, many years back, we were forced to use LPG in Indonesia, as Propane was not available in small tanks of 50 or 100 kg. Turns out, as a commercial gas, the manufacturer could, and would substitute butane for propane, hence radically changing the vapor pressure and dropping below the ideal 9 bar level we were seeking.

After a long hard struggle, we found a supplier willing to prepare an Industrial Standard Propane at the 95% with 9 bar pressure. Even then, we manifolded 3 tanks together, and struggled again to find the correct high flow pressure regulator, and occasionally even kept the tanks partially submerged in Warm Water about 50C

I was very disappointed with the level of customer service of the gas suppliers in the country at that time, about 5 years back.

[pulaunias]

Stephen,

Thanks for your input. We are experiencing basically the same problem here in China. I am exactly on this struggle to find 95% propane. The nasty thing here is that people might sell LPG (somtimes with additives, which makes industrial gas for welding, metal cutting) in the name of "propane", and most people either don't know or don't care.

I imagine that even manifolding three tanks together, the ultimaet utility of prpane could be inefficient; when liquid level drops it gets harder and harder to produce enough vapor to feed to the DJ. Eventually a lot of propane still remains in the tank while the DJ cannot run. Then you have to send it for refill; a wate of money.

Tha is why we decided to purchase a vaporizer; hopefully it eventually saves money. Do you use evaporizer now?

[djewell]

By turning the cylinder up-side-down, you disable the pressure blow-off in the shut-off valve, which is there for safety. You can draw liquid out of the valve this way. Just make sure the pressure is not too high. Sherwood make a shut-off valve for propane cylinders with a dip-tube to draw liquid from the bottom of the cylinder. Have you gas supplier look into buying several of these valves for you to use with your tanks.

[pulaunias]

By turning the cylinder up-side-down, you disable the pressure blow-off in the shut-off valve, which is there for safety.
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Thanks djewell,

By "pressure blow-off" you mean the relief valve right (wanna make sure we are talking about the same thing)? I scruple about that.

As to the Sherwood valve, if we buy several of these, we must un-install the original valve on the cylinder and replace with these Sherwood valves right? Or we just attach these Sherwood valves as additional fittings/accessories to the un-manipulated cylinders? If the former option, does it involve special safety inspections? I am not an expert in cylinders, although I use quite often.

Thanks again.

[djewell]

Yes, I meant the relief valve.

The Sherwood valve will replace the shut-off valve on your cylinders. The gas supplier fills the cylinder the same way as before. I am not aware of any special safety inspections, other than those required for the cylinder.