LP problem

[Jim Jarvis]

I have a problem with at least one side of my propane system. One tank runs fine until it gets to about one quarter full. It then cuts out. Switching to the other tank and everything runs as it should until that tank is empty. On the past weekend I tried an experiment. When the propane tank got to one quarter and shut off the generator I took that tank and installed it on the other side. Everything then ran normally for about 10 minutes, then it shut down. Now I could not get either tank to run on either side and was without propane on a rather cold night. First thing in the am nothing would run but then after a couple of hours the propane started to flow normally again from both tanks. The one tank that first cut out was frozen when I went to switch it. The outside temp was 8 degrees C. However the same thing has happened on warm summer days. The dealer is today replacing a controller, I think is what he said, on the one side that is usually the problem. Does anyone here have any similar experience I can draw on? Thank you in advance for any response.

[Charlie]

I had a total loss of propane after the first tank which was on the door side of the coach emptied and switched to the driver's side. Replaced the regulator and everything was fine until the tanks switched again. This time I started looking for problems. What I found was oil in the cross over pipe from the driver's side of the trailer.

I have in depth experience with propane systems. My analysis of the problem was who ever cut the threads on the pipe did not clean the pipe. To cut threads on pipe, oil is used as a lubricant to cool the the thread cutting machine dies and prevent the threads from galling.

Pull the hose to the regulator from the driver's side and check for any oily residue. If so, the pipe will have to be cleaned with solvent and the oil probably has ruined your regulator. I found that the oil had was migrated as far as the hose that ties the regulator to the main header that feeds all of the trailer's systems and was trapped in low spot. I was lucky that there was it did not get any further. Don't let anyone tell you the oil came from the propane. Odds are probably less than 1 in 10,000,000 it came out of your tanks.

[Jim Jarvis]

Thank you Charlie. I will have a look at that.

[rlrich]

I drain a few ounces an "oily substance" out of my low point main line every few months. This after totally removing and completely cleaning my cross over pipe and replacing both regulators the first time I encountered this problem. I had the same experience with my previous trailer. I know this is not residual thread cutting oil. There is simply too much of it and it is a recurring situation. After some reading I suspect this substance to be propylene.

Refer to paragraph 3 of this link:

http://propanepower.com/3.html

I was wrong in my post concerning this subject a number of months ago. I'm now assuming it is not oil as I previously stated, but an oily-like substance (possibly propylene). My mistake in relating my solution to my propane flow problem.

[Charlie]

"Refer to paragraph 3 of this link:

http://propanepower.com/3.html


"The purity of the HD-5 grade motor fuel adds longevity and efficiency to forklift engines by eliminating most of the carburetor, regulator, and starting difficulties inherent with the use of commercial grade propane which has a much higher propylene content. Propylene, the main impurity found in commercial grade propane, is the black, oily-like substance which mechanics often find, much to their dismay, clogging and fouling propane fuel systems."



Sorry....have to disagree with this statement. Propylene is typically obtained via two main routes: either as a co-product of the refinery catalytic cracking process used to make gasoline or as a co-product of the steam cracking process used to make ethylene.

For simplicity's sake I will not dicuss the catalytic cracking process for gasoline.

About the other process, propylene is produced in the refinery when ethane feed stock is introduced into a high temp furnace about 1250F with high pressure steam. The main bi-products of what is termed temperature conversion or "cracking" are ethylene (C2H4) and propylene (C3H6). Through a series of towers (fracinators) the products are separated. Ethylene and propylene are feed stock in other processes to create plastic and other products.

In either process the last separation is in a column called a C3= splitter. Propylene (C3H6) is lighter in composition than propane (C3H8) therefore it exits the column at the top and the propane at the bottom. Both propylene and propane at atmospheric conditions are colorless gases and highly flammable. They become liquid when compressed and pressurized about 180# and leave the process unit as a liquid to be stored in tanks.

Any entrained residue resulting from the cracking process would exit the bottom of the C3= splitter with the propane. It is the refinery's responsibility to make sure this material is not transported when propane leaves the refinery. The possibility of finding oil in a propane system does exist but should be rare.
It is not propylene!!!!

[rlrich]

Whatever is is or isn't it keeps getting into my propane lines and I keep draining it to prevent it from reaching any of my LP appliances.

[Jim Jarvis]

Just to let you know Charlie, you were right. Cleaned the regulator and no problems. Thank you.