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Oil accumulation in propane tank

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We have an Onan propane generator. It runs off Liquid rather than vapor. I had it serviced at an authorized Onan center. They replaced “Coverter-lpg” and fuel line. Told me I had oil in tank and not to use until I got oil removed from tank. Have called two Large RV service centers and propane supplier. All three said they have never heard of that problem and offered me no solution.  Tech who worked on my unit told me the unit would run off vapor or liquid and to simply put a “T” in vapor line and run to generator. I called Onan corporate office help line and they told me to call service center. A bit of a catch 22. Any suggestions would be greatly appreciated. Thanks, Chuck


 

 

 

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Chuck,

Welcome to the FMCA Forum.

Had a coach with exactly the same setup (Liquid LP Onan generator).

Had a good working relationship with an engineer at Marshall Gas who made the majority of the regulators for RV's.  At his recommendation I converted to high pressure vapor.

Turn off/close liquid port and run generator until it quits to deplete the propane in the line.

Turn off/close the vapor port.

"T" in between tank and house regulator (i.e. high pressure vapor).

I added a propane speced ball valve off the "T" so I could turn off propane to the generator without interrupting flow to house regulator.

Then moved the line from liquid port to the new port on the "T".

Install cap on the liquid port.

Been over a decade running like that and no problems.

The  longer hydrocarbon chain oil or mercaptan in the bottom of the tank will NOT vaporize at ambient temperatures so is not going to get into the line to the generator.

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Chuck, Brett's Thoughts work real well to re leave the long-chain hydrocarbons from the supply side of the LP source. The  "T" trap is a common solution as it lets the oil  drop out of the vapor line.

A common problem with LP powered backup generators for a stick and brick location when there is no NG source to connect to.

Rich.  

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There is a long thread about this occurrence, on irv2.com.  That person got oil in the regulator and low-pressure lines. From that thread I learned Ethyl Mercaptan  contains no oil. When I was a firefighter I was taught it was an oily substance, now I  know that was not true.

nj.gov/health/eoh/rtkweb/documents/fs/0894.pdf

This explains in detail what Brett talked about: https://www.tarantin.com/blog/propane-101/oil-from-the-vaporizer

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Propane under high temperatures will drop the oil out of the vapour 

when running a water heated vaporizer you need to add a 140 degree inline thermostat if you are using this in a hot climate 

or if the coolant water you are using is to hot  

running off high pressure vapour from tank is good unless you are in cold weather and constant run with a low fuel level as tank could start to ice and lower the pressure 

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If you run liquid to the motor it needs a vaporizer and needs to be heated or it will freeze  up

unless direct injected which I doubt  

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7 hours ago, bm02tj said:

If you run liquid to the motor it needs a vaporizer and needs to be heated or it will freeze  up

unless direct injected which I doubt  

Understood. That is why the regulator on the liquid LP Onan generators is inside the generator very near the engine exhaust manifold.  The regulator (a very common one) requires a high-temp silicone gasket vs "regular gasket".  Have overhauled several and removed tablespoons of a light viscosity grease-like substance that was clogging them up.

Would be interested in a link to a "A water heated vaporizer" on an RV".

Just never heard of one.

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If you stop in at a shop that does propane conversions or a shop that does forklift repairs 

Or check with your local propane supplier they should be able to point out a shop to see 

Impco was a brand I was familiar  with 

not sure if they where used on and RV's

 

 

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