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Large propane tank +small demand =regulator freeze?

Solid_Fuel_Man
Solid_Fuel_Man Member Posts: 2,646
I was talking to a local propane supplier about some troubleshooting. He said last winter he had a couple of accounts with 500+ gallon tanks with small demands which had experienced first stage regulator freeze-ups. He said with the same L.P. supply, they didn't have the same freezing issues with his larger usage accounts.

We were having this discussion because I was proposing the same scenario with my own home. He said the tanks were properly purged and methinal added at that time.

Any ideas? We thought that due to the low draw and large wetted surface od the tank the methinal was not vaporizing with the L.P. and allowing the water to freeze in the regulator? He said he changed the first stage regulator which got things back up and running. Also the frozen regulators all had water coming out of them when they thawed out in the shop....
Serving Northern Maine HVAC & Controls. I burn wood, it smells good!

Comments

  • hot_rod
    hot_rod Member Posts: 22,022
    Here is some good info on LP and water content. Sounds like water in the tank and possibly some water in the LP they deliver.

    http://www.propanecouncil.org/uploadedFiles/REP_11992 Methanol to Control Water Freezing Report.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    ZmanSolid_Fuel_Man
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,453
    you answered your own question. water in the tank that isn't supposed to be their

    I don't believe usage is a factor. If anything higher usage would be more likely to cause freezing
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    That's what would seem to be the case. However he said he hadn't had any other regulator freezing problems. Only in two accounts with large tanks and small draws. That's what seemed so contradictory.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • JUGHNE
    JUGHNE Member Posts: 11,042
    So those 2 accounts could have old LP that was wet. Everyone else has freshened up their tanks and diluted the water, or burned it off in mild weather when freezing would not have been a concern.
    Just a WAG.
    Solid_Fuel_Man
  • Henry
    Henry Member Posts: 998
    We have tables for the amount of surface needed to evaporate at low temperatures. The surface area has to increase for higher consumption. It is very common to have very large storage tanks for use with generators. But a heating load or stove has no effect on these large tanks.- in sub zero weather. It is definitely a water problem.
    Zman
  • Gilmorrie
    Gilmorrie Member Posts: 185
    As Henry stated, when propane evaporates, the remaining liquid is reduced in temperature, and the pressure of the propane drops. Large users often have fired evaporators to maintain the pressure during winter weather.
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
    Thanks all, this completely confirmed all that makes sense. This supplier (local 4 man show) was just telling me about this anomaly and we were discussing possible causes.

    None of these had vaporizors. Just wetted surface evaporation.

    I am all set for my own 500gal horizontal tank. By my calcs it has the potential to last 5 years. If I only use L.P. for occasional heat, as my current range and dryer use 50gal per year.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!