Propane

There are many people who take it for granted or simply don’t know the facts about propane. They think it is an excellent Survival fuel choice for heating and cooking and don’t have to worry about an abundant supply of foreign oil or be affected by a ‘Peak Oil’ meltdown. There are a number of common misunderstandings about propane including where it comes from and how long it can be stored?

Propane and Extreme Cold: How does cold weather affect Propane?

Propane is stored as a liquid under pressure and as the pressure is lowered it boils to produce a vapor that is drawn off at the top for a generator engine to use as the fuel.  Because propane boils at -44° (below zero), the gas will be frozen if it can not absorb enough ambient heat to compensate for the boiling process. The bigger the cylinder is compared to the amount of load, the warmer it is outside, the warmer the cylinder is kept, all are a determining factor in the likelihood of a cylinder freezing up. 

If a sweat or frost line forms around the cylinder at the level of the fuel, this is a telltale sign that the cylinder is over-worked and is in the process of freeze up.  If the gas does freeze, it will stop producing vapor and the pressure inside the cylinder will drop to as low as zero psi which will cause the engine to stop running. 

There are a number of steps that you can take to cold-weather protect propane systems:

Sheltering and insulating the propane tank and line is the most practical approach to prevent propane freeze-up. To beat even the coldest weather, install an explosion-proof light that can be turned on when needed for heat. A small, insulated frame shelter is adequate. Heat stripping can also be used. A commercial product similar to electric heat tapes, but designed for propane tanks, is also available. Loose snow piled all around the propane tank often proves to be an effective insulation. If you have a permanent bulk propane tank, bury it to protect its contents from periods of severely cold weather. To prevent propane regulator and line freeze-up, insulate the system. See the suggestions for sheltering and insulating oil-fired supply systems, above.

Propane Generators and super-cold temperatures:

If winter temps of ‘0’f and colder are common in your area propane generators when needed could be problematic. All propane generators need a specific volume of vaporized propane to start and run at and produce full power (watts). That’s why each of them has a pressure regulator to ensure the correct volume of propane is delivered to the motor.

Depending on the size of your propane generator (horsepower/watts) and using a horizontal or vertical tank during temps of let’s say ‘0’f and colder, the limited volume of vaporized propane available may not be enough to run the generator at full power or not at all if it’s close to 44f below! Now your stove may work appear to work fine including your furnace, although they will be at a lower BTU output.

If your temperatures get to minus 44f (-44f) and below, propane will not vaporize at all and turns back into a liquid again. Believe it or not, they sell electric blankets for propane tanks and heat tapes for the lines and regulators.

Where does Propane come from?
Propane is a hydrocarbon (C3H8) and is sometimes referred to as liquefied petroleum gas, LP-gas or LPG. Propane is produced from both natural gas processing and crude oil refining in roughly equal amounts. It is nontoxic, colorless and virtually odorless. As with natural gas, a strong identifying odor is added so the gas can be readily detected.

Liquefied petroleum gas (LPG) consists mainly of propane, propylene, butane, and butylene in various mixtures. However, for all fuels in the United States, the mixture is mainly propane. Chemical Properties: LPG, like natural gas and unlike gasoline, is a simple mixture of hydrocarbons, mainly propane/propylene (C3S) and butane/butylene (C4S).

The most important statement in the second sentence and is the one that shocks most people. Propane is produced only from OIL or NATURAL GAS! Propane does not come from drilling wells in the ground and pumping it out. It only comes from refining oil or natural gas. Bottom line; if there is no oil or natural gas available, there is no propane!

What is the Shelf-Life of Propane?
Propane has an indefinite shelf-life. It will last and be good to use literally forever. The only long term storage issue propane has is the container it’s stored in. Most all tanks are made from steel with some smaller RV tanks made from aluminum and lately some are now being made from a translucent fiber glass resin compound and they’re called ‘Clear-View’ which allows you to see the liquid propane level inside. As we know steel rusts and as the tank begins to rust it can cause a pin hole and the propane will leak out. Proper tank maintenance is needed and will allow many years of safe storage.

What is the Life of a Propane Tank?
Cylinders (tanks) are subject to recertification (also known as requalification) twelve years from their date of manufacture and every five years after that. For example, a cylinder manufactured in January of 2000 will have to be recertified in January of 2012 meaning if you take your bottle to the propane company in April of 2012 to be refilled, it will have to be re-qualified by authorized personnel before it can be filled. The tanks have the date of manufactured stamped on the protective top collar.

Painting Propane Tanks?
Propane tanks, like ASME stationary LP Gas tanks, must be painted a reflective color to avoid overpressure situations caused by the sun beating down on them and overheating the Propane inside.

How should smaller Propane tanks be stored?
Propane tanks should be stored outside. Do not store any propane tanks in the garage or any other indoor areas at any time, even during the winter months. If the tanks may be subjected to excessive heat, like from direct sunlight or desert high temperatures the tanks should only be filled to 80 percent of the tank's capacity. This is to allow for some liquid propane expansion that might occur during hot days.

Propane is stored under high pressure!
ASME propane tanks are built to 250# working pressure. Under normal circumstances, the vapor pressure at 100ºF is 172 psi. The colder it gets the lower the vaporized pressure is. By the time the temp gets to -44f there will be no vaporized pressure.

Propane is a gas that when compressed turns into a liquid for storage and transport. That’s why you can hear it slosh around inside the tank when you move it. A pressure regulator must always be used with propane as it reduces the tank pressure from approximately 172 PSI to an appliance working pressure of around 10-12 PSI then fed to the appliances, lanterns, etc for burning.

Interesting links:

http://www.propane-generators.com/propane_usage.php

Keeping Your House Operating During A Cold Alaska Winter:

https://uaf.edu/files/ces/publications-db/catalog/eeh/EEM-04955.pdf