Glossary of Propane Terms

LP-Gas is a term used to describe certain combinations of hydrocarbon fuels, the most common of which are butane, isobutane, propane, or a mixture of all three.

LP-Gas enjoys an advantage over other fuels in that it can be transported and stored as a liquid under reasonable pressures, yet can be handled as a gas when released to atmosphere or moderate pressures. When expanding from the liquid phase to the gaseous phase, each cubic foot of liquid expands into many times its original volume (273 times when expanded to atmospheric pressure), making it possible to transport large amounts of energy in relatively small containers.

NPGA, NFPA, Propane Education & Research Council


When LP-Gas was first isolated, it was primarily butane. Since that time, technology has developed to the point that the product being marketed today is primarily propane, which has a great deal more versatility due to its lower boiling point and proportionately higher storage pressure. For the purposes of this section, we will use the term "Propane" since the other LP-Gases can be used and perform in a similar manner, a number of technical considerations which we won't get into here.

Firm Fuel means a contractual agreement between a user and a utility company requiring the utility to furnish gas to the user on a year-round basis.

Interruptible Fuel  means a contractual agreement between a utility and user allowing the utility to discontinue service to the user during peak periods of demand.

Base Load Fuel means propane or propane/air being supplied to a user as a primary fuel where natural gas is not available.

Stand-By Fuel as used here on the SES Web Site, is intended to indicate undiluted propane, or a propane/air mixture being supplied as a replace for natural gas.

Stand-By Plant as used here on the SES Web Site, is intended to mean a storage and handling system with accessory equipment: vaporizer, etc. to facilitate the use of propane to produce a standby fuel for natural gas (See Stand-by Fuel).

Peak Shaving Plant as used here on the SES Web Site, refers to the use of undiluted propane or a propane/air mixture to augment or to be mixed with natural gas to eliminate periodic peaks in the consumption of natural gas. The equipment used for a peak shaving plant in industrial facilities is identical to that used for a stand-by plant, but with the addition of control equipment to limit the consumption of natural gas. A controller in the natural gas line controls the flow of natural gas to a predetermined maximum consumption (peak) and the propane will automatically feed to make up the difference between the controlled flow and the actual plant consumption. Generally, undiluted propane cannot be used in such circumstances unless the addition of the undiluted propane into the natural gas is extremely small (under 10% of the total flow). Since the total flow may easily fluctuate to momentary peaks, requiring the addition of a higher percentage of stand-by fuel, propane/air is generally used for this purpose.

Storage Facility is a term for a system of storage tanks and handling equipment to allow transfer from truck transports or railcars into storage tanks and transfer from storage tanks into accessory equipment designed to convert the liquid propane into a gaseous from for use as a fuel for either stand-by or peak shaving.

Vaporizer A device that receives liquid propane from a storage facility and adds heat to convert the liquid into a gaseous state for use as a stand-by or peak shaving fuel. While small amounts of propane vapor can be withdrawn directly from vapor space in the storage tanks, this would require the heat for vaporization to come from the atmosphere. This would soon result in the tank being refrigerated, reducing the pressure within the tank and its ability to supply vapor. Therefore, a vaporizer is used to add heat from a source than that the atmosphere.

Propane/Air indicates a mixture of propane and air which will result in a mixed gas which will produce burning characteristics in existing burners similar to that produced by the natural gas. While the mixture thus created is not an absolutely perfect replacement, the differences are extremely hard to detect in normal
burning processes.

Compatible Mixture is a mixture of propane and air, which, when burned in natural gas burners, will produce results similar to the combustion characteristics
of natural gas.

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