Relative Density of LPG
Relative Density of LPG
Relative density of LPG is measured for both liquid LPG density and gaseous LPG density. The relative density of LPG liquid is compared to water whilst the relative density of LPG gas is compared to air.
Relative density of LPG liquid is about half that of water at 495 kg/m3 (25°C) vs 1,000 kg/m3 (4°C) for water.
Relative density of LPG gas is 1.55 times heavier than air at 1.898 kg/m3 vs 1.225 kg/m3 for air (both 15°C at sea level).
Relative density of LPG gas is 1.882kg/m3 at 0°C & 1ATM (0 psig), which is STP (Standard Temperature & Pressure), the difference being a lower temperature.
Specific gravity of LPG gas depends on whether it is propane, butane or an LPG gas mixture of the two. Specific gravity of LPG gas as propane is 1.882 kg/m3 (at STP).
Specific Gravity of LPG Gas – Specific Gravity of Propane Gas – Propane SG
Specific gravity of propane gas (Propane SG) – one cubic foot of propane weighs 0.1145 vs one cubic foot of air at 0.0807 lbs (at STP). So, the relative density of propane gas is 1.42 (at standard temperature and pressure).
Specific Gravity (SG) is defined as the ratio of relative density of the material to the density of water at the same temperature. Specific gravity of LPG (propane) gas goes from 1.5219 kg/m3 to 1.882 kg/m3, depending on the temperature, as specific gravity varies with temperature.
Specific gravity of LPG (propane) gas at STP is 1.882 kg/m3 at 0°C (32°F) & 1ATM (STP) or 1.5219 kg/m3 at 20°C.
Specific gravity of LPG (propane) gas at NTP is 1.5219 kg/m3 at 20°C (68°F) & 1ATM (NTP – Normal Temperature and Pressure)
Specific gravity of propane gas at STP – One cubic foot of propane weighs 0.1145 vs one cubic foot of air at 0.0807 lbs (at STP).
As propane is heavier than air, it will settle in low spots.
Specific Gravity of LPG Liquid – Propane
Specific gravity of LPG liquid is 0.495 at 25°C or 0.585 at -40°C.
Specific gravity of LPG liquid – Relative density of LPG (propane) liquid and water is 0.495 (25°C) and 1.000 (4°C), respectively.
Specific gravity of LPG liquid – One litre of LPG weighs 0.51kg whilst one litre of water weighs 1kg.
Specific gravity of propane liquid – One gallon of propane weighs 4.23 lbs whilst one gallon of water weighs 8.34 lbs.
Relative Density of LPG Liquid – Specific Gravity of Liquid Propane – Specific Gravity of LPG
Density of LPG – PropaneDensity of LPG liquid is lighter than water by about half. The relative density of LPG liquid – specific gravity of liquid propane is 0.495 (at 25°C). One litre of propane liquid weighs 0.51kg. The relative density of LPG liquid is one gallon of liquid propane weighs 4.24 lbs
LPG (propane) expands at 1.5% per 5.55°C temperature increase. In other words, the density changes.
So, if the gas bottle was filled by volume on a hot day, it would have less gas, in kg, than a gas bottle filled on a cold day.
That’s why it is frequently measured and sold in kg.
Most auto LPG bowsers and tanker delivery trucks have an automatic correction factor so it can be delivered and/or sold in litres.
Unlike water, 1 kilogram of LPG (propane) does NOT equal 1 litre of LPG. Relative density of LPG liquid or specific gravity of liquid propane is about half that of water.
In Australia, where LPG is propane, 1kg of LPG has a volume of 1.96L.
The relative density of LPG liquid: 1L of propane liquid weighs 0.51kg.
The relative density of LPG liquid is 1 gallon of liquid propane weighs 4.24 pounds.
The relative density of LPG liquid – the specific gravity of LPG liquid – specific gravity of liquid propane – is 0.495 (at 25°C)
The relative density of LPG gas is 580.88 kg/m3 (at boiling point)
The relative density of LPG liquid – the specific gravity (SG) of Butane liquid is 0.601 (at 25°C)
The relative density of LPG gas – butane gas is 2.48 kg/m3 (at boiling point)
Specific Weight of Propane (LPG)
Propane weight: One gallon of propane weighs 4.24 pounds (4.24lbs/gal) or 0.51kg per litre (0.51kg/L). The specific weight of propane (LPG) is defined by the ratio of the weight to the volume. So, the specific weight of propane is 0.51kg per litre (0.51kg/L) or 4.24 pounds per gallon (4.24lbs/gal).
Relative Density of LPG Gas is Heavier than Air – Specific Gravity of LPG Gas – LPG-Propane is Heavier than Air
The LPG density, as gas, is about 1.9 times heavier than air. The relative density of LPG gas (specific gravity of LPG gas) is 1.898 kg/m3 (at 15°C and sea level). 1 ft3 of propane weighs 0.1162 pounds.
Relative density of LPG gas – Butane gas is 2.5436 kg/m3 (at 15°C and sea level)
In contrast, the density of Air is 1.225 kg/m3 (at 15°C and sea level).
So, relative density of LPG gas is heavier than air.
Note that LPG gas is also referred to as LPG vapour, which is the more technically correct term.
10 Important LPG – Propane Facts
1. LPG (or LP Gas) is the acronym for Liquefied Petroleum Gas or Liquid Petroleum Gas.
2. LPG is a group of flammable hydrocarbon gases liquefied through pressurisation.
They are, in most cases, used as fuel.
3. LPG comes from natural gas processing and petroleum refining.
4. There are a number of gases that fall under the “LPG” label.
These include propane, butane and isobutane (i-butane), as well as mixtures of these gases.
5. LPG gases are compressible into liquid at low pressures.
6. The common uses for LPG include use for fuel in heating, cooking, hot water and vehicles.
It is also utilised for refrigerants, aerosol propellants and petrochemical feedstock.
7. LPG is stored, as a liquid, in steel vessels ranging from small BBQ gas bottles to larger gas cylinders and storage tanks. (45kg gas bottles shown)
8. “Wet gas” is a term that is sometimes used to describe LPG, as a result of its liquidity.
9. An alternate reference for LPG (propane) is as a Natural Gas Liquid – NGL.
10. In nature, propane does not occur alone.
LPG = Propane
In Australia, LPG is propane.
It is also called LPG Gas, LP Gas, Propane, BBQ Gas, Camping Gas or Autogas.
LPG can be other gases in other countries.
LPG Gas Pressure Varies with Temperature – LPG Temperature
The pressure at which LPG transitions between liquid and vapour is called its vapour pressure. The pressure rises with LPG temperature. It generates 0 kPa at -43°C but at 38°C (100°F) it generates 1186kPa or 172 PSIG.
As mentioned before, LPG is stored in a gas bottle under pressure. LPG gas pressure varies with temperature. The term “pressure” refers to the average force per unit of area that the gas exerts on the inside walls of the gas bottle.
(LPG Gas Pressure-Temperature Chart shown)
LPG Pressure-Temperature ChartLPG gas pressure measurement is in kilopascals (kPa) or pounds per square inch (psi).
“Bar” is yet another unit of measure for LPG gas pressure.
1 Bar = 100 kPa, so it is metric based but not an SI unit of measure.
LPG gas pressure can vary based on temperature, as shown in the chart.
The level of fill in the gas bottle comes into play when the LPG is in use, as it affects the rate of vapourisation.
LPG is a liquefied gas. So, the LPG gas pressure inside the cylinder (LPG gas bottle pressure) will remain the same from full until the vaporistion of the last of the liquid LPG.
Then the LPG gas bottle pressure will fall, with the use of the last of the LPG vapour.
Odourant Added for Safety – Smell in Propane
In its natural state, LPG is an odourless gas.
The distinctive smell in propane that people associate with LPG is actually added to it as a safety measure.
Without the addition of a smell in propane, leaking gas could collect without detection.
Avoid Direct Contact – Cold Burns
Always use caution should to avoid direct exposure, as liquid LPG is cold enough to cause severe cold burns on exposed skin.
LPG Energy Content – Propane
LPG energy content is approximately 25MJ per litre. One gallon of propane has the LPG energy content of 91,547 BTU (60°F).
25MJ also converts to 6.9kWh.
Calorific Value – LPG energy content
The LPG energy content or calorific value of the gas used to heat water is no different than LPG used for other applications.
So, LPG energy content contains 25MJ per litre or 91,547 BTU (60°F) per gallon.
LPG Expansion – Gaseous Expansion
Gaseous expansionLPG expansion is 270 times the volume of gas to the volume of liquid. In other words, LPG expansion is to 270 times the volume when it goes from liquid to gas. So, 1L of liquid LPG (propane) expands to equal 270L of gaseous LPG expansion.
As there are 1000L in a cubic meter (M3), 1L of liquid LPG expands to 0.27M3.
Combustion of Propane Equation for Complete Combustion of Propane
In the presence of enough oxygen, the combustion of propane forms water vapour and carbon dioxide, as well as heat.
Combustion of Propane Equation for Complete Combustion of Propane:
Propane + Oxygen → Carbon Dioxide + Water + Heat
C3H8 + 5 O2 → 3 CO2 + 4 H2O + Heat
Incomplete combustion of LPG (propane) occurs when not enough oxygen is present.
Equation for incomplete combustion of propane results in the production of water, carbon monoxide, carbon dioxide and heat:
Equation for Incomplete Combustion of Propane
Equation for incomplete combustion of propane – LPG:
Propane + Oxygen → Carbon Dioxide + Carbon Monoxide + Water + Heat
2 C3H8 + 9 O2 → 4 CO2 + 2 CO + 8 H2O + heat
LPG Gas Temperature: LPG – Propane Flame Temperature
LPG gas temperature at which a flame burns is 1980°C.
When it is burning properly, the flame is blue.
A yellow or red flame is usually indicative of incomplete combustion.
Limits of Flammability
The lower and upper limits of flammability are the percentages of LPG that must be present in an LPG/air mixture. This means that between 2.15% and 9.6% of the total LPG/air mixture must be LPG in order for it to be combustible.
LPG Flash Point Temperature – Flash Point of Propane and Butane – Propane Ignition Temperature
Flash point of propane is −104°C (−155°F). Flash point of butane is −60°C (−76°F). The lowest propane ignition temperature or LPG flash point is -104°C or -156°F. This is the minimum propane ignition temperature at which propane will burn on its own after ignition.
Below this temperature, it will stop burning on its own.
However, if a source of continuous ignition is present, it will burn below -104°C.
Propane Auto Ignition Temperature (Propane Ignition Temperature) – Butane Auto ignition Temperature
Propane auto ignition temperature (propane ignition temperature) is 470°C – 550°C (878°F – 1020°F). The propane auto ignition temperature is the lowest propane ignition temperature at which it will spontaneously ignite in air. Butane auto ignition temperature is 405°C or 761°F.
Propane auto ignition temperature is when propane or butane ignites without an external source of ignition, like a spark or flame.
The propane auto ignition temperature decreases as the pressure or oxygen concentration increases.
LPG gas is heavier than air and will sink to and collect at the lowest point. If vented to the outside air, LPG will dissipate with the slightest movement of air.
With LPG vented into a sealed structure, with no air movement, the LPG gas will collect on the floor. It will rise toward the ceiling, as more LPG enters into the structure.
Molecular Weight for LPG – Propane – Butane – Isobutane
The molecular weight for LPG – Propane – is 44.097 kg/kmole.
The molecular weight for Butane (n-butane) is 58.12 kg/kmole.
For Isobutane (i-butane), the molecular weight is the same as for n-butane at 58.12 kg/kmole.
LPG Vapour (Gas) Use vs. Liquid Use
LPG (propane) supply is either liquid or vapour.
The difference is in the extraction from supply cylinder or vessel.
Most LPG applications use vapour.
Appliances such as water heaters, room heaters and cookers all use vapour.
If these appliances were to have liquid LPG flow to their burners, the result could be a fire or similar safety hazard.
This is why LPG cylinders should always be upright, so that any gas released is in vapour form only.
6 Things You Didn’t Know About LPG
While you may know some of these facts, chances are you don’t know all of them.
Have a read and learn more about:
1. Real LPG Explosions are Really Rare
2. Simulated Natural Gas from LPG
3. The Source of LPG
4. Australian Made Energy
5. LPG is a Renewable Energy Source
6. LPG is NOT Coal Seam Gas (CSG)
1. LPG Cylinder Explosions are Extremely Rare + Video
Propane tank peril courtesy of Myth Busters. Hollywood and the media would have you believe that LPG cylinder explosions are a common event.
In fact, explosions are quite rare and it is quite difficult to even make an LPG cylinder explode on purpose.
You’ll enjoy watching this Myth Busters Video where they try to make a cylinder explode.
Most gas explosions are the result of gas leaking into a confined space, like a kitchen.
This is no more likely with LPG than with piped natural gas.
Often, the gas bottle itself is not even involved in the event, as gas bottles are always stored outdoors.
2. Simulated Natural Gas from LPG
Most people have never even heard of Simulated Natural Gas (SNG) let alone know that it can be made with LPG.
Mixing vapourised LPG with air produces SNG.
We can SNG use in place of natural gas, as it has near identical combustion characteristics.
It can be used alone or mixed with regular natural gas.
There are no changes required in burners, regulators or gas jets.
There are a number of reasons to use SNG:
• To help meet peak demand when natural gas supplies are inadequate
• To operate while in preparation for the start-up of a natural gas supply
• As a stand-by in the event of a natural gas supply disruption
Simulated natural gas has a few names.
Besides SNG, it is also called propane-air and LPG-air.
3. The Source of LPG
Many people mistakenly think of LPG as a by-product.
In reality, LPG is a valuable co-product produced from gas fields and crude oil refining.
They process the gas stream from natural gas fields to separate the gases present.
These include methane, ethane, propane, butanes and pentanes.
Impurities are also removed, including water.
The produced gases are each funnelled into their own supply streams.
They capture propane and butane, the two common types of LPG, and store them in their liquefied form.
The same is true of crude oil refining.
The refinery process creates many co-products.
The co-products include gasoline, diesel fuel, asphalt base, heating oil, naphtha, kerosene and LPG.
4. LPG is Australian Made Energy
LPG is the only motor fuel in which Australia is self-reliant.
Unlike both petrol and diesel, for which Australia relies on imports, we produce more LPG than we consume.
Not only is Australia completely self-sufficient in LPG but it is also a net exporter of LPG.
In 2013, Australia produced 2.3 Million tonnes of LPG.
That satisfied the local demand of 1.5 million tonnes, with net exports of 815,000 tonnes.
5. LPG is now a Renewable Energy Source
LPG is now a renewable energy source
LPG has gone from being a traditional fossil fuel to a new form of renewable energy.
Scientists have created a genetically engineered version of the common E. coli bacteria.
This version produces propane (LPG).
So, LPG is now a renewable energy.
The bacteria consume sugar.
With genetic modification, and the help of a couple of enzymes, they make propane.
The propane produced is chemically identical to regular propane.
6. LPG is NOT Coal Seam Gas (CSG)
There is some confusion over what Coal Seam Gas (CSG) is and what it is not.
LPG is not CSG.
While CSG may contain various gases, typical CSG is 95% to 97% pure Methane.
LPG is not Methane.
LPG is Propane.