Base conditions
Encyclopedia
Base conditions consist of a specified absolute pressure
and temperature
. To ensure accuracy, it is important to refer to base conditions when measuring the volume of a sample of liquid or gas. This applies to both static measurement and flow measurement
.
of both gases and liquids depends on the pressure and temperature of the fluid. Thus volumes measured in cold conditions or in pressurised conditions will be lower than the same mass of fluid at warmer or depressurised conditions. This fact gives rise to the necessity of choosing a benchmark pressure and temperature in which all 'net' volumes will be expressed.
. Doubling absolute pressure doubles the density of a gas, and doubling absolute temperature halves the density. The number of molecule
s in a given gas volume depends on the pressure and temperature. This is why the pressure and temperature must be stated in order for a volume measurement to mean anything.
pumps that states that the volume is corrected to 15 °C (59 °F, or 60 °F in the U.S.) means that the measured volume has been compensated for thermal expansion
. One would otherwise get a larger mass of gasoline in a tank filled in cold weather (which is unfair to the business) and less when it is warm (which is unfair to the consumer).
Base conditions are often defined jurisdictionally. For example:
s generally need the base conditions for each flow meter to be configured.
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
and temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
. To ensure accuracy, it is important to refer to base conditions when measuring the volume of a sample of liquid or gas. This applies to both static measurement and flow measurement
Flow measurement
Flow measurement is the quantification of bulk fluid movement. Flow can be measured in a variety of ways.Positive-displacement flow meters acumulate a fixed volume of fluid and then count the number of times the volume is filled to measure flow...
.
Pressure and temperature
The densityDensity
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
of both gases and liquids depends on the pressure and temperature of the fluid. Thus volumes measured in cold conditions or in pressurised conditions will be lower than the same mass of fluid at warmer or depressurised conditions. This fact gives rise to the necessity of choosing a benchmark pressure and temperature in which all 'net' volumes will be expressed.
Ideal gas law
The density of a gas at a specific pressure can be estimated by using the ideal gas lawIdeal gas law
The ideal gas law is the equation of state of a hypothetical ideal gas. It is a good approximation to the behavior of many gases under many conditions, although it has several limitations. It was first stated by Émile Clapeyron in 1834 as a combination of Boyle's law and Charles's law...
. Doubling absolute pressure doubles the density of a gas, and doubling absolute temperature halves the density. The number of molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s in a given gas volume depends on the pressure and temperature. This is why the pressure and temperature must be stated in order for a volume measurement to mean anything.
Density correction
Density correction is also performed on liquids under measurement. For instance, the sticker on gasolineGasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
pumps that states that the volume is corrected to 15 °C (59 °F, or 60 °F in the U.S.) means that the measured volume has been compensated for thermal expansion
Thermal expansion
Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...
. One would otherwise get a larger mass of gasoline in a tank filled in cold weather (which is unfair to the business) and less when it is warm (which is unfair to the consumer).
Legal definitions
Legal regulations usually require that sales to end customers be compensated to the legally defined base conditions. Where regulations do not require the use of a specific set of base conditions, contractual partners may be free to choose their own base conditions.Base conditions are often defined jurisdictionally. For example:
Flow computers
Flow computerFlow computer
A flow computer is an electronic computational device which implements the required algorithms to turn the raw data received from flow meters to which it is connected into volumes at base conditions....
s generally need the base conditions for each flow meter to be configured.