Basic Concepts of Pressure Units and the Meaning of “Kilogram”
In industrial and everyday applications, the “kilogram” commonly referred to by people does not denote the unit of mass, the kilogram, but ratherKilogram-force per square centimeter (kgf/cm²)It is an abbreviation for a unit of engineering pressure. Whether it’s compressed air or water, when we refer to “8 kilograms of pressure,” the physical meaning is the same: a force of 8 kilograms acts on each square centimeter of surface area.
Conversion of 8 kg of compressed air to water pressure values
From the perspective of pure pressure values,An air pressure of 8 kilograms is equivalent to a water pressure of the same numerical value.. To ensure a more accurate understanding, it can be converted into international standard units:
- Megapascal (MPa）: 8 kgf/cm² is approximately equal to 0.785 MPa, In engineering practice, it is often simplified as 0.8 MPa.
- Ba (bar）: 1 kgf/cm² is approximately equal to 0.98 bar, 8 kilograms of pressure is approximately equal to 7.84 bar, in engineering it is often approximated as 8 bar.
- Equivalent water column height: 1 MPa The pressure is approximately equivalent to a 100-meter water column. Therefore, 0.8 MPa The pressure is equivalent toAn 80-meter-high water columnThe hydrostatic pressure generated.
Differences in the Physical Properties of Gas Pressure and Liquid Pressure
Although the values can be converted to one another numerically, compressed air (a gas) and water (a liquid) exhibit significant differences in their physical properties, which are of great importance in practical applications:
- CompressibilityAir is highly compressible, with significant volume changes during storage and release; in contrast, water is virtually incompressible, allowing for more direct and stable pressure transmission.
- Energy storageCompressed air systems can store substantial elastic potential energy and, when released instantaneously, deliver significant impact forces; hydraulic systems, on the other hand, are primarily used for smooth power transmission.
- Leakage impactGas leaks cause a rapid and often undetectable drop in pressure, while liquid leaks typically manifest as visible dripping or spraying.
Compressor Parameters and System Selection in Practical Applications
In configurationAir compressor parametersAt that time, understanding pressure conversions helps in selecting the appropriate equipment. If the system requires an output of 8 kg (0.8 MPa) of pressure, the air compressor’s rated discharge pressure must be greater than or equal to this value. At the same time, since gas flowing through pipelines incurs pressure losses, in practical selection it is customary to allow for a margin. 0.1 到 0.2 MPa The margin. When carrying outPressure conversionDuring system design, it is imperative to clearly delineate the physical interface between gases and liquids and to ensure that the pressure ratings of the piping network, valves, and actuating components are adequate. 0.8 MPa safety requirements.