Compressors and compressed air: basic terms
Understand the parameters. Find the cause of a problem. Each term includes an explanation, an example and a route to a calculation or specific solution.
45 practical explanations across five topics
Basics, units and parameters
What the figures in a quotation mean and how to compare them correctly.
Compressed air
What compressed air is, what it is used for and why choosing a compressor alone is not enough.
Flow and air delivery: l/min, m³/min and FAD
How much air a compressor actually delivers and under which reference conditions.
Compressor intake capacity versus actual delivered air
Why geometric intake displacement is not the air delivery available to your machines.
Working pressure: what compressor pressure do you need?
Choose pressure based on consumer requirements and losses at actual demand.
Gauge and absolute pressure: bar(g) and bar(a)
What a pressure gauge shows and why volume calculations require absolute pressure.
Pressure units: bar, Pa, kPa, MPa and psi
Conversions and the difference between changing units and converting gauge pressure.
Volume and flow: m³, Nm³ and reference conditions
The same quantity of air can have different volumes. Pressure, temperature and humidity matter.
Compressor power input, output and efficiency
Distinguish package electrical input, motor output and delivered air quantity.
Specific energy consumption of compressed air
How many kWh you need per m³ and how to compare machines at the same pressure.
Compressor types and control
How machines work and how to match air production to demand.
Screw compressor: principle and applications
Compression between rotors, oil-injected and oil-free designs, and selection for industrial operation.
Piston compressors: principles and applications
How a piston compressor works and why duty cycle matters when selecting one.
Oil-free compressors and oil-free air
No oil in the compression chamber does not automatically mean clean air at the point of use.
Compressor frequency control: VSD and inverter
How speed changes match delivery to demand and when this control is worthwhile.
Variable-speed compressor efficiency curve
How to read part-load performance data and assess the actual operating profile.
Load/unload control and idle running
Why a compressor consumes electricity even when it supplies no air to the network.
Compressor duty cycle and allowable load
Running time, pauses and start frequency must suit the design of the specific machine.
Master and cascade compressor control
The difference between pressure cascading and central control of the entire compressor room.
Air quality and treatment
Water, oil and particles. What to remove and how to verify it.
ISO 8573-1: compressed air quality classes
How to read three separate classes for particles, water and total oil.
Oil in compressed air
Where oil contamination comes from, how to prevent it and how to verify treatment results.
Pressure dew point
The temperature below which condensate or frost starts to form at a given pressure.
Relative and absolute air humidity
Why the same humidity percentage does not mean the same water content, and how it relates to dew point.
Condensate: why water forms in piping
Water enters with the intake air. Cooling compressed air can turn it into liquid.
Refrigerated versus adsorption dryer
How the two technologies differ in principle, achievable dew point and operating costs.
Compressed air filtration
Particles, droplets and vapours require different treatment principles. One filter cannot solve everything.
Coalescing filter
Combines small water and oil droplets into larger ones that can be removed from the air.
Activated carbon filtration
Oil vapour adsorption, air pretreatment and timely replacement of saturated media.
Cyclone water separator
Removes entrained liquid droplets but does not reduce water vapour content like a dryer.
Automatic condensate drain
How to remove liquid from a filter or air receiver without wasting compressed air.
Condensate oil separator
Treating drained condensate is a different process from cleaning compressed air.
Class 0 according to ISO 8573-1
An individually specified stricter limit, not automatically zero contamination.
Oil aerosols versus oil vapours
Oil droplets and gaseous oil molecules require different filtration and measurement methods.
Solid particles in compressed air
Dust, rust and wear debris: why filter pore size alone does not establish purity.
Distribution systems and compressor rooms
How to deliver air to the machine and remove heat from the compressor room.
Air receiver: function and volume selection
Air storage for a short peak and more stable operation. Not a replacement for insufficient supply.
Pressure loss in distribution systems
Why pressure at the machine during demand is lower than in the compressor room, and how to find the cause.
Compressed air pipe sizing
Choose internal diameter according to flow, length, fittings and permitted loss.
Ring-main air distribution
Supply from two directions and options for expanding or isolating part of the network.
Compressor room ventilation and cooling
Heat removal, cool air supply and checking ventilation resistance.
Compressed air aftercooler
Cools air after compression and helps separate water before downstream treatment.
Compressor noise: dB(A), sound pressure and sound power
How to compare noise data and why distance and room conditions matter.
Consumption, savings and operation
Where costs arise and what to monitor in daily operation.
Compressed air leaks
Leaks consume produced air. Measurement shows where to start repairs.
Cost of producing 1 m³ of compressed air
Electricity, idle running, maintenance and delivered volume determine the true cost of air.
Compressor waste heat recovery
Savings come from heat you actually use at the right time and temperature.
Compressor operating hours and service intervals
Why monitoring one counter is not enough and when calendar-based maintenance takes priority.
Compressor oil separator
Returns oil to the lubrication circuit. Do not confuse it with a waste condensate separator.
Pressure switch – pressostat
Switches according to a pressure band. It is neither a pressure regulator nor a safety valve.