Compressed Air Dictionary

  • ABS: A non-toxic plastic sometimes used as a piping material in compressed air installations
  • Absolute pressure: The pressure with reference to absolute zero (i.e. with reference to a perfect vacuum) Absolute pressure equals the sum of the atmospheric pressure and gauge pressure
  • Absolute temperature: The temperature measured from Absolute Zero, using the Kelvin scale
  • Activated carbon: A form of carbon characterised by high adsorptive capacity for gases, vapours or solids
  • Adsorption: Natural action of a gas, vapour or liquid being attracted to and held on the surface of a solid
  • After cooler: A heat exchanger for the reduction of temperature of air after compression
  • After cooling: The removal of heat from the air after compression is complete
  • Air compressor: A machine which compresses air to a pressure higher than its inlet pressure
  • Air receiver: A tank in which compressed air is stored storage, also called a pressure vessel
  • Ambient temperature: The temperature of the surrounding environment in which the equipment is working
  • Atmospheric pressure: The pressure exerted by the atmosphere
  • Ball valve: A device that shuts off flow by means of a hollow spherical component (ball)
  • Bourdon tube gauge: An instrument that senses and records pressure. The pressure energy detected is converted into mechanical movement, i.e. moving a pointer on a dial
  • Carbon dioxide: Colourless, odourless, incombustible gas. It is a major greenhouse gas, contributing to climate change (global warming)
  • Carbon monoxide: Colourless, odourless, incombustible, toxic gas
  • Celsius: A temperature scale on which the freezing point of water is 0 degrees Celsius and the boiling point of water is 100 degrees Celsius (at one atmosphere of pressure. Celsius is the term preferred for centigrade)
  • CE Mark: Denotes compliance with European directives
  • CFM: Commonly used abbreviation for ‘cubic feet per minute’, a figure applied to the output of a air compressor
  • Chemical energy: The energy in chemical bonds holding the atoms of a compound together. Food, wood, batteries, and fossil fuels possess chemical energy
  • Coalesce: To bring together fine liquid particles or mist s to form larger particles as liquid droplets
  • Competent person: A legal phrase to identify a person who performs the activities required by the Pressure Systems Safety Regulations for compressed air systems.  The competent person may be required to produce schemes of examination or to do examinations
  • Compressor capacity: The actual volume rate of flow compressed and delivered at the standard discharge point, at stated inlet conditions, usually expressed in terms of Free Air Delivered
  • Condensate: The water formed in a compressed air system from water vapour due to a decrease in air temperature and or an increase in pressure. Often contaminated with oil and solid particles
  • Constant: A quantity that does not change its value, no matter what happens to other related variables, usually represented by the letter K
  • Coolant: A fluid (liquid or gas) used to remove heat from compressed air
  • Demand: The amount of compressed air required by tools and equipment
  • Desiccant: A chemical possessing a strong affinity for water
  • Dew point:  The temperature at which air is fully saturated with water vapour at the pressure prevailing
  • Directly proportional: The process by which both quantities decrease or increase with each other
  • Discharge outlet (port or valve): Hole or valve through which gas or air leaves the compressor
  • Displacement:  The volume displaced by the compression element of the first stage per unit of time (e.g. litres per second, cubic feet per minute)
  • Distribution system: A network of pipes installed from point to point in a factory that delivers compressed air to a point of use
  • Drains: Devices that collect condensate from a compressed air system. Often fitted to air receivers, filters, dryers or piping
  • Dryer: A device that reduces the water vapour content of the compressed air
  • Efficiency: Produced with minimum effort or energy
  • Filter: A device to remove contaminants from compressed air
  • Filtration: A physical process that selectively removes gases, vapours, liquids or solids from compressed air by providing a barrier to such particles
  • Fahrenheit: A temperature scale on which the freezing point of water is 32 degrees F and the boiling point of water is 212 degree F (at one atmosphere of pressure)
  • Flow controller: A device which varies the amount of air flowing through it
  • Fossil fuels: Carbon-rich fuel formed from the remains of ancient animals and plants. Coal, oil, and natural gas are all fossil fuels
  • Foul sewer: Main drains used for the disposal of waster water of domestic or industrial origin, which comes under the responsibility of the local Water Authority
  • Free Air: Air at the atmospheric conditions at the inlet point unaffected by the compressor
  • Free Air Delivered (FAD): The Free Air Delivered by a compressor is the actual volume which it will compress and deliver at the stated pressure, at the intake temperature and pressure.  FAD is expressed in cubic feet per minute or litres per second.
  • Full load: The compressor is producing air and operating at full capacity
  • Galvanized steel: Coated with zinc to reduce effects of corrosion
  • Gauge pressure: Pressure as shown or indicated on a gauge or instrument
  • Generator: A device or machine that converts mechanical energy into electrical energy
  • General Gas Law: States how the pressure, volume and temperature interact
  • Hazard: Anything that can cause harm e.g. in the workplace: lifting, machining, working from ladders
  • Heat recovery: Process whereby the waste heat generated by a compressor which would otherwise be wasted is saved and re-used
  • High pressure:  System pressure over 40 bar
  • Higher Efficiency Motor (HEM):  Motor which uses up to 3% less electricity than a standard motor, by virtue of an improved design
  • Humidity: The degree of water vapour in the atmosphere
  • Inlet port (or valve): Hole (or valve) through which air enters the compressor
  • Inter cooling: The removal of heat from the air between stages in multi-stage compression
  • Inversely proportional: The process by which one quantity decreases when another increases
  • Kinetic energy: The energy possessed by a moving object
  • Low pressure: Generally considered to be between atmospheric pressure and 20 bar
  • Lubricant: A fluid (generally an oil) used to overcome friction between surfaces that come into continuous moving contact
  • Normal: Denoted by the prefix ‘n’ denoting a standard condition of temperature and humidity
  • Non-renewable energy resource: Energy resource that is either replenished very slowly or is not replenished at all by natural processes
  • Off load: The compressor is switched on i.e. running but the compressor is not producing air
  • Oil injected (lubricated): An air compressor in which oil is injected into the chamber during the compression process to limit the temperature rise in the chamber
  • On load: The compressor is producing air, either at part load or full load
  • Over pressurisation: To exceed the system design pressure
  • Packaged air compressor: Self contained unit consisting of compressor and prime mover together with accessories for its safe operation
  • Parameter: A physical quantity that can be measured, e.g. volume, pressure
  • Part load: The compressor is producing air, but not at full capacity
  • Pattern of use: Describes the way in which tools and equipment are used
  • Piping: A pipe or system of pipes used for the conveyance of compressed air
  • Piston: Mechanical device which has a plunging or thrusting motion
  • Pneumatics: The science systems driven by compressed air
  • Point of use: The point at which the compressed air performs its useful work, i.e. air tools or equipment
  • Positive displacement: The action of a compressor type that traps and compresses a measured volume of air between the fixed and moving parts raising the pressure, reducing the volume and then delivering to the system
  • Potential energy: Potential energy is stored energy, energy that can be released or harnessed to do work (chemical energy is a form of potential energy)
  • Power: The rate at which energy is transferred or converted per unit of time, quoted in Watts
  • Pressure band: The difference between the specified upper and lower limit of pressure in which compressors are required to operate
  • Pressure drop: The drop in pressure between any two specified points in a system
  • Pressure ratio: (total): The ratio between the absolute discharge pressure and the absolute inlet pressure
  • Pressure relief (safety) valve: A device to limit the maximum system pressure by allowing escape of the compressed air to atmosphere when a dangerous limit has been reached. Also called a safety valve or a pressure relief valve (PRV)
  • Pressure reducing valve (pressure regulator): A device which reduces the incoming pressure to a lower level and maintains it irrespective of inlet pressure and outlet flow rate changes
  • Pressure vessel: Air storage tank or air receiver
  • Primary energy source:  An energy sources available directly from the environment e.g. coal, oil and natural gas, sun, wind, geothermal and hydropower
  • Prime mover: A self-propelled machine, e.g. an electric motor or internal combustion engine, used to drive machinery
  • Purity: Free from contaminants. Air purity is the degree of cleanliness required for an application (often referred to as “air quality”)
  • Reciprocating: A machine in which a piston moves alternately backward and forward in a cylinder
  • Refrigerant: A fluid used for cooling that, when it changes from a liquid to a gas, takes heat from its surroundings (in this case compressed air)
  • Refrigerant dryer: A device which recycles a fluid (a refrigerant) between liquid and gas stages producing a cooling effect on the compressed air
  • Renewable energy: Energy resource that can be replenished within a finite time period.
  • Ring main: An air main that begins and ends at the compressor so that every usage point has two possible routes of supply
  • Risk: The chance, great or small, that someone will be harmed by the hazard
  • Roots blower: A positive displacement rotary machine used for compressed air applications at low pressures up to 1.5 bar
  • Rotary: Compressors where the air is compressed by circular motion
  • Run-on timer: A time related control that switches off the prime mover when the compressor has been off-load for a specified period of time
  • Secondary energy source: Energy sources derived from a primary energy source. The most common secondary energy source is electricity
  • Sensor: An electronic device used to measure a physical characteristic such as pressure or temperature and convert it into an electronic signal
  • Service pipe: A pipe to deliver gas, oil, water, steam or air to and around a site
  • Shut off valve: Device incorporating means to close off supply of air flow
  • Signal switch: A switch (mechanical or electronic) which responds to the signal from a sensor
  • Single line main: Piping arrangement whereby various branches are taken from a single pipe such that each usage point has one route of supply
  • Standard: To indicate that the figures quoted are derived at a standard temperature and humidity, the ‘s’ prefix is used, e.g. scfm – standard cubic feet per minute
  • System pressure: Normal operating pressure, often referred to as “working pressure”
  • Tertiary energy source: An energy source derived from secondary energy sources
  • Thermodynamics: The science of the conversion of heat to other forms of energy
  • Utility: A domestic or industrial service company, e.g. gas, oil, water, electricity
  • Variable speed drive (VSD): Electronic device which when fitted to a motor can vary the speed of a compressor and vary its air output
  • Water vapour: The gaseous state of water

 

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