ABRASION - The wearing away of a surface by rubbing, as with sandpaper on wood.
ABRASION RESISTANCE - The ability of a material to resist surface wear.
ABRASIVE EROSION - Erosive wear caused by the relative motion of solid particles which are entrained in a fluid, moving nearly parallel to a solid surface.
ABSOLUTE TEMPERATURE SCALE - A scale of temperature measurement in which zero degrees is absolute zero.
ABSOLUTE ZERO - A hypothetical temperature at which there is total absence of heat. Since heat is a result of energy caused by molecular motion, there is no motion of molecules with respect to each other at absolute zero. It is theoretically the coldest possible temperature.
ABSOLUTE ZERO TEMPERATURE - Temperature measured from absolute zero (-459.67°F, or -273.16°C).
ABSORBENT - A material which, due to an affinity for certain substances, extracts one or more such substances from a liquid or gaseous medium with which it contacts. Calcium chloride is an example of a solid absorbent, while solutions of lithium chloride, lithium bromide, and ethylene glycols are liquid absorbents.
ABSORPTION TOWER - A tower or column, which effects contact between a rising gas and a falling liquid, so that part of the gas may be taken up by the liquid.
ACCELERATION - The rate of change of velocity, as a function of time. Expressed in m/s.
ACCEPTABLE WELD - A weld that meets all of the requirements and the acceptance criteria prescribed by the welding specifications.
ACCUMULATOR - Storage tank which receives liquid refrigerant from evaporator and prevents it from flowing into suction line before vaporizing
ACID ATTACK - Caused by an incomplete flushing after an acid cleaning process of boilers or similar equipment.
ACID CLEANING - The process of cleaning the interior surfaces of steam generating units by filling the unit with dilute acid accompanied by an inhibitor to prevent corrosion and by subsequently draining, washing, and neutralizing the acid by a further wash of alkaline water.
ACIDIC - The reaction of a substance with water resulting in an increase in concentration of hydrogen ions in solution (see acid).
ACTIVATED ALUMINA - Chemical which is a form of aluminum oxide. It is used as a drier or desiccant.
ACTIVATED CARBON - Is a specially processed carbon, used as a filter drier. Commonly used to clean air.
ACTIVATED SLUDGE - An aerobic biological process for conversion of soluble organic matter to solid biomass, removable by gravity or filtration.
ACTUATOR - The portion of a regulating valve, which converts mechanical, fluid, thermal, or electrical energy; into mechanical motion to open or close the valve seats or other such devices.
ADJUSTABLE DIFFERENTIAL - A means of changing the difference between the control cut-in and cutout points.
ADJUSTABLE RESISTOR - A resistor whose value can be mechanically changed, usually by the use of a sliding contact.
AERATION - Exposing to the action of air, like blowing air through water before discharging to a river.
AERODYNAMIC NOISE - Also called generated noise, self-generated noise; is noise of aerodynamic origin in a moving fluid arising from flow instabilities. In duct systems, aerodynamic noise is caused by airflow through elbows, dampers, branch wyes, pressure reduction devices, silencers and other duct components.
AGITATOR - A device used to cause motion in confined fluids.
AIR CLEANER - A devise used to remove air borne impurities.
AIR CONDITIONING -The process of treating air to simultaneously control its temperature, humidity, cleanliness, and distribution to meet the requirements of the conditioned space.
AIR COOLER - A factory-encased assembly of elements whereby the temperature of air passing through the device is reduced.
AIR GAP -The space between magnetic poles, or between the rotating and stationary assemblies in a motor or generator.
AIR VENT - Valve, either manual or automatic, to remove air from the highest point of a coil or piping assembly.
AIR-COOLED CONDENSER - Heat of compression is transferred from condensing coils to surrounding air. This may be done either by convection or by a fan or blower.
ALKALI - A substance having marked basic properties. Applying to hydroxides of potassium, sodium, lithium, and ammonium. They turn red litmus to blue. Includes hydroxides of the alkaline earth metals of barium, strontium, and calcium.
ALKALINE - Having a pH greater than 7.
ALLEN TYPE SCREW - A screw with a recessed hex shaped head.
ALLOY - A substance having metal properties and being composed of two or more chemical elements of which at least one is a metal.
ALLOY STEEL - Steel containing specific quantities of alloying elements (other than carbon)and commonly accepted amounts of manganese, copper, silicon, sulfur, and phosphorus).
ALTERNATING CURRENT (AC) - Electric current in which the direction of the current alternates or reverses. In a 60 Hertz (cycle) current, the direction of current flow reverses in 1/120th of a second; most commonly used current.
ALTERNATOR - A device which converts mechanical energy, into alternating current.
ALTIMETER - An instrument used to measure the height above a reference point, such as ground or sea level.
ALUM - Is an aluminum sulfate or filter alum. Acts in the range of 5.0 to 8.0 pH.
ALUMINA - Aluminum oxide occasionally found as an impurity in water in very small amounts.
AMBIENT CONDITIONS - The conditions of temperature, pressure, and humidity, existing around an instrument.
AMBIENT NOISE -The normal sound in a room or other location.
AMERICAN STANDARD PIPE THREAD - A type of screw or thread, commonly used on pipe fittings to assure a tight seal.
AMERICAN WIRE GAUGE (AWG) - A system used in the United States for measuring the size of solid wires.
AMMETER - An instrument for measuring the magnitude of electric current flow.
AMMONIA - Chemical combination of nitrogen and hydrogen (NH3). Ammonia is a very efficient refrigerant and identified as R-117.
AMPERAGE - An electron or current flow of one coulomb per second, past a given point in a circuit.
AMPERE - The unit used for measuring the quantity of an electrical current flow. One ampere represent a flow of one coulomb per second.
AMPERE HOUR - A term used for rating battery capacity. As stated, an ampere for an hour; ex: 5 amperes for 20 hours = 100 amp hour on a 20 hr rating.
AMPERE TURNS - A term used to measure magnetic force. It represents the product of amperes, times the number of turns of the coil, in an electromagnet.
AMPLIFICATION - The process of obtaining an output signal greater than the input signal, through auxiliary power controlled by the input signal. The process of increasing the strength, current, power, or voltage, of the signal.
AMPLITUDE - The maximum instantaneous value of alternating current or voltage. It can be in either a positive or negative direction. The greatest distance through which an oscillating body moves from the mid point.
ANALYSIS - The process of determining the composition of a substance, by chemical or physical methods.
ANEMOMETER - An instrument for measuring the velocity of a fluid.
ANGLE VALVE - A type of globe valve design, having pipe openings at right angles to each other. Usually one opening on the horizontal plane and one on the vertical plane.
ANODE - In electrolysis or electrochemical corrosion, a site where metal goes into solution as a cation leaving behind an equivalent of electrons to be transferred to the opposite electron, called the cathode.
ANSI - American National Standard Institute, which is an organization defining standards for computer language.
ANTI-CORROSIVE ADDITIVE - A lubricant additive to reduce corrosion.
ANTI-FOAM ADDITIVE (FOAM INHIBITOR) An additive used to reduce or prevent foaming.
ANTIFOULANTS - Are materials which prevent fouling from depositing on heat transfer equipment. Materials that prevent deposits forming; include anti- oxidants, metal coordinators, and corrosion inhibitors. Compounds that prevent deposition are surfactants. They act as detergents or dispersants.
ANTIFREEZE - Compounds of glycol’s or alcohol’s, that lower the freezing point of cooling water systems.
ANTIOXIDANT - A substance which when added in small amounts to petroleum products, will delay or inhibit undesirable changes; such as the formation of gum, sludge, and acidity, which are brought about by oxidation.
ANTI-OXIDANT - An additive for the purpose of reducing the rate of oxidation and subsequent deterioration of the material.
ANTI-SCUFFING LUBRICANT - A lubricant that is formulated to avoid scuffing.
ANTI-SEIZURE PROPERTY - The ability of the bearing material to resist seizure during momentary lubrication failure.
ANTI-WEAR ADDITIVE - A lubricant additive to reduce wear.
API - American Petroleum Institute.
API GRAVITY (API DEGREE) - A measure of density used in the US petroleum industry.
ARC FURNACE - An electric furnace, in which heat is produced by an arc between two electrodes.
ARC WELDING - A group of welding processes which produce coalescence of metals by heating them with an arc, with or without the application of pressure, and with or without the use of a filler metal.
ARCHIMIDES PRINCIPAL - States that an upward force acting on a body wholly or partly submerged in a fluid, is equal to the weight of the fluid displaced, and acts through the center of gravity of the fluid displaced, or the center of buoyancy.
ARMATURE - the rotating part of an electric motor or generator. The moving part of a relay or vibrator.
ARMATURE TESTER - Any device used for locating faults or defects in the armature winding.
AROMATICS - A group of hydrocarbons of which benzene is the parent. They are called "aromatics" because many of their derivatives have sweet or aromatic odorous.
ASHRAE - The American Society of Heating, Refrigeration, and Air Conditioning Engineers.
ASME - American Society of Mechanical Engineers.
ASPECT RATIO - The ratio of the length to the width, of a rectangular air grille or duct.
ASPIRATION - Production of movement in a fluid by suction created by fluid velocity.
ASTM - American Society for Testing and Materials.
ASYNCHRONOUS - Not having the same frequency. Out of step, or phase.
ATMOSPHERE - Is the mixture of gases and water vapor surrounding the earth.
ATMOSPHERIC ELECTRICITY - Is static electricity, produced between cloud fronts in the atmosphere.
ATMOSPHERIC PRESSURE - Pressure exerted by the weight of the atmosphere; standard atmospheric pressure is 101.325 kPa or 1.01325 bars or 14.696 psia or 29.921 inches of mercury at sea level.
ATOM - The smallest complete particle of an element, which can be obtained, yet which retains all physical and chemical properties of the element.
ATOMIC NUMBER - The number of protons found in the nucleus of an atom, of an element.
ATOMIC WEIGHT - The weight of an elementary atom, in relation to the weight of an atom of hydrogen. A hydrogen atom being taken as 1.00g.
ATOMIZE - Process of changing a liquid to minute particles or a fine spray.
AUTOMATIC CONTROLLER - A device that measures the value of a measured variable, and operates to correct or limit the deviation from a selected reference. Both measuring and control applications.
AUTOMATIC DEFROST - System of removing ice and frost from evaporators automatically.
AUTOMATIC EXPANSION VALVE (AEV) - A type of metering device that senses low-side pressure and modulates in order to maintain low-side pressure constant.
AUTOMATIC EXTRACTION UNIT TURBINE - Bleeds off part of the main steam flow at one, two, or three points. Valved partitions between selected stages control the extracted steam pressure at the desired level. When extracted steam flowing through the unit does not produce enough shaft power to meet the demand, more steam flows through the turbine to exhaust. Located between steam supply and process steam headers.
AUTOMATIC FROST CONTROL - Control which automatically cycles refrigerating system to remove frost formation on evaporator.
AUTOMATIC GOVERNING SYSTEM - A system which correlates steam flow, pressure, shaft speed, and shaft output, for any one turbine unit.
AUTOMATIC RESET (INTEGRATION) - Is a type of control, in which the controller output, changes at a rate proportional to the deviation or error. The output will continue to change as long as any deviation or error exists.
AUTOMATION - The employment of devices, which automatically control one or more functions.
AUTOTRANSFORMER - A transformer in which both primary and secondary coils, have turns in common. The step up or step down of voltage, is accomplished by taps in common windings.
AUXILIARY CONTACTS - A set of contacts that perform a secondary function, usually in relation to the operation of a set of primary contacts.
AVAGADRO'S HYPOTHESIS - States that equal volumes of different gases, at the same temperature and pressure, will contain equal numbers of molecules.
AVAGADRO'S NUMBER (N) - The number of elementary units such as atoms, formula units, molecules, or ions, that constitute one mole of the said particle.
AVERAGING ELEMENT - A thermostat sensing element which will respond to the average duct temperature.
AXIAL FLOW COMPRESSOR - Uses rotor blades shaped like airfoils, to bite into the air, speed it up, and push it into the subsequent stationary blade passages. These passages are shaped to form diffusers, that slow up the incoming air, and make it pressurize itself by catching up with the air ahead of it.
AZEOTROPE - Having constant maximum and minimum boiling points.
AZEOTROPIC MIXTURE - Example of azeotropic mixture - refrigerant R-502 is mixture consisting of 48.8 percent refrigerant R-22 and 51.2% R-115. The refrigerants do not combine chemically, yet azeotropic mixture provides refrigerant characteristics desired.
Engineering & Technical Terms A
Sources :
Wikipedia
The Power Engineering Dictionary
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