The Aggregates & Recycling Information Network

Glossary: E

  • Earth Electrode

    A conductive part or group of parts in intimate contact with, and providing an electrical connection with, earth.

  • Earth Testing

    Tests to ensure that the resistance between the earth electrodes (ie earth plates, rods etc) and the general mass of earth does not exceed a prescribed value.

  • Earth-fault Current

    A current that flows from phase conductors to earth or protective conductors etc from the point of an insulation breakdown.

  • Earth-fault Protection

    A system of protection designed to cause the supply to an electrical circuit or system to be interrupted automatically when the leakage current to earth exceeds a predetermined value.

    Also: earth-leakage protection

  • Earth-leakage Circuit-breaker

    A device which disconnects the electricity supply if the voltage on non-current-carrying metalwork or the out-of-balance current in the supply due to leakage exceeds a predetermined value.

  • Earth-leakage Protection

    A system of protection designed to cause the supply to an electrical circuit or system to be interrupted automatically when the leakage current to earth exceeds a predetermined value.

    Also: earth-fault protection

  • Earthing Conductor

    A protective conductor connecting the main earthing terminal or main earthing bar to the earth electrode. Also used to describe an earth wire bonded from the metal work of an isolating switch (for example) to the cable armouring feeding it.

  • Earthmover tyre
    Earthmover Tyre

    A name given to tyres of large diameter with particular tread patterns fitted to mobile plant (earth moving plant) to differentiate them from tyres for road vehicles.

  • Easement

    A liability attaching to land, whereby some person other than the owner has certain clearly defined rights over it and in perpetuity. Alternatively, a right over land granted in perpetuity by the owners to some person for a specific purpose, eg passage, laying of mains drainage etc.

  • Easting

    The distance in metres of a point east or west of a north-south axis. May also be referred to as an easting, in which case all distances measured to the east are regarded as being positive.

    Also: departure

  • Eccentric

    Displaced with reference to a centre, eg the eccentric section of the shaft generating the motion of a four-bearing screen.

  • Eddy Current

    In most cases unwanted currents generated by a magnetically induced electromotive force in a closed conductive path, such as the core of an electric machine, resulting in a waste of energy.

  • Eddy Current Systems

    Eddy current systems are used to separate non-ferrous metals from a waste stream or processed aggregate.

    They create an 'eddy current' by spinning ferrite ceramic or rare earth magnets at high speeds. These eddy currents induce different reactions in different metals according to that metals density and resistivity. Light but conductive metals such as aluminium are easily levitated and can then be separated using dividers, chutes or similar.

  • Edge Bedding

    Laying of stone with the bed plane running vertically and at right angles to the face of the wall.

  • EDM

    abbr. electronic distance measurement

    A very accurate method of measuring distance by means of an electronic device. Most EDM instruments are operated by infra-red light or laser, with the beam being directed at a target which may be some kilometres away, and give a direct reading with an accuracy of 1 in 10,000 or better.

  • Effective Value

    The root-mean-square value of an alternating current or voltage.

  • Efficiency
    1. The ratio of useful output energy to input energy.
    2. The efficiency of a simple machine is defined as the ratio of the force ratio to the movement ratio.

    Also: screening efficiency

  • EIA

    abbr. environmental impact assessment

    The procedure that must be followed for certain types of project before they can be given ‘development consent’ (under the Town and Country Planning (Environmental Impact Assessment) Regulations 1999). The procedure is a means of drawing together, in a systematic way, an assessment of a project’s likely significant environmental effects.

  • Elastic Limit

    The stress level above which a material remains permanently deformed when the stress is removed.

  • Electrical motor
    Electrical Motor

    A motor powered by electricity rather than fuel.

  • Electromagnet

    A current-carrying coil with a soft iron core, which has appreciable magnetic effect only when there is a flow of current.

  • Electromagnetic Induction

    The production of an induced voltage in a circuit by means of the magnetic flux cutting the circuit. In order for an induced current to flow in a closed circuit the conductors and the magnetic field must move relative to each other.

  • Electromagnetic Screen

    A screen to which is attached an electrically operated vibrator unit consisting of an armature and a stator connected to a halfwave rectified single-phase ac supply, which imparts a linear motion, usually of high frequency and low amplitude, to the screen.

  • Electromotive Force

    The voltage applied to an electrical circuit which causes current to flow.

    abbr. emf

  • Electronic Distance Measurement

    A very accurate method of measuring distance by means of an electronic device. Most EDM instruments are operated by infra-red light or laser, with the beam being directed at a target which may be some kilometres away, and give a direct reading with an accuracy of 1 in 10,000 or better.

    abbr. EDM

  • Electrostatic Precipitator

    An apparatus for removing dust from dust-laden air by creating electric charges on the dust particles, causing them to be attracted to a collecting plate.

  • Element

    In relation to time study, a distinct part of an operation selected for convenience of observation, measurement and analysis. BS 42003.

  • Elevating Scraper

    A self-loading bowl scraper able to operate without the help of a pusher dozer except in very difficult conditions. It is fitted with an elevating conveyor with flights at regular intervals which, as the scraper moves forward, carry the material sliced off from the ground up into the bowl.

  • Elevation
    1. A view of a component or assembly drawn in projection on a vertical plane, eg an end elevation.
    2. The height of a point above sea level.
  • Elevator

    A continuous line of buckets attached by pins to two endless chains running over tracks and driven by sprockets; alternatively, the buckets are attached to a rubber belt. Used for raising loose materials or slurries at high angles or vertically.

    Also: bucket elevator

  • Elutriation

    Process of dividing fine particles into size fractions according to their rate of fall through an upward current of water.

  • Eluvial Deposit

    Rocks which have disintegrated through natural causes but which, unlike alluvial material which is transported away by water, have remained in situ.

  • Elvan

    Cornish name for quartz-porphyry and similar dyke rocks.

  • Empirical Formula

    A formula based on experience or the results of experiments, not deduced from theoretical considerations.

  • Emulsion
    1. Bitumen emulsions, in which the bitumen is dispersed in water, through the use of emulsifying agents, as small globules permitting use at lower temperatures.
    2. Explosive emulsions are mixtures of fuel and oxidizers (mainly nitrates) in a ratio of approximately 1:10, which have good water resistant properties and chemical stability. Emulsion/ANFO blends can be used to suit particular circumstances.
  • Encapsulated screen
    Encapsulated Screen

    A vibrating screen which is covered and attached to static equipment, especially the pan below the screen, by flexible fabric often incorporating rubber so as to contain all the dust generated by the screening process.

  • Energy Factor

    The amount of explosive energy required to break a unit volume of rock (MJ/m3) which may be used as a blast design criterion.

  • Environmental Impact Assessment

    The procedure that must be followed for certain types of project before they can be given ‘development consent’ (under the Town and Country Planning (Environmental Impact Assessment) Regulations 1999). The procedure is a means of drawing together, in a systematic way, an assessment of a project’s likely significant environmental effects.

    abbr. EIA

  • Environmental Statement

    The document that describes the process and findings of an Environmental Impact Assessment. The Environmental Statement is usually submitted with a planning application.

  • Eocene

    An epoch of the Tertiary period between 54 and 38 million years ago.

  • Epicyclic Gear

    A system of gears in which one or more gear wheels travel round the inside or outside of another gear wheel, the axis of which is fixed.

  • Equipotential Bonding

    Electrical connection putting various exposed conductive parts and extraneous conductive parts at a substantially equal potential.

  • Equity

    The shares of a company which do not bear fixed interest, ie the ordinary shares.

  • Equivalent Continuous Sound Level

    The constant sound intensity level which in the course of continuous exposure for 8h would result in the same energy dosage as that due to the actual exposure.

    abbr. Leq

  • Erosion

    The wearing away of parts of the Earth’s surface by the action of natural agents such as ice, water and wind.

  • Evaporites

    Rocks, such as anhydrite, rock salt, potash, salt etc, formed by evaporation of lakes or seas.

  • Excitation Time

    The minimum time for which an electric current must flow in the fusehead of a detonator to ensure its ignition.

  • Expanded Metal

    A metal network made by stamping and stretching sheet metal to form an open mesh. Used as reinforcement in concrete, in the manufacture of safety guards for machines etc.

  • Explosives Store

    Premises registered in accordance with section 21 of the Explosives Act 1875; a magazine licensed in accordance with sections 6 to 8 or a store licensed in accordance with section 15 of the 1875 Act.

  • Explosives Strengths

    The strength of explosive per unit of volume or weight expressed as a percentage of the value of blasting gelatine or ANFO as standard.

    Also: bulk strength and weight strength

  • Explosives Supervisor

    The appointed person in overall, day-to-day charge of work with explosives who must have successfully completed a course of training.

  • Exposed Aggregate

    A decorative concrete finish in which the mortar is removed to expose the coarse particles at the surface.

  • Extrapolation

    The continuance of the line of a graph beyond the points for which values are available, in order to estimate values beyond the range of those points.

  • Extrusion

    The process of producing rods, tubes and various solid and hollow sections, by forcing suitable metals and plastic materials through a die.

  • Extrusive

    Describes igneous rocks that solidify on the surface of the ground.