F — Dictionary of Quarrying Terms

FPC: Factory Production Control. An European term for Quality Assurance.

fabric filters: Dust-collection devices in the form of vertical bags or sleeves with the lower ends closed. Dust-bearing gases pass into the sleeves through the fabric, the cleaned gas leaving by the open upper ends and dust being deposited on the outer surface of the sleeves.

fabrication: The preparation in a workshop of the steel members of a building framework for later erection on site.

face: An exposed surface of pay mineral, usually near vertical.

face left and right: The positions of a theodolite when, viewed from the eyepiece, the vertical circle is to the left and right of the telescope respectively.

face profiling: The process of producing a diagram showing variations in the face to be taken into account by the blast design. Often achieved by using EDM and computer.

faceshovel: An excavator which digs away from itself into a bank or face with a toothed bucket fixed to a rigid arm supported by the boom; its crowd action provides a powerful digging force.

factor of safety: The ratio, allowed for in design and manufacture, between the breaking load on a member or structure and the safe permissible load on it.

fail safe: Design in which control or structural failure leads to automatic operation of protective devices and the cutting-off of the power supply.

farad: The capacitance of a capacitor between the plates of which there appears a difference of potential of one volt when it is charged by a quantity of electricity equal to one coulomb. Symbol: F.

Faraday’s law: Faraday’s law of electromagnetic induction states: ‘The magnitude of the electromotive force induced in a circuit is proportional to the rate of change of magnetic flux linking the circuit.’

fault: A plane of fracture in a rock body, along which there has been displacement. See ‘normal fault’ and ‘reverse fault’.

fault breccia: The shattered rock material along a fault plane.

fault plane: Any surface along which relative movement between adjacent rock masses has taken place.

feed box: A box, usually mounted on the feed end of a screen, used to reduce the velocity of the feed and to distribute it across the full width of the screen.

feeder: Machine which performs a conveying operation over a short distance and through which the rate of flow of material in a processing plant can be controlled.

feldspar: A family of rock-forming minerals consisting of aluminous silicates of barium, calcium, potassium and sodium. They occur as constituents of igneous rocks.

field book: The book used by a surveyor to record his field measurements.

field conveyor: A belt conveyor system for the overland transportation of excavated sand and gravel or rock crushed by an in-quarry mobile crusher.

field regulator: A variable resistance for varying the current in the field winding of an electric machine.

filler: A finely divided mineral powder added to road tar, bitumen or the like, or to a mixture containing the same, in order to effect some desired change in the properties of the binding material.

fine-adjustment screw: see ‘tangent screw’.

fine aggregate: Graded material which, in the case of concrete aggregate, is smaller than 4mm, and for road-making material is below 2mm.

fines: 1 Particles finer than 63μm. 2 Sometimes used synonymously with ‘fine aggregate’.

finger car: A concrete block transporter which moves the blocks in an automated sequence from the press to the curing point.

fishing tool: A tool used to recover broken bits or other drilling equipment from a borehole.

fishtail bit: A bit used for rotary drilling through soft ground.

fixed assets: Relatively long-term resources of a company, acquired not for disposal but to assist in the earning of profit, eg land, buildings, plant and machinery.

fixed costs: Costs which are not affected by variations in output but may change over a period of time, eg rates.

flake deck: A deck fitted to a screen for the purpose of removing excess flaky material from a product, usually achieved by the fitting of elongated slots narrower than the nominal size.

flakiness index: An index of particle shape determined by means of a test described in BS EN 933 Part3. This European test replaces the former flakiness test BS 812 Part 105 and produces different values.

f1ameproof: Term applied to the enclosures of electric machines. These are such that gas or dust cannot get inside the machine and sparking within the casing of the machine cannot affect inflammable concentrations of vapour or dust which surround the machine.

flash point: The lowest temperature at which a heated liquid gives off sufficient vapour to flash on the application of a small flame.

Fleming’s rule: A method of indicating the directions of current, motion and magnetic field in a conductor in a magnetic field by extending the thumb, forefinger and second finger at rightangles. The thumb points in the direction of motion, the forefinger that of the field and the second finger the direction of the current. The right hand is used for generator action and the left for motor action.

flexible cable: A cable designed to be movable while in use.

flexible coupling: A coupling used to connect two shafts in which rigid alignment is not possible. Typically the drive is transmitted between flanges on the shafts through a flexible disc or bushes.

flexible pavement: Any pavement in which high-strength concrete is not used as a construction layer.

float: In a network, the spare time available for a non-critical activity. The time available for an activity or path in addition to its duration, BS 2300l.

flocculation: Coalescence of minute particles into floccules to accelerate settlement as part of dewatering or thickening of a pulp. Chemicals are used to promote adhesion.

floor: 1 The stratum immediately below a seam of coal or stratified mineral deposit. 2 The base of an excavation.

flotation: A mineral processing operation which involves conditioning the surfaces of mineral grains in water so that certain minerals can be collected into air bubbles and carried to the surface to effect separation. Uses include the cleaning of fine coal and the removal of contaminants from flint glass sand.

flotation reagent: A chemical required to obtain suitable conditions for the successful operation of a flotation process. see ‘collectors’, ‘regulators’ and ‘frothers’.

flow diagram: A diagram or model which shows the location of specific activities carried out and the routes followed by workers, materials and equipment in their execution.

flow divider valves: Hydraulic valves used to give priority to the flow requirements of a particular service. When these requirements are met, the remainder of the flow is diverted to another service or returned to the reservoir.

flowsheet: A diagrammatic representation of the flow of material through a processing plant, showing the sequence of operations and their interrelationship.

fluid coupling: A device used to gradually apply a high-inertia load to an electric motor or diesel engine.

flume: A concrete, steel or wooden trough used to convey pulp or water.

fluvial: Relating to a river; a deposit produced by the action of a river.

fluvioglacial: May be applied to sediment transported and deposited by melt water from a glacier or ice sheet.

flux: A substance added to a solid to increase its fusibility. In soldering and welding it is added to the molten metal to dissolve oxide films which prevent adhesion.

flux oil: A substantially non-volatile diluent used for reducing the viscosity of bitumen.

fly-rock: Material which is projected outside the declared danger zone by a quarry blast. Fly-rock may be caused by poor blast design or unexpected zones of weakness in the rock.

flywheel: Large-diameter wheel keyed to the end of the shaft of machines such as jaw crushers and the function of which is to restrict fluctuations of speed by absorbing and releasing quantities of kinetic energy for small speed variations.

fold: A bend in bedded rocks.

follower: 1 In surveying, the man who holds the rear end of the tape or chain and is responsible for lining-up the leader at each tape or chain length. 2 The driven wheel of a pair of wheels engaging with each other.

foot screws: The three screws used for leveling a survey instrument.

foot valve: A non-return valve attached to the lower end of a pump suction pipe. Also known as a clack valve.

footwall: The rock immediately underlying a mineral deposit.

FOPS cab: A driver’s cab providing protection from falling objects (falling object protection structure).

force: That influence which causes, or tends to cause, a change in the shape or size or the state of motion of a body. Unit: Newton.

force ratio: The ratio of load to effort; may also be called mechanical advantage.

fork-lift truck: A vehicle with a power-operated fork at the front which can be raised or lowered as required for loading, transporting and unloading packages. The packages are usually stacked on pallets which provide sufficient ground clearance for the fork prongs to pass beneath them.

form factor: The ratio rms value/mean value of an alternating quantity such as a current or a voltage.

formwork: Temporary boarding or sheeting erected to contain freshly placed and compacted concrete until it has gained sufficient strength to be self-supporting. The appearance of the finished concrete depends on the face texture and stiffness of the formwork.

foundation bolt: A bolt with its threaded end projecting above the foundation and secured so as to hold down a steel structure against wind loads or machinery against its vibration.

four-bearing screen: A mechanically vibrated screen in which the circular motion is generated by eccentrics incorporated in the vibrator shaft acting through two outboard bearings on the base-frame and two inboard bearings on the side-plates.

four-stroke cycle: An internal combustion engine cycle completed in four piston strokes. On the first downward stroke induction takes place, followed by compression during the subsequent upward stroke; after combustion the power stroke and on the next upward stroke the exhaust gases are expelled.

fractional exposure: The measure of the combined effect when the daily exposure is to a number of different sound-intensity levels each for its own period of time. It is the actual energy dosage received during each period expressed as a fraction of that corresponding to 90dB(A) for 8h and is used in determining whether the daily exposure is acceptable.

fracturing: Breaking of rock with or without movement of the broken pieces.

fragmentation: A term associated with rock quarrying to describe the degree of breakage by blasting evident in a rock pile.

frequency: The number of cycles which take place in one second. Symbol: f. Unit: hertz (Hz).

fretting: 1 A form of wear encountered when surfaces are subject to continuous relative movement of small amplitude, eg in bearings supporting shafts which oscillate through a small angle, in ball or roller races of machines subject to vibration while stationary etc. 2 The condition of early stages of wear of a road surface as evidenced in the loss of small-size aggregate from the bound surface.

friction: The resistance to motion when it is attempted to slide one surface over another with which it is in contact.

friction course: An asphalt mix designed to produce a high voids content and good texture to give improved drainage and skid resistance characteristics, together with reduced noise under traffic.

friction loss: The power absorbed in the sliding contacts of an electric machine.

frost heave: The formation of ice lenses in the lower layers of a road which may cause surface heaving.

frost shattering: A natural process which occurs when water penetrates a road surface and expands as it freezes.

froth flotation: see ‘flotation’.

frothers: A type of flotation reagent which, when dissolved in water, imparts to it the ability to form a stable froth.

frustum: 1 The remainder of a cone or pyramid whose upper part has been cut off by a plane parallel to its base. 2 The part of a cone or pyramid intercepted between two planes.

fuel: A substance which, when burned, produces heat energy. An ingredient in an explosive which reacts with an oxidizer to form gaseous products of detonation.

fuel injection: A method of operating an internal combustion engine by injecting liquid fuel directly into the induction pipe or cylinder during the suction-stroke.

full dip: The maximum angle, measured in a vertical plane, between the plane of the stratum and the horizontal. The vertical section containing the full dip is at right angles to the line of strike. Also known as true dip.

full-wave rectification: The use of a bridge or double-diode rectifier to obtain a rectified current which flows during both halfcycles of the alternating voltage.

fumes: Cloud of airborne particles, generally visible, less than 1μm in size, of low volatility and formed by condensation of vapours or by chemical reaction. Noxious or poisonous fumes liberated from a blast may be due to low-fume-quality explosives or inefficient detonation.

fuse: An overcurrent protection device which prevents excessive currents from flowing in a circuit by the melting of a fuse element. See ‘safety fuse’.

fusing factor: The ratio, greater than unity, of the minimum fusing current to the current rating.