W — Dictionary of Quarrying Terms

wagon drill: A drilling machine mounted on a light, wheeled carriage.

walking dragline: A large heavy dragline fitted with a walking device consisting of a pair of shoes which rest on the ground while an eccentric or a hydraulic mechanism lifts the tub and propels the dragline forward between them before moving the shoes forward for the next lift.

Ward-Leonard speed control: One of the most versatile methods of speed control of a dc motor. It involves the use of a separate motor generator set to supply a variable voltage to the armature of the machine under control. Used in controlling the speeds of the motors in large electrically operated shovels.

washery: A coal-preparation plant in which a cleaning process is carried out.

washing barrel: An aggregate-washing device consisting of a rotating cylinder fitted internally with lifters which lift and move the aggregate along the barrel either with (uniflow) or against (contraflow) the wash water.

washing screen: An inclined vibratory screen with spray bars fixed above the deck. High-pressure water jets remove dust, loam and clay from the feed and assist in providing a tumbling action to give improved cleaning.

water absorption: An aggregate property which can be tested to indicate porosity and hence strength and likely resistance to weathering.

water coupling: see ‘water swivel’.

water hammer: A hammer-like blow caused by a sudden high pressure in a pipe when the flow is stopped by the closing of a valve too rapidly.

water resistance: A qualitative measure of the ability of an explosive or blasting agent to withstand exposure to water without deteriorating or becoming desensitized.

water swivel: A means by which flushing water can be fed into a hollow drill rod or stem as it rotates.

water table: The upper limit or surface of the ground water or zone of permanent saturation. It may follow approximately the profile of the land surface.

water/cement ratio: The ratio of the weight of water to the weight of cement in a concrete. The higher the water/cement ratio, the lower the compressive strength of the concrete.

waterbound macadam: A form of road construction consisting of broken stone, slag or gravel, intimately interlocked and compacted in the presence of water, the binding agent being loam, sand, stone particles or the like.

watt: A rate of working of one joule per second, ie the work done by a force of one newton in moving through a distance of one metre in one second. Symbol: W.

wattless component: see ‘reactive component’.

wattmeter: An instrument for measuring the power in an electrical circuit.

wavelength: The distance between corresponding points on two successive waves. Symbol: A.

wayleave: A right in the nature of an easement granted for a limited period by a landdowner to another party.

wearing course: Obsolete term for that part of the road surfacing which directly supports the traffic now described as surface course.

weathering: Changes in rocks which occur as the result of the action of rain, snow, hail, wind, heat and cold, exposure to air and other atmospheric and chemical processes.

weber: The magnetic flux which, linking a circuit of one turn, produces in it an electromotive force of one volt as it is reduced to zero at a uniform rate in one second. Symbol: Wb.

wedge-wire screen: A screen deck comprising wires of wedge-shaped cross-section spaced from each other at a fixed dimension; the underflow thus passes through an aperture of increasing cross-section.

weight: The force of gravity acting on a body at the Earth’s surface. Weight = mass x acceleration due to gravity. Units: newtons.

weight strength: The strength of an explosive per unit weight, expressed as a percentage of the value for blasting gelatine or ANFO as a standard.

weighting: Applying factors or weights to each of a number of observations in order to represent their relative significance in calculating for instance a weighted average.

welding: The heating of two metal surfaces until they melt and fuse together.

wet-mix macadam: A roadbase material consisting of graded crushed rock or slag usually premixed with a controlled amount of water sufficient for adequate compaction.

wet pit: A sand and gravel excavation in land lying below the water table. Working may be by dragline excavator or pontoon-mounted pump etc.

wet screening: The addition of water to the feed or the spraying of water on to the screen deck in order to improve screening efficiency and increase capacity.

wet suppression: Dust control in processing operations by the use of water sprays into crushers, on to screens or conveyor belt transfer points.

whinstone:A trade term describing a tough fine-to-medium grained igneous rock such as basalt, dolerite etc.

white metal: A tin-base alloy used for lining bearings.

whole-circle bearing: Whole-circle bearings are measured clockwise from north, from 0° to 360°. See ‘azimuth’.

winding: The insulated conductors which carry the current in an electric machine or transformer.

winning: The several operations involved in breaking the rock from the solid and loading it for transport to the treatment plant.

winze: A vertical or steeply inclined shaft which has been driven downwards.

wire drawing: The process of reducing the diameter of rod or wire by passing it through a series of dies having successively smaller diameters.

wireline drilling: A method of drilling using a wireline core barrel in which the drill rods remain in the hole and the core barrel is retrieved by an overshot lowered through the rods on the end of a wire line after the water swivel has been removed; this results in much time-saving when deep holes are drilled.

work: Work is done when a force is applied to a body and the body moves in the direction of the force. Unit: joule (J), equal to one newton-metre.

work cycle: The sequence of elements which is required to perform a task or to yield a unit of production. The sequence may sometimes include occasional elements. BS 4200l.

work measurement: The determination of the proper time to allow for the effective performance of a specific task. It is concerned with investigating, reducing and subsequently eliminating ineffective time, ie time during which no effective work is being performed.

work study: Term for the techniques used in analysing the methods used in carrying out an operation and of measuring the work involved.

workability: Term used to describe the ease with which concrete can be compacted. Wet concretes are workable but weak. Workability can be measured by the slump test and the compacting factor test.

working capital: The capital available to meet the day-to-day expenses of running the business. This is the excess of current assets (mainly trade debtors, stock, cash at bank and in hand) over current liabilities (mainly trade creditors and bank overdrafts).

wound-rotor motor: An induction motor the ends of the rotor windings of which are connected to slip-rings through which external resistance may be added to the rotor circuit for starting purposes. Used for duties in which on-load starting is required.