The Aggregates & Recycling Information Network

Glossary: N

  • National Grid
    1. Lines of reference drawn on a map to permit the precise location of particular features.
    2. High-voltage electrical power distribution system.
  • National Vocational Qualification

    Qualification requiring both evidence of knowledge and ability to carry out a job, ie performance.

    abbr. NVQ

  • Natural Asphalt

    A bituminous deposit formed in oil-bearing strata by the disappearance of volatiles.

  • Near-mesh Material

    Material approximating in size to the aperture size in the screen deck, usually within ±25% of the aperture size.

  • Net Present-day Value

    The value at the present time of future cash flows.

    abbr. NPV  

  • Network

    A network, as used in planning an operation, is a diagram in which each line representing an activity begins and ends at a circle, which represent the start and finish of an event. The network shows the logical sequence of events and the time for each event is included in the network.

  • Network Analysis

    A technique used by managers as an aid in planning and controlling their operations. It allows the control cycle to be completed rapidly and therefore frequently.

  • Newton

    The force which imparts to a body of a mass of 1kg an acceleration of 1m/s2.

    Symbol: N

  • Nip Angle

    The angle between the faces of a crusher.

  • Nip Point

    A point of hazard on a conveyor where the clearance between the moving belt and the static structure, such as a chute, or at the convergence of the moving belt and a drum, is such that parts of a person could be trapped.

  • Nitroglycerine

    A liquid high explosive, prepared by treating glycerine with a mixture of concentrated nitric and sulphuric acids; used as a basic sensitizer in some commercial explosives.

  • Nitrous Fumes

    Poisonous reddish-brown fumes which are produced when ANFO containing insufficient oil is detonated and when nitroglycerine explosives burn instead of detonating.

  • Nominal Screening Size

    A notional size at which it is intended to divide a feed by screening.

  • Nominal Size

    The limit or limits of particle size used to describe a product of a sizing operation.

  • Nomogram

    Chart of scaled lines for facilitating calculations. A simple nomogram consists of three straight lines arranged in such a way that, when a straight-edge is placed so as to join values of two of the variables, the corresponding value of the third variable can be read off at the intersection of the straight-edge and the third line.

  • Non-return Valve

    A valve which allows flow in a pipe in one direction only. One use of this type of valve is on the delivery side of a pump used to dewater a deep pit to prevent the column of water in the delivery pipe flowing back. In hydraulic systems the valve element is usually a ball which is returned to its seat by a light spring when flow ceases.

    Also: check valve

  • Nonel System

    A non-electric system of applying short-delay detonators to down-the-hole in intiation of quarry blasts.

    See also: shock tube

  • Normal Fault

    A fault which hades towards the downthrow side.

  • Northing

    The distance in metres north or south of an axis which runs east and west. When referred to as northing, all distances to the north are regarded as being positive. 

    See also: co-ordinates and latitude

  • Notifiable

    A term created by the Quarry Regulations 1999 to describe a tip or excavation that presents a significant hazard and must, therefore, be notified to the Inspectorate. Likely to include all structures described as ‘classified’ under previous regulations.

  • NPV

    abbr. Net present-day value.

    The value at the present time of future cash flows.

  • NVQ

    abbr. National Vocational Qualification

    Qualification requiring both evidence of knowledge and ability to carry out a job, ie performance.