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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.



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


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



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.


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.