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Annex I Definitions applicable for the purposes of Annexes II to V

United Kingdom

Original text. Later amendments are not shown.

For the purpose of Annexes II to V, the following definitions apply:

  1. (1)

    ‘Impeller’ means the rotating component of a rotodynamic pump which transfers energy to the water;

  2. (2)

    ‘Full impeller’ means the impeller with the maximum diameter for which performance characteristics are given for a pump size in the catalogues of a water pump manufacturer;

  3. (3)

    ‘Specific speed’ (ns) means a dimensional value characterising the shape of the water pump impeller by head, flow and speed (n):

    n s = n × Q BEP 1 ∕ i H BEP 3 4 [min–1]

    Where

    • ‘Head’ (H) means the increase in the hydraulic energy of water in meters [m], produced by the water pump at the specified point of operation,

    • ‘Rotational speed’ (n) means the number of revolutions per minute [rpm] of the shaft,

    • ‘Flow’ (Q) means the volume flow rate [m3/s] of water through the water pump,

    • ‘Stage’ (i) means the number of series impellers in the water pump,

    • ‘Best efficiency point’ (BEP) means the operating point of the water pump at which it is at the maximum hydraulic pump efficiency measured with clean cold water,

  4. (4)

    ‘Hydraulic pump efficiency’ (η) is the ratio between the mechanical power transferred to the liquid during its passage through the water pump and the mechanical input power transmitted to the pump at its shaft;

  5. (5)

    ‘Clean cold water’ means clean water to be used for pump testing, with a maximum kinematic viscosity of 1,5 × 10–6 m2/s, a maximum density of 1 050 kg/m3 and a maximum temperature of 40 °C;

  6. (6)

    ‘Part load’ (PL) means the operating point of the water pump at 75 % of the flow at BEP;

  7. (7)

    ‘Over load’ (OL) means the operating point of the water pump at 110 % of the flow at BEP;

  8. (8)

    ‘Minimum Efficiency Index’ (MEI) means the dimensionless scale unit for hydraulic pump efficiency at BEP, PL and OL;

  9. (9)

    ‘C’ means a constant for each specific water pump type quantifying the differences in efficiency for different pump types.