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Fittings in a centrifugal pump system comprise all piping components which function to change the piping's direction, to install piping branches, and/or to provide a transition between different pipe cross-sections.

Fittings should be shaped to offer the least possible resistance to flow in order to minimise pressure losses (see system head); where this involves increased manufacturing costs, these should be weighed against the corresponding gains in economic efficiency.

Common fittings:

Pipe bends

  • Pipe bends should have a radius of curvature of R > 2 2∙ D + 100 +100 mm (D = pipe diameter) particularly if they are fitted immediately upstream of pump suction nozzles. Pipe bends fabricated from cylindrical segments welded together should consist of at least six segments for a 90° bend.
    See Fig. 1 Fitting

Fitting: 90° pipe bend Fig. 1 Fitting: 90° pipe bend


  • Y-branches' fluid dynamic characteristics make them preferable to tees.
    See Fig. 2 Fitting

Fitting: Y-branch Fig. 2 Fitting: Y-branch


  • Its face-to-face length (L) should be approximately L = 5 ∙ (D2 – D1)
    (D = pipe diameter) when used as a diffuser in flow direction. Diffuser outlets (e.g. in the case of low-lift pumping stations and pumps for use in low-lift pumping stations should be sized such that the discharge velocity (v) (see Flow velocity) is 1.0 to 1.5 SPdL m__s SPdL.
    See Fig. 3 Fitting

Nozzle-shaped reducer

  • In contrast to a diffuser, the face-to-face length of a fitting used as a reducer can be much shorter. A nozzle-shaped reducer features favourable flow characteristics.
    See Fig. 4 Fitting

Fitting: Nozzle-shaped reducer Fig. 4 Fitting: Nozzle-shaped reducer

Reducer for avoiding air pockets

  • Eccentric reducers should be installed in horizontal suction lines to avoid the formation of air pockets (see Formation of air pockets).
    See Fig. 5 Fitting

Fitting: Reducer for avoiding air pockets Fig. 5 Fitting: Reducer for avoiding air pockets

Branch fitting for avoiding air pockets