The centrifugal pump is a hydraulic turbomachine capable of processing fluid through centrifugal effect in fixed and rotating channels that are always open, without altering the fluid's compressibility. Hence the name centrifugal pump. The mechanical movement imparted by the motor to the impeller provides kinetic energy to the flow (acceleration in a radial direction) which is then transformed into pressure energy in the subsequent diverging channels.

The main components of a horizontal centrifugal pump with mechanical seal are:


  • The impeller is the main component of the centrifugal pump and the moving part with which the fluid exchanges energy. Made of plastic material reinforced with fibers (PP + FRP or PVDF + CF depending on the use of the centrifugal pump and the processed fluid), it consists of a series of curved blades forming channels that increase with the radius. The open impeller allows the passage of slightly dirty liquids, while the processing of fluids with viscosities up to 500 CPS or specific weights up to 1.9 kg/L is guaranteed by the solid and concentric movement of the impeller relative to the motor, connected via a transmission shaft.
    It is possible to achieve different volumetric flows [m3/h] and heads [m] by controlling the diameter of the impeller, the curvature, the height, and the number of blades.

    For each impeller, there will be a characteristic curve of the centrifugal pump, that is, what head can be achieved given a certain flow rate, the operating range, and the working point.

  • The pump body or volute, snail-shaped, with an increasing section in the direction of motion, allows the axial suction of the fluid and radial discharge upwards. Besides directing the flow, it is also fundamental for the performance of the centrifugal pump: the increasing area appropriately slows down the fluid, so the kinetic energy is transformed into pressure energy.
  • The mechanical bellows seal is the component that works by friction, therefore subject to greater wear, and ensures the isolation of the fluid and the hydraulic part from the outside. It consists of a mobile part that rotates together with the impeller and a fixed part locked relative to the static components of the centrifugal pump. Normally a centrifugal pump reaches rotational speeds of about 3000 rpm, so very high temperatures are reached in a very short time. It is crucial that the mechanical seal is always cooled (by the working liquid itself) and that the centrifugal pump is never operated dry, otherwise there is a risk of melting the fixed components.
    The parts that work by friction are made of silicon carbide which ensures less wear, has greater mechanical and chemical resistance, and better withstands thermal shocks allowing it to work at higher temperatures.

  • The external casing is the assembly of connecting flanges and lantern that connects the motor to the hydraulic part, keeping the latter isolated from the outside. A solid structure minimizes unwanted vibrations and friction, extending the life of the centrifugal pump.
  • The motor is the part that transmits motion. In most common cases, it is a 2-pole electric motor (about 3000 rpm). Depending on the number of revolutions, it is possible to obtain different characteristic curves of the centrifugal pump.

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